Culture conditions during growth of Lactobacillus reuteri DSM 17938 affect the ability of cells to produce 3-hydroxypropionic acid by glycerol bioconversion
Résumé
Objectifs/Objectives In the framework of bioeconomy, 3-hydroxypropionic acid (3-HP) is gaining interest due to its desirable industrial applications. Among non-GMO microorganisms naturally able to produce 3-HP, L. reuteri is a promising candidate thanks to its ability to produce 3-HP from glycerol, a by-product in biodiesel manufacturing industries [1]. Owning the G.R.A.S. status, the bacteria can synthesize vitamin B12, an essential co-factor for the first enzyme of the bioconversion metabolic pathway. Moreover, it does not consume glycerol as a carbon source, thus avoiding the by-products that can hinder conversion yield and further in situ extraction [2]. The 3-HP production is achieved by a 3-stages process: cell growth, biomass harvesting and concentration and bioconversion that is performed by the resting cells supplied by glycerol in fed-batch mode. However, the 3-HP synthesis leads to an inhibition of the producing cells, thus justifying the necessity of improving their physiological state [1]. In such context, this work deals with a better understanding of the effect of culture conditions on L. reuteri growth and bioconversion performances. Matériels et Méthodes/Materials and methods A Plackett-Burman experimental matrix was designed to test the effects of 11 growth factors on the growth and bioconversion ability of L. reuteri DSM 17938: glucose, yeast extract, phytone-peptone, 1,2-propanediol (1,2-PDO), cysteine, betaine plus KCl, Tween 80, vitamin B12, pH, base solution and temperature. Statistical analyses were performed to identify the significant effects at 95% to 99,9% confidence intervals for coefficient estimations. Résultats principaux/Main Results Among the studied factors, pH, yeast extract, cysteine, base solution did affect neither the growth nor the ability to produce 3-HP. Meanwhile, the presence of 1,2-PDO and higher glucose concentration in growth medium led to higher biomass concentration. In contrary, lower cultivation temperature negatively affected the growth.