PRODUCTION OF XYLANOLYTIC ENZYMES DURING GROWTH ON PULVERIZED GRASS BY ASPERGILLUS OCHRACEUS-42

Xylanase and beta-xylosidase with activity of 6.46 U mg(-1) and 0.500 U mg(-1), respectively, were produced extracellularly by Aspergillus ochraceus during growth on pulverized grass in liquid state fermentation, compared to 9.3 U mg(-1) and 0.74 U mg(-1) when pure xylan was used. The culture filtrate was devoid of any cellulase activity. Xylanolytic enzymes were produced optimally in 144 h of incubation on 1% pulverized grass, pH 6.5. About 8.43% (w/w) sugars were liberated from alkali-treated grass in 6 h by the synergistic effect of xylanolytic enzymes. The half-lives for xylanase and beta-xylosidase at 50 degrees C were 210 min and 300 min, respectively, and half-life increased with the increase in protein concentration. Both mono- and divalent cations, especially K+ and Zn2+, exhibited a profound effect on the rate of enzyme saccharification.