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La ct ic Acid Ba ct e r ia ( pa ge 1 )
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La ct ic Acid Ba ct e r ia
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La ct oba cillu s a cidoph ilu s
Th e ba ct e r iu m is a m e m be r of t h e n or m a l flor a of h u m a n s, fou n d in t h e or a l ca vit y , t h e sm a ll in t e st in e, a n d t h e va gin a l e pit h e liu m , w h e r e it is t h ou gh t t o pla y a be n e ficia l r ole . Th e or ga n ism is ge n e r a lly t h e fir st ba ct e r iu m list e d a s
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pr e se n t in pr obiot ic con coct ion s.
Micro and Nano- Particle Techniques
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La ct ic Acid Ba ct e r ia ( LAB ) are Gram-positive , non-sporeforming cocci, coccobacilli or rods with a AdChoices
DNA base composition of less than 53mol % G +C. They generally are non respiratory and lack Web Review of Todar's Online Textbook of
catalase. They ferment glucose primarily to lactic acid, or to lactic acid, CO2 and ethanol . All LAB grow anaerobically, but unlike most anaerobes, they grow in the presence of O
as "aerotolerant 2004 - Vol 304: p. 1421) . Deadly" Bacteriology. . (SCIENCE Magazine - June 4, "The Good, t he Bad , and t he
2 anaerobes". Although they lack catalase , they possess superoxide dismutase and have alternative means to detoxify peroxide radicals, generally through peroxidase enzymes.
Although many genera of bacteria produce lactic acid as a primary or secondary end-product of sour cream, cheesemaking, bacteriocins , cheese, curds, yogurt , butter, buttermilk, thermophilus , Leuconostoc, lactic acid , Lactobacillus , acidophilus , Streptococcus homolactic , heterolactic , Lactococcus , Tag words : lactic acid bacteria, LAB,
fermentation, the term La ct ic Acid Ba ct e r ia is conventionally reserved for genera in the order lactococcus genome, probiotics. nicin, lantibiotics, vaccine delivery,
Lact obacillales, which includes Lact obacillus , Leuconost oc, Pediococcus , Lact ococcus and St rept ococcus , in addition to Carnobact erium , Ent erococcus, Oenococcus, Tet ragenococcus , Vagococcus, and Weisella.
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Because they obtain energy only from the metabolism of sugars, lactic acid bacteria are restricted
Bacteria to environments in which sugars are present. They have limited biosynthetic ability, having evolved
in environments that are rich in amino acids, vitamins , purines and pyrimidines, so they must be
Fermentation
cultivated in complex media that fulfill all their nutritional requirements . Most are free-living or live
Lactobacillus
in beneficial or harmless associations with animals, although some are opportunistic pathogens . They are found in milk and milk products and in decaying plant materials. They are normal flora of humans in the oral cavity, the intestinal tract and the vagina, where they play a beneficial role.
A few LAB are pathogenic for animals , most notably some members of the genus St rept ococcus . In humans, St rept ococcus pyogenes is a major cause of disease (strep throat, pneumonia, and other pyogenic infections, scarlet fever and other toxemias), St rept ococcus pneum oniae causes lobar pneumonia, otitis media and meningitis; some viridans and nonhemolytic oral streptococci play a role in dental caries and may be an insidious cause of endocarditis. The pathogenic streptococci are dealt with elsewhere in the text. This chapter deals primarily with LAB in association with food and dairy microbiology, to a lesser extent with LAB as beneficial components of the human normal flora and probiotics.
Lactic acid bacteria are among the most important groups of microorganisms used in food fermentations. They contribute to the taste and texture of fermented products and inhibit food Lactic acid bacteria are among the most important groups of microorganisms used in food fermentations. They contribute to the taste and texture of fermented products and inhibit food
D iffe r e n t ia l ch a r a ct e r ist ics of la ct ic a cid ba ct e r ia ba se d on m or ph ology a n d ph ysiology Ge n u s
Lact obacillus Ent erococcus Lact ococcus Leuconost oc Pediococcus St rept ococcus
Ch a r a ct e r ist ic
Morphology rods
cocci CO2 from
cocci
cocci
cocci cocci in tetrads
glucose * ±
+ − − Growth
at 10°C ±
+ ± − at 45°C
− ± ± in 6 .5% NaCl
± ± − at pH 4 .4
± + − at pH 9 .6
− − − Lactic acid
+ posit ive; - n e ga t ive ; ± va r ie s be t w e e n spe cie s * t e st for h om o- or h e t e r ofe r m e n t a t ion of glu cose : - h om ofe r m e n t a t ion
+ h e t e r ofe r m e n t a t ion
chapter continued
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Feat ured Microbe
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Web Review of Todar' s Online Text book of Bact eriology. "The Good, t he Bad, and t he Deadly" . (SCI ENCE Magazine - June 4 , 2004 - Vol 304 : p. 1421 ).
Tag words: lact ic acid bact eria, LAB , hom olact ic, het erolact ic, Lact ococcus, Lact obacillus , acidophilus, St rept ococcus t herm ophilus, Leuconost oc, lact ic acid, cheese, curds , yogurt , but t er , but t erm ilk, sour cream , cheesem aking , bact eriocins, nicin, lant ibiot ics , vaccine delivery , lact ococcus genom e, probiot ics.
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La ct ic Acid Ba ct e r ia ( pa ge 2 )
( This chapt er has 5 pages) © 2011 Kennet h Todar, PhD
M e t a bolism
The essent ial feat ure of LAB m et abolism is efficient carbohydrat e ferm ent at ion coupled t o subst rat e- level phosphorylat ion . Adenosine t riphosphat e ( ATP) generat ed is subsequent ly used for biosynt hesis. LAB as a group exhibit an enorm ous capacit y t o degrade different carbohydrat es and relat ed com pounds . Generally, t he predom inant end product is lact ic acid ( > 50% of sugar carbon ) . However, LAB adapt t o various condit ions and change t heir m et abolism accordingly . This m ay lead t o significant ly different end- product pat t erns.
Based on sugar ferm ent at ion pat t erns , t wo broad m et abolic cat egories of LAB exist : hom oferm ent at ive and het eroferm ent at ive . The first cat egory , h om ofe r m e n t a t ive LAB, includes som e lact obacilli and m ost species of ent erococci , lact ococci , pediococci , st rept ococci, t et ragenococci , and vagococci , t hat ferm ent hexoses by t he Em bden - Meyerhof ( E- M ) pat hway. The second cat egory , h e t e r ofe r m e n t a t ive LAB, includes leuconost ocs, som e lact obacilli, oenococci, and weissella species . The apparent difference on t he enzym e level bet ween t hese t wo cat egories is t he presence or absence of t he key cleavage enzym es of t he E- M pat hway ( fruct ose 1 , 6- diphosphat e ) and t he PK pat hway ( phosphoket olase ) .
