Research Of Single Cell Protein Production By Compound Strains Solid Fermented From Corn Straw

Crop straw is recognized as the largest renewable resources in the world.As the most common crops straw,corn straw as reserves rich in China.But due to various reasons,corn straw resources have not been effectively utilized,even by waste incineration,this not only waste resources,also brought environmental problems.Using microorganism transformed corn straw into single cell protein,not only improve the utilization efficiency of corn straw resource,but also effectively alleviate environment pollution problem caused by the burning of corn straw.This article mainly discusses the use of corn straw to produce single cell protein including breeding,materials in the process of pretreatment and optimize the fermentation conditions were studied.The cellulase producing ability of Aspergillus oryzae,Aspergillus niger,Trichoderma viride and Aspergillus carbonarius were tested,in order to obtain cellulase high-yield strain to degrade corn straw,and the results show that Aspergillus niger is the most potential strains to degrade corn straw.Sorts of nitrogen source,inoculation amount,dosage of bran and twain-80 of medium for Aspergillus nige were optimized to obtain more cellulase though single factor experiment.The ratio of material to water,initial pH value and fermentation time were further optimized by orthogonal experiment.The results showed that Aspergillus niger on the corn stover substrate enzyme production conditions: corn stover 16 g,bran 4 g,with 5% ammonium nitrate as the nitrogen source,adding 0.2% twain-80,Aspergillus niger spore quantity of 10%,the ratio of material to water 1:2.5,temperature 30 ℃,initial pH6,fermentation time 72 h.Ultraviolet and nitrosoguanidine composite mutagenesis was used to Aspergillus niger,in order to further improve the ability of enzyme production of Aspergillus niger and obtain the efficient degradation of cellulase production strain.Four forward mutation strains were find out on coongo red-CMC solid medium,and then determined that U2 is the strain has yield of cellulase by solid-state fermentation of after screen.Based on U2 strains,mutagenesis,again with nitrosoguanidine to get 3 of forward mutation strain.finally,selscted N2 as the strain that used to fermented corn straw by solid-state fermentation of after screen,not only for it has a 32.14 U filter paper activity,and 36.53% higher than starting strain,but also for it’s Stable genetic traits.It is shown that the concentration of sulfuric acid pretreatment of corn straw 1%,sodium hydroxide with 0.2mol/L,biological pretreatment 5days can improve the efficiency of enzymatic hydrolysis of corn stalk through single factor test.On the basis of the comparision of three kinds of pretreatment of corn stalk.The results show that the most significant effect of sodium hydroxide pretreatment,followed by biological pretreatment,again is sulfuric acid pretreatment,which all can improve the efficiency of enzymatic hydrolysis of corn stalk,and this increase after pretreatment of straw is closely related to ability improve of celluluase adsorption to corn stalk.From the point of quality loss,biological pretreatment is minimum.In order to improve the specificity of biological pretreatment,avoid cellulose is a large number of degradation,utilizing the center combination test of processing conditions are optimized solution: Y=-625.1075+101A+58.92B+17.46C+18.757D+19.2AB-0.18AC+1.575 AD+0.32BC-1.95BD-0.785CD-11.62A2-18.52B2-0.10788C2-0.18125D2.Throughthe response surface analysis,the optimal fermentation conditions were as follows: pH value 5.48,inorganic sulfuric acid solution containing manganese sulfate 0.54 g / L,fermentation temperature 36.25,loading capacity 9.86 g.Through the comparison of different time after the pretreatment of corn straw by Phanerochaete chrysosporium,corn straw digestion performance,it is concluded that the shorter time pretreatment,can increase the ability of corn straw sugar.Compared with biological pretreatment and alkali pretreatment,biological pretreatment can better keep the protein in maize straw.Optimized by orthogonal experiment,it is concluded that biological pretreatment of corn stalk fermentation to produce single cell protein,the optimal conditions for: solid-liquid ratio 1:2.5,biological pretreatment four days,the initial pH6,12 g loading quantity.The content of total protein was 30.93%,the true protein increased to 16.26%,the total amino acid was 12.1% after acid hydrolysis,and the increment was 62.44%,126.46% and 166.45% respectively.The nutritional value of corn straw was significantly improved.