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

• DOI: 10.1016/j.psep.2024.04.016
• Publication Date: 2024-04-05T22:54:05Z
• Authors: Rongrong Xie; Blessing Danso; Jianzhong Sun; Michael Schagerl; Rania Al-Tohamy; Sameh S. Ali
• Keywords: Malachite green; 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. Streptomyces sp. 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.