Assessment of some wild Aspergillus species for cellulase production and characterization

Abstract

Fifteen Aspergillus species were used to evaluate their potentialities for cellulase production under submerged fermentation. The isolates were grown on carboxymethylcellulose (CMC) agar medium for detection of cellulase activity andAspergillus oryzae S/92Gbr exhibited maximum clear zone (40 mm) around the colony. Protein content and cellulase activity of the filtrates were determined and biomass was harvested from the culture. All the species produced significant (p<0.05) amount of reducing sugar and protein; and showed correlation with protein content and reducing sugar level. Biomass did not show correlation with increase of cellulase activity. In all cases maximum β-glucosidase exhibited compare to FPase and isolate A. oryzaeS/92Gbr showed the highest β-glucosidase (2.5 U/ml), CMCase (2.4 U/ml), Avicilase (2.1 U/ml) and FPase (1.5 U/ml) activity. The optimum pH and temperature of the enzyme estimated as 5 and 45°C, respectively and the highest activity ranges around at pH 4-6 and 40-50°C. The highest activity was observed after 7 days of incubation at pH 5.6 and 28°C when CMC was used as substrate. The enzyme activity strongly inhibited by Cu2+, Hg2+, Fe3+, Zn2+, Ag+ and K+ and increased by Mg2+ and Mn2+ about 40%. The Km values estimated as O.44, 0.48, 0.54 and 0.74% by A. oryzae S/92Gbr, Aspergillus flavusS/23Ogr, Aspergillus cervinus S15/Pf and Aspergillus ochraceus S/56Y, respectively that revealed the enzyme contained good reducing sugar releasing capacity. Key words: Aspergillus spp., protein, biomass, cellulase activity, Km value.