Biosynthesis and biodegradation of poly(3-hydroxybutyrate) from Priestia flexa; A promising mangrove halophyte towards the development of sustainable eco-friendly bioplastics.

The protracted persistence of petrochemical plastics in the environment and their non-biodegradability impede the survival of living creatures. Recently, biopolymers are being thoroughly researched as a potential replacement for conventional plastics. This present study sought to locate Poly(3-hydroxybutyrate) synthesizing bacterial species prevalent in the mangrove ecosystem. Six halophilic bacterial isolates were obtained from the mangrove habitat, four isolates displayed superior cell dry weight as well as PHB accumulation. Isolate PMPHB5 showed the highest cell dry weight (4.92 ± 0.02 g/L), while the maximum PHA yield (80%) was found with PMPHB7. Hence, PMPHB7 was chosen for further optimization of carbon source wherein glucose demonstrated improved cell growth as well as PHB production. The characterization of the PHB granules was performed by FT-IR spectroscopy and FE-SEM EDX. The presence of characteristic elements in the sample was confirmed using EDX. Isolate PMPHB7 was further identified as Priestia flexa through 16S rRNA gene sequencing (GenBank accession number: ON362236) and a phylogenetic tree was constructed to reveal the molecular relationships of this organism with others. The solvent-cast biopolymer film was made to check the biodegradability of the extracted PHB. When buried in soil, it was found that the biopolymer film exhibited approximately 73% biodegradation after 21 days. Thus, the present study sheds light on the potential of mangrove-associated halophytes to efficiently produce PHB that is readily biodegradable in soil.