Study On Bio-pretreatment Of Bamboo Culms For Ethanol Conversion

Fuel ethanol produced from lignocellulose has been indicated to be a promisingalternative to the conventional fossil fuel. The complex structure of lignocellulose causesits natural resistance to enzymatic hydrolysis and bioconversion, which prevents theeconomical utilization of cellulosic material as biofuel feedstocks. This study hasestablished a bio-pretreatment method with Echinodontia taxodii which was suitable forPhyllostachys pubescence for the first time and explored its effect on following enzymaticsaccharification and ethanol fermentation.The results showed that the lignin content has decreased by40.7%while the reducingsugar yield and glucose yield of bamboo culms were256.20±18.97mg/g substrate and194.52±4.05mg/g substrate respectively when the ethanol production reached82.07±1.49mg/g substrate which was improved by204%,181%and121%after60daysof bio-pretreatment. Supplement of oxygen into bio-pretreatment system could shorten thepretreatment time to a half and the ethanol production could reach88.98±3.70mg/gsubstrate.The determination of extracellular enzymes from E.taxodii during pretreatmentshowed that degradation of lignin was mainly caused by Laccase whose maximumenzymatic activity could reach203±29IU/g substrate while manganese peroxidase andextracellular substances which was ferric reduction also did some synergy at the earlystage of pretreatment. The final lignin degradation could be47.9%and the low activitiesof extracellular cellulase and hemicellulase were the key factors to limited decompositionof polysaccharide.What’s more, the study of changes in adsorption properties of bamboo culmsindicated that the increase of pore size would improve access of cellulose to cellulase anddecrease substrate heterogeneity after bio-pretreatment, which greatly improved affinity ofcellulose to cellulase, thus leading to higher enzymatic hydrolysis.Overall, the selective biodegradation of lignin by E.taxodii made cellulose in bambooculms become more accessible to cellulase and the increased affinity between substratesand cellulase was the direct reason for enhanced enzymatic hydrolysis.