Acid Prehydrolysis
Bioresource Technology 36 ( 1991 ) 77-82
Common Aspects of Acid Prehydrolysis and Steam Explosion for Pretreating Wood
Hans E. Grethlein
Michigan Biotechnology Institute, PO Box 27609, Lansing, Michigan 48909, USA
& Alvin O. Converse
Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA
Abstract
The initial rate of hydrolysis using cellulase from Trichoderma reesei for various wood samples is directly proportional to the surface area available to the enzyme. Both dilute acid hydrolysis in a continuous flow reactor or autohydrolysis in a steam exploder are similar pretreatment methods in that they increase the pore volume of the wood by removing hemicellulose which increases the surface area available to the enzyme. Thus, pretreated wood samples by either method with the same available surface area give essentially the same initial rate of hydrolysis; and, the increase in rate of hydrolysis is controlled by the severity of the pretreatme~t. Key words ': Pretreatment, enzymatic hydrolysis, acid hydrolysis, autohydrolysis, steam explosion, Trichoderma reesei, wood hydrolysis.
INTRODUCTION It is generally recognized that native cellulosic substrates cannot be hydrolyzed rapidly with cellulase without a pretreatment (Millet et al., 1975, 1979; Grethlein, 1980; Chang et al., 1981; Ladisch et al., 1983). This is true for any type of cellulase system (Hart et al., 1981; Ryu et aL, 1982; Avgerinos & Wang, 1983; Bachmann et al., 1983; Holtzapple & Humphrey, 1984). A recent review (Grethiein, 1984) indicates that there are many pretreatment methods and a better understanding of why pretreatments work or do not
77
work is desired. The objective of this paper is to help define what is required of a pretreatment and how to select the best one. Whether one uses cellulase or acid as the catalyst for the hydrolysis of a heterogeneous substrate such as cellulose, the catalyst must be able to contact the glucosidic bonds.
Common Aspects of Acid Prehydrolysis and Steam Explosion for Pretreating Wood
Hans E. Grethlein
Michigan Biotechnology Institute, PO Box 27609, Lansing, Michigan 48909, USA
& Alvin O. Converse
Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA
Abstract
The initial rate of hydrolysis using cellulase from Trichoderma reesei for various wood samples is directly proportional to the surface area available to the enzyme. Both dilute acid hydrolysis in a continuous flow reactor or autohydrolysis in a steam exploder are similar pretreatment methods in that they increase the pore volume of the wood by removing hemicellulose which increases the surface area available to the enzyme. Thus, pretreated wood samples by either method with the same available surface area give essentially the same initial rate of hydrolysis; and, the increase in rate of hydrolysis is controlled by the severity of the pretreatme~t. Key words ': Pretreatment, enzymatic hydrolysis, acid hydrolysis, autohydrolysis, steam explosion, Trichoderma reesei, wood hydrolysis.
INTRODUCTION It is generally recognized that native cellulosic substrates cannot be hydrolyzed rapidly with cellulase without a pretreatment (Millet et al., 1975, 1979; Grethlein, 1980; Chang et al., 1981; Ladisch et al., 1983). This is true for any type of cellulase system (Hart et al., 1981; Ryu et aL, 1982; Avgerinos & Wang, 1983; Bachmann et al., 1983; Holtzapple & Humphrey, 1984). A recent review (Grethiein, 1984) indicates that there are many pretreatment methods and a better understanding of why pretreatments work or do not
77
work is desired. The objective of this paper is to help define what is required of a pretreatment and how to select the best one. Whether one uses cellulase or acid as the catalyst for the hydrolysis of a heterogeneous substrate such as cellulose, the catalyst must be able to contact the glucosidic bonds.
References: Avgerinos, G. C. & Wang, D. I. C. (1983). Selective solvent delignification for fermentation enhancement. Biotechnol. Bioeng., 25, 67-83. Bachmann, A., Baugh, K., Beard, V., Colberg, E J., McCarty, P. L. & Young, L. (1983). Heat treatment of organics for increasing anaerobic biodegradability. Report No. SERI/ STR-231-1769, Solar Energy Research Institute, Golden, Colorado. Bertran, M. S. & Dale, B. E. (1985). Enzymatic hydrolysis and recrystallization behavior of initially amorphous cellulose. Biotechnol. Bioeng., 27, 177-81. Chang, M. M., Chou, T. Y. & Tsao, G. T. (1981). Structure, pretreatment and hydrolysis of cellulose. Adv. Biochem. Eng., 20, 15-42. Converse, A. O., Kwarteng, I. K., Grethlein, H. E. & Ooshima, H. (1989). Kinetics of thermochemical pretreatment of lignocellulosic materials. App. Biochem. Biotech., 20/21, 63-78. Cowling, E. B. (1975). Physical and chemical constraints in the hydrolysis of cellulose and lignocellulosic materials. Biotechnol. Bioeng. Symp., 5, 163-82. Dekker, R. E H. & Wallis, A. E A. (1983). Enzymatic saccharification of sugarcane bagasse pretreated by autohydrolysis -- steam explosion. Biotechnol. Bioeng., 25, 3027-48.