<i>Pseudomonas oleovorans</i> as a Source of Poly(β-Hydroxyalkanoates) for Potential Applications as Biodegradable Polyesters

TLDR

Pseudomonas oleovorans was cultivated in media containing n‑alkanoic acids (formate to decanoate) as the sole carbon source. The bacterium produced intracellular poly(β‑hydroxyalkanoates) only from hexanoate and longer n‑alkanoic acids, achieving up to 30 % dry‑weight yields on octanoate or nonanoate, with copolymers containing up to six distinct monomers, molecular weights between 90 k and 370 k, and higher‑molecular‑weight polymers from hexanoate/heptanoate, thereby yielding a novel class of biodegradable thermoplastics.

Abstract

Pseudomonas oleovorans was grown in homogeneous media containing n -alkanoic acids, from formate to decanoate, as the sole carbon sources. Formation of intracellular poly(β-hydroxyalkanoates) was observed only for hexanoate and the higher n -alkanoic acids. The maximum isolated polymer yields were approximately 30% of the cellular dry weight with growth on either octanoate or nonanoate. In most cases, the major repeating unit in the polymer had the same chain length as the n -alkanoic acid used for growth, but units with two carbon atoms less or more than the acid used as a carbon source were also generally present in the polyesters formed. Indeed, copolymers containing as many as six different types of β-hydroxyalkanoate units were formed. The weight average molecular weights of the poly(β-hydroxyalkanoate) copolymers produced by P. oleovorans ranged from 90,000 to 370,000. In spite of the higher cell yields obtained with octanoate and nonanoate, the use of hexanoate and heptanoate yielded higher-molecular-weight polymers. These copolyesters represent an entirely new class of biodegradable thermoplastics.