Swiss cheese which is large holed is ripened with the help of CO 2 producing (causing holes) bacterium called Propionibacterium
sharmanii. Roquefort cheese uses Penicillium roqueforti while, Camembert cheese employs Penicillium camemberti for ripening.s Bread: Dough used for making bread is fermented by using Saccharomyces cerevisiae (Baker’s yeast). Yeast secretes three
enzymes; amylase (causes breakdown of starch into maltose sugar), maltase (converts maltose into glucose) and zymase (for
fermentation). Release of carbon dioxide and ethyl alcohol makes bread porous and soft.
s Dosa, Uppma and Idli: The dough of rice and black gram is fermented by bacteria Leuconostoc and Streptococcus species.
Carbon dioxide produced during fermentation causes puffing of dough.
s Toddy: Traditional, refreshing drink of South India made by fermentation of sap of palms. It is an aromatic wine with 4% alcohol,
mild intoxicating and sweet drink. Toddy left for few hours undergo fermentation to form alcoholic beverage. Longer fermentation
(upto a day) yields stronger, more sour and acidic drink. In some part of India, toddy is evaporated to produce jaggery.
INDUSTRIAL PRODUCTS
s Fermentative ability of microbes is used industrially to obtain number of products valuable to human beings. Common ones are:
- Alcoholic Fermentation: Yeast Saccharomyces cerevisiae (Brewer’s yeast) is used for production of beverages like wine,
beer, whisky, brandy or rum, by fermenting malted cereals and fruit juices, to produce ethanol. Different types of alcoholic
drinks are produced depending on type of the raw material used for fermentation and type of processing. Wine and beer are
filtered, pasteurised and bottled without further distillation. Distillation of fermented broth is carried out for producing hard
liquors like whisky, brandy and rum. - Antibiotics: Antibiotics are chemicals produced by microbes which can kill or retard the growth of harmful microbes without
adversely affecting the host. E.g., penicillin obtained from fungus Penicillium notatum, inhibits the growth of bacterium
Staphylococcus aureus.
Antibiotics function either as bactericides (killing bacteria) or bacteriostatic (inhibiting growth of bacteria). This is done by:
(i) Disruption of wall synthesis. (ii) Inhibiting functioning of 30S and 50S ribosomes. (iii) Disruption of repair and synthesis of
plasmalemma. (iv) Inhibition of aa-tRNA binding to ribosome. (v) Inhibition of translation.
Characteristics of Good AntibioticsHarmless to host with no side effects Quick action Ability to destroy pathogenHarmless to normal microflora of alimentary canal Effective against all strains of pathogens The resistance of pathogen to existing antibiotics is generally produced due to extrachromosomal genes present in plasmids.
They can pass from one bacterium to another due to transformation and transduction. As a result of repeated transformation,
certain strains of bacteria have become multiresistant or superbugs, e.g., MDR (multidrug resistant).
Chemicals, Enzymes and other bioactive molecules
(a) Organic Acids
Organic Acids Microbes
(i) Acetic acid Bacteria: Acetobacter aceti
(ii) Citric acid Bacteria: Aspergillus niger, Mucor; Yeast: Candida lipolytica
(iii) Lactic acid Bacteria: Streptococcus lactis, Lactobacillus; Fungi: Rhizopus
(iv) Butyric acid Bacteria: Clostridium acetobutylicum(b) Enzymes
s Enzymes are proteinaceous substances of biological origin, capable of catalysing biochemical reactions without undergoing any
change.
Enzyme Microbes Functions
(i) Proteases Aspergillus and Bacillus
species
(i) Clearing beer and whisky
(ii) Softening of bread and meat
(iii) Manufacturing liquid glue
(ii) Amylase Aspergillus, Rhizopus and
Bacillus species(i) Production of alcoholic beverages from starchy materials
(ii) Clearing turbidity in juices caused by starch