Solid-state fermentation of cornmeal with the basidiomycete Hericium erinaceum for degrading starch and upgrading nutritional value

The ability of the basidiomycete Hericium crinaceum to degrade starch and upgrade nutritional value of cornmeal during solid-state fermentation was studied. On the basal medium which consisted of cornmeal and salt solution, H. erinaceum produced a strong alpha-amylase on the 15th day after inoculation, which resulted in a 52% degradation of the starch. By supplementation with 5- 15 g soybean meal per 100 g cornmeal the alpha-amylase activity and degradation rate of starch was raised significantly (P < 0.01). Prolongation of fermentation time from 15 to 30 days did not increase significantly the degradation rate of starch, though the alpha-amylase activity reached its maximum value of 179 U/g on the 20th day after inoculation. Under conditions close to the theoretical optimum fermentation conditions, that was after 25 days at 25 degreesC in the medium with added 15 g soybean meal per 100 g cornmeal, the starch content in the product decreased from 63% to 22% (P < 0.001) and protein content increased from 12% to 17% (P < 0.01). In the protein in the product, the lysine content was increased from 36 to 56 mg/g and tryptophan from 9 to 13 mg/g. Using egg protein as a standard, an evaluation on the protein quality of the fermented product showed that it was superior to that of the nonfermented control and to other cereals, was close to that of soybean and chicken, but was inferior to that of milk and red meats. (C) 2002 Elsevier Science B.V. All rights reserved.