RESUMO
The influence of environmental factors such as glycerol concentration, time of production, presence of Escherichia coli, and two different strains of Lactobacillus reuteri (ATCC 55730 and ATCC 53608) on 3-hydroxypropionaldehyde (3-HPA) production was analyzed. Additionally, the influence of those factors on gene expression in the 3-HPA production pathway was evaluated. The genes studied were GldC, cbiP, and Lreu_1734. The results of this study showed that the principal environmental factors that influence 3-HPA production are glycerol concentration and Lactobacillus reuteri strain. As glycerol concentration increased, 3-HPA content increased. The greatest 3-HPA concentration (56.6 mM ±5.99) was achieved by L. reuteri ATCC 55730. Gene expression was also affected by environmental factors. Factor that showed the greatest influence were also strain and glycerol concentration. The genes cbiP, GldC, and Lreu_1734 had basal gene expression in glycerol absence; however, glycerol regulated its expression. Glycerol induced overexpression of cbiP and GldC genes (Strain ATCC 53608), probably to ensure its efficient utilization. On the contrary, glycerol concentration suppressed Lre_1734 expression in both analyzed strains, as a mechanism for 3-HPA accumulation. Down-regulation was observed in all the genes tested in strain ATCC 55730, probably due to feedback inhibition by 3-HPA.