Exploring the diverse potentials of Planococcus sp. TRC1 for the deconstruction of recalcitrant kraft lignin

Abstract

Kraft lignin (KL) is the chief contaminant which is responsible for dark coloration, toxicity and high chemical oxygen demand (COD) of paper pulp mill effluent. The present study investigated the diverse potentials of Planococcus sp. TRC1 in the biodegradation of KL. Preliminary evaluation indicated that the strain was able to grow on broad spectrum of lignin-derived compounds, decolorize lignin-mimicking dyes and catabolize substrates of ligninolytic enzymes. Response surface methodology (RSM) was executed to perform the optimization of different process parameters. The results displayed that Planococcus sp. TRC1 could completely utilize 100 mg L⁻¹ of KL and 78% of 200 mg L⁻¹ of KL as sole source of carbon with concurrent reduction in COD and color. The biokinetic details of KL biodegradation showed that the values of $\mu^{*}$, µ _max, $q^{*}$ and q _max were 0.018 h⁻¹, 0.01 h⁻¹, 0.023 g g⁻¹ h⁻¹ and 0.05 g g⁻¹ h⁻¹, respectively. UV–visible spectrophotometry, SEM and FTIR indicated the significant alterations in the surface morphology, functional groups and chromophores during the course of biodegradation. XRD revealed the emergence of peak signifying the formation of low molecular weight intermediates after bacterial treatment. Considering the environmental impact, bacterial-treated KL illustrated less phytotoxicity using Vigna radiata seed bioassay. These results suggested that Planococcus sp. TRC1 could be a promising strain for the degradation of KL in an ecofriendly way.