Poly-β-hydroxybutyrate (PHB) production potential of naturally existing cyanobacterial blooms

Detrimental effects imposed by petrochemical plastics on the environment are among the most often discussed concerns in the current era. Although the scientific community has discovered numerous eco-friendly alternatives, the cost of manufacture has restricted the usage of such material. The present study focused on the direct utilization of naturally existing cyanobacterial blooms to extract biodegradable poly-β-hydroxybutyrate (PHB) aiming to minimize the cost of production by eliminating the need for growing of cyanobacterial monocultures. This attempt provides remedies for plastic pollution and hazardous cyanobacterial blooms simultaneously. Fresh cyanobacterial bloom samples were collected from the hypereutrophic Beira Lake, Colombo. They were maintained under in vitro conditions for 7 days, provided with a 12/12 hours light/dark cycle, and deprived of an external supply of nutrients. PHB production was optimized for Nitrogen, Phosphate, and Carbon sources: glucose, sucrose, and lactose. The extracted PHB was quantified by spectrophotometric analysis. Structure confirmation was carried out using FTIR and Raman spectroscopy. The mean percentage weight of PHB yield was 7.13 ± 0.12% w/w. Optimization studies showed that nitrate deficiency and the presence of glucose as an exogenous carbon source imposed a stimulatory effect for PHB accumulation by cyanobacteria. The maximum amount of PHB (9.6% w/w) was found to be accumulated by cyanobacteria on the fourth day following the bloom sample collection. Hence, the present study proposes a sustainable utilization method of cyanobacterial blooms as a promising source for PHB production.