Effects of nutritional enrichment on acid production from degenerated (non-solventogenic) Clostridium acetobutylicum strain M5

Abstract

Clostridium acetobutylicum has been used as a microbial platform for the production of butanol, acetone, and butyrate from biomass. This study examined the effect of nutritional enrichment on the production of acetate and butyrate by C. acetobutylicum in culture, and tested whether this nutritional change could shift metabolic flux in these microbial cells. The degenerated (non-solventogenic) C. acetobutylicum M5 strain, which lacks the pSOL1 plasmid that contains genes responsible for solvent production, was cultured in the rich medium, C. acetobutylicum medium 1 (CAM1). As a control, M5 strain was also cultured in clostridial growth medium (CGM). Batch fermentation of M5 strain in CAM1 achieved a cell density of 23.7 (OD 600), which was 2.55 times that obtained when these cells were cultured in CGM. Fermentation in CAM1 yielded volumetric acetate and butyrate productivities of 0.42 g/L/h and 1.06 g/L/h, respectively, which were 2.33 and 1.33 times the values obtained in CGM. Nutritional enrichment also increased the acetate-to-butyrate ratio, which was 0.39 g/g for M5 cells grown in CAM1 and 0.25 g/g for those grown in CGM. These findings demonstrate that the tested nutritional enrichment triggers a metabolic shift in the acid production of a degenerated C. acetobutylicum in culture.

Metabolic Engineering of Escherichia coli for the Production of Hyaluronic Acid From Glucose and Galactose

“…The resulting values were presented as gDCW per liter. Concentrations of glucose and galactose in broth were determined using high performance liquid chromatography (HPLC; 1515, Waters, USA) equipped with refractive index detector (2414, Waters) (Woo et al, 2018). A MetaCarb 87H column (Agilent, USA) was used with a mobile phase of 0.01 N H 2 SO 4 at 25°C at a flow rate of 0.5 mL/min.…”

Sporulation in solventogenic and acetogenic clostridia

“…Even though no consensus on the location, number, or type of mutations causing degeneration exists, the cell physiology of these degenerated strains is similar. Changes in medium composition were reported to prevent (Woo et al 2018 ) or reestablish the solvent and sporulation ability, but the molecular mechanism is still unknown (Lv et al 2016 ).…”

Pathway dissection, regulation, engineering and application: lessons learned from biobutanol production by solventogenic clostridia

“…However, when the accumulation of acids is at a high level, the acidification of the cytoplasm or anion accumulation can dramatically inhibit cell growth and solvent production [141]. Therefore, improving cellular tolerance towards carboxylic acids (acetate and butyrate) could prolong cell growth to achieve a higher cell density and result in synthesis of more acids during the acidogenic stage [142,143], and then increase butanol production at the solventogenic phase [144].…”