Bisulfite as scavenger for enhanced biotechnological production of 3-hydroxypropionaldehyde by Lactobacillus reuteri

• Specific yield of 3-HPA is high with cells from the early stationary phase.
• Sulfite and 3-HPA are both toxic for Lactobacillus reuteri.
• The 3-HPA-Sulfite adduct is not toxic for L. reuteri.
• Use of sulfite to scavenge 3-HPA during production increases specific yield.

Lactobacillus reuteri converts glycerol into 3-hydroxypropionaldehyde (3-HPA), a promising preservative and chemical precursor. Production of 3-HPA by L. reuteri is limited due to the toxicity of 3-HPA to the producing cells. To circumvent this toxicity, the suitability of bisulfite as 3-HPA scavenger during production was assessed. Concentrations of 400 mM 3-HPA or bisulfite caused a viable cell number decrease from 1010 to 107 and 108 cells/ml, respectively, in 1 h. In contrast, the 3-HPA-bisulfite adduct was not toxic for the cells.Cells exhibiting high specific 3-HPA yield in a standardized glycerol conversion test were used to test bisulfite as scavenger during 3-HPA production. Addition of bisulfite (pH 5.8) after 2, 25, and 50 min resulted in conversion of 591 ± 15 mM glycerol within 2 h, similar to the rates under control conditions without bisulfite (501 ± 22 mM). Furthermore, cells from the production with bisulfite were still biological active after 3 consecutive production cycles, converting in total 974 ± 8 mM glycerol in 4 cycles, whereas cells from the control virtually lost their capability to utilize glycerol after two cycles and converted 695.5 ± 3.5 mM.Our results demonstrate the suitability of bisulfite to scavenge 3-HPA to obtain high yields during biotechnological production by the food grade microorganism L. reuteri.