Study On High-yield Laccase Of Myrothecium Vertrucaria And Its Immobilization Application

The comprehensive utilization of corn stover is an issue that require doing be addressed.Lignocellulose?cellulose,hemicellulose and lignin?is the major component and account for about 80%of corn stover.Lignocellulose is a very ideal renewable alternative resource for fossil fuel.Biomass conversion based on sugar platform has gradually become a major mean of corn stover utilization.Nevertheless,the enzymatic reaction is blocked due to the complex structure of corn stover.Laccase,as one of the lignin degradation enzymes,has been widely used in the degradation and modification of lignin.However,due to the low activity and high cost.The production of laccase is far behind the need.The production of laccase with higher storage stability,durable,reusable,lower cost,and more p H resistance becomes an emerging trend and interest in bioethanol and biodiesel field.In this study,a lignin degradation strain-Myrothecium vertrucaria was used as the starting strain to improve the laccase activity after optimizing the culture medium and joint mutagenesis.The properties of the laccase was characterized after purified.Furthermore,the laccase was immobilized on recoverable magnetic nanoparticle,the properties and stability after immobilization were studied.The application of immobilized laccase on lignin degradation and cellulose conversion was tested.The main results are as follows:?1?The laccase activity increased from 1602.34 U/L to 4378.16 U/L,which was 173.24%higher than that of the original medium after optimized the induction medium.?2?A mutant 3H6 with high laccase production was obtained after the combination of ARTP and UV mutagenesis.The laccase activity reach 9025.54 U/L?in the induction fermentation medium?increased 463.28%compared with the original strain?in the original fermentation medium?.?3?The molecular weight of the laccase was about 65 k Da.The optimum temperature and p H were 30?and 4.5,respectively.The characteristic absorption peak is 340 nm,which showed the white laccase.?4?Laccase was immobilized on polyethylenimine modified recyclable Fe₃O₄-NH₂magnetite nanoparticles by metal affinity adsorption.The immobilization efficiency and yield were 84.5%and 87.6%,respectively at a concentration of 2.0 mg/ml and 30 minutes.The activity remains nearly 50%and 80%after 6 rounds reuse and 10 days storage periods,respectively.?5?The degradation rate of lignin can reach 40.76%at 50 U/g immobilized laccase and 72h.The cellulose conversion was improved 32.46%after the recovery of immobilized laccase.