H om ola ct ic Fe r m e n t a t ion
Under condit ions of excess glucose and lim it ed oxygen , hom olact ic LAB cat abolize one m ole of glucose in t he Em bden - Meyerhof pat hway t o yield t wo m oles of pyruvat e.
I nt racellular redox balance is m aint ained t hrough t he oxidat ion of NADH, concom it ant wit h pyruvat e reduct ion t o lact ic acid. This process yields t wo m oles of ATP per glucose consum ed . Represent at ive hom olact ic LAB genera include Lact obacillus , Lact ococcus, Ent erococcus , St rept ococcus and Pediococcus species .
The t ransport and phosphorylat ion of sugars occur by ( 1 ) t ransport of free glucose and phosphorylat ion by an ATP- dependent hexose kinase ( ot her sugars, such as m annose and fruct ose , ent er t he m aj or pat hways at t he level of glucose - 6- phosphat e or fruct ose - 6- phosphat e aft er isom erizat ion or phosphorylat ion or bot h) ; or ( 2 ) t he phosphoenolypyruvat e ( PEP) sugar phosphot ransferase syst em ( PTS) , in which PEP is t he phosphoryl donor for t he upt ake of sugar . Som e species of LAB use t he PTS for t ransport of galact ose only ; ot hers use t he PTS for all sugars.
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Bacteria Fermentation Gram Bacteria Stain
Th e pa t h w a y of h om ola ct ic a cid fe r m e n t a t ion in La ct ic Acid Ba ct e r ia
H e t e r ola ct ic Fe r m e n t a t ion
Het eroferm ent at ive LAB ut ilize t he phosphoket olase pat hway ( pent ose phosphat e pat hway) t o dissim ilat e sugars . One m ole of glucose- 6 - phosphat e is init ially dehydrogenat ed t o 6- phosphogluconat e and subsequent ly decarboxylat ed t o yield one m ole of CO2 . The resulting pentose- 5 - phosphate is cleaved into one m ole glyceraldehyde phosphat e ( GAP) and one m ole acet yl phosphat e. GAP is furt her m et abolized t o lact at e as in hom oferm ent at ion , wit h t he acet yl phosphat e reduced t o et hanol via acet yl- CoA and
acet aldehyde int erm ediat es. Theoret ically , end- product s ( CO 2 , lact at e and et hanol) are produced in equim olar quant it ies from t he cat abolism of one m ole of glucose . Obligat e
het eroferm ent at ive LAB include Leuconost oc, Oenococcus, Weissella , and cert ain lact obacilli.
Th e pa t h w a y of h e t e r ola ct ic a cid fe r m e n t a t ion in La ct ic Acid Ba ct e r ia
Lact ic acid bact eria have a very lim it ed capacit y t o synt hesize am ino acids using inorganic nit rogen sources. They are t herefore dependent on preform ed am ino acids being present in t he growt h m edium as a source of nit rogen . The requirem ent for am ino acids differs am ong species and st rains wit hin species . Som e st rains are prot ot rophic for m ost am ino acids, whereas ot hers m ay require 13 –15 am ino acids. Since t he quant it ies of free am ino acids present in t heir environm ent are not sufficient t o support t he growt h of bact eria t o a high cell densit y, t hey require a prot eolyt ic syst em capable of hydrolyzing pept ides and prot eins in order t o obt ain essent ial am ino acids. All dairy lact ococci used for acidificat ion of m ilk ( e . g. , in cheese m anufact ure) have prot eolyt ic act ivit y. The lact ococcal prot eolyt ic syst em consist s of enzym es out side t he cyt oplasm ic m em brane , t ransport syst em s, and int racellular pept idases . The prot eolyt ic act ivit y of LAB cont ribut es addit ionally t o t he developm ent of t he flavor , arom a and t ext ure of ferm ent ed product s . For m any variet ies of cheeses, such as Swiss and Cheddar , desirable " flavor t ones" are derived by prot eolysis.
L. Pla n t a r u m D e t a ils- Am bio
Offer Everyt hing About L .Plant arum Get Top Lact obacillus Plant arum Now am bio . co . kr
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La ct ic Acid Ba ct e r ia ( pa ge 3 )
( This chapt er has 5 pages) © 2011 Kennet h Todar, PhD
Fe r m e n t a t ion of Foods by La ct ic Acid Ba ct e r ia
Many hum an foods are plant s or anim al product s which have been ferm ent ed by lact ic Feat ured Microbe
acid bact eria, since t hese bact eria possess propert ies t hat can benefit food product ion or conversion. The acidic and organolept ic propert ies of ferm ent ed foods result from t he m et abolic act ivit ies of t hese m icroorganism s. Foods such as ripened cheeses, ferm ent ed
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sausages , sauerkraut and pickles have not only a great ly ext ended shelf life com pared t o
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t he raw m at erials from which t hey are derived , but also arom a and flavor charact erist ics cont ribut ed direct ly or indirect ly by t he ferm ent ing organism s.
www.realbrewersyeast. com small and large scale brewing
Ferm ent ed dairy product s have been m ade for t housands of years , but only wit hin t he
L.PlantarumDetails-Ambio
last cent ury have t he m icrobiological bases of t hese ferm ent at ions been elucidat ed . Lact ic
Offer Everything About
acid bact eria are t he principal organism s involved in ferm ent ing dairy product s. Prior t o
L.Plantarum Get Top t he availabilit y of st art er cult ures, m ilk ferm ent at ions relied on t he LAB nat urally present
in raw m ilk . The first com m ercial st art er cult ures were unknown m ixes of m icrobes from
Lactobacillus Plantarum Now
raw m ilk t hat were prepared in Denm ark around end of t he 19t h cent ury . I n t he 1930s ambio.co. kr
and 40 s, t he idea of pure single- st rain st art er cult ures evolved.
