Enzymatic and genetic characterization of lignin depolymerization by Streptomyces sp. S6 isolated from a tropical environment

• Published in: Scientific reports Vol. 10; no. 1; p. 7813
• Main Authors: Riyadi, Fatimah Azizah, Tahir, Analhuda Abdullah, Yusof, Nurtasbiyah, Sabri, Nurul Syazwani Ahmad, Noor, Megat Johari Megat Mohd, Akhir, Fazrena Nadia M. D., Othman, Nor’azizi, Zakaria, Zuriati, Hara, Hirofumi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.05.2020; Nature Publishing Group
• Subjects: 45/23; 45/47; 631/326/2522; 631/61/168; Alcohol oxidase; Alcohol Oxidoreductases - genetics; Aromatic compounds; Aryl-alcohol oxidase; Biodegradation; Biodegradation, Environmental; Biofuels; Biomass; Butyric acid; Carbon sources; Chromatography; Depolymerization; Dodecane; Ethanol; Ethanol - metabolism; Gas chromatography; Genomes; Guaiacol; Humanities and Social Sciences; Laccase; Laccase - genetics; Lignin; Lignin - chemistry; Lignin - genetics; Lignin - metabolism; Lignin peroxidase; Mass spectrometry; Mass spectroscopy; Mineralization; Molecular weight; multidisciplinary; Peroxidase - genetics; Peroxidases - genetics; Polymerization; Science; Science (multidisciplinary); Streptomyces; Streptomyces - enzymology; Streptomyces - genetics; Tropical environment; Tropical environments
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-020-64817-4

The conversion of lignocellulosic biomass into bioethanol or biochemical products requires a crucial pretreatment process to breakdown the recalcitrant lignin structure. This research focuses on the isolation and characterization of a lignin-degrading bacterial strain from a decaying oil palm empty fruit bunch (OPEFB). The isolated strain, identified as S treptomyces sp. S6, grew in a minimal medium with Kraft lignin (KL) as the sole carbon source. Several known ligninolytic enzyme assays were performed, and lignin peroxidase (LiP), laccase (Lac), dye-decolorizing peroxidase (DyP) and aryl-alcohol oxidase (AAO) activities were detected. A 55.3% reduction in the molecular weight (Mw) of KL was observed after 7 days of incubation with Streptomyces sp. S6 based on gel-permeation chromatography (GPC). Gas chromatography-mass spectrometry (GC-MS) also successfully highlighted the production of lignin-derived aromatic compounds, such as 3-methyl-butanoic acid, guaiacol derivatives, and 4,6-dimethyl-dodecane, after treatment of KL with strain S6. Finally, draft genome analysis of Streptomyces sp. S6 also revealed the presence of strong lignin degradation machinery and identified various candidate genes responsible for lignin depolymerization, as well as for the mineralization of the lower molecular weight compounds, confirming the lignin degradation capability of the bacterial strain.