CONICET | Buscador de Institutos y Recursos Humanos

Growth response and enzyme activity of Ulocladium botrytis LPSC 813 on carboxy-methylcellulose under a pH-range Mario C. N. Saparrat1,2,*, Angélica M. Arambarri2 & Pedro A. Balatti1 1INFIVE, CONICET-UNLP, La Plata, Arg. 2Instituto Spegazzini, UNLP, La Plata, Arg. *masaparrat@yahoo.com.ar Ulocladium botrytis LPSC 813, a fungus from Scutia buxifolia leaf-litter, was cultured both on a liquid and solid medium with sodium-carboxy-methylcellulose (CMC, 0.5 %) as sole C source and different buffer solutions, to evaluate its growth under a pH-range between 4.0 and 10.0. Solid-state fermentation (SSF) cultures on S. buxifolia leaves were also carried out for analyzing the ability of the fungus for modifying the substrate and for producing the cellulase complex. The effect of pH and reaction buffer on endoglucanase activity of the water-soluble fraction (WSF) from SSF cultures was also analyzed as well as its stability against different pH values. Growth on CMC-agar media was maximum at pH 6.0 after 7 incubation days. However, highest biomass levels from liquid cultures with CMC were registrated at pH 8.0 after the 7 days of incubation. The strain on SSF cultures reduced the mass of the leaves at a 5.8 % and increased the pH of the WSF compared to uninoculated ones as well as produced extracellular activities of 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) after 30 days of incubation. This enzyme activity on CMC revealed maximal levels at pH 6.0 when Mc Ilvaine buffer (2.1-9.0) was used in the reaction, and higher ones when 150 mM sodium tartrate (pH 5.0) was used as reaction buffer compared to sodium acetate and Mc Ilvaine buffers. Likewise, it was stable at pH 7.0 and 25 ºC for 24 h. Key words: alkaline soil, cellulolysis, endoglucanase, growth, leaf-litter, Ulocladium botrytis