Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) using agro-industrial effluents with tunable proportion of 3-hydroxyvalerate monomer units.

With increasing concerns about future oil depletion and plastic pollution, bioplastics saw an increasing interest from scientists and industrials. Among bioplastics, the polyhydroxyalkanoates (PHA) are a promising family of polyester which are both biosourced and biodegradable. Biosynthesized by microorganisms, especially bacteria, control of their monomeric composition, and thus their thermal and mechanical properties, is still a challenge to really make tailor-made syntheses. Moreover, one way to decrease the high cost of production is to use waste as substrates for the microorganisms. In this study, a marine bacteria, Halomonas sp. SF2003 was grown on agro-industrial effluents as the sole carbon sources and was able to produce poly(3-hydroxybutyrate) (PHB) with a productivity of 1.3 g·L in 40 h of culture and a number-average molar weight of 342,000 g·mol. With the addition of valeric acid in the substrates, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) with controlled proportion of hydroxyvalerate (HV) monomers were obtained. Their thermal and mechanical characteristics were investigated as a function of HV amount and showed a decrease of the glass transition and melting temperatures and in Young modulus with the HV content increase.