Production of hexanoic acid from d-galactitol by a newly isolated Clostridium sp. BS-1

Abstract

In a study screening anaerobic microbes utilizing D: -galactitol as a fermentable carbon source, four bacterial strains were isolated from an enrichment culture producing H₂, ethanol, butanol, acetic acid, butyric acid, and hexanoic acid. Among these isolates, strain BS-1 produced hexanoic acid as a major metabolic product of anaerobic fermentation with D: -galactitol. Strain BS-1 belonged to the genus Clostridium based on phylogenetic analysis using 16S rRNA gene sequences, and the most closely related strain was Clostridium sporosphaeroides DSM 1294(T), with 94.4% 16S rRNA gene similarity. In batch cultures, Clostridium sp. BS-1 produced 550 ± 31 mL L⁻¹ of H₂, 0.36 ± 0.01 g L⁻¹ of acetic acid, 0.44 ± 0.01 g L⁻¹ of butyric acid, and 0.98 ± 0.03 g L⁻¹ of hexanoic acid in a 4-day cultivation. The production of hexanoic acid increased to 1.22 and 1.73 g L⁻¹ with the addition of 1.5 g L⁻¹ of sodium acetate and 100 mM 2-(N-morpholino)ethanesulfonic acid (MES), respectively. Especially when 1.5 g L⁻¹ of sodium acetate and 100 mM MES were added simultaneously, the production of hexanoic acid increased up to 2.99 g L⁻¹. Without adding sodium acetate, 2.75 g L⁻¹ of hexanoic acid production from D-galactitol was achieved using a coculture of Clostridium sp. BS-1 and one of the isolates, Clostridium sp. BS-7, in the presence of 100 mM MES. In addition, volatile fatty acid (VFA) production by Clostridium sp. BS-1 from D-galactitol and D: -glucose was enhanced when a more reduced culture redox potential (CRP) was applied via addition of Na₂S·9H₂O.

Isolation, characterization, and quantification of Clostridium kluyveri from the bovine rumen

“…By comparison, an unclassified saccharolytic isolates from sludge, Clostridium sp. strain BS-1 (most closely related phylogenetically to Clostridium sporosphaeroides), has been reported to ferment a mixture of D-galactitol and Na acetate to a maximum concentration of 3 g caproic acid L −1 ; further, caproic acid production was limited by its toxicity to this strain (Jeon et al 2010). Currently, industrial use of caproic acid is modest, primarily as a precursor for synthesis of flavorants.…”

Changing Dietary Calcium-Phosphorus Level and Cereal Source Selectively Alters Abundance of Bacteria and Metabolites in the Upper Gastrointestinal Tracts of Weaned Pigs

“…Another interesting finding was the diet effect on gastric, ileal, and colonic caproate, which differed among gut sites, indicating that different caproate-producing bacteria dominated at the three gut sites. Caproate-producing bacteria can be found within different Clostridium clusters, such as clusters I, IV, XI, and XIV (41)(42)(43)(44)(45).…”

Fermentative production of short-chain fatty acids in Escherichia coli

“…Clostridium sp. BS-1 and Megasphaera elsdenii were used to produce hexanoic acid from D-galactitol and sucrose, respectively (Choi et al, 2013;Jeon et al, 2010). In addition, Clostridium acetobutylicum has been engineered for high-level butyrate production (Jang et al, 2013).…”