Biodegradation of polyhydroxyalkanoate film in soil: a sustainable approach for bioplastic management

Polyhydroxyalkanoate (PHA) is a sustainable bioplastic biomaterial primarily produced by microorganisms and has demonstrated the ability to produce PHA. This work aims to characterize PHA derived from the novel biosurfactant-producing bacterium isolated from an industrial site, Bacillus cereus ST001. A comprehensive investigation of the time-dependent degradation of PHA film by novel microorganisms isolated from contaminated industrial sites under natural soil conditions has received little attention. In this context, the environmental biodegradability of B. cereus ST001, which produces PHA films, in typical natural soil settings was also studied. Microscopic examination, employing dyes, confirmed the presence of PHA, and molecular analysis indicated the presence of the PHA synthase gene (phaC) and PHA depolymerase gene (phaZ) genes. The extracted PHA was analyzed using Fourier transform infrared spectroscopy (FTIR) and ¹H nuclear magnetic resonance (NMR) spectroscopy, revealing characteristics similar to those of a homopolymer of PHA, specifically polyhydroxybutyrate (PHB). The polymer was stable up to 150 °C and showcased 64% crystallinity. The polymeric film showed a degradation rate of 80% of the initial film biomass after 180 days of incubation in soil. These findings highlight the potential of B. cereus ST001 as a dual-purpose strain for PHB biosynthesis and degradation, shedding light on the future of bioplastics and sustainable waste management techniques. This aligns with the concept of a circular economy and sustainable production and consumption patterns.