球磨生物炭的性质及其对大肠杆菌和金黄色葡萄球菌的毒性效应研究

Properties of ball-milled biochar and its toxic effects on E.coli and S.aureus

为研究球磨生物炭的微生物毒性效应,采用元素分析、比表面积分析(BET)、扫描电子显微镜(SEM)及傅立叶红外(FTIR)表征等手段研究了500℃裂解小麦秸秆生物炭(BC)和球磨生物炭(BM)的性质,采用毒性暴露实验分析了不同浓度(0、10、20、50、100、200 mg·L^-1)下两种生物炭对大肠杆菌(Escherichia coli)ATCC 25922和金黄色葡萄球菌(Staphylococcus aureus)ATCC 25923的毒性效应。结果表明:BC的比表面积为98 m^2·g^-1,而BM的比表面积提升到309 m^2·g^-1,球磨可以增加生物炭中含氧官能团的数量;在0.9%NaCl溶液中,添加10 mg·L^-1的BM时,S.aureus存活率为90.1%,E.coli存活率为98.2%。当浓度增大到200 mg·L^-1时,S.aureus的存活率降低为23.5%,E.coli的存活率仍可达91.8%;而在LB培养基中,BM浓度为200 mg·L-1时,S.aureus的存活率增加到58.1%;相同条件下,BM对微生物的毒性显著强于BC,这可能与粒子大小差异相关。而BM对革兰氏阳性菌S.aureus的毒性显著强于革兰氏阴性菌E.coli,这可能与E.coli产生的胞外聚合物(EPS)有关;添加活性氧自由基(ROS)消除剂N-乙酰半胱氨酸(NAC)发现,氧化损伤是造成S.aureus细胞死亡的主要原因,但是纳米颗粒对细胞的机械碰撞等其他因素也有可能是BM产生毒性的原因。研究表明BM对微生物具有一定的环境毒性效应,因此在BM使用过程中应注意其可能的环境影响。

Ball milling is effective in changing the particle size distribution of biochar(BC);however,it can cause toxic effects during the utilization of biochar.Therefore,it is essential to analyze the microbial toxicity of ball-milled biochar(BM).In this study,element analyses,BET,SEM,and FTIR detection were conducted to characterize the properties of wheat straw biochar prepared at 500℃ and BM.The effects of different concentrations of BC(0,10,20,50,100 mg·L^-1,and 200 mg·L^-1)on the ROS content and survival rate of bacteria were studied to confirm the effects of BC and BM on Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923,respectively.The re-sults showed that the specific surface area of BC was 98 m^2·g^-1,and the surface area of BM increased to 309 m^2·g^-1.Ball milling could lead to an increase in the oxygen-containing functional groups in biochar.In the 0.9%NaCl solution,when mixed with 10 mg·L^-1 BM,the sur-vival rate of S.aureus was 90.1%,and the survival rate of E.coli was 98.2%.The survival rate of S.aureus decreased to 23.5%,and the sur-vival rate of E.coli remained at 91.8%,when the concentration of BM was increased to 200 mg·L^-1.However,in the LB medium,the surviv-al rate of S.aureus increased to 58.1%when the concentration of BM was 200 mg·L^-1.Under the same conditions,the toxicity of BM on mi-croorganisms was significantly higher than that of general BC,which might be related to the differences in particle size.The toxicity of BM on S.aureus was significantly higher than that on the gram-negative bacteria,E.coli,which may be related to the extracellular polymeric substances(EPSs)produced by E.coli.By adding N-acetyl cysteine(NAC),an ROS eliminating agent,we found that oxidative damage was the main cause of cell death in 5.aureus,and other factors such as mechanical damage of BM nanoparticles in cells might also be the basis of the toxic effects caused by BM.As this study concludes that BM shows toxic effects on microorganisms,it is necessary to consider environmental effects when BM is being used.