Biosynthesis of polyhydroxyalkanoates from polyethylene terephthalate monomers by newly isolated bacterium Kosakonia cowanii EP30

The escalating global environmental burden of polyethylene terephthalate (PET) waste necessitates sustainable bioupcyling process. Here, we report the statistically guided optimization of polyhydroxyalkanoates (PHAs) biosynthesis by Kosakonia cowanii EP30, a newly isolated bacterium from a plastic recycling industry, utilizing PET monomers, terephthalic acid (TPA) and ethylene glycol (EG), as a carbon sources. PHA synthesizing bacterial strains were tested using the two specific dyes Nile Blue A fluorescence stain and Sudan Black B. The PHA positive isolates exhibited bright orange fluorescence and black granules, respectively. Using 16S rRNA sequencing, strain EP30 was identified as Kosakonia cowanii , reported here for the first time for PHA accumulation using PET monomers. By applying the two-step optimization strategy, including Plackett-Burman and Central Composite Design, the key factors related to nutritional and physical parameters were optimized. In the TPA based medium, we achieved a notable PHA yield of 0.17 g/L from a CDW of 2.6 g/L, resulting in a PHA content of 6.53%. On the other hand, for EG-based optimized media, production of 0.13 g/L PHA was achieved from 2.55 g/L CDW showed the presence of 5.09% PHA. This optimization strategy gives roughly threefold improvement as compared to non-optimized conditions. GCMS and FTIR analysis revealed the production of mcl-PHA. Based on the findings obtained in this study, K. cowanii EP30 carry out efficient upcycling of PET monomers to produce biodegradable plastics.