| Summary: | The buffalo is an amazing ruminant. Its ability to degrade lignin, which has been recently reported, is most likely due to unique rumen microorganisms with lignin-degradation potential. Our goal was to explore the lignin-degradation potential of ruminal microorganisms, in which ligninolytic enzyme encoding genes were involved to provide ideas for revealing the mechanism of lignin degradation by buffalo. In this study, a bacterium strain identified as <i>Bacillus cereus</i> AH7-7 was isolated from the buffalo (<i>Bubalus bubalis</i>) rumen. After whole-genome sequencing, the results demonstrated that <i>B. cereus</i> AH7-7 had laccase, cytochrome P450 and vanillin alcohol oxidase-encoding genes. Sixty-four genes of <i>B. cereus</i> AH7-7 were involved in multiple aromatic metabolic pathways, such as phenylalanine metabolism and aminobenzoate degradation. A positive reaction resulting in guaiacol medium indicated that laccase secretion from <i>B. cereus</i> AH7-7 increased with time. A biodegradation experiment revealed that a significant reduction in kraft lignin content (25.9%) by <i>B. cereus</i> AH7-7 occurred at the end of 6 days of incubation, which confirmed its lignin-degradation capacity. Overall, this is the first report showing that <i>B. cereus</i> AH7-7 from the buffalo rumen can degrade lignin, and revealing the encoding genes of lignin-degrading enzymes from genome level.
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