Ferm ent ed dairy product s are enj oying increased popularit y as convenient , nut rit ious, Web Review of Todar' s Online Text book of Deadly" Bact eriology. "The Good, t he Bad, and t he
st able, nat ural , and healt hy foods . Lact ic acid bact eria are t he principal organism s 2004 - Vol 304 : p. 1421 ). . (SCI ENCE Magazine - June 4 ,
involved in t he m anufact ure of cheese, yogurt, but t erm ilk, cot t age cheese, sour cream and cult ured but t er . I n som e ferm ent ed dairy product s , addit ional bact eria, referred t o as
Tag words: lact ic acid bact eria, LAB , hom olact ic, het erolact ic, Lact ococcus, secondary m icroflora, are added t o produce carbon dioxide, which influences t he flavor Lact obacillus , acidophilus, St rept ococcus
and alt ers t he t ext ure of t he final product .
t herm ophilus, Leuconost oc, lact ic acid, cheese, curds , yogurt , but t er , but t erm ilk, sour cream , cheesem aking , bact eriocins,
Sausage is one of t he oldest processed m eat product s . The writ ings of ancient Egypt ians nicin, lant ibiot ics , vaccine delivery , lact ococcus genom e, probiot ics.
described t he preservat ion of m eat by salt ing and sun drying. The ancient Babylonians, Greeks, and Rom ans used sausage as a food source during t im es of war . Microorganism s were recognized as being im port ant t o t he product ion of sausages about 1921. I n t he 1940s and 1950s, pure m icrobial st art er cult ures consist ing of lact ic acid bact eria becam e
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available but t heir use was not widespread unt il t he early 1980s.
Bacteria Lactobacillus The ferm ent at ion of veget ables, a pract ice t hat originat ed in t he Orient , has been used as
a m eans of preserving food for m ore t han 2 , 000 years . I n t he t hird cent ury B. C . , during
Fermentation
t he const ruct ion of t he Great Wall of China, t he Chinese produced ferm ent ed veget ables ( cabbages, radishes, t urnips, cucum bers, et c. ) on a large scale. The m ost com m on ferm ent ed veget ables available in t he Unit ed St at es are pickles, sauerkraut , and olives. Carrot s , cauliflower, celery, okra, onions, and sweet and hot peppers also are sold as ferm ent ed veget able product s.
Generally LAB t hat are im port ant in t he ferm ent at ion of food product s ( dairy, m eat , veget ables, fruit s, and beverages ) , include only cert ain species of t he genera Lact obacillus , Lact ococcus, St rept ococcus , Leuconost oc and Pediococcus . Som e of t hese species are also m em bers of norm al flora of t he m out h , int est ine , and vagina of m am m als.
I n volve m e n t of la ct ic a cid ba ct e r ia in t h e m a n u fa ct u r e of fe r m e n t e d da ir y pr odu ct s
Pr odu ct
Pr in cipa l a cid
pr odu ce r s
Se con da r y m icr oflor a
Cheese
Lact ococcus lact is
Colby , cheddar,
subsp . crem oris
None
cot t age , cream
Lact ococcus lact is subsp . lact is
Lact ococcus lact is Cit + Lact ococcus lact is subsp. lact is Penicillium
Blue subsp . crem oris roquefort i Lact ococcus lact is
subsp . lact is
None Mozzarella ,
St rept ococcus t herm ophilus
provolone, Lact obacillus Rom ano ,
delbrueckii
subsp.
parm esan bulgaricus Lact obacillus
helvet icus
St rept ococcus Propionibact erium t herm ophilus
freudenreichii subsp . sherm anii
Swiss Lact obacillus delbrueckii subsp. bulgaricus
Lact obacillus helvet icus
Ferm ent ed m ilk St rept ococcus
t herm ophilus None Yogurt
Lact obacillus delbrueckii subsp. bulgaricus
Lact ococcus lact is Leuconost oc sp. Cit + But t erm ilk
subsp . crem oris Lact ococcus lact is subsp . lact is
Lact ococcus lact is subsp . lact is
Lact ococcus lact is Sour cream
subsp . crem oris None Lact ococcus lact is
subsp . lact is
La ct oba cilli
Lact obacillus is very het erogeneous genus, encom passing species wit h a large variet y of phenot ypic, biochem ical , and physiological propert ies. Most species of lact obacilli are hom oferm ent at ive, but som e are het eroferm ent at ive . The genus has been divided int o t hree m aj or subgroups and over 70 species are recognized . Group I lact obacilli are obligat ely hom oferm ent at ive and produce lact ic acid as a m aj or end product ( > 85 % ) from glucose. They are represent ed by L . delbrueckii and L. acidophilus . They grow at 45 oC but not at 15 oC. Group I I , also hom oferm entative , grow
at 15 oC and show variable growth at 45oC . Represented by L . casei and L. plantarum, t hey can produce m ore oxidized ferm ent at ions ( e . g . acet at e) if O2 is present . Group I I I lact obacilli are het eroferm ent at ive . They produce lact ic acid from glucose, along wit h CO 2 and et hanol . Aldolase is absent and phosphoket olase is present . Represent at ive species include L . ferm ent um , L . brevis and L. keferi.
Lact obacilli are oft en found in dairy product s, and som e species are used in t he preparat ion of ferm ent ed m ilk product s. For exam ple L . delbrueckii subsp bulgaricus are used in t he preparat ion of yogurt ; L. acidophilus is used in t he preparat ion of acidophilus m ilk ; L. helvet icus , as well as L. delbrueckii subsp bulgaricus , are used t o m ake Swiss, Mozzarella, provolone, Rom ano , and parm esan cheeses. Ot her species are used in t he product ion of sauerkraut , silage and pickles. The lact obacilli are usually m ore resist ant t o acidic condit ions t han are ot her LAB, being able t o grow at pH values as low as 4 . This enables t hem t o cont inue t o grow during nat ural lact ic ferm ent at ions when t he pH has dropped t oo low for ot her LAB t o grow , so t hey are oft en responsible for t he final st ages of m any lact ic acid ferm ent at ions.
Many sausage ferm ent at ions include a Lact obacillus species . L . plant arum is used in st art er cult ures for t he m anufact ure of sum m er sausage , pepperoni and salam i.
The nat ural ferm ent at ion of cabbage t o m ake sauerkraut involves L . brevis and L. plant arum in t he final succession of m icrobe. The st art er cult ures for m anufact ure of cucum ber pickles includes L . brevis and L . plant arum . L . plant arum is t he m ost essent ial species in pickle product ion , as it is for sauerkraut . Like cucum bers, olives are ferm ent ed under condit ions sim ilar t o t hose of ot her veget able product s. The m icrobial populat ion responsible for t he ferm ent at ion of olives differs from t hat of sauerkraut and pickles m ainly because t he higher salt concent rat ion of t he brine prevent s m any salt- sensit ive st rains from growing and provides an advant age t o salt - t olerant st rains. LAB becom e prom inent during t he int erm ediat e st age of ferm ent at ion . L. m esent eroides and P.
plant arum and L . brevis being t he m ost im port ant .
