The Breeding Of High-yield Cellulase Strain And Its Application In The Production Of Feed Protein By Fermentation Bean Dregs

Due to the rapid development of the economy, people’s living standards are greatlyimproved and enhanced, and the demands for high-protein foods are grown exponentially, soit has caused shortage and scarcity of protein feed. In China, because people treat soybeandregs with indifference, it has caused waste of soybean dregs resource. If we can changesoybean dregs to high-protein feed, so it can not only reduce the cost of high-protein feed, butalso use the soybean dregs resource.This paper included: The soil-samples were collected under the accumulated witheredleafage, and cellulose decomposing microorganisms were separated from soil-samples. Ahigh cellulase-producing strain F6was isolated through the experiments of cellulose-congored medium and liquid fermentation, and using strain F6as the original strain, a high activecellulose decomposing mutant strain SY901was obtained by compound mutagenesis.Through strain SY901, Geotrichum candidum link and Candida tropicalis fermented soybeandregs, the fiber-content of soybean dregs was reduced and the protein-content in thefermentation product was enhanced. The main results were as follow:(1) Study on the determined condition of CMCase activity. The six conditions whichaffected determination of CMCase activity were enzymatic reaction time, initial pH,enzymatic reaction-temperature, substrate concentration, wavelength, the addition of crudeenzyme and substrate that were carried on the single factor experiment. Orthogonalexperiment was carried out on the basis of the single-factor experiments, and the bestdetermined conditions of CMCase activity were obtained as following: the initial pH6.2, therespectively added volume of crude enzyme and substrate2mL, reaction-temperature40℃,reaction time30min, wavelength520nm, and substrate concentration10g/L.(2) Screening strains with the capacity of decomposing cellulose. In advantage ofcellulose-congo red medium, twelve cellulase-producing strains were separated. A highcellulase-producing strain F6was isolated through the experiment of liquid fermentation, theactivity of FPase reached233.317U/mL, and the activity of CMCase reached905.335U/mL.(3) Breeding of strain with high-yield cellulase. Using strain F6as the original strain, ahigh active cellulose decomposing mutant strain SY901was obtained after several steps ofUV and EMS mutagenesis. The activities of FPase and CMCase yielded by this high-yieldstrain were2428.085U/mL and3598.484U/mL, respectively. And they were increasedrespectively by10times and4times than initial strain F6.(4) Screening of complex strains for soybean dregs fermentation. Strain F6, strain SY901,Rhodotorula glutinis, Geotrichum candidum link and Candida tropicalis was respectivelyinoculated on the medium in which soybean dregs as unique carbon source, and the growth conditions of these strains were observed. The results showed that compared to the blankcontrol, the increased content of crude protein was greater than7.0%on average when usingstrain SY901, Geotrichum candidum link and Candida tropicalis for soybean dregs. Themulti-strain fermentation was fermented by random combination of the three strains, and theresults showed that compared to the blank control, co-fermentation of muti-fungus withsoybean dregs could increase the crude protein content by11.96%, and the crude proteincontent reached to26.76%.(5) Response surface methodology was used to optimize condition for solid statefermentation of soybean dregs. The optimal condition for the solid state fermentation:fermentation temperature31.5℃, vaccination proportion1:1:3, fermentation time8days, andunder this fermentation medium condition, the true protein was11.4%.