Enzymatic Conversion of Lignocellulosic Materials to Sugars

Abstract

Abstract Cellulase was produced by cultivating T. reesei QM 9414 and MCG 77 on spruce sulfite pulp. The solid enzyme prepared by acetone precipitation had 0.73 FPU/mg, 0.2 units ß-glucosidase/mg and 10 units xylanase/mg. The average molecular weight was 48000 dalton. Analytical and preparative (20 mg) separation of the cellulase by chromatofocusing revealed the presence of 18 different proteins. Identified were: two exocellulases (C1 -enzymes), five endocellulases (Cx -enzymes), one ß-glucosidase, one galacto-mannase, two xylanases and one ß-xylosidase. The cellulase was used to hydrolyze cellulose (spruce sulfite pulp) and various lignocellulosic waste materials (newspaper, wheatstraw, cornstover, wood and reed grass a.o.). With 10, 5, 2.5, 1 and 0.5% cellulose slurries percentage of saccharification (24 hours) was 25, 42, 45, 53 and 69 %. Saccharification increased with increasing enzyme concentration up to a level of 0.60 FPU/ml and 0.36 units ß-glucosidase/ml. A further increase of either one of the enzymes did not improve hydrolysis. The various lignocellulosic materials were mechanically pretreated and yield of hexoses upon enzymatic hydrolysis (10 FPU/g, 50°C, pH 4.8, 48 – 75 hours) was on average 50 – 60% of the theory. The sugars in raw materials and hydrolysates were determinated by capillary GC as alditol acetates or by HPLC. These methods were preferred since other determinations gave either too high (dinitrosalicylic acid procedure) or too low (glucose oxidase assay) values when employed with lignocellulosic hydrolyzates.