Biosynthesis, property comparison, and hemocompatibility of bacterial and haloarchaeal poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Polyhydroxyalkanoates (PHAs) are a class of natural biopolyesters accumulated intracellularly by many microorganisms. These polymers have attracted particular attention as green plastic in biomedical and industrial applications due to their good biodegradability and biocompatibility. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is one of the most common members of PHAs. However, there is no report comparing the properties of PHBV from different groups of producers, e.g., bacteria and haloarchaea. In this study, two types of PHBV copolymers were synthesized in Halogranum amylolyticum and Ralstonia eutropha, respectively, by feeding different carbon sources. They possessed a similar concentration of 3HV monomers (21 mol%) and were named PHBV-H (produced by H. amylolyticum) and PHBV-B (produced by R. eutropha) based on their source. Interestingly, they exhibited different behaviors especially in thermal stability, melting temperature, crystallinity percentage, and mechanical properties. Furthermore, the films of PHBV-H and PHBV-B possessed different surface properties, such as surface roughness, wettability, and surface free energy. The value of hemolysis on the PHBV-H film was lower in comparison with the PHBV-B film, although both values were within the limit of 5% permissible for biomaterials. Notably, few inactivated platelets adhered to the surface of the PHBV-H film, whereas numerous activated platelets were seen on film PHBV-B. These results indicated that PHBV-H was a better potential component of blood-contact biomaterials than PHBV-B. Our study clearly revealed that the properties of PHAs are source dependent and haloarchaeal species provide a new opportunity for the production of desired PHAs.