Polyhydroxyalkanoates (PHAs) are biodegradable polymers with immense potential in addressing the global plastic pollution crisis and advancing sustainable bioplastics production. Among the various microbes known for PHA production, extremophilic bacteria possess unique capabilities to thrive under extreme conditions, making them attractive candidates for PHA synthesis. Furthermore, the utilization of renewable feedstocks for PHA production aligns with the growing demand for sustainable bioplastic alternatives. A diverse range of extremophilic bacteria, especially halophiles and thermophiles, has provided cost-competitive platforms for producing customized PHA polymers. Extremophilic bacteria offer unique advantages over mesophiles due to their contamination resistance, high cell density growth, and unique culture conditions. The current status of Halomonas spp. as a chassis further allows exploration of metabolic engineering approaches to overcome the challenges associated with current industrial biotechnology. This article especially focuses on extremophilic bacteria and explores recent advances in utilizing renewable feedstocks such as lignocellulosic biomass, agro-industrial residues, and waste streams for PHA production. The integration of biorefinery concepts and circular economy principles in PHA manufacturing is also examined. This review is an attempt to provide an understanding of renewable substrates as feedstocks and emerging trends in PHA production by extremophilic bacteria. It underscores the pivotal role of extremophiles and sustainable feedstock sources in advancing the feasibility and eco-friendliness of PHAs as a promising biopolymer alternative.

Polyaromatic hydrocarbons (PAHs) are a group of organic pollutants commonly found in the environment due to industrial activities, incomplete burning of fossil fuels, and oil spills. Bioremediation of PAHs has emerged as a promising approach. This study investigated the biodegradation of PAHs (anthracene, naphthalene, phenanthrene, anthraquinone, and anthrone) at 100 ppm to 1000 ppm in the presence of glucose and glycerol by a biosurfactant-producing strain of Pseudomonas aeruginosa NG4. The quality of the biosurfactant produced by the bacterial strain was analyzed via emulsion index (E24), drop-collapse assay, and oil displacement assay. The PAH degradation efficiency was studied by HPLC and degradation metabolites were analyzed using GC-MS. Among all five PAHs (fed at 300 ppm), the highest degradation rates of 91.16 ± 3.64% naphthalene and 41.16 ± 1.64% anthrone were observed by P. aeruginosa NG4 after 10 days of incubation. The assessment of degradation intermediate metabolites revealed the PAH catabolism via the dioxygenase route, which plays a key role in the breakdown of these aromatic compounds. Biodegradation of anthrone by P. aeruginosa NG4 at a 300 ppm level in the media was reported for the first time. This study highlights the potential of P. aeruginosa NG4 as a candidate for the development of bioremediation strategies to mitigate environmental pollution caused by persistent organic pollutants like PAHs.