Screening and characterization of novel lipase producing Bacillus species from agricultural soil with high hydrolytic activity against PBAT poly (butylene adipate co terephthalate) co-polyesters

The use of poly (butylene adipate-co-terephthalate) (PBAT) has increased widely but PBAT-degrading bacteria have rarely been studied. During this study, we used farm soil (Shaanxi (yuan Jia cun)) to isolate and identify PBAT-degrading bacteria (Bacillus strains). We then accessed the effect of growth factors on PBAT degradation as well as the lipase activity of PBAT-degrading bacteria. Most active strains (SUST B, SUST B and SUST B) were selected for degradation study. The lipase activity under different pH, temperature, degradation products, and carbon sources was studied. The degradation mechanism was investigated using attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. The results showed that each strain had a significant degrading effect on PBAT. Under certain conditions, the lipase activity of strain SUST B was 10.42 U/mL and degraded 10.5% of PBAT films. Results of the study displayed a significant change in PBAT properties throughout the experiment. The pH of the degradation solution also displayed significant reduction throughout the experiment and reached a minimum value at the end of the experiment. The secreted lipase enzyme catalyzed the degradation of ester bonds present in the PBAT structure. Terephthalic acid, 1, 4-butanediol, and adipic acid were the by-products of this reaction. Strains utilize these products as carbon sources hence completely degrading PBAT. The bioremediation of PBAT in the environment can be achieved using these strains. Graphical abstract: [Figure not available: see fulltext.]