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<p>This study present <i>Achromobacter xylosoxidans</i> RS1 as a facultative bacterium capable of simultaneous lignin modification and direct hydrogen production from untreated food waste—a dual metabolic capability that offers new opportunities for consolidated bioprocessing by <i>Achromobacter</i> species. <i>A. xylosoxidans</i> RS1 achieved 55.2% lignin decolorization over seven days in mineral salt medium, with HPLC detection of the aromatic intermediate ferulic acid (2.2&#xa0;mg/L) confirming active oxidative lignin catabolism. Plate assays revealed robust hydrolytic enzyme activities, including proteases (20.5&#xa0;mm), amylases (17.5&#xa0;mm), xylanases (16.8&#xa0;mm), and cellulases (8.2&#xa0;mm). Whole-genome sequencing produced a 6.58 Mbp draft genome encoding 50 carbohydrate-active enzymes (CAZymes), including one AA10 lytic polysaccharide monooxygenase, five AA3 oxidases, one AA7 oxidase, and seven CE1 esterases. These enzymes support enhanced cellulolytic, xylanolytic, and lignin-modifying activities. Batch dark fermentation experiments demonstrated that <i>A. xylosoxidans</i> RS1 produced hydrogen yields ranging from 0.506 to 0.946&#xa0;mol H₂ mol⁻¹ substrate across xylose, glucose, carboxymethyl cellulose, starch, and untreated food waste. Xylose supported the highest hydrogen production potential (225 mL, 0.735&#xa0;mol H₂ mol⁻¹ substrate) with rapid production kinetics, indicating efficient pentose utilization. In contrast, untreated food waste yielded the maximum molar hydrogen output (165 mL, 0.946&#xa0;mol H₂ mol⁻¹ substrate), attributable to its heterogeneous carbohydrate composition that enhanced enzymatic accessibility and substrate solubilization. These findings indicate that <i>A. xylosoxidans</i> RS1 harbors a functional repertoire of oxidative CAZymes and hydrogen-metabolism pathway, enabling it to valorize food waste into hydrogen. The draft genome provides a valuable resource for further studies on facultative bacteria in waste-to-energy applications.</p>

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Genome analysis of Achromobacter xylosoxidans RS1 reveals carbohydrate-active enzymes linked to lignin modification and dark fermentative hydrogen production from food waste

  • 期刊论文

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  • 发表日期：

    2026年5月6日

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  • Tawaf Ali Shah,
  • Ayesha Ameen,
  • Hani Mohammed Ali,
  • Molalign Assefa

摘要

This study present Achromobacter xylosoxidans RS1 as a facultative bacterium capable of simultaneous lignin modification and direct hydrogen production from untreated food waste—a dual metabolic capability that offers new opportunities for consolidated bioprocessing by Achromobacter species. A. xylosoxidans RS1 achieved 55.2% lignin decolorization over seven days in mineral salt medium, with HPLC detection of the aromatic intermediate ferulic acid (2.2 mg/L) confirming active oxidative lignin catabolism. Plate assays revealed robust hydrolytic enzyme activities, including proteases (20.5 mm), amylases (17.5 mm), xylanases (16.8 mm), and cellulases (8.2 mm). Whole-genome sequencing produced a 6.58 Mbp draft genome encoding 50 carbohydrate-active enzymes (CAZymes), including one AA10 lytic polysaccharide monooxygenase, five AA3 oxidases, one AA7 oxidase, and seven CE1 esterases. These enzymes support enhanced cellulolytic, xylanolytic, and lignin-modifying activities. Batch dark fermentation experiments demonstrated that A. xylosoxidans RS1 produced hydrogen yields ranging from 0.506 to 0.946 mol H₂ mol⁻¹ substrate across xylose, glucose, carboxymethyl cellulose, starch, and untreated food waste. Xylose supported the highest hydrogen production potential (225 mL, 0.735 mol H₂ mol⁻¹ substrate) with rapid production kinetics, indicating efficient pentose utilization. In contrast, untreated food waste yielded the maximum molar hydrogen output (165 mL, 0.946 mol H₂ mol⁻¹ substrate), attributable to its heterogeneous carbohydrate composition that enhanced enzymatic accessibility and substrate solubilization. These findings indicate that A. xylosoxidans RS1 harbors a functional repertoire of oxidative CAZymes and hydrogen-metabolism pathway, enabling it to valorize food waste into hydrogen. The draft genome provides a valuable resource for further studies on facultative bacteria in waste-to-energy applications.