Tham khảo tài liệu 'integrated waste management volume ii part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 342 Integrated Waste Management - Volume II glucosidases with high glucose tolerance. P-glucosidases with Ki up to 1400 mmol L-1 have been reported Decker et al. 2000 and these could be cloned into the cellulase-producing microorganisms to produce a more efficient enzyme mixture. The removal of sugars during hydrolysis by ultrafiltration or by employing the simultaneous saccharification and fermentation process SSF where the sugars produced during enzymatic hydrolysis are simultaneously fermented to ethanol have also been reported as alternatives to overcome the problem of enzyme inhibition by the final products of carbohydrate degradation Sun Cheng 2002 Jeffries Jin 2000 . It has been shown that ethanol also inhibits cellulases although less intensely when compared to glucose Holtzapple et al. 1990 Chen Jin 2006 . Cellulases inhibition by ethanol follows a noncompetitive inhibition pattern for ethanol concentrations less than 4 M and when the ethanol concentration is increased the enzyme is denatured. Ethanol also interferes with enzyme manly cellobiohydrolases adsorption to cellulose and modifies the cooperative effect between cellobiohydrolases and endoglucanases Ooshima et al. 1985 Holtzapple et al. 1990 . During the pretreatment the lignocellulose degradation products and hemicellulosederived monomeric sugars formed and released into the liquid fraction prehydrolysate have also been shown to inhibit enzymes activities since the remaining solid fraction amorphous cellulose and lignin is absorbed with this liquid up to 60-90 of its total weight. Among these degradation products we can mention organic acids acetic acid formic acid and levulinic acid sugar degradation products furfural from xylose and 5-hydroxymethylfurfural - HMF - from hexoses at high temperature and pressure and lignin degradation products vanillin syringaldehyde and 4-hydroxybenzalde-hyde Palmqvist et al. 1999a Cantarella et al. 2004 . However the inhibition of enzymatic hydrolysis by these .
