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Yeasts able to grow on D-xylose were screened for the ability to hydrolyze xylan. Xylanase activity was found to be rare; a total of only 19 of more than 250 strains yielded a positive test result. The activity was localized largely in the genus Cryptococcus and in Pichia stipitis and its anamorph Candida shehatae. The ability to hydrolyze xylan was generally uncoupled from that to hydrolyze cellulose; only three of the xylan-positive strains also yielded a positive test for cellulolytic activity. Of the 19 xylanolytic strains, 2, P. stipitis CBS 5773 and CBS 5775, converted xylan into ethanol, with about 60% of a theoretical yield computed on the basis of the amount of D-xylose present originally that could be released by acid hydrolysis. MATERIALS AND METHODS Microorganisms. More than 250 yeast strains from the culture collection of the National Research Council of Canada were screened. All showed positive or variable growth on D-xylose according to Barnett et al. (1) and included species from the following genera: Ambrosiozyma, Brettanomyces,

Process conditions for the acid hydrolysis of pine hemicellulose and cellulose have been described which provide a biocompatible sugar solution. By using an improved strain of recombinant Escherichia coli, strain KOll, hydrolysates supplemented with yeast extract and tryptone nutrients were converted to ethanol with an efficiency of 85% to over 100% on the basis of monomer sugar content (approximately 72 glliter) and with the production of 35 g of ethanol per liter in 48 h. In the process described, approximately 347 liters of ethanol could be produced per dry metric ton of lignocellulose.

The relative amount of ethanol and xylitol accumulated in aerobic batch cultures of Pachysolen tannophilus and Candida guilliermondii on D-xylose depended on the extent of limitation by biotin. In high biotin media P. tannophilus favored ethanol production over that of xylitol while C. guilliermondii favored xylitol formation. However, as the extent of biotin limitation increased, the ratio of ethanol to xylitol produced by both organisms increased. The results are of interest in efforts to control such ratios.