1. WELCOME

2. Submitted to :
MS.Diana ,
Assistant professor,
Department of Micribiology.
Submitted by :
P.Pugazhenthi,
I- Msc,Microbiology.
Lactobacilli- Homo and Hetero lactic acid
Fermentation and its nutritive value

3.  Fermentation is a metabolic process in which
an organism converts a carbohydrate, such as
starch or a sugar, into an alcohol or an acid. For
example, yeast performs fermentation to obtain
energy by converting sugar into alcohol.
Bacteria perform fermentation, converting
carbohydrates into lactic acid. The study of
fermentation is called zymology.

5.  Lactobacillus is
a genus of Grampositive, facultative
anaerobic or microaerophilic, rodshaped,
non-spore-forming bacteria.
 They are a major part of the lactic acid
bacteria group.
(i.e. they convert sugars to lactic acid

6. Lactic acid fermentation
In this pathway pyruvate is reduced to lactic
acid. This is a single step reaction carried out
by Lactic acid bacteria (LAB)
There are two types of lactic acid
fermentation.
 Homo lactic fermentation
 Hetero lactic fermentation

8. Homolactic acid fermentation
In homolactic fermentation, end product is
lactic acid.
Pyruvate is reduced to lactate or lactic acid
by the enzyme lactate dehydrogenase
(Pyruvate reductase).
Homolactic bacteria: Streptococcus
thermophiles, Streptococcus lactis,
lactobacillus lactis, Lactobacillus bulgarius,
Pediococcus, Enterococcus

9. Application
Homolactic fermentation is important in
dairy industry for souring of milk to produce
various fermented products
Streptococcus mutant, a bacteria
responsible for dental caries is a homolactic
fermenting bacteria.
Lactobacillus spp in the digestive tract of
human helps in digestion of lactose present in
milk.
Lactobacillus spp are used as probiotic.

10. Heterolactic fermentation
In hetero lactic fermentation, end product
is ethanol and CO2 in addition to lactic
acid.
In this reaction glucose is first
metabolized to pyruvate, acetic acid and
CO2 by Pentose phosphate pathway.
Pyruvate is then reduced to lactic acid
whereas acetic acid is reduced to ethanol
and CO2.
Heterolactic bacteria: Leuconostoc
mesenteroides, Lactobacillus bifermentous,
Leconostoc lactis