Hexanoic acid production from lignocellulosic hydrolysates via simultaneous glucose–xylose utilization by carbon catabolite repression-relaxed Clostridium sp. JS66 with in situ adsorption

초록

Microbial production of hexanoic acid (HA) from lignocellulosic biomass faces key challenges, including inefficient xylose metabolism, carbon catabolite repression (CCR), and product inhibition. To address these limitations, Clostridium sp. JS66 was subjected to adaptive laboratory evolution in xylose medium, enhancing the xylose consumption rate from 0.02 to 0.26 g/L/h, representing a 13-fold improvement. Additional N-methyl-Ń-nitro-N-nitrosoguanidine-induced random mutagenesis generated a CCR-relaxed strain exhibiting simultaneous utilization of glucose and xylose. Whole-genome resequencing identified mutations putatively linked to sugar metabolism. To alleviate product toxicity of HA, SP850 adsorptive resin was introduced for in situ product removal, maintaining a low broth-phase HA concentration. With adsorptive resin, the CCR-relaxed strain produced 22.18 g/L of HA from glucose and xylose with a productivity of 0.15 g/L/h and a yield of 0.33 g/g sugars in serum bottles, and produced 38.63 g/L of HA with a productivity of 0.13 g/L/h and a yield of 0.25 g/g sugars in a 3-L bioreactor at pH 6.0. For practical applications, non-detoxified hydrolysates from silvergrass and pinewood were used as feedstocks. The CCR-relaxed strain metabolized glucose, xylose, arabinose, and mannose with relaxed CCR, producing 20.39 g/L and 20.32 g/L of HA from silvergrass and pinewood hydrolysates, respectively. This study demonstrates that alleviating CCR and mitigating product inhibition through in situ adsorption can provide a sustainable platform for efficient HA production from lignocellulosic feedstocks. © 2026 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC license. http://creativecommons.org/licenses/by-nc/4.0/

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