Abstract
A thermohalophilic fungus,
Aspergillus terreus
AUMC 10138, isolated
from the Wadi El-Natrun soda lakes in northern Egypt was exposed successively to
gamma and UV-radiation (physical mutagens) and ethyl methan-sulfonate (EMS; chemical
mutagen) to enhance alkaline cellulase production under solid state fermentation
(SSF) conditions. The effects of different carbon sources, initial moisture,
incubation temperature, initial pH, incubation period, inoculum levels and different
concentrations of NaCl on production of alkaline filter paper activity (FPase),
carboxymethyl cellulase (CMCase) and β-glucosidase by the wild-type and mutant
strains of
A. terreus
were evaluated under SSF. The optimum
conditions for maximum production of FPase, CMCase and β-glucosidase were found to be
the corn stover: moisture ratio of 1:3(w/v), temperature 45 °C, pH range, 9.0–11.0,
and fermentation for 4, 4 and 7 day, respectively. Inoculum levels of 30% for
β-glucosidase and 40% for FPase, CMCase gave the higher cellulase production by the
wild-type and mutant strains, respectively. Higher production of all three enzymes
was obtained at a 5% NaCl. Under the optimized conditions, the mutant strain
A. terreus
M-17 produced FPase (729 U/g), CMCase (1,783 U/g), and
β-glucosidase (342 U/g), which is, 1.85, 1.97 and 2.31-fold higher than the wild-type
strain. Our results confirmed that mutant strain M-17 could be a promising alkaline
cellulase enzyme producer employing lignocellulosics especially corn stover.