In: Biology
Answer of question a
Biofuel indusry prefers to use non food plants or their components (because grains or fruits are important for food security and should not be diverted towards biofuel industry). The chief non food component of plants is cellulose. It can not be digested by humans. Wild mushrooms are picked for biofuel enzyme assay because mushroom is heterotroph. It degrades and breaksdown cellulose and several other macromolecules in order to draw it's nutrition.
Biofuel enzyme assay focusses on cellulose degrading capability of fungal enzymes like cellulases so that cellulose can be converted to it's monomer glucose and then to alcohol for biofuel production.
Answer of question b
The natural substrate for enzyme cellobiase (A type of cellulase) is cellobiose. Cellobiose is a disaccharide of beta glucose.
Answer of question C
The product of cellobiase action upon 1 molecule cellobiose is two molecules of glucose.