Statins produced by the yeast variety is ________ which have been commercialised as blood-cholesterol lowering agents.

Monascus purpureus

The correct answer is Option (3) - Monascus purpureus

Statins produced by the yeast Monascus purpureus have been commercialised as blood-cholesterol lowering agents. It acts by competitively inhibiting the enzyme responsible for synthesis of cholesterol.

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.

Cyclosporin A is a bioactive molecule that is widely used as an immunosuppressive agent in organ transplant patients. It plays a crucial role in preventing organ rejection by suppressing the immune system's response to the transplanted organ. This important medication is derived from the fungus Trichoderma polysporum.

Bacteria Bacillus thuringiensis (often written as Bt ) is an example of microbial biocontrol agents that can be introduced to control butterfly caterpillars. These are available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae. In the gut of the larvae, the toxin is released and the larvae get killed.