Hyper production of ?-glucosidase by an Aspergillus sp

Comparative production of cellulases by mutants of Penicillium janthinellum NCIM 1171 and its application in hydrolysis of Avicel and cellulose

Mutants of Penicillium janthinellum NCIM 1171 were evaluated for cellulase production using both submerged fermentation (SmF) and solid state fermentation (SSF). Mutant EU2D-21 gave highest yields of cellulases in both SmF and SSF. Hydrolysis of Avicel and cellulose were compared using SmF and SSF derived enzyme preparations obtained from EU2D-21. Surprisingly, the use of SSF derived preparation gave less hydrolysis compared to SmF derived enzymes. This may be due to inactivation of β-glucosidase at 50°C in SSF derived enzyme preparations. SmF derived enzyme preparations contained both thermostable and thermosensitive β-glucosidases where as SSF derived enzyme preparations contained predominantly thermosensitive β-glucosidase. This is the first report on less thermostability of SSF derived β-glucosidase which is the main reason for getting less hydrolysis.

Strain improvement of Penicillium janthinellum NCIM 1171 for increased cellulase production

The strain of Penicillium janthinellum NCIM 1171 was subjected to mutation involving treatment of Ethyl Methyl Sulfonate (EMS) for 24h followed by UV-irradiation for 3min. Successive mutants showed enhanced cellulase production (EMS-UV-8), clearance zone on Avicel containing plate (SM2) and rapid growth on Walseth cellulose agar plates containing 0.2% 2-deoxy-d-glucose (SM3). These mutants were transferred to Walseth cellulose plates containing higher concentration (1.5%) of 2-deoxy-d-glucose (SM4) in which only five mutants showed clearance zone on SM4. All these mutants showed approximately two-fold increase in activity of both FPase and CMCase in shake flask culture when grown on basal medium containing CP-123 (1%) and wheat bran (2.5%). The enzyme preparations from these mutants were used to hydrolyze Avicel. Higher hydrolysis yields of Avicel were obtained with enzyme preparations of EU1. This is the first report on the isolation and selection of mutants based on hydrolysis of Avicel, which is the most crystalline substrate.

A simple and nondestructive method for the separation of polysaccharides from beta-glucosidase produced extracellularly by Aspergillus niger

An apparatus based on electrophoresis has been devised that removes noncovalently bound polysaccharides from extracellular proteins of Aspergillus niger with concomitant partial beta-glucosidase purification and concentration. The apparatus consists of a series of three chambers separated by polyacrylamide gels. Dialyzed and concentrated crude extract of Aspergillus niger containing beta-glucosidase was poured into the middle chamber, while smaller anodic and cathodic chambers contained buffer. When electric current was applied, negatively charged protein-polysaccharide complexes moved toward the anode. Most of the negatively charged proteins, including beta-glucosidase, crossed the gel barrier into the anodic compartment, while neutral polysaccharides were either trapped in the gels or remained in the middle chamber. In this way, 125 ml of dialyzed and concentrated crude extract of Aspergillus niger was processed. Therefore, after 24 h of electrophoresis, 68% of the proteins and 90% of the beta-glucosidase activity, but only negligible amounts of polysaccharide, were transferred to the anodic chamber. The removal of high-molecular-weight polysaccharide from beta-glucosidase had a detrimental effect on the stability of the enzyme.

Protection of Aspergillus niger cellulases by urea during growth on glucose or glycerol supplemented media

The cellulase enzymes of Aspergillus niger were found to undergo catabolite repression in the presence of glucose and glycerol accompanied by sudden drop in pH of the fermentation medium below 2.0. This sudden drop in pH caused inactivation of cellulolytic enzymes produced by Aspergillus niger. The supplementation of nitrogen sources, especially urea, protects A. niger cellulases from inactivation caused by a sudden drop in pH, since urea helped to maintain the pH of the fermentation medium between 3.5 and 4.5. The role of urea in the protection of cellulase was more prominent when it was used in combination with glycerol (5%).

Optimization of cellulase production by Aspergillus niger NCIM 1207

Aspergillus niger NCIM 1207 produces high levels of extracellular beta-glucosidase and xylanase activities in submerged fermentation. Among the nitrogen sources, ammonium sulfate, ammonium dihydrogen orthophosphate, and corn-steep liquor were the best for the production of cellulolytic enzymes by A. niger. The optimum pH and temperature for cellulase production were 3.0-5.5 and 28 degrees C, respectively. The cellulase complex of this strain was found to undergo catabolite repression in the presence of high concentrations of glucose. Glycerol at all concentrations caused catabolite repression of cellulase production. The addition of glucose (up to 1% concentration) enhanced the production of cellulolytic enzymes, but a higher concentration of glucose effected the pronounced repression of enzymes. Generally the growth on glucose- or glycerol-containing medium was accompanied by a sudden drop in the pH of the fermentation medium to 2.0.