BIO 425Industrial Microbiology

Lecture 2Major classes of products and processes and microorganisms involved in these

processes

Content outline

• Major classes of products

• The ‘fermentation’ concept

• The yeast

• Oriental fermented food and typical examples

M/o’s and industry

• Overall reaction characterizing the application:

• Substrate (raw material) + m/o’s

New products

Major classes of products

• Pharmaceutical compounds(Antibiotics, steroid drugs, Insulin and interferon etc.)

• Commercially valuable chemicals(Solvents, enzymes etc.)

• Food supplements(Mass production of bacteria, yeast, algae)

• Alcoholic and non-alcoholic beverages

Major classes of products-contd

• Vaccines(Immunizing antigens)• Deterioration of material by microorganisms

(including leather, wood, textiles, metals)• Analytical microbiology(A variety of products are

assessed through microbial products - like aminoacids, antibiotics and vitamins), other: evaluating wood, paint preservation, efficacy testing of sterilization procedure

History of fermentation

• Dates back hundreds of years.

• Fermented foods are available since Roman times by utility and manipulation of several cell constituents.

Fermentation

• Fermentation • Nominated by Pasteur, 18th century.• Observed: Alcohol production from grape

yeast mixtures during production of sour wine.

• Each type of fermentation: mediated by a specific microorganism which gains energy during the process.

Function of yeast

• Commonly used a leavening agent in baking during ancient times by Jews, Egyptians, Greeks and Romans.

• Pure cultures of Saccharomyces cerevisiae (Baker’s yeast): mixed with the bread dough to bring derived changes in texture and flavor-e.g. for process

Simple reaction for Baker’s yeast

• C6H12O6 Ethanol + CO2

Fermented foods are universal

• Principal thing is sugar conversion to lactic acid by the action of lactobacilli.

• Mold action on different compounds are also applicable.

• E.g. Lactic acids, drinks, cheese making and pickles throughout the world.

• Oriental foods in Japan, e.g Shoyu, Miso….• Oriental foods in Africa e.g. Idli, Kishk, Ogi,

Mahewu

Traditional fermented food

• Koji method:

• Japanese produced several enzymes through solid state cultures of several m/o;

• on a number of cereals, e.g. barley, wheat, soybeans and rice.

Traditional fermented food

• Species: Molds like Aspergillus, Rhizopus, Monascus

• Enzyme source in the manufacture of shoyu, miso and saké(wine from rice) .

More about ‘koji’

• A mold-cultured meal.

• Aspergillus, Rhizopus spp., cultured on parts of rice or wheat and water to make mash,

• then subjected to enzymatic saccharification, lactic fermentation and yeast fermentation.

Shoyu

Digest mold cultured soybeans & wheat in different ratios; (50:50 usual.) in the presence of about 17% salt,

Ferment the mash with Lactobacilli and yeasts

Press the well-aged mash (after 6-8 months)

Liquid part obtained is pasteurized to make the final product

(Miso. approx. the same thing)

Saké

• Rice wine

• Prepared by digesting a mixture of cooked rice and molded rice (rice-koji) in water,

• while fermenting the mash with Lactobacilli and yeasts

• Japanese annual consumption: 1,220,000 kL

High quality Saké rice- var. Yamada Rishiki

Saké making

Tempeh

• Indonesian food

• Cooked whole soybeans, cultured with Rhizopus oligosporus,

• wrapped in banana leaves left for about 40 hours at about 30°C (Eaten fresh or after deep frying).

Miso

• Japanese semi-solid salty food.

• Made from soybeans, rice or barley;

• and salt by fermentation of Lactobacillus (after addition of Aspergillus oryzae).

Milled rice, 600kgSoybeans,1000kg Koji starterAspergillus oryzae

Soaked in water

Steaming, 45 min.

Cooling to 30° C

Koji making

Dehulled

Soaked in water

Autoclaving

Fermentation, 30° C, 1-3 months

Remove to another tank , pasteurize, obtain Miso, 3300 kg

(0.1 % for rice, 109 spore/g)

Koji making unit

Alcoholic beverage production

Wine: ♣ Raw material: Mainly grapes, cherry, tangerine,

orange, blueberry, raspberry, strawberry and banana

♣ Fruity character: by volatile compounds like terpenes.

♣ Mainly blend of flavor and chemical complexity at fermentation stage (tannins, phenolics, malic acid).

Wine production

• Two steps of fermentation:

• Alcoholic fermentation (yeast)

• Malolactic fermentation (lactics)

(Malic acid Lactic acid + CO2)

Important microbial genera

• Introduced by grape skins:

• Yeasts: Kloeckera, Hanseniaspora (mainly present)

• Candida, Metschnikowia, Cryptococcus, Pichia and Kluvyeromyces.

• Saccharomyces cerevisiae (< 50 cfu / g)

Important microbial genera-2

• Lactobacillus, Leuconostoc and Pediococcus spp.

• Gluconobacter oxydans

• Acetobacter aceti

• Acetobacter pasteurianus (main acetic acid bacteria spp.)

LITERATURE CITED

• Forsythe, S.J. The Microbiology of Safe Food, Blackwell Science, Cambridge, 2000.

• Wood, B. J. B., Microbiology of Fermented Foods, Vol.1 and 2, Blackie Academic and Professional, London, Second edition, 1998.