Study On Single Cell Protein Production By Mixed Strains Solid Fermentation From Wheat Straw

Cellulose is the most extensive nature of carbohydrates,at the same time,it is also the number of the largest renewable resources on the earth.At present,only a small portion of cellulose has been used,the vast majority of cellulose is not only isted,but cause environmental pollution.The use of microbial cellulase production will be transformed into much-needed energy,food and chemical raw materials for mankind.It is great practical significance that solving problem including environmental pollution,food shortages and energy crisis.This study mainly include following content:Under different conditions including media,culture time,culture temperature,initial pH,inoculum,nitrogen content and cultivation methods,the cellulase activity of FPU,β-gluase,CMC and C₁ were determined,these cellulose come from 4 single bacteria production.Further to determine the optimal conditions for fermentation bacteria.In the different culture conditions,the enzyme activity,reducing sugar and protein content of multi-bacteria mixed fermentation were measured,determine the optimal conditions of multi-bacteria mixed fermentation,crude fiber,SCP and amino acid content were compared fermentation of straw before and after.The results were as follows:1.The optimum fermentation medium of Aspergillus niger:pH:5.5,nitrogen sources:(NH₄)₂SO₄,the water content:150%,wheat straw:wheat bran ratio is 2: 3;the optimum fermentation medium of Penicillium glaucum:pH:4.5,nitrogen sources:(NH₄)₃PO₄,the water content:200%,wheat straw:wheat bran ratio is 3: 2;the optimum fermentation medium Triehoderma viride:pH:5.5,nitrogen sources: (NH₄)₃PO₄,the water content:150%,wheat straw:wheat bran ratio is 4:1;the optimal fermentation medium Rhizopus nigricans:pH:4.5,nitrogen sources:(NH₄)₂SO₄, the water content:200%,straw:wheat bran ratio is 2:3.2.The single bacteria ferment in the semi-confined conditions,4 kinds of bacteria vigorous vegetative growth and producing greater cellulase activity.Aspergillus niger culture time:60h,culture temperature:35℃,initial pH:7.0,inoculum:15%, nitrogen content:0.6%,in this condition,the cellulase activity of FPU,β-gluase, CMC and C₁ from Aspergillus niger production respectively is 0.52U/mg,1.78U/mg, 6.35U/mg,3.87U/mg.Penicillium glaucum culture time:72h,the culture temperature:40℃,initial pH.5.0,inoculum:15%,nitrogen content:0.6%,in this conditions,the cellulase activity of FPU,β-gluase,CMC and C₁ from Penicillium glaucum production respectively is 0.78U/mg,3.96U/mg,5.36U/mg,1.57U/mg. Trichoderma viride culture time:96h,culture temperature:35℃,initial pH:5.5, inoculum:20%,nitrogen content:0.4%,in this condition,the cellulase activity of FPU,β-gluase,CMC and C₁ from Trichoderma viride production respectively is 0.42U/mg,0.25U/mg,3.26U/mg,3.46U/mg.Rhizopus nigricans culture time:72h, culture temperature:35℃,initial pH:6.5,inoculum:20%,nitrogen content:0.8%, in this condition,the cellulase activity of FPU,β-gluase,CMC and C₁ from Rhizopus production respectively is respectively 0.35U/mg,0.71U/mg,1.23U/mg,0.29U/mg.3.The components of straw had varying degrees of changes after 4 kinds of bacteria fermented.The degradation of cellulose and hemicellulose is the largest Aspergillus niger fermented straw,were 4.9%and 2.3%,protein content increased up to 4.33%,followed by the Penicillium glaucum and Rhizopus nigricans.The degradation of cellulose and hemicellulose of Rhizopus nigricans is the least,1.2% and 0.4%,the raise of protein content is the least,it is 1.24.In the straw medium,it had the worst growth.4.The FPU activity double bacteria mixed fermentation is higher than single bacteria fermentation,when Aspergillus niger:Rhizopus is 1:3,the FPU enzyme activity at a maximum is 0.86.the size of the order of protein content raise as follows:Aspergillus niger+ Rhizopus nigricans＞Aspergillus niger+Penicillium glaucum＞Aspergillus niger+Trichoderma viride,when Aspergillus niger: Rhizopus nigricans is 1:3,the protein content raise maximum is 7.58%,the best culture conditions of double bacteria as following:Aspergillus niger:Rhizopus nigricans is 1:3,pH:6.5,culture time:60h,the optimum temperature:35℃.In these conditions,the degradation of straw cellulose is 45.3%,it is lower than the 8.3% before fermentation,comparing Aspergillus niger and Rhizopus nigricans single fermentation of cellulose content decreased by 3.4%and 7.0%;hemicellulose degradation is 15.6%,than before fermentation to reduce by 3.3%,Aspergillus niger and Rhizopus nigricans fermentation single straw hemicellulose content decreased by 1.0%and 2.9%;protein content increased to 8.7%,increase 5.6%than before fermentation,Aspergillus niger and Rhizopus nigricans fermentation single straw protein content increased by 1.3%and 4.4%respectively.5.The protein content of Saceharomyees cerevisiae+Candia utilis is higher than Geotrichm candidum+Candia utilis.When Saceharomyees cerevisiae:Candida utilis is 1:1,the protein content maximum is 15.34%.when Saceharomyees cerevisiae: Candida utilis:Geotrichm candidum is 1:1:1,the protein content is 15.43%.the addition of Geotrichum candidum make protein content raise 0.08%than Saceharomyees cerevisiae fermentation.With the increase of types of mixed bacteria, the increase protein content is not obvious.6.Multi-mixed bacteria fermentation,the crude fiber of straw has different level low than pre-fermentation and single bacteria fermentation.After mixed bacteria fermentation,the straw cellulose degradation is 38.5%,the degradation rate is 28.2%; hemicellulose degradation is 13.7%,the degradation rate 27.5%;protein content increased to 15.43%,increasing 12.32%than before fermentation,in fermentation production,the amino acid composition were complete,essential amino acids closer to the UN Food and Agriculture Organization(FAO) standards.