Microbes in food manufacture
Dr. Aswartha Harinath Reddy M.Sc, Ph.D
Department of Life Sciences
Anantapur –A.P. India
ROLE OF MICRO-ORGANISMS:
Food engineering is one of the advanced technology to improve
the quality and quantity of food by using microorganism.
By food engineering, new food and high quality biological
products can be prepared using microorganisms.
Also, in industries microorganisms are used to preserve food and
destroys many pathogenic microbes and toxins.
The production and preservation of beverages like Ethanol, whisky,
brandy, beer and rum are done by Saccharomyces cerevisiae (Yeast).
Lactobacillus sp in the production of different milk products.
Antibiotics like Penicillin is one of the important antibiotic is produced
form Penicillium notatum.
Lipases, Proteases, Cellulases, Amino acids, Vitamins Produced from
Aspergillus and Penicillium sp.
Some of the vaccines also produced form E. Coli.
ROLE OF MICRO-ORGANISMS:
Lactobacillus is a genus of Gram-positive, facultative
anaerobic or micro-aerophilic, rod-shaped, spore-forming
Lactobacillus in food production:
• Lactobacilli are important in the production of fermented dairy
products [yogurt, cheese, kefir, koumiss, butter milk, pickles,
beer and used as probiotic.
If lactic acid bacteria producing entirely lactic acid
(homofermentation) as the major metabolic end-product is
All members of the Lactobacilli, Streptococcus, Lactococcus
and are homo-fermenters.
Homo lactic fermentation:
Lactic acid bacteria producing either a mixture of lactic acid,
carbon dioxide, acetic acid and/or ethanol is called Heterolactic
Some of the lactobacilli, while all Leuconostoc sp., as well as
some Lactobacilli are heterofermenters.
Lactobacillus as Probiotics:
Lactobacillus sp. has been used as probiotic organisms.
Lactobacillus importance as probiotic it improves intestinal
L. acidophilus has been used because it was thought to be the
dominant lactobacillus in the intestine.
However, a wide range of lactobacilli has been used in probiotic
preparations. These include: L. bulgaricus, L. casei, L. brevis, L.
lactis, L. fermentum, L. plantarum.
Lactobacillus as Beneficial Microorganisms:
L. acidophilus and L. plantarum are beneficial
microorganisms in the intestine, decrease the incidence of
Lactobacillus sp. can produce anti- microbial substances,
which have been observed to inhibit the growth of some
Lactobacillus used as a food preservative to Control of Food
Cultured butter milk: Lactobacillus lactis, Streptococcus lacti.
Acidophilus milk: L. acidophilus.
Yoghurt: S. thermophilus, L. bulgaricus.
Kefir: S. lactis, L. bulgaricus.
Yeast (Saccharomyces cerevisiae ):
Yeasts are eukaryotic, single-celled microorganisms classified
as members of the fungus kingdom, typically measuring 3–4
µm in size.
Most yeasts reproduce by process known as budding.
By fermentation, the yeast species Saccharomyces cerevisiae
converts carbohydrates to carbon dioxide and alcohols.
For thousands of years the carbon dioxide has been used in
baking and the alcohol in alcoholic beverages.
It is also a centrally important model organism in modern cell
Many types of yeasts are used for making many foods:
Brewer's yeast in beer fermentation and Baker's yeast in bread
Alcoholic beverages are defined as beverages that contain
This ethanol is almost always produced by fermentation under
anaerobic or low-oxygen conditions.
Brewing yeasts may be classed as Top-cropping and Bottom-
Top-cropping yeasts are so called because they form a foam at
the top culture during fermentation.
Ex: Saccharomyces cerevisiae.
Bottom-cropping yeasts are typically used to produce lager-
These yeasts ferment well at low temperatures.
Yeast, the most common one being S. cerevisiae, is used in
baking as a leavening agent, where it converts the
food/fermentable sugars present in dough into the gas carbon
This causes the dough to expand or rise as gas forms pockets or
bubbles. When the dough is baked, the yeast dies and the air
pockets "set", giving the baked product a soft and spongy
Brewer's yeast is also very rich in essential minerals and the B
vitamins (except B12).
Yeast extract is the common name for various forms of
processed yeast products made by extracting the cell contents
(removing the cell walls); they are used as food additives or
flavoring, or as nutrient for bacterial culture media.
Some probiotic supplements use the yeast S. boulardii to
maintain and restore the natural flora in the gastrointestinal
S. boulardii has been shown to reduce the symptoms of acute