Screening And Mutation Breeding Of Trichoderma Strains Degrading Sugarcane Bagasse Cellulose

China is the world's fourth largest country in the sugarcane production.Bagasse,as the by-product of the sugar industry,is also a kind of renewable biomass resources.Guangxi is the China's largest sugar cane sugar producing area,and it is rich in sugar cane resources.In order to make sugarcane bagasse high-value and resource utilization,it requires a strain or enzyme that can efficiently degrade cellulose and destroy the‘biomass recalcitrance'of the sugarcane bagasse fiber material.Pretreatment before enzymatic hydrolysis can increase the accessibility of enzymes and substrates to achieve a better enzymatic hydrolysis effect.Bagasse has the advantages of being renewable,low cost,biodegradation,and centralized source,and is suitable for industrial production and application.Cellulose-degrading strains can utilize cellulose biomass as a carbon source to produce a variety of high value-added products such as nanomaterials and xylo-oligosaccharides through liquid or solid fermentation.In this study,the cellulose-degrading bacterium Trichoderma sp.S-16selected from mildewed bagasse was used as the starting strain for mutagenesis,and the biological identification was carried out,and the strain was identified as Trichoderma.The strain is combined with ultraviolet(Ultraviolet,UV)and plasma(Atmospheric Room Temperature Plasma,ARTP)mutagenesis to obtain mutations with high yield cellulase and good genetic stability.Effectively improve cellulose degradation rate,and solve the problem of using sugarcane bagasse.Best UV irradiation time 4 min,and ARTP optimal irradiation time was 400s.Congo red medium by preliminary screening,Endoglucanase(CMC)activity as an indicator for rescreening,five subcultures get a high yield cellulase and good genetic stability strain A-8.In order to obtain high enzyme activity,the liquid fermentation of mutant strain A-8 was optimized from the aspects of fermentation cycle,carbon,nitrogen,p H,inoculation and temperature.Strain A-8 best fermentation culture cycle 5 d,best carbon filter paper,best nitrogen source(NH₄)₂SO₄,culture medium p H 4,optimum inoculum 8%,and temperature 30?;The CMC enzyme activity of strain A-8 was 6.13 U;it was 1.2 times higher than that before optimization.Enzymatic hydrolysis of unpretreated bagasse,acid pretreated bagasse and alkali pretreated bagasse,and the content of glucose and reducing sugar is obtained as follows:unpretreated bagasse(2.33 mg/m L and 3.21mg/m L,respectively),acid pretreated bagasse(4.05 mg/m L and 5.32 mg/m L,respectively),alkali pretreated bagasse(4.42 mg/m L and 5.97 mg/m L,respectively);Enzymatic hydrolysis was performed using scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR)and X-ray diffraction(XRD).It was found that the structure and functional groups of the residue changed,and the crystallization index decreased from 47.57%to 30.39%,in which the alkaline pretreatment bagasse showed better enzyme accessibility.The study results show that UV and ARTP mutagenesis can achieve very good mutagenic effects and enhance the cellulase production ability of Trichoderma sp..The mutant strain A-8 has good enzyme production ability and genetic stability,and can further improve the enzymatic degradation effect of sugarcane bagasse cellulose.