OPTIMIZATION OF SOLID STATE FERMENTATION PROCESS FOR PROTEIN ENRICHMENT OF POTATO STARCH RESIDUE WITH MIXED STRAINS

This study was to optimize the fermentation process for protein enrichment of potato starch residue (PSR) by solid state fermentation with mixed strains. Three single-factor experiments were conducted to optimize the fermentation conditions, and a Plackett-Burman design followed by a central composite design of response surface methodology was investigated to optimize the medium constituents. The optimal fermentation conditions were fermentation temperature 28 C, fermentation period 72 h and solids content was 40%. A combination medium of 19.75 g potato starch residue, 6.38 g wheat bran, 2.86 g corn meal, 2.62 g urea, 0.15 g K2HPO4, 0.15 g MgSO4 7H2O, 0.075 g MnSO4 H2O and 0.015 g Fe2(SO4)3 was optimum for maximum protein nitrogen content (3.75%) of fermented PSR, which was 3.4 fold over the raw material. The determination coefficient R2 (0.9889) and the adjusted determination coefficient R2(0.9790) indicated that the response equation provides a reasonable model for the central composite design experiment, and the lack of fit (P=0.0582) indicated that the model was adequate for prediction within the range of variables employed. Due to the high-yield of protein nitrogen obtained and the low-cost nature of the optimal medium, this study indicates a possibility to establish production of protein feed using PSR as a basic substrate.