Effect of lignocellulosic materials and chlorpyrifos pesticide on secretion of ligninolytic enzymes by the white rot fungus – Stereum ostrea

Abstract

The present study compared the effect of chlorpyrifos on secretion of ligninolytic enzyme by the white rot fungus – Stereum ostrea grown in the presence and the absence of Tectona grandis cubes under submerged liquid conditions. Significantly higher yields of laccase and manganese peroxidase to the extent of 164.30 and 59.28 U/ml were registered in control containing only teak wood cubes than in the culture on combination of cubes and chlorpyrifos with 111.65 and 47.24 U/ml, respectively on 10th day of incubation. Reversed pattern in lignin peroxidase secretion with peak values on 6th day of incubation was noticed in the culture of S. ostrea immobilized on Tectona grandis cubes under influence of chlorpyrifos. Under free state conditions, significantly higher secretions of laccase (125.33 U/ml) and manganese peroxidase (53.60 U/ml) occurred in chlorpyrifos-amended medium than in the medium devoid of chlorpyrifos on 10th day incubation. Under moderate shaking conditions, supplementation of wheat bran alone at 3% level to the medium resulted in enhanced (3–5 folds) secretions of laccase, manganese peroxidase and lignin peroxidase by S. ostrea in medium free of wheat bran on 12th and 10th day of incubations. The presence of chlorpyrifos in addition to wheat bran in the medium further raised production of ligninolytic enzymes – laccase, MnP and LiP to the level of 311.78, 130 and 3 U/ml respectively on the 12th (higher LAC and MnP secretions) and 10th (higher LiP secretions) day of incubations. Our data in the present study suggest that secretion of ligninolytic enzymes by the culture is dependent on the nature of lignocellulosic material used in the study and secretion of higher titers of ligninolytic enzymes on cubes of Tectona grandis in the absence of chlorpyrifos rather in the presence of chlorpyrifos occurred. For executing microbial applications, it is critical to understand how lignocellulosic materials and toxic xenobiotic pesticides interact with white rot fungi and possible role of ligninolytic enzymes in the bioremediation process.