Evolutionary engineering and chemical mutagenesis of Propionibacterium acidipropionici for improved propionic acid production from sugarcane-derived saccharides

Propionic acid (PA) is a 3-carbon carboxylic acid widely used in the chemical, food and pharmaceutical industries. Current production of PA is primarily via petrochemical routes and alternative sources using renewable feedstocks are desirable. The goal of the present study was to develop bacterial strains for efficient PA production by fermentation of sugarcane-derived saccharides in inverted sugarcane syrup. Adaptive evolution and random chemical mutagenesis of Propionibacterium acidipropionici were individually evaluated. Although evolutionary engineering proved to be a suitable strategy for producing strains tolerant to acid stress, chemical mutagenesis coupled with a novel screening methodology proved to be a superior strategy for strain improvement. The selected strain presented high PA productivity (0.55 g L−1 h−1) and titer (40 g L−1) in relation to the parental strain (0.38 g L−1 h−1 and 27 g L−1, respectively), in fermentations using inverted sugarcane syrup.