Appl Microbiol Biotechnol (1986)25:250--255 Applied Microbiology Biotechnology © Springer-Verlag 1986 Column cellulose hydrolysis reactor: An efficient cellulose hydrolysis reactor with continuous cellulase recycling Larry U. L. Tan, Ernest K. C. Yu, Nancy Campbell, and John N. Saddler Biotechnology and Chemistry Department, Forintek Canada Corp., S00 Montreal Rd., Ottawa, Canada K1G 3Z5 Summary. The use of a column cellulose hydroly- sis reactor with continuous enzyme recycling was demonstrated by incorporating a continuous ul- trafiltration apparatus at the effluent end of the column reactor. Using this setup, over 90% (w/v) cellulose hydrolysis was achieved, resulting in an average sugar concentration of 6.8% (w/v) in the effluent stream. The output of the system was 1.98 g of reducing sugar/1/h with a ratio of 87% (w/v) of the reducing sugars being monomeric sugars. Batch hydrolysis reactors were less effec- tive, resulting in 57% (w/v) of the cellulose being hydrolyzed. The output of the batch reactor was 1.33 g of reducing sugar/I/h with similar product concentrations and percentage of monomeric sug- ars. The ratio of reducing sugar/filter paper unit of cellulase activity for the column method was 69.1 mg/U as compared to only 21.2 mg/U for the batch reactor. Introduction The large accumulation of urban wastes with the concomitant dwindling of finite resources, ration- alize the need for recycling selected wastes. Waste recycling produces valued and useful products while at the same time, reduces disposal prob- lems. Such recycling processes would simulta- neously conserve our natural resources, lower the cost of waste disposal and reduce the amount of pollutants to our natural environment. Much of our present wastes are made up largely of cellu- lose (Sandhya et al. 1984). Such wastes include pulp and paper wastes derived from chipper Offprint requests to: Larry Tan houses, sludges and centricleaner rejects which are normally disposed in landfills. Half of Muni- cipal refuse is composed of either cellulose, sugar or starch which amounted to a 100 million tonnes/year in the United States alone. In addi- tion, cellulosic wastes could be derived from such sources as sugarcane bagasse, rice husks, fruit and vegetable processing plants, and corn crop resi- dues. In order to make use of such cellulosic wastes, they must first be hydrolysed to simple sugars which could then be fermented to a variety of products, some of which include ethanol, buta- nediol, acetone, butanol and citric acid (Detroy and St. Julian 1983). One of the more promising ways to hydrolyse the cellulose is by means of cel- lulolytic enzymes produced by a number of fungi and bacteria (Sandhya et al. 1984). Unfortunately, the cellulase enzymes are relatively expensive to produce, and because of the inherent recalcitrant nature of cellulose, high concentrations of en- zymes are necessary for efficient cellulose hydro- lysis. Ultimately, the cost of sugar production by the enzymatic hydrolysis of cellulosic substrates could be prohibitively expensive. However, if the cellulase enzymes were effectively recycled under nondenaturing conditions, the economics of the process would be more favorable. Previously, Gusakov et al. (1984) and Mandels et al. (1971) had developed column cellulose hy- drolysis reactors based on intrinsic properties of specific sources of cellulase to adsorb tenaciously to specific cellulose. Because of these require- ments, this type of reactor was restricted to very limited sources of enzyme and substrates. In addi- tion, the poor adsorption of specific cellulase components, especially cellobiase, was very poor in the above references and contributed to low glucose production in the hydrolysis product and reduced the possible synergistic effect of having