Insight into effects of long-chain fatty acids on propionic acid production in anaerobic fermentation: A case study of oleic acid and palmitic acid

This study revealed long-chain fatty acids(LCFAs) on propionic acid production by lipid anaerobic acidogenesis. Oleic acid and palmitic acid, the two most common LCFAs, were added into the acidogenic system to evaluate LCFAs type and concentration on the propionic acid production capacity. The results showed that when the concentration of oleic acid was 4 g/L, the content of volatile fatty acids(VFAs) was 1.3 times higher than that of the blank group(propionic acid was the main product, >70%). In contrast, palmitic acid and excess oleic acid inhibited propionic acid production(butyric acid was the main product). Propionic acid-producing bacteria were the dominant bacteria in an oleic acid production system. According to response surface analysis, the optimal concentration of oleic acid favoring for propionic acid production was 2.3 g/L and fermentation time was 7.4 days in this study. The results showed that a proper concentration of oleic acid has a promotion to propionic acid production. This study provides a theoretical basis for oleic acid to promote propionic acid production.