OPTIMIZATION OF CELLULASE-FREE XYLANASE PRODUCTION BY A NOVEL YEAST-STRAIN

A novel yeast strain, NCIM 3574, isolated from a decaying wood produce d up to 570 IU ml-1 of xylanolytic enzymes when grown on medium contai ning 4% xylan. The yeast strain also produced xylanase activity (40-50 IU ml-1) in the presence of soluble carbon sources like xylose or ara binose. No xylanase activity was detected when the organism was grown on glucose. The crude xylanase preparation showed no activity towards cellulolytic substrates but low levels of beta-xylosidase (0.1 IU ml-1 ) and alpha-L-arabinofuranosidase (0.05 IU ml-1) were detected. The te mperature and pH optima for the crude xylanase preparation were 55-deg rees-C and 4.5 respectively. The crude xylanase produced mainly xylose from xylan within 5 min. Prolonged hydrolysis of xylan produced xylob iose and arabinose, in addition to xylose, as the end products. The pr esence of arabinose as one of the end products in xylan hydrolysate co uld be due to the low levels of arabinofuranosidase enzyme present in the crude fermentation broth.