Evaluation of Lignin Degradation Potential of Fungi Isolated from Pulp and Paper Mill Effluent.

Abstract

Pulp and paper mill industries release an excessive amount of wastewater containing hazardous compounds which have an impact on every aspect of life. Effluent is required to be treated to minimize its severe effects on the environment. The biological approach is the most popular among all treatment techniques. Main goal of the study was to focus on the treatment of effluents from pulp and paper mills using native fungal strains. Sample was taken from pulp and paper mill industry located in district Kasoor, Lahore, Pakistan. Two strains SST-1 and SL-6 were selected after initial screening on the basis of their ability to degrade lignin using L-MSM as growth medium. In qualitative and quantitative enzyme screening, both fungal isolates exhibited positive activity for Ligninolytic enzymes production. Both the fungal strains were identified through morphologic, microscopic, and molecular method. Strain SST-1 was identified as Trametes hirsuta while SL-6 was identified as Aspergillus fumigatus. It was observed that both the strains grow well at pH 6.0 and temperature 30℃. Trametes hirsuta SST-1 and Aspergillus fumigatus SL-6 were observed to show maximum lignin degradation using ammonium sulfate and peptone as nitrogen sources respectively. A lab scale biological reactor was used for black liquor treatment. During first trial two separate reactors were run for both the fungal strains. Trametes hirsuta SST-1 demonstrated 47% reduction in lignin, 62% reduction in color, 59% reduction in phenol and 58% reduction in COD. Similarly, Aspergillus fumigatus SL-6 exhibited 41% reduction in lignin, 56% reduction in color,47% reduction in phenol and 45% reduction in COD. However, in second trial, co-cultivation of both strains showed enhanced activities with notable 74% reduction in lignin, 80% reduction in color, 84% in phenol and 67% reduction in COD. In phytotoxic activity germination rate of 90% and 80% was observed for the treated effluent of the first trial. Comparatively, seed germination activity of 100% was observed for the effluent of second trial. Moreover, in cytotoxic assay Trametes hirsuta and Aspergillus fumigatus treated black liquor showed 60% and 40% viability respectively whereas treated black liquor by the consortium showed viability rate of 70%. Both the strains exhibited significant lignin degradation ability and toxicity of the black liquor was considerably reduced.