Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) production from engineered Ralstonia eutropha using synthetic and anaerobically digested food waste derived volatile fatty acids

Ralstonia eutropha Re2133/pCB81 is able to utilize various volatile fatty acids (VFAs) (acetate, butyrate, lactate, and propionate) for polyhydroxyalkanoates (PHAs) production. Acetate and lactate resulted in poly(3hydroxybutyrate) P(3HB) production, butyrate in poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P (3HB-co-3HHx), and propionate in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P(3-HB-co-3HV). Various biomass yields i.e. (Y01s, 0.131 +/- 0.02 g/g acetate, 0.221 +/- 0.02 g/g butyrate, 0.222 +/- 0.05 g/g lactate, and 0.225 +/- 0.04 g/g propionate) and PHA yields (Y510, 0.01 +/- 0.001 g/g acetate, 0.11 +/- 0.004 g/g butyrate, 0.03 +/- 0.001 g/g lactate, and 0.18 +/- 0.005 g/g propionate) were observed with the different organic acids. When all the organic acids were mixed together R. eutropha Re2133/pCB81 had the following order of preference; lactate> butyrate> propionate > acetate. A response surface design study showed that in mixtures butyrate is the main organic acid involved in PHA production and acts as a precursor for HHx monomer units to produce copolymer P(3HB-co-3HHx). Food waste ferment (FWF) without any additional nitrogen source and precursors resulted in P(3HB-co-3HHx) accumulation (52 4% w/w with 18.5 3% HHx fraction). (C) 2019 Elsevier B.V. All rights reserved.