Inhibition and in situ removal of organic acids during glucose/glycerol co-fermentation by Lactobacillus reuteri

• We studied the effect of lactic acid and acetic acid on metabolism of L. reuteri.
• We analyzed the metabolic flux balance and migration.
• The adsorption properties of weak base anion resin D301G was explored.
• The effect of organic acid removed by resin on metabolism was studied.

Lactobacillus reuteri is a potential strain for the production of 1,3-propanediol and lactic acid due to its good safety. The aim of this work was to study the inhibition of lactic acid and acetic acid during fermentation, and thus, to investigate the effect of their in situ removal on the growth and metabolism of L. reuteri. The analysis of metabolic flux showed that both of lactic acid and acetic acid severely inhibited the fermentation. Only 30.11 mM and 66.85 mM glucose were consumed in 24 h under the initial concentration of 444 mM lactic acid and 415 mM acetic acid, respectively. The activity of the cell was dramatically decreased by the organic acid, furthermore, the production of 1,3-propanediol and lactic acid was impeded. The adsorption properties of anion exchange resin (D301G) were investigated to facilitate the removal of organic acid in situ during fermentation. The resin D301G was added at initial and during fermentation of 12 h, respectively, which showed different function on the metabolism of L. reuteri. Initial addition of resin increased the biomass of fermentation, while the glucose consuming and the 1,3-propanediol producing did not change significantly. The resin added at 12 h promoted the conversion of glycerol to 1,3-propanediol due to the NADH accumulation caused by the metabolic flux migration to acetic acid pathway, while the biomass decreased in small amount.