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 10
10 to 10
7 and 10
8 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 ¡À 15 mM glycerol within 2 h, similar to the rates under control conditions without bisulfite (501 ¡À 22 mM). Furthermore, cells from the production with bisulfite were still biological active after 3 consecutive production cycles, converting in total 974 ¡À 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 ¡À 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.
