Which among the following microbe is used for commercial and industrial production of citric acid ?

Aspergillus niger .

The correct answer is Option (4)- Aspergillus niger .

Microbes are also used for commercial and industrial production of certain chemicals like organic acids, alcohols and enzymes. Examples of acid producers are Aspergillus niger (a fungus) of citric acid, Acetobacter aceti (a bacterium) of acetic acid; Clostridium butylicum (a bacterium) of butyric acid and Lactobacillus (a bacterium) of lactic acid.

Cyclosporin A, that is used as an immunosuppressive agent in organ-transplant patients, is produced by the fungus Trichoderma polysporum.

Yeast (Saccharomyces cerevisiae) is used for commercial production of ethanol. Saccharomyces is also used in bread making.