Harnessing the potential of a novel lignin-degrading Streptomycessp. MS-S2 from wood-feeding termite for malachite green decolorization and detoxification

Lignin and synthetic dyes share complex structural similarities and relevant management difficulties, which should be effectively addressed towards environmental sustainability. Under this scope, the quest for oxidative enzyme-producing microorganisms with a view to efficiently valorizing organic pollutants is of utmost importance. The intestinal bacteria of wood-feeding termites represent a unique source of valuable enzymes. The decolorization efficiency of five different dyes, including malachite green (MG), methyl violet, anihiline blue, reactive red, and reactive blue, after 12 h of degradation by the MS-S2 bacterial strain was recorded to be 98.2, 17.5, 8.7, 4.6, and 3.28%, respectively. Several physico-chemical parameters were then optimized to accelerate MG degradation, including pH, temperature, glucose, and yeast extract concentration. Streptomycessp. strain MS-S2 completely decolorized MG (50 mg/L) within 2 h under optimized conditions when the cultivation medium was amended with 5 g/L glucose and 0.08 g/L yeast extract at pH 8 and incubated at 28 °C. After MG degradation, the enzyme activities of manganese peroxidase (4.605 U/L) and laccase (45.185 U/L) were estimated. To comprehend the degradation process of MG by the MS-S2 strain, UV-Vis spectroscopy, Fourier transform infrared (FTIR), and gas chromatography-mass spectrometry (GC-MS) analyses were carried out to ascertain the possible degradation mechanism. The metabolites identified, such as 2,6-Bis (tert-butyl) phenol and [4-(dimethylamino) phenyl] phenyl, suggest that MG was broken down into less toxic compounds for further degradation. MS-S2 exhibited outstanding characteristics that could make it suitable for the bioremediation of MG dye in an industrial setting.