Plastic pollution is steadily increasing as a major environmental problem. The global plastic production was approximately 390 million tons in 2021 [1]. It is predicted to exceed 650 million tons by 2050 [2]. The continuous rise in production, excessive usage, inappropriate waste disposal, and poor biodegradation have resulted in the accumulation of synthetic plastics in aquatic and terrestrial habitats [3]. Replacing petroleum-derived plastics with bioplastics is emerging as a sustainable solution in this regard. Bioplastics are polymers derived from biobased renewable resources [4]. Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics that are produced by numerous bacteria under conditions of nutritional stress. Polyhydroxybutyrate (PHB) is the most common and best studied PHA [5]. Physicochemical properties similar to those of conventional plastics make PHB ideal for various industrial applications in the food, pharmaceutical, and agricultural sectors [6], [7]. The commercialization of PHB is essential for developing a circular, bio-economy. Companies such as Biomer (Germany), Bio-on (Italy), Meridian Inc. (USA), and Kaneka Corporation (Japan) are important manufacturers of PHB [8], [9]. Since the production of PHB is increasing, it is expected that the waste volume of PHB-based plastics will be higher in the coming decades. Therefore, research on improving biodegradation, optimization of waste management strategies, and toxicity assessment of PHB degradation products are critically important [10].

Aerobic composting aids in minimizing the buildup of plastic waste derived from PHB [11], [12]. The process of composting involves the biological and thermophilic breakdown of waste into compost, facilitated by microorganisms and macroorganisms. This process necessitates a suitable chemical balance with ideal levels of carbon, nitrogen, and oxygen. The composting process follows a specific temperature pattern of the mesophilic phase (25–40°C), thermophilic phase (35–65°C), followed by the cooling phase and curing phase [13]. In this sense, PHB-degrading microorganisms that can grow under these temperature conditions play an important role in composting. PHB depolymerases (PHBDs) of microbial origin facilitate the biodegradation of PHB in nature [14]. In recent decades, numerous bacteria that produce PHBDs have been identified from different geographic locations [15]. Pseudomonas sp., Shewanella sp., Paenibacillus alvei, Aeromonas caviae, Alcanivorax sp., Ralstonia insidiosa [16], [17], [18], [19], [20], [21] are some of the examples. Molecular cloning and heterologous expression of PHBD genes in different host organisms to enhance the degradation of PHB is another approach that has been implemented. Extracellular PHBD genes from Alcaligenes faecalis AE122 [22], Pseudomonas stutzeri [23], Schlegelella sp. KB1a [24], and Caldimonas manganoxidans [1] have been successfully cloned and expressed in E. coli. On other occasions, PHBDs from the actinomycetes Streptomyces exfoliatus and Streptomyces ascomycinicus have been effectively cloned in Rhodococcus sp. T104 [25], [26].

Another biotechnologically relevant actinomycete, Nocardiopsis, has demonstrated the ability to produce PHBDs. There is an older report on the production of PHBD by N. aegyptia [27]. It has recently been revealed that the marine actinomycete N. dassonvillei (NCIM 5124) could degrade PHB [28]. The whole genome sequence of this organism is available [29], and an entry for a PHBD was noted [28]. To the best of our knowledge, no reports exist on the in vitro synthesis, overexpression, and characterization of PHBD from the genus Nocardiopsis, which prompted the current investigation. In this study, we report (i) phylogenetic relationship of the PHBD derived from N. dassonvillei NCIM 5124 with other PHBDs (ii) synthesis of codon optimized gene in an in vitro manner and its overexpression in E. coli BL21(DE3) (iii) purification of recombinant protein by affinity chromatography (iv) biochemical characterization of the recombinant PHBD (v) molecular docking studies for gaining insights into ligand-protein interactions, and (vi) the ability of the purified recombinant PHBD in degrading films of PHB and PHBVH.