Alkali And Combined Alkali And Acid Pretreatment Of Spent Mushroom Substrate For Reducing Sugar Production

Spent mushroom substrate (SMS) is the byproduct of mushroom industry. Mostof the SMS have been burnt, which is neither environment-friendly nor economic.Furthermore, the lack of sustainable utilization strategies has greatly restricted thedevelopment of the mushroom industry. As a kind of lignocellulosic biomasscontaining cellulose and hemicellulose, SMS has the potential to be used to produceethanol and many other value-added products.Under the best pretreatment conditions (1M KOH,80°C,90min;1M lime,80°C,120min;10M ammonia,70°C,120min), the total reducing sugar (TRS) yieldreached258.6,204.2and251.2mg/g raw SMS, which were respectively6.15,4.86,and5.98times of untreated SMS. The effects of pretreatment by above alkalinereagents and sulfuric acid on the composition and structure of SMS were evaluated toprovide comparative performance data.Pretreatment costs and environmental pollution are the main problems during theprocess of converting lignocellulose to reducing sugars. A new process, combinedalkali and acid (CAA) pretreatment followed by enzymatic hydrolysis, wasinnovatively proposed to improve the cost-effectiveness and avoid environmentalproblems. The applied reagents were KOH, ammonia and sulfuric acid. When theenzyme loading was25FPU/g cellulose and250XU/g xylase, the maximum TRSyield of254.7mg/g was attained with a pretreated SMS ratio of1:1:0.8using theabove reagents. This method without filtration, washing, buffer addition and spentliquid emission would have a good economic and environmental prospect.The SMS residue and hydrolysates after CAA pretreatment and enzymatichydrolysis process was converted to biofertilizer with Pichia farinose FL7. Theresults showed only9%hydrolysates was acquired.and a cell density of3.0×108cfu/g in biomass was attained. Such a product would not only present a viable meansof disposing treated biomass wastes, but could supply phyto-essential elementsremaining in SMS hydrolysates, such as ammonium, potassium which furtherenhanced the biofertilizer efficacy.The current research investigated the utilization of SMS as carbon source toculture a white-rot fungi, Phanerochaete chrysosporium. And it showed a strong ability of lignin and hemicellulose degradation which demonstrated this fungus had agood potential for biological pretreatment of SMS.