Prospect of Synechocystis sp. PCC 6803 for synthesis of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

Abstract

The rapidly growing use of petroleum-based plastics is contributing to severe environmental pollution, thereby putting the environment to a hard test. Research for alternative plastics is essential to substitute conventional plastics with a certain grade of biodegradability. One such potential material to replace petrochemical-based plastics is microbially originated polyhydroxyalkanoates. Among them, poly-β-hydroxybutyrate (PHB) is the most common and well-characterized member. However, studies demonstrate that the properties of PHB such as brittleness, low extension-to-break, and lack of flexibility limit its possible application whereas; copolymers have the properties which can overcome the limitations of PHB. In this study, Synechocystis sp. PCC 6803, a unicellular, non-diazotrophic cyanobacterium has been found to accumulate poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer under nitrogen and phosphorus-deficient conditions either using γ-butyrolactone alone or along with acetate as carbon source. The maximum copolymer accumulation i.e. 37.64% dry cell weight was recorded when the cultures were supplemented with 0.4% acetate and 0.01% γ-butyrolactone. The purity and mole fraction of the polymer was confirmed by proton nuclear magnetic resonance and fourier transform infrared spectroscopy. The material properties were assessed and found comparable with other polymers from bacteria and cyanobacteria. Thus, the test organism has the potential to be utilized for large scale biopolymer production and applications in various fields.