Biodegradative capacity of Bacillus megaterium and Ralstonia solanacearum on biodegradation of P(3HB) films in simulated soil

Abstract

Poly(3-hydroxybutyrate) is a microbial biodegradable bioplastic that has been used as a substitute for petrochemical-based plastics. It complete degradates in a microbiological environment containing microorganisms with biodegradative capacity, being its identification important to the comprehension of the biodegradation process. In addition, new methodologies that are closer to a natural microenvironment increase the reliability of the experiment. In this context, the present study analyses the degradation capacity of the Brazilian strains Ralstonia solanacearum RS and Bacillus megaterium CN3 on biodegradation of P(3HB) synthesized by Ralstonia solanacearum RS and commercial P(3HB). It was conducted under greenhouse conditions and P(3HB) production was performed in a bioreactor before extraction. Films were buried in the soil and removed at 20, 40, 60, 80, and 100 days intervals and analyzed by biodegradation percentage and differences in macro and microstructural characteristics. After 100 days of the experiment, the most degraded P(3HB) was the one produced by R. solanacearum RS, completely degraded (100%) in non-sterile soil. In addition, B. megaterium CN3 proved to be a potential degradative microorganism, degrading 88% of P(3HB)RS in sterile soil. The macroscopic analysis showed surface modifications over time, including cracks, holes, gradual mass loss and color changes. Microscopic analysis demonstrates the increase in the pore size and cracks confirming the steps of biodegradation. Therefore, the experiment proved to be able to simulate viable conditions for the growth of microorganisms and to evaluated the biodegradation capacity of bacteria.