Phytase production and phytic acid reduction in rapeseed meal by Aspergillus niger during solid state fermentation

The effect of moisture content of media, glucose, phosphate, some surfactants and gamma irradiation on the production of phytase and reduction of phytic acid in rapeseed meal by Aspergillus niger A-98 (local isolate) during solid state fermentation have been considered. Optimum moisture content of media for these processes was 60%. Glucose concentrations of up to 6% in solid state culture (SSC) increased the production of phytase, whereas 10 and 20% had an adverse effect. Addition of phosphate concentration by 0.5 mg per SSC system favoured the enzyme production. As to surfactants, addition of Tween 20, Tween 40, Tween 60, Tween 80 as well as oliec acid increased phytase production, however Triton X-100 had a negative effect. Tween 80 gave the highest level of phytase and 0.3% (v/w) concentration was the optimum. An experiment was conducted to study the efficiency of gamma irradiation on A. niger for increasing the production of phytase. Irradiation dose level at 1 kGy secreted the highest amount of phytase. The effects of all previously mentioned parameters on phytic acid content reduction showed a similar trend as for the enzyme production. (C) 2001 Elsevier Science Ltd. All rights reserved.