Study On Mutation Breeding Of Pleurotus Ostreatus Strain With High Yield Of Laccase And Lignin Degradation

Laccase has good prospects for development in the treatment of papermaking wastewater and dyeing wastewater,straw utilization,biological composting and food industry.But there are strains of slow growth,low yield,long laccase production cycle,which is not conducive to the industrialization of large-scale use of such shortcomings in present.The combination of physical mutagenesis and chemical mutagenesis has significant advantages compared with the traditional single mutagenesis.Compound mutagenesis can generally make up for the defects caused by the use of a single mutagenic agent,and the combination of different mutagenesis methods can play a complementary and synergistic role.In this paper,a high yield strain of laccase was obtained by compound mutagenesis,and the fermentation conditions of the strain were optimized.Using mutagenic strain to decompose alkali lignin,the products before and after reaction were analyzed,and the preliminary mechanism of lignin degradation was obtained.It provides a theoretical basis for the industrial fermentation production of laccase,treatment of papermaking wastewater and the utilization of straw in the future,which has great economic potential and far-reaching significance.High laccase production strain F-13 was obtained using composite mutagenesis,when Pleurotus ostreatus C1 was the original strain.The laccase production reached 172.0U/L,1.26 times higher than the original strain.The preliminary screening method of guaiacol color ring has been established,which has the characteristics of high efficiency and fast.It is of great significance for the breeding of strains.The fermentation conditions of mutant strains of F-13 were optimized.A large number of experimental studies were developed from culture conditions and nutrition conditions,respectively.The conclusion was obtained.The yield of laccase from the strain reached the highest in the oscillating culture mode,30?,glucose as carbon source,?NH₄?₂SO₄ as nitrogen source and adding 0.5mmol?L^-1 Cu²⁺,the maximum value was 235U/L,which was 36.6%higher than that of before optimization.The mechanism of degradation of mutant strains of alkali lignin was preliminarily explored and the structure of alkali lignin degradation products was characterized by using UV-Vis spectrophotometer,Fourier transform infrared spectroscopy?FTIR?,gas chromatography-mass spectrometry?GC-MS?,¹³C-NMR spectra and ¹H-NMR spectra and other characterization methods,and the results of the experimental analysis were obtained:the experimental results were concluded.The mutagenic strain F-13 has strong degradation effect on alkali lignin.Degradation products of aromatic compounds,carboxylic acids compounds and small molecular weight substances such as ethers,a lot of fatty ether substances,large amounts of aliphatic carbon chains and aliphatic chains of fatty series were detected.It has shown that the structure of the large molecule benzene ring in alkali lignin was destroyed,and the structure of alkali lignin was changed greatly.