St r e pt ococci a n d La ct ococci
Not e on St rept ococcal Classificat ion. Since 1985, m em bers of t he diverse genus St rept ococcus have been reclassified int o Lact ococcus, Vagococcus, Ent erococcus, and St rept ococcus , based on biochem ical charact erist ics , as well as ssRNA analysis. Hist orically, st rept ococci were segregat ed int o serological groups based on t he presence of specific carbohydrat e ant igens. Ant igenic groups, or Lancefield groups ( nam ed for Rebecca Lancefield, a pioneer in St rept ococcus t axonom y) , are designat ed by let t ers A t hrough O . Lancefield groups have proven t o correlat e well wit h t he current t axonom ic definit ions. The bet a - hem olyt ic st rept ococci found in hum ans cont ain t he group A ant igen, while " fecal st rept ococci" ( ent erococci ) cont ain t he group D ant igen. Group B st rept ococci, usually found in anim als, are a cause of m ast it is in cows, and have been im plicat ed in hum an infect ions. " Lact ic st rept ococci" ( st rept ococci and lact ococci) cont ain t he group N ant igen and are nonpat hogenic. However , Lact ococcus has been defined as a genus separat e from St rept ococcus . As lact ic acid bact eria, Lact ococcus lact is and St rept ococcus t herm ophilus are t he cornerst ones of cheese m anufact ure.
St r e pt ococcu s t h e r m oph ilu s
St rept ococcus t herm ophilus is an alpha- hem olyt ic species of t he viridans group. The bact erium is found in m ilk and m ilk product s. I t is not a probiot ic ( it does not survive t he st om ach) and generally is used in t he product ion of yogurt and t he m anufact ure of several t ypes of cheese, especially I t alian and Swiss cheeses. The organism is a m oderat e t herm ophile wit h an opt im al growt h rat e at 45 ° C. Alt hough S. t herm ophilus is closely relat ed t o ot her pat hogenic st rept ococci ( such as S . pneum oniae and S. pyogenes ) , S. t herm ophilus is classified as a non- pat hogenic, alpha - hem olyt ic species t hat is part of t he viridan' s group. I t is closely relat ed t o S . salivarius in t he oral cavit y .
La ct ococcu s la ct is
Lact ococcus is a genus of of LAB wit h five m aj or species form erly classified as Group N st rept ococci. The t ype species for t he genus is L . lact is , which has t wo subspecies, lact is and crem oris . Lact ococci differ from ot her lact ic acid bact eria by t heir pH, salt and t em perat ure t olerances for growt h.
Lact ococcus lact is is crit ical for m anufact uring cheeses such as Cheddar , cot t age , cream , Cam em bert , Roquefort and Brie, as well as ot her dairy product s like cult ured but t er , but t erm ilk , sour cream and kefir . The bact erium can be used in single st rain st art er cult ures, or in m ixed st rain cult ures wit h ot her lact ic acid bact eria such as Lact obacillus and St rept ococcus .
n isin food pr e se r va t ive Produce and export nisin ChiHonBio m anufact urer of nisin www . chihonbio . com /
chapt er cont inued Previous Page © Kennet h Todar, Ph . D . All right s reserved . - www . t ext bookofbact eriology. net
Kennet h Todar, PhD | Hom e | Table of Cont ent s |
I nst ruct or Aids | Cont act I nform at ion | Cit at ions & Adapt at ions
© 2008 Kennet h Todar, PhD - Madison , Wisconsin
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La ct ic Acid Ba ct e r ia ( pa ge 4 )
( This chapt er has 5 pages) © 2011 Kennet h Todar, PhD
Ba ct e r iocin s a n d LAB
Feat ured Microbe Class I bact eriocins or lant ibiot ics are sm all pept ides cont aining t he unusual dehydroam ino acids and t hioet her am ino acids lant hionin and 3- m et hyllant hionine, which are synt hesized by Gram - posit ive bact eria during post t ranslat ional m odificat ions. These
nisin food preservative
pept ides are t hought t o at t ach t o t he m em brane of t arget cells and, by an as yet
Produce and export nisin
unknown conform at ional rearrangem ent, lead t o increased perm eabilit y and disrupt ion of
ChiHonBio manufacturer of
t he m em brane pot ent ial. There are t wo t ypes of lant ibiot ics, t ypes A and B . The
nisin
lant ibiot ics produced by LAB all belong t o t ype A, which are elongat ed screw- shaped www.chihonbio.com /
pept ides, whereas t ype B lant ibiot ics are m ainly globular. Nisin produced by Lact ococcus lact is ssp. lact is has been st udied ext ensively . I t has a broad spect rum of act ivit y against
Artisan Quality Yeast
Gram - posit ive bact eria. The prim ary t arget is believed t o be t he cell m em brane . Unlike
Hand crafted ale pitches For
som e ot her ant im icrobial pept ides, nisin does not need a recept or for it s int eract ion wit h
www.realbrewersyeast. com small and large scale brewing
t he cell m em brane ; however, t he presence of a m em brane pot ent ial is required .
St a r t e r cu lt u r e s
Web Review of Todar' s Online Text book of Bact eriology. Deadly" 2004 - Vol 304 : p. 1421 ). . (SCI ENCE Magazine - June 4 , "The Good, t he Bad, and t he
Tag words: lact ic acid bact eria, LAB , hom olact ic, het erolact ic, Lact ococcus, Lact obacillus , acidophilus, St rept ococcus t herm ophilus, Leuconost oc, lact ic acid, cheese, curds , yogurt , but t er , but t erm ilk, sour cream , cheesem aking , bact eriocins, nicin, lant ibiot ics , vaccine delivery , lact ococcus genom e, probiot ics.
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Probiotics Bacteria Lactobacillus
St a r t e r cu lt u r e s con sist in g of la ct ic a cid ba ct e r ia a r e a dde d a t t h e be gin n in g of t h e ch e e se m a k in g pr oce ss. La ct ic a cid ba ct e r ia a r e e sse n t ia l for m a n u fa ct u r e of
ch e e se , yogu r t , sou r cr e a m , cu lt u r e d bu t t e r a n d m ost fe r m e n t e d m ilk pr odu ct s.
