Optimization Of Culture Conditions And Glycation Efficiency Of Degrading Lignocellulose From Inonotus Obliquus

Naturally occurring lignocellulose can be used as a renewable resource for the sustainable production of bioethanol.The bioconversion is still seldom applied at the industrial scale since the single conversion steps(pretreatment,hydrolysis,and fermentation)may exhibit low conversion rates,low efficiencies,or high costs.Although white rot fungi have been found to be able to biodegrade and convert lignocelluloses into platform chemicals,the biodegradation rate and efficiency depend on the white rot fungus species.The biodegradation selectivity of sugarcane bagasse by the white rot fungus Inonotus obliquus has not been reported.In this study,firstly,the selected degradation of lignin of sugarcane bagasse by Inonotus obliquus under submerged fermentation was optimized using the response surface methodology.(NH4)2SO4 was found to be the best nitrogen source.pH,Tween 80 and(NH4)2SO4 were the three main influencing factors.Under the optimized culture conditions[4%substrate,pH4.3,0.43%Tween 80,0.2%(NH4)2SO4],the selective index of lignin degradation of bagasse by I.obliquus was 1.33,which was 109.3%higher than that(0.64)of the control on Day 10.The dynamic biodegradation results showed that the contents of lignin,hemicelluloses,and cellulose decreased gradually with the process of fermentation,and the selective index showed a trend from high to low,reaching a maximum of 3.35 on Day 2.In merely two days,the fungus selectively degraded bagasse lignin by 13.31%,with only limited cellulose degradation(3.97%).High activities of manganese peroxidase(317.95 IU/mL)and lignin peroxidase(51.61 IU/mL)were observed in the bagasse culture on Day 6 and 4,respectively.After 12 hours of saccharification using the cellulase,the bagasse residue with 2-day fermentation by I.obliquus produced the total amount of reducing sugar of 264.8 mg/g and the maximum sugar yield was 30.1%.The bamboo fiber biodegradation results showed that,in the early stage of fermentation,the degradation of lignin and hemicellulose was higher than that of cellulose.The cellulose degradation increased in the late stage of fermentation.The bamboo fibers became softer and more easily bent.In conclusion,a highly efficient selective degradation culture system for I.obliquus submerged fermentation was established.The selective lignin-degradation of sugarcane bagasse was improved.The saccharification efficiency of the bagasse with a very short fermentation pretreatment was significantly improved.