Effect of different carbon sources on sulfate reduction and microbial community structure in bioelectrochemical systems

Microbial electrolysis cells (MECs) have rapidly developed into a promising technology to treat sulfate-rich wastewater that lacks electron donors. Hence, a better understanding of the effect on the microbial community structure caused by different sources in bioelectrochemical systems is required. This study sought to investigate the effect of different carbon sources (NaHCO₃, ethanol, and acetate were employed as sole carbon source respectively) on the performance of sulfate-reducing biocathodes. The sulfate reduction efficiency enhanced by the bioelectrochemical systems was 8.09 - 11.57% higher than that of open-circuit reference experiments. Furthermore, the optimum carbon source was ethanol with a maximum sulfate reduction rate of 170 mg L^-1 d^-1 in the bioelectrochemical systems. The different carbon sources induced significant differences in sulfate reduction efficiency as demonstrated by the application of a micro-electrical field. Microbial community structure and network analysis revealed that all three kinds of carbon source systems enriched large proportions of sulfate-reducing bacteria and electroactive bacteria but were significantly distinct in composition. The dominant sulfate-reducing bacteria that use NaHCO₃ and acetate as carbon sources were Desulfobacter and Desulfobulbus, whereas those that use ethanol as carbon source were Desulfomicrobium and Desulfovibrio. Our results suggest that ethanol is a more suitable carbon source for sulfate reduction in bioelectrochemical systems.

[Clinical application of multi-electrode synchronous radiofrequency ablation via switching controller for treating large hepatocellular carcinoma]

Objective: To explore the preliminary clinical efficacy and safety of multi-electrode synchronous radiofrequency ablation via switching controller for treating large hepatocellular carcinoma. Methods: A total of 20 patients with large hepatocellular carcinoma from minimally invasive Interventional department of Sun Yat-sen University Cancer Center were enrolled in this retrospective study from December 2013 to December 2014.The procedures were conducted with multi-electrode synchronous radiofrequency ablation via switching controller under CT guidance.The necrosis rate of tumor was assessed by the following imaging examination.The single factor analysis of variance (ANOVA) was employed to compare the total bilirubin, albumin, renal function, blood coagulation function before and after ablation, to evaluate the safety of treatment. Result: Twenty patients with a total of 31 lesions accepted 23 times ablation procedures using multi-electrode synchronous radiofrequency ablation via switching controller.The recent evaluation after treatment was as followed: complete necrosis rate 51.6% (16/31), nearly complete necrosis rate 22.6% (7/31), partial necrosis rate 9.7% (3/31), treatment effectiveness rate (necrosis rate > 50%) 83.9%.The necrosis rate which was less than half volume of the tumor was only seen in 5 cases with huge hepatocellular carcinoma (16.1%). No dead cases appeared after ablation procedures.The patients' total bilirubin elevated moderately after ablation procedures and reversed to normal level after liver function protection treatment.There were no statistical differences of renal function and blood coagulation function before and after ablation.After ablation procedures, 5 cases (21.7%, 5/23) appeared fever, 6 cases (26.1%) with vomiting, only 3 cases (13.0%, 3/23) with moderately severe pain in 3 days after ablation and remitted after taking oral analgesics in one week. Conclusion: The clinical efficacy of multi-electrode synchronous radiofrequency ablation via switching controller for large hepatocellular carcinoma is satisfactory with guaranteed security, which can be a choice for treating large hepatocellular carcinoma.