St art er cult ures play an essent ial part in t he m anufact ure of ferm ent ed dairy product s. They produce t he lact ic acid t hat coagulat es m ilk and t hey cont ribut e t o t ext ure, m oist ure cont ent , freedom from pat hogenic m icroorganism , and t ast e of t he product . The rat e of acid product ion is crit ical in t he m anufact ure of cert ain product s, e . g . Cheddar cheese. Depending on t he product , especially in m echanized cheese product ion unit s, st art ers m ay also be required t o produce acid at a consist ent ly fast rat e t hrough t he m anufact uring period each day and every day . The negat ive redox pot ent ial creat ed by st art er growt h in cheese also aids in preservat ion and t he developm ent of flavor in Cheddar and sim ilar cheeses. Addit ionally ant ibiot ic subst ances, now referred t o as bact eriocins, produced by st art ers, e. g . nisin , m ay also have a role in preservat ion.
Ecology of st art er bact eria Most st art ers in use t o t oday have t heir origins as lact ic acid bact eria nat urally present as part of t he cont am inat ing m icroflora of m ilk . These bact eria probably cam e from veget at ion in t he case of lact ococci or t he int est inal t ract in t he case of bifidobact eria, ent erococci and Lact obacillus acidophilus .
Modern st art er cult ures developed from t he pract ice of ret aining sm all quant it ies of whey or cream from t he successful m anufact ure of a ferm ent ed product on a previous day and using t his as t he inoculum or st art er for t he following day ’s product ion . I n t he foods Modern st art er cult ures developed from t he pract ice of ret aining sm all quant it ies of whey or cream from t he successful m anufact ure of a ferm ent ed product on a previous day and using t his as t he inoculum or st art er for t he following day ’s product ion . I n t he foods
Classificat ion of st art er cult ures While t he m icrobes used in t he m anufact ure of ferm ent ed dairy product s are generally lact ic acid bact eria, Propionibact erium sherm anii and Bifidobact erium spp . which are not lact ic acid bact eria, are also used . I n addit ion, ot her bact eria including Brevibact erium linens , responsible for t he flavor of Lim burger cheese; and m olds ( Penicillium species) are used in t he m anufact ure of Cam em bert , Roquefort and blue cheeses.
Pr obiot ics a n d La ct ic Acid Ba ct e r ia
Pr obiot ics are product s designed t o deliver pot ent ially beneficial bact erial cells t o t he m icrobiot ic ecosyst em of hum ans and ot her anim als. St rains of lact ic acid bact eria are t he m ost com m on m icrobes em ployed as probiot ics, especially Lact obacillus and Bifidobact erium species , but lact ococci, som e ent erococci and som e st rept ococci are also included as probiot ics.
La ct ic a cid- pr odu cin g Ba ct e r ia Use d a s Pr obiot ics
La ct oba cillu s La ct oba cillu s spe cie s a r e fa cu lt a t ive a n a e r obe s. Th e y gr ow in t h e pr e se n ce of O 2 , how ever, and m ay convert it to H 2 O or H 2 O2 . Lactobacilli norm ally pr e dom in a t e in t h e sm a ll in t e st in e, a n d t h e y a r e k n ow n for t h e ir be n e ficia l
e ffe ct s w h ich m a y a n t a gon iz e pot e n t ia l pa t h oge n s. Of t h e m or e t h a n 1 0 0 La ct oba cillu s spe cie s, t h e follow in g a r e com m on ly u se d pr obiot ics : L . a cidoph ilu s L . fe r m e n t u m L . pa r a ca se i L . br e vis L . ga sse r i L . pla n t a r u m L . bu lga r icu s L . h e lve t icu s L.reuteri L . ca se i L . j e n se n ii L . r h a m n osu s L . cr ispa t u s L . j oh n son ii L . sa liva r iu s
Bifidoba ct e r iu m Bifidoba ct e r iu m is n ot in clu de d in t h e t r a dit ion a l La ct ic Acid Ba ct e r ia du e t o it s
ge n e t ic u n r e la t e dn e ss, bu t t h e ba ct e r iu m h a s a h a bit a t t h a t ove r la ps w it h LAB ,
a n d it h a s a m e t a bolism t h a t pr odu ce s la ct ic a cid a s a pr im a r y e n d - pr odu ct of
fe r m e n t a t ion . Bifidoba ct e r ia a r e st r ict ly a n a e r obic a n d n or m a lly vie for pr e dom in a n ce in t h e la r ge in t e st in e. Am on g 3 0 spe cie s , t h ose r e cogn iz e d a s pr obiot ics in clu de:
B. a dole sce n t is
B. bifidu m
B. la ct is
Bifidoba ct e r iu m lon gu m . Bifidoba ct e r ia a r e a n obliga t e ly a n a e r obic ba ct e r ia , n ot cla ssifie d w it h t h e la ct ic a cid ba ct e r ia , bu t w h ich occu py sim ila r h a bit a t s a n d pr odu ce la ct ic a cid a s a sole e n d - pr odu ct . Th e y a r e a pr om in a n t Gr a m - posit ve
ba ct e r iu m in t h e la r ge in t e st in e ( colon) . Bifidoba ct e r iu m in fa n t u m is t h e pr e dom in a n t ba ct e r iu m in t h e in t e st in e of br e a st - fe d in fa n t s be ca u se m ot h e r ' s m ilk con t a in s a spe cific gr ow t h fa ct or t h a t e n r ich e s for t h e gr ow t h of t h e ba ct e r iu m in t h e la r ge in t e st in e ( colon) . Bifidoba ct e r iu m in fa n t u m is t h e pr e dom in a n t ba ct e r iu m in t h e in t e st in e of br e a st - fe d in fa n t s be ca u se m ot h e r ' s m ilk con t a in s a spe cific gr ow t h fa ct or t h a t e n r ich e s for t h e gr ow t h of t h e
St r e pt ococcu s St r e pt ococcu s spe cie s a r e n ot t ypica lly a ssocia t e d w it h h e a lt h be n e fit s a n d som e
a r e h igh ly pa t h oge n ic. H ow e ve r , on e fa cu lt a t ive a n a e r obic spe cie s , St r e pt ococcu s t h e r m oph ilu s , is k n ow n t o pr om ot e h e a lt h. I t is on e of t h e t w o pr im a r y spe cie s fou n d in yogu r t cu lt u r e s, t h e ot h e r be in g L . bu lga r icu s .
