<i>Bacillus</i> ‐Derived Polyhydroxybutyrate From Nutrient‐Rich Soils: Production, Structural Features, and Immunological Potential

ABSTRACT Polyhydroxybutyrate (PHB) is a biopolymer of growing interest due to its biodegradability and potential applications in biomedical and environmental fields. In this study, spore‐forming Bacillus species were isolated from nitrogen‐ and phosphorus‐rich agricultural soils in Uşak, Turkey, and evaluated for their PHB production capacity, structural characteristics, and potential immune interactions. Eight isolates were confirmed as Gram‐positive, spore‐forming bacilli capable of utilizing sucrose and glucose as carbon sources. PHB accumulation reached up to 87.15 μg/mL in isolate Y1, indicating that these bacteria can synthesize PHB even under nutrient‐rich conditions, likely as a metabolic adaptation to excess carbon and redox imbalance. Fourier‐transform infrared (FTIR) spectroscopy revealed characteristic ester and aliphatic bands consistent with PHB and other polyhydroxyalkanoates, with variations among isolates suggesting differences in polymer crystallinity and purity. In silico analyses predicted low binding affinities to COX‐2, TLR4, and IL‐6R, while molecular dynamics simulations indicated stabilization of protein structures upon PHB interaction. Toxicity predictions highlighted potential nephrotoxicity and blood–brain barrier penetration, but overall immunotoxicity, mutagenicity, and carcinogenicity were negligible. Collectively, these findings demonstrate that Bacillus isolates from nutrient‐rich soils are efficient PHB producers with structurally distinct polymers and a promising biocompatibility profile. These results underscore the potential of these strains for sustainable bioplastic production and advanced biomaterial applications, warranting further in vitro and in vivo validation.