Growth response and extracellular enzyme activity of Ulocladium botrytis LPSC 813 cultured on carboxy-methylcellulose under a pH range

Abstract

The fungus Ulocladium botrytis was isolated from Scutia buxifolia leaf litter and its growth was evaluated on both liquid and solid medium with sodium-carboxy-methylcellulose (CMC, 0.5%) as sole C source at a pH range between 4.0 and 10.0 and the synthesis of cellulose-degrading enzymes on litter. Growth on CMC-agar medium was maximum at pH 6.0, while in liquid CMC cultures, the highest biomass levels were found at pH 8.0 in both cases after 7 days of incubation. Cellulose-degrading enzyme activities such as β-glucosidase (2.40 U dry leaf g−1), cellobiohydrolase (3.92 10−3 U dry leaf g−1), and endoglucanase (2.01 U dry leaf g−1) activities were detected in water-soluble fractions of inoculated leaves after 30 days of incubation. Endoglucanase activity was maximum at pH 6.0 and relatively stable as the pH increase, being 100 and 60% stable at pH 7 and 8, respectively. As a consequence of these enzyme activities, leaf mass was reduced by 5.8%. Our findings suggest that U. botrytis contains a cellulose-degrading enzyme complex that, unlike other cellulolytic systems, can degrade recalcitrant plant litter under alkaline conditions.