The difference between total amino acid and crude protein could be accounted for by the presence of non-protein nitrogen (NPN) such as nucleic acid and chitin in the fungal mycelia (Mathot et al. 1992). In the fermented substrates, about 60–68 % of the total N is present as α amino N, the remaining N might be associated with the cell wall chitin of fungus, chitosan as polymeric hexosamine and in the purine and pyrimidine bases of the nucleic acids and nucleotides.