Environmental conditions during glycerol bioconversion affect 3‐hydroxypropionic acid bioproduction by Limosilactobacillus reuteriDSM 17938

Abstract 3‐Hydroxypropionic acid (3‐HP) is a platform molecule whose biological production was carried out by the bacterium Limosilactobacillus reuteri according to a two‐step process: first, a growth phase in batch mode on glucose, then a glycerol bioconversion into 3‐HP in fed‐batch mode. With the objective of improving 3‐HP bioproduction, this study aimed at defining the operating conditions during the bioconversion phase that increases the bioproduction performance. A central composite rotatable design 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 output variable (final 3‐HP quantity, 3‐HP production yield and production rate). Of them, 3‐HP final quantity and 3‐HP production yield were maximized at pH 6.0 and at specific glycerol feeding rates of 60 and 55 mg gly g CDW −1 h −1 , respectively. The specific 3‐HP production rate was the highest at the upper limit of the specific substrate feeding rate (80 mg gly g CDW −1 h −1 ) but was not affected by the pH. An additional experiment was carried out at pH 6.0 and a specific glycerol feeding rate of 80 mg gly g CDW −1 h −1 to validate the previous observations. In conclusion, the results showed a significant improvement of 3‐HP concentration by 13%, of specific production rate by 34% and of 3‐HP volumetric productivity by 39%, as compared to the initial values.