The Screening And Characterization Of A High-yield Cellulase Mutant Of Aspergillus Glaucus

Cellulose is the most abundant and renewable resource in the world. The conversion of cellulosic biomass into bio-energy, such as ethanol and hydrogen, will decrease the requairment of fossil energy and improve the environment. During the utilization of cellulosic biomass, bio-degradation is regarded as the perfect choice. A present limitation is the low activity of cellulase producting strain. So, it's the key step to obtain high-yield and high activity cellulase producing strains for an industrial development in the future.Cellulase producing strain Aspergillus glaucus XC9 was selected as the initial strain for mutation. Several mutant strains with high cellulase activities were obtained after being treated multiplicatively with UV-ray,ethyl methane sulphonate(EMS)and LiCl. The mutants exhibited distinct differences in physical properties and anti-suppress to glucose compared to the initial strain. Among the mutants, strain EU7-22 expressed the highest cellulase activities, its CMC activity was as two times as the initial strain.Several single factors on liquid fermentation of strain EU7-22 were studied in this research. The appropriate conditions for cellulase production were achieved as: straw powder quantity 2%, peptone quantity 0.1%, culture volume 60mL/300 mL, loading strain age 3~5 d,pH6～7, and 35℃, respectively. The orthogonal experiments showed the preferable conditions for cellulase production as: straw powder quantity 3%,peptone quantity 0.5%,original pH 5, and temperature 35℃. Under such conditions, the CMCase and FPA activities of EU7-22 were obtained as 110 IU/mL and 2.8 IU/mL, respectively, after 4~5 d fermentation.The enzymatic properties of cellulase from mutant strain EU7-22 were studied in this research. The optimum pH for CMCase and FPA activity were 4.2 and 4.8, respectively. The cellulase exhibited the highest activity at the temperature of 60℃. However, the enzyme turned to less stability with the increasing of temperature. The CMCase and FPA activity of cellulase decreased to 38.5% and 30%, respectively, after being incubated at 60℃for 4 h.The saccharification was carried out in a system containing 3% straw powder, using 8% (v/v) crude cellulase solution. The maximal reducing sugar was obtained as...