Glycerol and glucose co-fermentation by 1,3-propanediol producer Limosilactobacillus reuteri: A kinetic study of batch and continuous cultivations

The conversion of glycerol into 1,3-propanediol (1,3-PDO) has gained significant attention as a sustainable pathway within the biodiesel production chain. Limosilactobacillus reuteri, a bacterium capable of efficiently converting glycerol to 1,3-PDO, holds promise for this application. In industrial biotechnology, the development of kinetic models is important for bioreactor design, process analysis and scalability, supporting the advancement of biorefineries and the bioeconomy. This study focuses on investigating the kinetics of co-fermentation of glucose and glycerol by L. reuteri, utilizing data from previous batch culture experiments. Three different models were evaluated for these batch runs, and the parameters were adjusted using the Levenberg-Marquardt algorithm in conjunction with an integration method. The results from these previous batch experiments indicate that pH did not significantly influence the specific growth rate of the bacterium. However, as expected, reducing the temperature from 37 to 30(degrees)C resulted in a 60% reduction in the growth rate. Moreover, continuous co-fermentation experiments were conducted, and a simple kinetic model was proposed. The advantage of the continuous process is that the productivity of 1,3-PDO is 3.5 times higher compared with co-fermentation in batch mode. Notably, this study represents the first attempt to model continuous co-fermentation under a range of dilution rates (0.25-0.9 h(-1)), identifying a dilution rate of 0.5 h(-1) as the optimal condition to produce 1,3-PDO, considering productivity and substrate conversion. The findings of this research contribute valuable insights for future investigations on the viability of 1,3-PDO production from glycerol, particularly within the context of waste valorization.