基于细菌学研究改性生物炭对抗生素的降解机制

分别选取3个裂解温度下制备的改性生物炭——MBC350，MBC500和MBC700，2种抗生素——磺胺甲噁唑（SMX）和氯霉素（CAP），考察MBCs对SMX和CAP生物降解的影响及生物降解过程中Pseudomonas stutzeri和Shewanella putrefaciens的细菌学特征.结果表明，在低浓度MBCs培养的细菌体系中，SMX和CAP的去除主要依靠细菌P.stutzeri和S.putrefaciens的生物降解；而在高浓度MBCs培养的细菌体系中，SMX和CAP的去除主要依靠MBCs的吸附.其主要是由于随着MBCs浓度的增加，对SMX和CAP的吸附量提高，同时促进细菌的繁殖，导致溶液中较少的SMX和CAP被细菌生物降解.MBCs提高了P.stutzeri细胞膜中饱和脂肪酸含量，抑制了S.putrefaciens中饱和脂肪酸的合成.特别是P.stutzeri中脂肪酸C10：0和C15：1，cis-10消失；而S.putrefaciens中逆式脂肪酸C14：1，cis-9和C15：1，cis-10生成.此外，应用基因绝对定量技术发现MBCs显著提高了细菌P.stutzeri的基因表达拷贝数，抑制了S.putrefaciens的基因表达拷贝数.但细菌P.stutzeri和S.putrefaciens的基因表达拷贝数均随着MBCs浓度的增加而增加.因此，本研究表明低浓度MBCs有利于SMX和CAP的生物降解，而高浓度MBCs促进细菌的生长量，脂肪酸和基因表达拷贝数.

Effects and mechanisms of modified-biochar on biodegradation of antibiotics as revealed by bacteriological characteristics

Three kinds of modified-biochar including MBC350, MBC500 and MBC700, and two types of antibiotics sulfamethoxazole (SMX) and chloramphenicol (CAP), were selected to investigate effects of different MBCs on biodegradation of SMX and CAP and the bacteriological characteristics of Pseudomonas stutzeri and Shewanella putrefaciens. The results showed that in the bacterial system cultured with low-concentration MBCs, the removal of SMX and CAP mainly depended on biodegradation by P. Stutzeri and S. putrefaciens. While in the bacterial system cultured with high-concentration MBCs, the removal of SMX and CAP was mainly by the adsorption onto MBCs. The adsorption capacities of SMX and CAP onto MBCs and the bacterial growth all increased as the concentrations of MBCs increased, leading to the decrease in the concentrations of antibiotics in the solution and the biodegradation efficiency. The content of fatty acids of P. stutzeri was significantly improved, while the fatty acids synthesis of S. putrefaciens was inhabited in the presence of MBCs. In particular, the components C10:0, C15:1, cis-10 of P. stutzeri were disappeared, and the components of trans-unsaturated fatty acids of S. putrefaciens were generated, such as C14:1, cis-9 and C15:1, cis-10. Additionally, by using absolute quantitative technique, the gene copies number of P. stutzeri was clearly improved, while it was inhabited for S. putrefaciens in the presence of MBCs. But the gene copies numbers of P. stutzeri and S. putrefaciens were increased with the increasing concentrations of MBCs. Therefore, this study showed that low-concentration MBCs were conducive to the biodegradation of SMX and CAP. While the bacteriological characteristics, such as bacterial growth, fatty acid and copy number of bacterial gene expression, were all promoted in the presence of high-concentration MBCs.