Research On Mutation Breeding Of Microwave On White-rot-fungi For High-yield Of Laccase And Biodegradation Of Lignin

At present,straw is a great development potential biomass resources. But straw utilization rate is not high. Mainly because the fiber structure of straw is very complicated, especially lignin package seriously hindered the enzyme solution. Degradation lignin by yellow Phanerochaete Chrysosporium have certain practical significance on effectively use and transform the straw resources、expand industrial raw material source of fermentation products、reduce rice for industrial、reduce the cost of fermented.This paper research on mutation breeding of Microwave on White-rot-fungi for high-yield of laccase.Culture medium is optimizated for laccase prodiction and laccase was purificated. At the same time research on the solid fermentation by soybean straw, straw stalk, corn straw and several as the substrate was taken. Surface morphology change of degradation of straw fibre also be preliminary explorated.The main contents and results are summarized as follows:1. Microwave irradiation with the condition of circulating cooling water used to mutate breeding of yellow Phanerochaete Chrysosporium. According the effect of microwave power and irradiation time to fatality and mutation rate of yellow Phanerochaete Chrysosporium defined the best the best mutation conditions were the microwave power of400W and irradiation length of120s. The positive mutation rate reached67%.7stable Mutants of laccase activity at high level were found.The optimal mutant W4S12reached2.75U/mL,69.1%higher than the parent strain..2. Solid-state fermentation mutant W4S12, the single factors of medium composition was optimized. From these results the fermentation process was optimized by response surface method, as follows:The optimized medium composition contained(g/L):CuSO40.016、 MgSO40.25、Guaiacol2.53mL; others(g/L):(NH4)2SO415、KH2PO44.0、CaCl20.2、 FeSO4·7H2O0.1、ZnSO4·7H2O0.1.3. Separation and Purification laccase by DEAE-52Ion exchange chromatography.the laccase activity is1.703U/mLand Acetate buffer (pH4.6) containing0.1mol·L-1NaCl20mmol·L-1is eluent.Secondly by Dextran G-100gel filtration chromatography, the laccase activity is0.457U/mL.The corresponding purification fold were14.46.39.99and the corresponding recoveries were25.30%,16.47%.4. Degradation of straw optimal conditions for white rot fungi by single factor and orthogonal experiments:the synthetic medium amount respectively werelOmL.12mL、12mL、14mL; by5.0g straw as substrate in the processes of degradation soybean straw, rice straw, corn stover and corn cob. Seed liquid addition respectively were1.1mL.0.8mL.1.1mL and 8mL. pH respectively were4.5,5,4, and4.5.And the lignin degradation rate were50.50%,48.65%,72.8%and62.4%respectively.5. Observion was taken by SEM on straw apparent structure before and after fermentation. Conclusion was founded that the hole of straw surface and the inner surface increased, increasing the surface roughness increases. At the same time decomposition of soybean straw in the functional group changes was detected with FTIR. Lignin related peaks (1099cm-1,1057～1038cm-1) relative intensity decreases, and phencyclidine related peaks (1643～1608cm-1,1510～1508cm-1) relative to the intensity of the increase, suggests that some macromolecular lignin cracked into small molecule or lignin monomer. In addition, compared to other peaks relative intensity changes, discovery of lignin benzene ring compounds content reduced.