Endospore bioaugmentation accelerates and stabilizes biodegradation of poly(butylene succinate-co-adipate) in seawater

• Deep-sea Bacillus 1589B3-3 rapidly hydrolyzes PBSA in seawater. • Endospore embedding accelerates marine PBSA mass loss by eight times. • Bioaugmentation resolves site-dependent variability in PBSA biodegradation. • Indigenous marine microbes rapidly mineralize the released hydrolysates. The biodegradability of poly(butylene succinate- co -adipate) (PBSA) in marine environments is highly variable, depending on site and season. To address this, we aimed to enhance and stabilize the PBSA degradation rate by introducing PBSA-degrading endospore-forming bacterium through bioaugmentation. The isolated strain 1589B3-3 degraded PBSA films in both marine mineral medium and artificial seawater supplemented with yeast extract media, breaking them down into water-soluble organic compounds, some of which were further metabolized. In a biochemical oxygen demand biodegradation test using seawater, these compounds showed 64.9% biodegradability after 10 days. The mass loss rate of endospore-embedded PBSA films immersed in sterile artificial seawater was approximately eight times greater than that of PBSA films without endospores. These results suggest that once the endospores of strain 1589B3-3 embedded in a PBSA film germinate, the polymer undergoes enzymatic hydrolysis, and the resulting hydrolysates are readily mineralized in seawater, presumably by the indigenous microbial community. This approach thereby improves the robustness of PBSA biodegradation in marine environments.