Towards an extractive bioconversion of 3‐hydroxypropionic acid: study of inhibition phenomena

Abstract BACKGROUND 3‐hydroxypropionic acid (3‐HP) microbial synthesis through glycerol bioconversion by Lactobacillus reuteri is at the moment characterized by too low performances to consider production at industrial scale. To avoid its toxic accumulation in the medium and to recover this molecule of interest, 3‐HP in situ reactive extraction from bioconversion broth was investigated using a hollow fiber membrane contactor (HFMC) in order to intensify its production. The so‐called integrated system was compared with the conventional bioconversion system. The impact of the extractive bioconversion on the overall production performance and on cell physiological state was studied. RESULTS Results underlined drastic inhibitory effects on the producing bacteria, especially under extractive bioconversion conditions despite the use of a HFMC supposed to avoid direct contact between organic phase and bacteria. Indeed, the extractant phase components (trioctylamine in n ‐decanol) were found to be toxic for the cells (due to solubility and by direct contact). These phenomena were increased by the presence of 3‐hydroxypropionaldehyde (3‐HPA) and 3‐HP produced during glycerol bioconversion. These cumulative effects induced complete loss of the cell membrane integrity and esterase activity after 1.5 h of extractive bioconversion. When the bioconversion was conducted alone, the bacterial inhibition was lower, as around 50% of L. reuteri cells remained active with unaltered membrane after 3 h. Hypotheses concerning the mechanisms of action of the observed inhibitions were proposed and discussed. CONCLUSIONS This work highlighted the importance of performing such an integrative approach to address specific questions prior to the optimization of the whole process. © 2017 Society of Chemical Industry