Production of electricity and reduction of high-fat diet-induced IL-6 by glucose fermentation of Leuconostoc mesenteroides

Abstract

Electrogenic bacteria can mediate electron transfer to conserve energy and promote growth. To examine bacterial electrogenicity, an L. mesenteroides EH-1 strain was cultured in rich media in the presence and absence of 2% glucose. After 12 h incubation, glucose triggered fermentation of L. mesenteroides EH-1 to produce >10 mmol/l acetate and elicit electricity measured by voltage changes. The electricity production was mediated by glucose fermentation since pre-treatment of L. mesenteroides EH-1 with furfural, a fermentation inhibitor, completely diminished the voltage increases. The deficiency of furfural pre-treated L. mesenteroides EH-1 in electricity production can be restored by the external addition of acetate into the bacterial culture, suggesting the function of acetate as an electron donor. Oral administration of HFD-fed mice with L. mesenteroides EH-1 in the presence or absence of glucose significantly attenuated the high level of pro-inflammatory IL-6 cytokine in blood. Bacterial electricity can be elicited by fermentation. Supplementation of fermenting and electrogenic L. mesenteroides EH-1 may provide a novel approach for the reduction of pro-inflammatory IL-6 cytokine that increased in chronic inflammation, autoimmune diseases, cancers, and infections.

Keywords: Electrogenic; Fermentation; IL-6; L. mesenteroides.

Fig. 1

Glucose fermentation of L. mesenteroides EH-1 produced SCFAs and electricity. (a) L. mesenteroides EH-1 (LM) was incubated in rich media (M) containing phenol red with and without glucose (Glu) for 12 h. The fermentation indicated by color changes of phenol red from red to yellow. (b) Five SCFAs in fermentation media were quantified by GC-MS analysis. (c) Electricity measured by voltage changes (mV) was detected for 300 min after adding media (M) or media with glucose (Glu) alone, L. mesenteroides EH-1 (LM) alone or L. mesenteroides EH-1 plus 2% glucose (M + LM + Glu) on the surface of anode. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2

Inhibition of glucose fermentation impeded electricity production of L. mesenteroides EH-1. (a) Media (M) with L. mesenteroides EH-1 (LM) plus glucose (Glu) in the presence or absence of furfural (F) were cultured for 12 h. The color change of phenol red in culture media of L. mesenteroides EH-1 plus glucose from red to yellow indicated the occurrence of fermentation. (b) L. mesenteroides EH-1 bacteria were pre-treated with or without furfural for 12 h. After pre-treatment, bacteria plus glucose were added onto the surface of anode for measurement of voltage changes (mV) for 300 min. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

Addition of acetate elicited electricity of bacteria pre-treated with furfural. (a) The surface of anode was placed with media (M) containing heat-killed (Killed LM) alone or live L. mesenteroides EH-1 (M + LM) plus acetate (1, 5 or 10 mmol/l). (b) The surface of anode was placed with media containing furfural pre-treated L. mesenteroides EH-1 in the presence or absence of 10 mmol/l acetate.

Fig. 4

Effect of L. mesenteroides EH-1 administration on IL-6 level in HFD-fed mice. Mice were fed with a standard vivarium-provided chow diet (N) or HFD and treated with glucose (Glu), L. mesenteroides EH-1 (LM) or L. mesenteroides EH-1 with glucose by oral gavage. Some mice were fed with HFD and treated with L. mesenteroides EH-1 with glucose in the presence of GLPG-0974 (I). The mean ± SD for three separate experiments with four mice per group was calculated. ∗p < 0.05. ∗∗p < 0.001. (two-tailed t-test).