Ligninolytic behavior of the white-rot fungus Stereum ostrea under influence of culture conditions, inducers and chlorpyrifos.

The production of three ligninolytic enzymes, laccase (LAC), manganese peroxidase (MnP) and lignin peroxidase (LiP) by the white-rot fungus, Stereum ostrea, was significantly more in Koroljova liquid medium in the presence of chlorpyrifos under shaking conditions than under stationary conditions. These enzymes were secreted into the broth to the extent of 214.37, 82.75 and 8.05 U/ml under influence of chlorpyrifos on 10th day of incubation in comparison with 138.06, 51.85 and 6.44 U/ml, respectively, under similar conditions in control. Maximum production of LAC, MnP and LiP on liquid medium with/without chlorpyrifos under stationary conditions did not exceed 80-85, 33-40, 0.6-0.7 U/ml, respectively. Among lignosulfonic acid, veratryl alcohol (VA), gallic acid (GA) and tannic acid tested, GA induced maximum production of LAC (300.53 U/ml) and MnP (181.66 U/ml) after 10 days of growth in the presence of chlorpyriphos, while maximum LiP (1.134 U/ml) was produced when grown with the inducer VA during this period. Our data suggest that chlorpyrifos and inducers interacted positively in producing higher amounts of the ligninolytic enzymes in S. ostrea.

Bio-bleaching of Remazol brilliant blue-19 by Stereum ostrea.

Efficiency of white-rot fungi-Stereum ostrea (S. ostrea) as a test culture and Phanerochaete chrysosporium (P. chrysosporium) as a reference culture in colour removal from a textile dye, Remazol brilliant blue-19 (RBB-19) in medium was compared in this study. S. ostrea was more efficient than P. chrysosporium in decoloration process. Different parameters pH, temperature, sources of carbon and nitrogen, stationary and shaking conditions were optimized for bleaching of dye by the fungal cultures. Optimal growth conditions for decoloration of dye by both cultures were pH 5.0, temperature 35 °C, glucose and fructose as best carbon source at 1 % level, peptone and urea as best nitrogen source and shaking conditions (150 rpm). Culture broth free of colour (99 % of decoloration) was achieved with S. ostrea as against 70 % decoloration by P. chrysosporium on 6th day of incubation. Adsorption of dye to fungal biomass as reflected by colour coating on biomass and participation of lignolytic enzymes in colour removal appeared to be mechanisms involved in decoloration process. The ability of both fungal cultures in removal of colour in effluents with dyes collected from silk saree-weaving cottage unit was tested. S. ostrea was also found to be more effective in colour removal from effluent. S. ostrea appears to be a promising culture for application of bioremediation in decoloration of dyes.

Enhanced Production of Ligninolytic Enzymes by a Mushroom Stereum ostrea.

The white rot fungi Stereum ostrea displayed a wide diversity in their response to supplemented inducers, surfactants, and copper sulphate in solid state fermentation. Among the inducers tested, 0.02% veratryl alcohol increased the ligninolytic enzyme production to a significant extent. The addition of copper sulphate at 300 µM concentration has a positive effect on laccase production increasing its activity by 2 times compared to control. Among the surfactants, Tween 20, Tween 80, and Triton X 100, tested in the studies, Tween 80 stimulated the production of ligninolytic enzymes. Biosorption of dyes was carried out by using two lignocellulosic wastes, rice bran and wheat bran, in 50 ppm of remazol brilliant blue and remazol brilliant violet 5R dyes. These dye adsorbed lignocelluloses were then utilized for the production of ligninolytic enzymes in solid state mode. The two dye adsorbed lignocelluloses enhanced the production of laccase and manganese peroxidase but not lignin peroxidase.

Kinetic properties of manganese peroxidase from the mushroom Stereum ostrea and its ability to decolorize dyes.

Manganese peroxidase (MnP) was isolated from the culture filtrate of the wood log mushroom Stereum ostrea (S. ostrea), grown on Koroljova medium, and then purified by ammonium sulfate [70% (w/v)] fractionation, DEAE-cellulose anion exchange chromatography, and Sephadex G-100 column chromatography, with an attainment of 88.6-fold purification and the recovery of 22.8% of initial activity. According to SDS-PAGE the molecular mass of the MnP was 40 kDa. The optimal pH and temperature were found to be 4.5 and 35 degrees C, respectively. The enzyme was stable even after exposure to a pH range of 4.5 to 6.0, and at temperatures of up to 35 degrees C at a pH of 4.5 for 1h. The K(m) and V(max) values for the substrate phenol red were found to be 8 micronm and 111.14 U/mg of protein, respectively. The MnP also oxidized other substrates such as guaiacol, DMP, and veratryl alcohol. Sodium azide, EDTA, SDS, Cu(2+), and Fe(2+), at 1-5 mM, strongly inhibited enzyme activity, whereas Ca(2+) and Zn(2+) increased enzyme activity. The participation of the purified enzyme in the decolorization of dyes suggests that S. ostrea manganese peroxidase could be effectively employed in textile industries.

Lignolytic Enzymes of a Mushroom Stereum ostrea Isolated from Wood Logs.

Production of lignolytic enzymes by the mushroom fungus Stereum ostrea in liquid medium under conditions of vegetative growth was examined for 10 days in comparison to the reference culture Phanerochaete chrysosporium. Though growth and secretion of extracellular protein by S. ostrea were comparable to those of P. chrysosporium, yields of laccase enzyme by S. ostrea were higher than laccase titres of P. chrysosporium by more than 2 folds on the peak production time interval (IVth day of incubation). S. ostrea yielded titres of 25 units of laccase/ml as against 8.9 units of laccase/ml on the IVth day of incubation. Stereum ostrea also exhibited activities of other lignolytic enzymes, lignin peroxidase (LiP) and manganese peroxidase (MnP), higher than the reference culture. Growth of S. ostrea on the medium in the presence of Remazol orange 16 resulted in the decolourisation of dye, confirming the presence of lignolytic enzymes. S. ostrea appears to be a promising culture with complete lignolytic system.