Tag: biology

Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. Various strains of A. niger are used in the industrial preparation of citric acid and gluconic acid.

S. cerevisiae is known for its role in food production. It is the critical component in the fermentation process that converts sugar into ethyl alcohol (ethanol), an ingredient shared in beer, wine and distilled beverages. It is also used in the baking process as a leavening agent; yeast releasing gas into their environment results in the spongy-like texture of breads and cakes. 

S. cerevisiae is known for its role in food production. It is the critical component in the fermentation process that converts sugar into ethyl alcohol (ethanol), an ingredient shared in beer, wine and distilled beverages. It is also used in the baking process as a leavening agent; yeast releasing gas into their environment results in the spongy-like texture of breads and cakes. 

In a bread dough, where the oxygen supply is limited, the yeast can only partially breakdown the sugar. Alcohol and carbon dioxide are produced in this process known as alcoholic fermentation. The carbon dioxide produced in these reactions causes the dough to rise, and the alcohol produced mostly evaporates from the dough during the baking process. During fermentation, each yeast cell forms a centre around which carbon dioxide bubbles form. Thousands of tiny bubbles, each surrounded by a thin film of gluten form cells inside the dough piece. The increase in dough size occurs as these cells fill with gas.

Yogurt is a food produced by bacterial fermentation of milk. The bacteria used to make yogurt are known as yogurt cultures. Fermentation of lactose by these bacteria produces lactic acid, which acts on milk protein to give yogurt its texture and its characteristic tang. Some representative strains of yogurt cultures are Streptococcus lactis, S. cremoris, S. thermophilus, Lactobacillus bulgaricus, L. acidophilus, and L. plantarum.

Vitamin B$ _{12}$ cannot be made by plants or animals as only bacteria have the enzymes required for its synthesis. Members of the genus Propionibacterium are widely used in the production of vitamin B$ _{12}$.

Baker's yeast is the common name for the strains of yeast commonly used as a leavening agent in baking bread and bakery products, where it converts the fermentable sugars present in the dough into carbon dioxide and ethanol. Baker's yeast is of the species Saccharomyces cerevisiae, which is the same species (but a different strain) commonly used in alcoholic fermentation, which is called as brewer's yeast.

Microorganisms isolated based on their ability to degrade hydrocarbons often belong to the genus Pseudosmonas. These bacteria have several catabolic pathways and are easily handled and grown in the laboratory. Pseudomonas putida, a Gram-negative proteobacterium, possesses the outstanding ability to tolerate high concentrations of different hydrocarbons.