Study Of Corn Stalk Solid-state Co-fermentation To Produce Single Cell Protein (SCP) Fodder

Biological degradation of corn stalk to produce single cell protein(SCP) fodder with Aspergillus niger and Saccharomyces cerevisiae of astronautics mutant have been studied in this paper. At first, mutant strains Aspergillus niger ZM-8 with high activity of cellulase and Saccharomyces cerevisiae YB-6 with strong growth ability of producing SCP were screened from their parent strains of A. niger by treatment of space conditions, and then the conditions for production cellulase of Aspergillus niger ZM-8 was discussed and the parameters of mix-strains corn stalk solid fermentation to produce SCP fodder was explored ,and the corn stalk solid fermentation technology was suggested at last. All of these may be summarized as follows:1. Mutant strains of Aspergillus niger ZM-8 with high activity and stability of cellulase and Saccharomyces cerevisiae YB-6 with a great deal of biomass in enzymolysis liquid were selected from their parent strains. Under some conditions, the enzyme activities of ZM-8 toward FPA, C1, CMCase andβ-Glase respectively reached 1.84μ/mL,0.27μ/mL,8.16μ/mL and 20.14μ/mL. Cellulase activities of ZM-8 were about 2.1, 3.5, 1.7, 1.8 times as compared to those of the parent strain, the rate of production of reducing sugar resulting from corn stalk was 3.86%, which was about 80% increase of the crude strain. Under 30℃cultivating 72 hours, the accumulate of biomass of YB-6 was about 27g/L, which was about 34% higher than that of the original strain.2. At first, the fermentation systems of ZM-8 were studied for producing cellulase. The result showed that the way of solid fermentation was obvious better than that of liquid fermentation, the time of reaching maximal enzyme activities was only 1/3 and the enzyme activities were about 2 times as compared to those of the liquid fermentation. Then the optimal constitution and conditions of corn stalk solid fermentation to produce cellulase were studied. The results suggested that: the optimum fermentation medium contained 80% corn stalk powder, 20% wheat bran, a solid: liquid of 1:8, 0.6%nitrogenous amount, nitrogen source was (NH₄)₃PO₄, 0.05% MgSO₄.7HO₂, 0.01% KH₂PO₄, 1:30(w/w)inoculums and the optimum condition was at the initial pH6.5, 35℃,for 72h. Under the optimized medium and fermentation condition, the activities of FPA and CMC respectively reached 5.25μ/mL (before the optimum being1.84μ/mL), 19.60μ/mL (before the optimum being 8.16μ/mL).3. The mix-strain corn stalk solid fermentation of ZM-8 strain and YB-6 strain had been studied, and a best kind of mix-strains ferment system had been optimized out. It showed that the ZM-8 was 1:30(w/w) inoculated first, and the YB-6 was 10% inoculated after 24 hours of the ferment to proceed the mix-strain solid ferment for 48h.Under the best process condition, the cellulose and hemicellulose's content of the solid ferment product were respectively fallen from 40.82% and 28.40% to 29.55% and 18.55%, the rate of degradation reached 30.42% and 37.16%. The lignin content was nearly invariable. The gross protein content was 27.12%, which was about 50% increase of the content of the product that fermented by only the ZM-8 strain and 437% increase of the content of corn stalk. After being baked dry for 24h under the temperature 65℃, the product had the color of grain yellow and smelled strong grain-fried scent, which could be used as comparative good protein fodder.