En t e r ococcu s Fou n d in a n u m be r of pr obiot ic pr odu ct s, t h e fa cu lt a t ive a n a e r obe En t e r ococcu s
fa e ciu m is in va r ia bly a com pon e n t of t h e n or m a l in t e st in a l m icr obiot a a n d is con side r e d a be n e ficia l m icr obe. H ow e ve r , E. fa e ciu m h a s e volve d fr om a r e la t ive ly n on pa t h oge n ic com m e n sa l ba ct e r iu m t o t h e t h ir d m ost com m on ca u se of h ospit a l- a cqu ir e d in fe ct ion s a n d n ow a ccou n t s for ove r 1 0 % of e n t e r ococca l clin ica l isola t e s . Fu r t h e r m or e , it h a s de ve lope d e x t e n sive r e sist a n ce t o
a n t ibiot ics, w h ich it is ca pa ble of t r a n sfe r r in g t o ot h e r ba ct e r ia .
The hum an body , prim arily t he gast roint est inal t ract , is hom e t o a large num ber of different species of bact eria, and it is likely we could not survive wit hout t heir presence. Two of t he m ost com m on bact eria t hat com prise t he int est inal m icrobiot a ( "norm al flora" ) are Lact obacillus acidophilus and Bifidobact erium bifidum . Hence , t hey are a m ain com ponent of probiot ics.
The indigenous bact eria of hum ans serve a wide range of funct ions , which include m anufact ure of som e B vit am ins and vit am in K , synt hesis of som e digest ive enzym es ( e . g. lact ase) , com pet it ion wit h pat hogens for colonizat ion sit es, product ion of ant ibact erial and ant ifungal subst ances t hat prot ect against harm ful organism s , product ion of chem icals t hat have been shown t o be ant i- carcinogenic , and st im ulat ion of t he developm ent and act ivit y of t he im m une syst em .
The nat ural balance of t he body ’s bact eria can be upset by several fact ors such as cert ain m edicines, ant ibiot ics and st eroids, increased acidit y in t he digest ive syst em caused by st ress, lack of sleep and poor diet , const ipat ion or diarrhea , yeast overgrowt h , fat igue, I BS and ot her int est inal condit ions .
I t has been been suggest ed , in a few cases proven , t hat one way t o com bat t hese condit ions is by supplem ent at ion of t he diet wit h probiot ic bact eria in nat ural foods or art ificial supplem ent s.
Probiot ics have been recom m ended or suggest ed for pat ient s receiving radiat ion t reat m ent , individuals who have recurrent t hrush, vaginal yeast infect ions, or urinary t ract infect ions , persons suffering from irrit able bowel syndrom e ( I BS) or ot her bowel problem s , for t ravelers abroad t o prot ect against food poisoning and during any period where ant ibiot ics m ay be t aken .
L. Pla n t a r u m D e t a ils- Am bio Offer Everyt hing About L .Plant arum Get Top Lact obacillus Plant arum Now am bio . co . kr
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La ct ic Acid Ba ct e r ia ( pa ge 5 )
( This chapt er has 5 pages) © 2011 Kennet h Todar, PhD
Th e follow in g se ct ion t h a t focu se s on La ct ococcu s la ct is a s t h e
Feat ured Microbe
pr ot ot ypica l la ct ic a cid ba ct e r iu m . La ct ococcu s la ct is e x h ibit s vir t u a lly a ll of t h e for e goin g ch a r a ct e r ist ics a n d a pplica t ion s of a
nisin food preservative la ct ic a cid ba ct e r iu m . Th is ba ct e r iu m is ch ose n be ca u se of it s pr e e m in e n ce in ch e e se m a k in g a n d it s st a t u s a s t h e n a t u r a l
Produce and export nisin
n om in e e a s t h e st a t e m icr obe of t h e da ir y st a t e of W iscon sin .
ChiHonBio manufacturer of nisin www.chihonbio. com/
Artisan Quality Yeast
Hand crafted ale pitches For small and large scale brewing www.realbrewersyeast .com
Bact eriology. Web Review of Todar' s Online Text book of Deadly" 2004 - Vol 304 : p. 1421 ). . (SCI ENCE Magazine - June 4 , "The Good, t he Bad, and t he
cheese, curds , yogurt , but t er , but t erm ilk, t herm ophilus, Leuconost oc, lact ic acid, Lact obacillus , acidophilus, St rept ococcus hom olact ic, het erolact ic, Lact ococcus, Tag words: lact ic acid bact eria, LAB , sour cream , cheesem aking , bact eriocins,
lact ococcus genom e, probiot ics. nicin, lant ibiot ics , vaccine delivery ,
La ct ococcu s la ct is. UW D e pa r t m e n t of Ba ct e r iology st r a in LcL 3 2 5 UW . M a gn ifica t ion 2 0 0 0 0 X . Sca n n in g e le ct r on m icr ogr a ph by Jose ph A. H e in t z , Un ive r sit y of W iscon sin - M a dison .
Lact ococcus lact is is a m icrobe classified inform ally as a Lact ic Acid Bact erium because it ferm ent s m ilk sugar ( lact ose) t o lact ic acid. Lact ococci are t ypically spherical or ovoid cells, about 1 . 2 µm by 1 . 5 µm , occurring in pairs and short chains . They are Gram - posit ive, non m ot ile , and do not form spores . Lact ococci are found associat ed wit h plant m at erial , m ainly grasses , from which t hey are easily inoculat ed int o m ilk . Hence, t hey are found norm ally in m ilk and m ay be a nat ural cause of souring . Lact ococcus lact is has t wo subspecies, lact is and crem oris, bot h of which are essent ial in m anufact ure of m any variet ies of cheese and ot her ferm ent ed m ilk product s.
Lact ococcus lact is is relat ed t o ot her lact ic acid bact eria such as Lact obacillus acidophilus in our int est inal t ract and St rept ococcus salivarius in t he m out h . However, Lact ococcus does not norm ally colonize hum an t issues and differs from m any ot her lact ic acid bact eria in it s pH, salt, and t em perat ure t olerances for growt h, which are im port ant charact erist ics relevant t o it s use as a st art er cult ure in t he cheesem aking indust ry .
