Optimum Conditions of Sweet Potato Residue by Solid-State Fermentation

This experiment was conducted to select the best single strain and their mixed proportion and fermentation route,then adopted orthogonal experiment optimized conditions of sweet potato residue by mixed bacteria solid-state fermentation,to improve the content of crude protein of the product. Firstly,adopted four strains of yeast,four strains of Aspergillus,five strains of Bacillus subtilis and one strain of Lactobacillus were under the same fermentation condition and the content of crude protein of products was the measure indicator for single strain selection; then selected the best route by four best single strains which have selected before; At last,An orthogonal experiment of four factors at four levels L16( 44) included fermentation time,fermentation temperature,the amount of nitrogen source and the amount of strains were used for determined the optimum fermentation conditions by tested the content of crude protein in products. The result showed that the strain numbered as Aspergillus 41126,Bacillus subtilis Y111,Candida utilis and Lactobacillus were the best single strain; secondary fermentation was the optimum fermentation route and( Aspergillus ∶ Candida utilis = 2 ∶ 1) +( Candida utilis ∶Lactobacillus ∶Bacillus subtilis = 1∶1∶1) was the best strains combination and proportion,and the highest crude protein was 15. 11 %. The optimum conditions as follow: time of fermentation,3 d; temperature of fermentation,28 ℃; the amount of nitrogen source,1 %; the amount of strains,3 %. Under the above conditions,crude protein content in the fermented products was 12. 35 %,which was higher 85. 99 %than that before fermented with equal urea added,energy and amino acids also improved different degree,especially several essential amino acids improved obviously.