No abstract

The development of agar plate screening techniques has allowed the isolation of mutants of Trichoderma reesei capable of synthesizing cellulase under the conditions of a high concentration of glucose. Mutants resistant to catabolite repression by glycerol or glucose were isolated on Walseth's cellulose (WC) agar plates containing 5% glycerol or 5% glucose, respectively. Mutants resistant to catabolite repression by glycerol were not derepressed enough for the production of cellulase on WC agar plates containing 5% glucose or in flask cultures with a mixture of 1% Avicel and 3% glucose. On the contrary, two mutant strains resistant to catabolite repression by glucose (KDD-lO and DGD-16) produced large clearing zones on WC agar plates containing 5% glucose. Both strains could begin to produce CMCase even in the presence of residual glucose and finally produced 1.5 times the CMCase activity, in flask cultures on 1% Avicel and 3% glucose, than that with 1% AviceI alone. These results suggest that KDD-lO and DGD-16 are comparatively derepressed by glucose foe cellulase production. 2875The industrial use of cellulase for the conversion of cellulose to glucose has beep handicapped by the relatively high cost of cellulase. 1) Therefore, it seemed useful to obtain microorganisms with high cellulase producing abilities. Among cellulolytic microorganisms, T. reesei is known to be the highest producer of cellulase, and many reports have appeared on T. reesei mutants capable of hyperproduction of cellulase.2 '" 14)We also began to improve the cellulase producing ability of T. reesei KY 746, which was derived from QW 9414 by monocolony isolation, and developed a semiquantitative plate assay method for selecting fungal mutants showing hyperproduction of cellulases. 15 ) In order to lower the cost of cellulase, inexpensive carbon sources are also necessary for cellulase production. We think that molasses, extensively used in the fermentation industry, and agricultural wastes, such as t Production of Ethanol from Biomasses. Part II. whey, rice straw and bagasse, may be available for cellulase production. Glucose and other easily metabolizable sugars inhibit the formation of cellulase by the mechanism of catabolite repression. 16 ) When a large amount of molasses, which contains high concentrations of glucose and fructose, is used for cellulase production, catabolite repression will occur. To overcome these problems, cellulase mutants resistant to catabolite repression have been sought, and among those found MCG-77 (Natick)4) and C-30 (Rutgers)6) have been well investigated. When these mutants were used for cellulase· production in liquid cultures, the addition of only 1% glucose to the cellulose medium 4 ) or to the 1% cellobiose medium instead of 1%cellulose was made. 12 ) But, there has been no report on the cellulase production in a liquid culture under the conditions of a high concentration of glucose such as in the case of the addition of 3% glucose to acel-

Wemainly investigated ethanol production from cellulosic biomasses, for renewable alternatives to petroleum, as sources of fuels. Cellulase production is one of the most important processes for the successful enzymatic conversion of cellulosic biomasses to fuel ethanol. Much research on cellulolytic enzymes has been carried out in the last 30 years and Trichoderma reesei was selected as the best cellulase producer by M. Mandels and E. T. Reese et al. (reviewed by M. Mandels1*). The improvement ofcellulase production using T. reesei has been investigated in many laboratories and strains showing cellulase hyperproductivity such as MCG772) (Natick Laboratories) via QM 9414 and Rut C-303) (Rutgers University) via Rut NG-14 were obtained. Wehave also attempted the improvement of cellulase production through mutation of T. reesei

The development of agar plate screening techniques has allowed the isolation of mutants of Trichoderma reesei capable of synthesizing cellulase under the conditions of a high concentration of glucose. Mutants resistant to catabolite repression by glycerol or glucose were isolated on Walseth's cellulose (WC)agar plates containing 5%glycerol or 5%glucose, respectively. Mutants resistant to catabolite repression by glycerol were not derepressed enough for the production of cellulase on WCagar plates containing 5% glucose or in flask cultures with a mixture of 1 % Avicel and 3%glucose. On the contrary, two mutant strains resistant to catabolite repression by glucose (KDD-10 and DGD-16) produced large clearing zones on WCagar plates containing 5% glucose. Both strains could begin to produce CMCaseeven in the presence of residual glucose and finally produced 1.5 times the CMCaseactivity, in flask cultures on 1%Avicel and 3%glucose, than that with 1%Avicel alone. These results suggest that KDD-10and DGD-16are comparatively derepressed by glucose for cellulase production.