Lact ococcus lact is is vit al for m anufact uring cheeses such as Cheddar , Colby , cot t age cheese, cream cheese, Cam em bert , Roquefort and Brie, as well as ot her dairy product s like cult ured but t er , but t erm ilk , sour cream and kefir . I t m ay also be used for veget able ferm ent at ions such as cucum ber pickles and sauerkraut . The bact erium can be used in single st rain st art er cult ures, or in m ixed st rain cult ures wit h ot her lact ic acid bact eria such as Lact obacillus and St rept ococcus species.
When Lact ococcus lact is is added t o m ilk , t he bact erium uses enzym es t o produce energy ( ATP) from lact ose. The byproduct of ATP product ion is lact ic acid. The lact ic acid curdles When Lact ococcus lact is is added t o m ilk , t he bact erium uses enzym es t o produce energy ( ATP) from lact ose. The byproduct of ATP product ion is lact ic acid. The lact ic acid curdles
Fe r m e n t e d da ir y pr odu ct s w h e r e in La ct ococcu s la ct is is t h e pr im a r y or ga n ism in volve d in m a n u fa ct u r e.
Pr odu ct Pr in cipa l a cid pr odu ce r s
Se con da r y m icr oflor a
Cheese Lact ococcus lact is
ssp . crem oris None Colby , Cheddar, cot t age , cream
Lact ococcus lact is ssp . lact is
Cit rat e Lact ococcus lact is + Lact ococcus ssp . crem oris
lact is ssp . lact is Blue
Penicillium roquefort i Lact ococcus lact is
ssp . lact is
Ferm ent ed m ilk Lact ococcus lact is
Leuconost oc spp . ssp . crem oris
Cit rat e + Lact ococcus But t erm ilk
lact is ssp . lact is Lact ococcus lact is
ssp . lact is
None Sour cream
Lact ococcus lact is ssp . crem oris
Lact ococcus lact is ssp . lact is
La ct ococcu s la ct is . M a gn ifica t ion 1 5 0 0 X. Ph a se m icr ogr a ph cou r t e sy of T . D . Br ock , Un ive r sit y of W iscon sin - M a dison.
Ch e e se
Cheese m aking is essent ially a dehydrat ion process in which m ilk casein, fat and m inerals are concent rat ed 6 t o 12- fold, depending on t he variet y . The basic st eps com m on t o m ost variet ies are acidificat ion, coagulat ion , dehydrat ion, and salt ing . Acid product ion is t he m aj or funct ion of t he st art er bact eria. Lact ic acid is responsible for t he fresh acidic flavor of unripened cheese and is im port ant in coagulat ion of m ilk casein , which is accom plished by t he com bined act ion of rennet ( an enzym e) and lact ic acid produced by t he m icrobes. During t he ripening process t he bact eria play ot her essent ial roles by producing volat ile flavor com pounds ( e . g. diacet yl, aldehydes ) , by releasing prot eolyt ic and lipolyt ic enzym es involved in cheese ripening , and by producing nat ural ant ibiot ic subst ances t hat suppress growt h of pat hogens and ot her spoilage m icroorganism s. For Cheddar and Colby cheese product ion , st art er cult ures include st rains of Lact ococcus lact is ssp . crem oris and / or lact is. Likewise, blue cheeses require Lact ococcus lact is ssp. crem oris or lact is, but t he m old Penicillium roquefort i is also added as a secondary cult ure for flavor and blue appearance.
W iscon sin ' s u n iqu e ch e e se cu r ds , Colby , a n d doz e n s of va r ie t ie s of Ch e dda r a r e m a de e x clu sive ly w it h st r a in s of La ct ococcu s la ct is. I m a ge s cou r t e sy of W iscon sin Ch e e se M a r t , M ilw a u k e e W iscon sin .
Cu lt u r e d Bu t t e r, Bu t t e r m ilk a n d Sou r Cr e a m
Sour cream is m ade from cream t o which a st art er cult ure of Lact ococcus lact is has been added t o coagulat e t he cream and t o enhance it s flavor . But t erm ilk is also m ade wit h Lact ococcus lact is in order t o acidify , preserve and flavor t he m ilk . Diacet yl, m ade from cit rat e by Lact ococcus, gives but t erm ilk it s dist inct t ast e and enhances it s st orage propert ies . Lact ococcus lact is or m ixed cult ures t hat cont ain Lact ococcus lact is, plus a Leuconost oc species are used. I n t he m aking of cult ured but t er , fat ( cream ) is separat ed from skim m ilk by cent rifugat ion of m ilk . The cream is past eurized and inoculat ed wit h select ed st art er cult ures. The ripened cream is t hen churned . The cream separat es again int o cream but t er and it s byproduct , sour but t erm ilk.
N isin
Nisin is an ant ibiot ic - like subst ance , called a bact eriocin , produced by t he " food grade" st art er st rain , Lact ococcus lact is ssp . lact is . I t is a nat ural ant im icrobial agent wit h act ivit y against a wide variet y of Gram - posit ive bact eria, including food - borne pat hogens such as List eria , St aphylococcus and Clost ridium . The prim ary t arget of nisin is believed t o be t he cell m em brane . Unlike som e ot her ant im icrobial pept ides , nisin does not need a recept or for it s int eract ion wit h t he cell m em brane ; however, t he presence of a m em brane pot ent ial is required . Nisin is a nat ural preservat ive present in cheese m ade wit h Lact ococcus lact is ssp. lact is, but it is also used as a preservat ive in heat processed and low pH foods . Since nisin cannot be synt hesized chem ically, t he nisin - producing Lact ococcus lact is st rains are used for it s indust rial synt hesis .
The first est ablished use of nisin was as a preservat ive in processed cheese product s , but num erous ot her applicat ions in preservat ion of foods and beverages have been ident ified.
I t is current ly recognized as a safe food preservat ive in approxim at ely 50 count ries. Nisin has been used as a preservat ive in various past eurized dairy product s and canned veget ables, baked, high - m oist ure flour product s , and past eurized liquid eggs. There is int erest in t he use of nisin in nat ural cheese product ion . Considerable research has been carried out on t he ant i - list erial propert ies of nisin in foods and a num ber of applicat ions have been proposed. Uses of nisin t o cont rol spoilage lact ic acid bact eria have been ident ified in beer , wine, alcohol product ion , and high acid foods such as salad dressings . Product ion of highly purified nisin preparat ions has led t o int erest in t he use of nisin for hum an ulcer t herapy and m ast it is cont rol in cat t le.
La ct ococcu s la ct is
a n d t h e m ole cu le, N isin . M odifie d Sca n n in g EM fr om pr ofoodin t e r n a t ion a l . com w it h pe r m ission .
