Optimizing biocatalytic potential of Dipodascus australiensis M-2 for degrading lignin under laboratory conditions

Abstract

In present research, a potent fungal strain was isolated from paper mill effluent (black liquor) in order to investigate its potential for the biodegradation of lignin. Two step strategy was used to screen most efficient fungal strain having ability to growin MSM-black liquor medium and to degrade alkali lignin.The results of initial screening indicated that the strain M-2 produced comparatively higher ligninolytic zone on MSN agar plates supplemented with black liquor (BL) and alkali ligninase compared to the other isolates.The results of 18S rRNA gene sequencing revealed that strain M-2 showed ≥ 99% sequence homology with Dipodasceus australiansis.The process for the biodegradation of lignin was optimized using Taguchi Orthogonal Array design. Under optimized conditions of pH 9, 40 °C and 4% inoculum, a maximum of 89% lignin was degraded with 41% color reduction after 8 days of incubation period by Dipodasceus australiansis M-2. The pH and temperature were found to be significant terms with the p-values of 0.002 and 0.001 respectively. The laccase activity of the Dipodascus australiensis was found to be maximum of 1.511 U/mL. The HPLC analysis of lignin biodegradation indicated sharp transformation of peaks as compared to the control. Our results suggested that the strain Dipodascus australiensis M-2 possess excellent lignin degradation and color reduction capability and can be applied in waste treatment systems for pulp and paper mill effluent. In present work we are reporting first hand information regarding biodegradation of lignin by a potent strain of Dipodascus australiensis and statistical optimization of the bioprocess.