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Optimization of the glycerol bioconversion into 3-hydroxypropionic acid (3-HP) by Lactobacillus reuteri in bioreactor

Abstract : 3-Hydroxypropionic acid (3-HP) is a platform molecule whose biological production involves the bacterium Lactobacillus reuteri, according to a two-step process: a growth phase in batch mode on glucose, then a glycerol bioconversion into 3-HP in fed-batch mode. With the objective of improving the 3-HP bioproduction, the thesis aims at (1) identifying the nutritional and environmental conditions implemented during the growth phase to improve the subsequent production of 3-HP and (2) searching the operating conditions during the bioconversion phase that increase the 3-HP bioproduction performance. Growth conditions that influence the subsequent 3-HP production were determined using a Plackett and Burman experimental design involving 11 factors. Supplementing the growth medium with vitamin B12 and cysteine showed a negative effect on this subsequent production. The addition of glucose, phytone peptone, Tween 80, 1,2-propanediol and betaine to the culture medium, combined with an optimal pH of 6 during growth, enhanced the subsequent production of 3-HP and the bioconversion duration. The addition of yeast extract and the type of neutralizer showed no significant effect. However, since these results were obtained at a glycerol feeding rate value set at 0.5 g h-1, the process improvement was limited. The bioconversion conditions were then studied according to a central composite rotatable design that allowed testing various pH levels and specific glycerol feeding rates. By establishing response surfaces, optimal conditions have been identified, that were different depending on the considered variable (concentrations, yields, rates). Additional validation experiments made it possible to verify the relevance of the selected conditions, with a significant improvement of the bioprocess productivity by 96 %. Finally, intracellular pH and energy level were proposed to explain the degradation of 3-HP production ability.
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Submitted on : Friday, October 22, 2021 - 4:31:25 PM
Last modification on : Friday, August 5, 2022 - 2:41:13 PM
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  • HAL Id : tel-03396301, version 1

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Thi Lan Phuong Nguyen. Optimization of the glycerol bioconversion into 3-hydroxypropionic acid (3-HP) by Lactobacillus reuteri in bioreactor. Bacteriology. Université Paris-Saclay, 2021. English. ⟨NNT : 2021UPASB016⟩. ⟨tel-03396301⟩

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