St a r t e r Cu lt u r e s
St art er cult ures have crucial roles t o play during all phases of t he cheese m aking and m at urat ion process. As t he cult ure grows in t he m ilk , it convert s lact ose t o lact ic acid. This ensures t he correct pH for coagulat ion and influences t he final m oist ure cont ent of t he product . The rat e of acid product ion is crit ical in t he m anufact ure of cert ain product s,
e . g. Cheddar cheese. I n m echanized operat ions, st art ers are oft en required t o produce acid at a consist ent ly fast rat e t hrough t he m anufact uring period each and every day . During ripening , cult ure, lipolyt ic and prot eolyt ic enzym es are released from t he bact eria t hat add a balanced arom a, t ast e, t ext ure, and surface appearance t o t he product . The negat ive redox pot ent ial creat ed by st art er growt h in cheese also aids in preservat ion and t he developm ent of flavor in Cheddar and sim ilar cheeses. Addit ionally , ant ibiot ic - like subst ances produced by st art ers ( e. g . nisin ) m ay also have a role in preservat ion.
A com m e r cia lly - a va ila ble st a r t e r cu lt u r e . Th e de scr ipt ion r e a ds " D ir e ct se t M e soph ilic Cu lt u r e - La ct ococcu s la ct is a n d La ct ococcu s cr e m or is . For h a r d a n d fr e sh ch e e se s - Ch e dda r, Colby , Fe t a, Ch e vr e a n d ot h e r s. Use 1 / 4 t sp. pe r 2 - 3
ga llon s of m ilk for h a r d ch e e se s a n d 1 / 4 t sp . pe r 3 - 5 ga llon s of m ilk for soft
ch e e se s. Th is pa ck a ge con t a in s e n ou gh D ir e ct se t M e soph ilic cu lt u r e t o se t 1 6
ga llon s of m ilk. St or e r e fr ige r a t e d ( 4 0 - 4 5 D e g F) . Th is cu lt u r e doe s n ot con t a in rennet."
h t t p :/ / w w w . t h e gr a pe. n e t
La ct ococcu s
a n d V a ccin e D e live r y
A recent ly discovered applicat ion of Lact ococcus lact is is in t he developm ent of vaccine delivery syst em s . The bact erium can be genet ically engineered t o produce prot eins from pat hogenic species on t heir cell surfaces . I nt ra nasal inoculat ion of an anim al wit h t he m odified st rain will elicit an im m une response t o t he cloned prot ein and provide im m unit y t o t he pat hogen . For exam ple, if one wished t o provide im m unit y t o St rept ococcus pyogenes , t he causat ive agent of st rep t hroat , Lact ococcus could be engineered t o present t he conserved port ion of t he st rept ococcal M prot ein required for st rept ococcal adherence and colonizat ion t o t he nasopharyngeal m ucosa . The result ing local im m une response could prot ect t he individual from st rep t hroat caused by t he st rept ococcus t hat exhibit s t hat form of t he M prot ein . This approach t heoret ically can be adapt ed t o any pat hogen t hat colonizes and or/ ent ers via a m ucosal surface in hum ans or anim als. This includes hum an pat hogens such as St rept ococcus pyogenes , St rept ococcus pneum oniae , Haem ophilus influenzae , Mycobact erium t uberculosis , Bordet ella pert ussis and Neisseria m eningit idis , am ong ot hers .
More t han 4 m illion deat hs per year are due t o respirat ory diseases. Econom ical and effect ive vaccines against respirat ory pat hogens are needed for im plem ent at ion in poorer count ries where t he disease burden is highest . Following respirat ory t ract infect ion, som e pat hogens m ay also invade t he epit helial t issue , achieving syst em ic circulat ion and spread t o ot her organs. Nasal adm inist rat ion of different ant igen form ulat ions using Lact ococcus lact is as a delivery vehicle has shown prom ising result s in t he induct ion of im m une More t han 4 m illion deat hs per year are due t o respirat ory diseases. Econom ical and effect ive vaccines against respirat ory pat hogens are needed for im plem ent at ion in poorer count ries where t he disease burden is highest . Following respirat ory t ract infect ion, som e pat hogens m ay also invade t he epit helial t issue , achieving syst em ic circulat ion and spread t o ot her organs. Nasal adm inist rat ion of different ant igen form ulat ions using Lact ococcus lact is as a delivery vehicle has shown prom ising result s in t he induct ion of im m une
Lact ococcus lact is has been shown t o deliver ant igens t hat st im ulat e m ucosal im m unit y t o nonrespirat ory pat hogens , as well, including HI V, Hum an papillom a virus and t he m alarial parasit e.
Som e of t he research papers t hat have em ployed Lact ococcus lact is as a vect or for vaccine delivery are cit ed below.
Lee, M. H . , et al . 2001. Expression of Helicobact er pylori urease subunit B gene in Lact ococcus lact is MG 1363 and it s use as a vaccine delivery syst em against H . pylori infect ion in m ice. Vaccine 2001. 19 : 3927- 3931.
Ribeiro, L . A . , et al . 2002. Product ion and Target ing of t he Brucella abort us Ant igen L7 / L 12 in Lact ococcus lact is: a First St ep t owards Food- Grade Live Vaccines against Brucellosis. Applied and Environm ent al Microbiology 2002. 68 : 910- 916.
Xin , K. Q. , et al. 2003 I m m unogenicit y and prot ect ive efficacy of orally adm inist ered recom binant Lact ococcus lact is expressing surface - bound HI V Env . Blood 2003.
10: 223 - 228. Robinson , K. , et al. 2004. Mucosal and cellular im m une responses elicit ed by recom binant
st rains of Lact ococcus lact is expressing t et anus t oxin fragm ent C. I nfect ion and I m m unit y 2004. 72 : 2753– 2756.
Berm udez - Hum aran, L. G . , et al. 2005. A Novel Mucosal Vaccine Based on Live Lact ococci Expressing E7 Ant igen and I L- 12 I nduces Syst em ic and Mucosal I m m une Responses and Prot ect s Mice against Hum an Papillom avirus Type 16- I nduced Tum ors . The Journal of im m unology 2005. 175: 7297- 7302.
Buccat o, S . , et al. 2006. Use of Lact ococcus lact is Expressing Pili from Group B St rept ococcus as a Broad - Coverage Vaccine against St rept ococcal Disease. The Journal of