Factors influencing Polyhydroxybutyrate-co-hydroxyvalerate production from Cyanobacteria for biomedical applications

Abstract

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) derived from cyanobacteria is an environmental-friendly biodegradable polymer. The low yield of PHBV production is the main obstacle to the commercial production and the medical applications. Therefore, the manipulation of PHBV production could potentially overcome this obstacle. This doctoral thesis investigated evolutionarily divergent of the cyanobacteria obtained from local habitat of Thailand, including freshwater environments, hot spring areas, and solar saltern fields. Among the tested strains, Synechocystis sp. AARL T020, a hot spring cyanobacterium, showed a high PHBV accumulation rate with a fascinating 3-hydroxyvalerate mole fraction. A two-stage cultivation strategy with multiple organic carbons supplementation was a successful technique in maximizing cyanobacterial PHBV productivity. An optimized medium in the first stage of cultivation provided a 4.9-fold increasing in the biomass production. Subsequently, the addition of acetate, glycerol, and propionate in the second stage of cultivation can induce a significant biomass and the PHBV productivity. With this strategy, the final biomass production and PHBV productivity were increased by 7.0-fold and 14.7-fold, respectively. The GC-MS, FTIR, and NMR analyses confirmed that the obtained PHBV consisted of two sub-units of 3-hydroxyvaryrate and 3-hydroxybutyrate. Interestingly, the cyanobacterial PHBV exhibited lower thermal properties and crystallinity index which generating lower heating demand during the manufacturing process. Additionally, the biological assessment revealed cytocompatibility on 3T3-L1 preadipocyte cells. This research finding triggered the potential of cyanobacteria for the sustainable PHBV production, which could be applied as an alternative polymer for desired applications, such as drug delivery systems for lipoblastoma cancer, or incorporated biomaterial for wound healing.