Studies On The Degradation Characteristic And Recycle Of Spent Mushroom Compost

Mushroom industries generate lots of spent mushroom compost（SMC）annually.Without proper disposal,these abandoned cultivation matrix would cause multiple environmental problems.The recycle of SMC is one of the methods to realize the reduction of SMC.However,researches on the recycle of SMC nowadays less focus on the degradation of SMC.So this study investigated the degradation characteristic of SMC by Clostridium thermocellum,and on this basis,the pretreatment of SMC was explored,and SMC was degraded by C.thermocellum for hydrogen production and saccharification.Though SMC could be utilized without any pretreatment by C.thermocellum,grinding,washing and chemical pretreatment could improve the fermentation performance of SMC,and consequently increased the hydrogen production by 48.48%,62.09%and 2.61 times,respectively.It shows that SMC is a potential cheap substrate for consolidated bioprocessing,but pretreatments are needed to degrade SMC more effectively.Short-time alkaline peroxide pretreatment,which is treating the SMC by 8%NaOH and 15%H₂O₂ for 10 min,could increase the hydrogen production of SMC fermentation by over three times and improve the enzymatic degradability remarkably.Besides,the recalcitrance of different particle size fractions of SMC were different and it is suitable to sieve the SMC before utilization.The nutritive character of SMC makes it possible to simplify the medium when fermentation for hydrogen production with the SMC as substrate.A simple and economic formula to ferment the SMC for hydrogen was made up of 4%SMC,0.25 g/L reduced glutathione and 5.5 g/L dipotassium phosphate,and the initial pH value of medium should be adjusted to about 7.5.Mixed the NaOH pretreated SMC and raw SMC for hydrogen production could obtained relatively high hydrogen production with a simplified medium.Without sterilization,the production of hydrogen was instable,and influenced by multiple factors,such as the medium composition and the microbial species in SMC.Adding isooctyl alcohol polyoxyethylene ether（JFC-E）to the SMC fermentation system of C.thermocellum could accumulate glucose.The saccharification result of JFC-E method was connected with the degradation property of substrate,and adding glass beads or Cellic?CTec2（CTec2）could facilitate the accumulation of glucose.Two-stage method for saccharification with addition of JFC-E and CTec2 could obtain 48.41 g/L glucose when the feeding loading was 15%.Besides,the ethanol fermentation efficient of the saccharification liquid prepared by two-stage method could reach over 90%.So the two-stage method has practical application values.This study used the SMC to produce hydrogen and do saccharification,investaged the degradation characteristics of SMC,so as to provide basic guidance for the degradation of SMC and point out the feasible direction of SMC recycling.The simplification of medium and the JFC-E saccharification system provided new ideas for better utilization of the SMC.