On the succinic acid production from xylose by growing and resting cells of Actinobacillus succinogenes: a comparison

Succinic acid is a key platform chemical in modern biochemical manufacturing. Optimization of the production of succinic acid production in terms of product titers and economy of resources is of vital importance. In this work, we have studied the succinic acid production by using both produced using growing and resting cells of Actinobacillus succinogenes. First, the process catalyzed by resting cells was enabled by the development of a two-step inoculum strategy which was crucial for the bacterial adaptation to the carbon source. The process was performed in the absence of nitrogen source, disabling cell duplication, and restricting endogenous respiration. While the product yields were almost identical when using growing cells (0.44 g.g(-1)) and cells in resting state (0.43 g.g(-1)); very interestingly, the by-product formation was dramatically reduced when operating with resting cells. Next, the format of resting cells was studied; biofilms were found to be more active than cells in suspension, in terms of specific activity, but the lower cellular concentration in biofilms affected negatively the acid final titers. Finally, a complete and simplified kinetic model was proposed and successfully fitted to the relevant retrieved data of biomass, substrate, products, and by-products both in production with growing and resting cells. These results pave the way for the optimization of succinic acid production processes with reduced nitrogen source consumption, promoting a higher selectivity to the target acid, which facilitates the subsequent downstream separation operations.