Study On The Screening And Degradability Of Poly-(Butylene Succinate)

The excessive use of non-biodegradable materials which cannot be naturally cleaned has been causing disasters to both environment and human society. Therefore, it is urgent to develop biodegradable materials that can be completely decomposed by environmental microorganisms in very short period and eventually returned to nature as nontoxic chemicals, such as H2O, CO2. Currently, many biodegradable materials, including PHB, PLA, PCL, PBS have been created and produced at industrial scale. Among these materials, PBS was emphasized by"Eleventh Five-Year Plan"due to its prevalent application as packing materials, agricultural film, and medical products. The early study on PBS was focused on its synthesis and production; however, after its industrial production has been realized, how to evaluate its degradability need to be completed quickly.In this study, the PBS-degrading strains were screened and isolated from the natural environment. The degradation capability of strain in the liquid medium was evaluated and the properties of PBS before and after degradation were investigated. In addition, the related factors involved in PBS degradation were studied and the degradation efficiency under various conditions was compared. At last, the feasibility of PBS degradation in mixed-culture was investigated.The main results of this project are as follows:1. Strain HX01 of the best growth and the best ability for PBS degradation was isolated using PBS as sole carbon source and cultivate, and had been identified to been Rhodococcus sp. through 16SrDNA identification.2. The degradability of PBS particles in liquid-degradation of strain HX01 was evaluated by weight loss method, and the degradation rate reached to 7.3% after 15 days. The study found the balance between HX01 biomass and PBS-degradation rate within 15 days. The color of PBS surface was changed from white to cream yellow after degradating culture. In addition, uniform holes were detected on PBS's surface through SEM, which formed by HX01 degradation .3. Culture condition with 15 g/L PBS(50 mL/250 mL system), 30oC, initial pH 8.0 was found to be optimal for degrading PBS by HX01. Under these conditions, degradation rate of PBS reached to 13.7% after 14 days.4. 100 mg/L carbon resources, including glucose, sucrose, soluble starch, succinic acid, were added into degradation-media, respectively, and the degradation rate of PBS by HX01 decreased. In addition, 100 mg/L butanediol and butyl acetate were added respectively into the medium, which enhanced the degradation of PBS. The degradation efficiencies got the same in the different forms of nitrogen source ions.5. The degradation efficiency of the PBS particles in the different environment system was investigated, and the results showed that cells cultured in liquid shake-flask exhibited higher degradation efficiency. This may be ascribed to abundant degrading microorganisms and appropriate degradation conditions. 6. Effect of mixed culture of strains HX01 and S6 on the degradation efficiency was investigated, and the degradation efficiency increased significantly, compared with the pure culture of HX01 and S6, respectively. The degradation rate of PBS by mixed-culture system reached to above 9% after 7 days.