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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-

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A thermophilic fungus, strain A-13I, isolated from a soil sample produced cellulases in the culture fluid. The fungus (strain A-13I) was identified as Therrnoascus aurantiacus Miehe from its taxonomical characteristics. The cellulases of T. aurantiacus A-131 were produced constitutively without cellulase inducers. Moreover, their production was induced markedly by amorphous polysaccharides containing {J-I, 4 linkages such as alkali-treated bagasse and xylan rather than crystalline cellulose. The cultivation of T. aurantiacus A-131 at 45°C with 4% alkali-treated bagasse led to the production of about 70Ujml of CMCase after 4 days. The thermostability of the cellulolytic enzymes 'of T. aurantiacus A-131 was excellent and virtually no decreases in their activities were seen after preincubation at 60°C for 24 hr.Various cellulolytic enzymes have been reported to be produced by many microorganisms. Among the latter, Trichoderma reesei is generally regarded as the best producer of cellulases. In order to improve the cellulase productivity, the mutation of T. reesei has been attempted in combination with optimization of the culture conditions.! -8) As a result of these studies, the cost of cellulase production using T. reesei has become low. Because T. reesei is a mesophilic fungus, it needs cooling with water on cultivation especially in the tropics, where cellulosic biomasses are abundant. Moreover, the upper limit of the thermal stability of the cellulolytic enzymes of T. reesei is below SO°C, and on saccharification of cellulose at this temperature, contamination by thermotolerant microorganisms belonging to the genus Bacillus sometimes occurs. 9 ) Thus, T. reesei is not suitable as a producer of cellulases in the tropics.There have been many. reports of thermophilic cellulase producing microorganisms. 1O -17 ) Among the latter, Thermoactinomyces sp.,l°) Sporotrichum cellulophilum ll • 12 ) and Thielavia terrestris I2 ,13) were thought to be promising because of their relatively high cellulase productivities in liquid cultures. But, the productivities and properties of theri cellulases were not sufficient for effective saccharification of cellulose compared with those in the case of T. reesei, despite their temperature stability. We searched for new thermophilic cellulase producing microorganisms with CMCase productivities as high as those of T. reesei and with cellulolytic enzymes that are stable at high temperature such as 60°C or above. As a result of our screening, Thermoascus aurantiacus A-13I, which had been isolated from a soil sample, was found to be very suitable for this purpose. This paper deals with the cellulase production of T. aurantiacus A-13I, its enzymatic properties and its application for the saccharification of cellulose.