Fungi are most efficient producers of large variety of enzymes and chemicals. Their ability to grow at low pH values and high salt concentrations and to utilize C5 and C6 sugars as substrates makes them favorable for industrial application. They can withstand extreme high and low temperatures also. Their mode of reproduction so as to give high number of multiples within short term is another advantage. They require little space to work and it is easy to maintain the consistency of the reaction when compared to the other organisms. Extracellular liberation of their products makes it easier to extract and purify. All the commercially valuable fine and bulk products produced by them can be categorized into their primary as well as secondary metabolites.