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. 2025 Feb:418:131952.
doi: 10.1016/j.biortech.2024.131952. Epub 2024 Dec 4.

Caproic acid production is linked to biomass activity during xylose fermentation

Iglesias-Riobó J  1 , Mauricio-Iglesias M  2 , Carballa M  2
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Free article

Caproic acid production is linked to biomass activity during xylose fermentation

Iglesias-Riobó J et al. Bioresour Technol. 2025 Feb.
Free article

Abstract

This study aims at addressing inconsistencies in literature regarding the organic loading rate (OLR) and hydraulic retention time (HRT) effect on caproic acid production, using biomass activity as an indicator. Xylose was fully consumed in the reference CSTR and SBR (HRT = 1-day; OLR = 12 gCOD/(L·d)), but different caproic acid yields (0.02 vs 0.11 Cmol/Cmol-s) were observed, which was linked to differences in biomass activity (12 vs 3.5 g/(g VSS·d)). At HRT 0.5 days, xylose conversion was incomplete and lactic acid and ethanol appeared, reducing caproic acid production. However, increasing xylose concentration in the feeding to 24 g COD/L did not change the caproic acid yield (0.12 Cmol/Cmol-s), which was explained by similar biomass activity as in the reference SBR (4.8 g/(g VSS·d)). These findings indicate that the SBR is the optimal configuration, since it allows maintaining a low biomass activity and therefore a high caproic acid yield.

Keywords: CSTR; Hydraulic retention time; Organic loading rate; SBR; Solid retention time.

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Conflict of interest statement

Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: [Marta Carballa reports financial support was provided by European Regional Development Fund. Juan Iglesias-Riobó, Miguel Mauricio Iglesias and Marta Carballa report financial support was provided by Xunta de Galicia. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper].

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