Decolorization of lignin-mimicking dyes by Stenotrophomonas sp. CFB-09: Enzyme activity, transformation dynamics and process optimization

Abstract

Increased discharge of dyes into the environment and consequent contamination of water bodies have been issues of public health concern due to the toxicity of dyes. In this study, the ability of Stenotrophomonas sp. CFB-09 to decolorize lignin-mimicking dyes [Congo red (CR), toluidine blue (TB), methyl blue (MB), remazol brilliant blue R (RBBR) and indigo carmine (IC)] and produce ligninolytic enzymes were investigated. Dye decolorization activity was carried out qualitatively on plates and quantitatively by UV–Vis spectrophotometric analysis of broths. Influence of process parameters (initial pH, incubation temperature and media composition) on dye decolorization were also determined. Identification of biodegradation products was done by GC-MS. Results revealed that Stenotrophomonas sp. CFB-09 decolorized dyes by concomitantly producing ligninolytic enzymes and achieved ≥90% decolorization of 25 mg/L CR, MB, RBBR, and IC and 75.0–86.5% decolorization of 100 mg/L of IC, CR and MB at 120 h. Lignin peroxidase exhibited the highest activity among ligninolytic enzymes studied on all dyes. Optimum decolorization for all dyes was achieved at pH 8.0 and 35 °C in the presence of oil palm empty fruit bunch (OPEFB). Findings show that the ligninolytic bacterium, Stenotrophomonas sp. CFB-09 has potentials for application in bioremediation of dye containing effluents.