Study-on Screening And Identified Of A Lignin-Degradation Fungal Endophyte From Pigeon Pea[Cajanus Cajan(L.)Millsp.] And Its Lignocellulose Degradation Characteristics

Lignocellulose is considered to be the only renewable resource of providing liquids,gases as well as solid fuels in nature,and lignocellulose can also be used as a raw material for the production of various chemicals on a large scale.Lignocellulosic resources are abundant in China,but at present the utilization rate of lignocellulose is relatively low.The main reason is that the lignin in lignocellulose is difficult to be degraded and transformed,thus it greatly reduces the utilization of cellulose and hemicellulose.In nature,the degradation of lignin is mainly accomplished through the microorganisms,among them fungus are currently the most promising microorganisms for the degradation of lignin,therefore,the endophytic fungus in pigeon pea were used as the research object in this study.In this study,an endophytic fungus that specifically degradation of lignin was screened from 180 strains isolated endophytic fungus of pigeon pea,furthermore,its morphological and molecular biology characteristics were identified.Combined treatment of a novel fungal endophyte coupled with ultrasound assistance was conducted to treat birch sawdust,and removal ratio of lignin and retention ratio of cellulose are used as evaluation indexes to optimize the conditions in the treatment process.Finally,the effects of ultrasound treatment,fungal treatment and combined treatment on the degradation of lignocellulose in birch sawdust were compared.The results of this study are as follows:1)An endophytic fungus that specifically degradation of lignin was screened out and it was systematically classified and identified;.A strain of pigeon pea endophyte fungus M-16 that specifically degradation of lignin was screened by the plate color reaction and lignin degradation experiment.The endophyte fungus M-16 was identified as Myrothecium verrucaria by using morphology and molecular biology.Therefore,the endophyte fungus M-16 was used as a research strain for subsequent experiments.2)The optimal conditions for endophytic fungus coupled with ultrasound assistance treatment were determined by optimizing the ultrasound treatment time,power and fungal treatment time,materials to liquid ratio,pH,temperature;The results show that the optimum combination treatment conditions were confirmed as ultrasound treatment time 20 min,power 200W,the materials to liquid ratio 1:20,temperature 30 ?,time 4 days and pH 7,respectively.Under this process conditions,the final removal ratio of lignin was as high as 67.95%,and the retention rate of cellulose was up to 79.63%.3)Ultrasound treatment,fungal treatment and endophytic fungus coupled with ultrasound assistance treatment were compared for lignocellulose degradation in birch sawdust;Those three methods were used to treat the birch sawdust,and the composition of the treated birch sawdust were measured.The results showed that:the combined treatment has the best effect on birch sawdust,its lignin degradation can reach 67.95%,which is 4.94-fold and 1.49-fold of the ultrasound treatment and fungal treatment,respectively.The untreated and treated birch sawdust were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy,the changes in chemical structure and apparent structure indicate:the endophytic fungus coupled with ultrasound assistance treatment had the greatest damage to the internal structure of lignocellulose,and some internal functional groups of lignin were destroyed.The effect of fungal treatment followed,but the effect of ultrasound treatment was the worst.From the above,In this paper,we first screened an endophytic fungus that specifically degraded lignin,and the combined treatment of fungal endophyte coupled with ultrasound assistance in this paper were used to degrade lignin in natural lignocellulosic raw birch sawdust,the lignin degradation is higher and the retention rate of cellulose is also relatively high.This method has many advantages,such as shorter reaction time compared to other fungal treatments,mild reaction conditions,environmentally friendly,low processing costs,and ease of industrial application.Therefore,the combined treatment of fungal endophyte coupled with ultrasound assistance is an efficient and environmentally-friendly treatment technology,which is expected to be applied in the future industrial production process.