Microbial production of poly(3-hydroxybutyrate) from volatile fatty acids using the marine bacterium Neptunomonas concharum

Volatile fatty acids (VFAs) produced from bioresources are considered as cost-effective and environmentally friendly feedstocks for microbial fermentation. In this study, the suitability of VFAs including acetate, propionate, and butyrate as carbon sources for poly(3-hydroxybutyrate) (PHB) production by Neptunomonas concharum was assessed. In shake-flask culture, N. concharum was found to effectively convert acetate and butyrate to PHB, achieving production titers of 1.81 and 2.69 g/L, respectively. When acetate and butyrate were provided simultaneously, the strain preferentially assimilated butyrate. Unsterile cultivations were conducted to study the possibility of using butyrate in an open cultivation process. N. concharum produced 3.49 g/L PHB with a yield of 0.39 g PHB/g butyrate in shake flask cultivations. In a 5-L bioreactor, the maximal cell dry mass reached 35.07 g/L, containing 15.51 g/L PHB. These results indicate that butyrate is a promising substrate for effective PHB production by N. concharum in open and unsterile fermentation. © 2020 Elsevier Ltd