Impacts Of Lignocellulose Composition And Features On Biomass Digestibility And Cellulase Production In Trichoderma Ressei

Crop residues provide enormous resources for biofuel production.However,biomass recalcitrance and high cost in cellulase enzymes are major factors affecting biofuel production.In this study,two independent experiments were conducted to investigate the impacts of lignocellulose features on biomass saccharification and cellulases secretion in Trichoderma ressei.In the first experiment,three fiber crops(Jute,Kenaf,and Ramie)were determined with distinctive lignocellulose features and different biomass digestibilities after various conventional pretreatments.Compared with raw materials,three fiber crops were examined to have enhanced hexoses yields(%cellulose)up to 1.9-4.8 folds from enzymatic hydrolyses of the steam-exploded stalks.Sequential dilute chemical pretreatments achieved increased hexoses yields up to 2.8-7.6 folds,and also achieved the high sugar-ethanol conversion rates from 41%to 53%.Without steam explosion,three crops exhibited increased hexoses yields under extremely high concentrations of NaOH(12%-16%),but had much lower sugar-ethanol conversion rates from 23%to 27%.While kenaf and ramie mainly showed removal of hemicelluloses with steam explosion,jute exhibited an effective co-extraction of hemicelluloses and lignin,which largely reduced its cellulose DP,hemicellulosic Xyl/Ara,and G-monomer.These findings explained why jute had the highest hexoses yield among the three crops and also suggested that G-monomer and Xyl may interact in a manner that mainly determines wall polymers co-extraction with steam explosion.In the cellulases production experiment,30 types of Miscanthus straws from 4 species and Rut-C30,a commonly used Trichoderma ressei strain,were used as inducing substrates and production strain,respectively.Comparative analysis indicated that 1%NaOH pretreatment could distinctively enhance the cellulases induction efficiencies of lignocellulose substrates in T.ressei.The enzyme activities of induced cellulases could be minimized while cell wall polymers of lignocellulose substrates are extracted from the pretreatment.Furthremore,the lignocellulose features of substrates laregely affect cellulases production in including cellulose crystallinity(CrI)as a negative factor,and non-KOH-extractable hemicellulosic Ara level as a positive factor.Correlation analysis revealed that biomass digestibility of lignocellulose substrates positively correlated with the enzyme activities of induced cellulases.