Fractionation of medium-chain-length polyhydroxyalkanoate biosynthesized by pilot-scale production for improving material properties

Abstract

Medium-chain-length polyhydroxyalkanoate (MCL-PHA), a biodegradable and biocompatible material, is a biopolyester that obtains great attention, especially in the medical area. By focusing on a range of fractions of MCL-PHA, a clear understanding of the thermal behavior and the crystalline structure, especially the tensile properties, have been gained. In this study, we successfully biosynthesized the MCL-PHA in 300 L pilot-scale fermentation by Pseudomonas putida, and all the chemomechanical properties have been characterized. The obtained MCL-PHA (A-original) was fractionated by using a chloroform/methanol mixture into several fractions (A-1, A-2, A-3, and A-4) with different comonomer compositions consisting of 3-hydroxydecanoate (3HD), 3-hydroxyoctanoate (3HO), and 3-hydroxyhexanoate (3HHx). It is crucial to demonstrate the mechanical characteristics of the MCL-PHA fraction in this area of application, which has not previously been studied. We found that the fractions of natural MCL-PHA exhibited distinctive thermal properties with different crystalline patterns, giving rise to the overall behavior of the as-produced MCL-PHA blend primarily dependent on a fraction of high 3HD content. It can be concluded that there are 2 fractions (A-2 and A-3) that have more strength and flexibility than the as-produced MCL-PHA (A-original), indicating that these fractions are suitable for use as medical elastomers.