Study On The Degradation Of Cephalosporins By Probiotics Bacillus Clausii

In recent years,the abuse of cephalosporins has led to their extensive presence in sewage.At the same time,the traditional sewage treatment technology can not remove cephalosporins from the pharmaceutical wastewater completely.Their entry into the environment will lead to the emergence of drug-resistant bacteria,aggravate the spread of antibiotic-resistant-genes and pose threaten seriously to human health.In this paper,for the biodegradation of cephalosporin antibiotics,single strains of Bacillus clausii that carrying the ?-lactamase encoding gene bcl1 were obtained from commercial probiotics.In addition,abilities to degrade cephalosporin antibiotics(cefuroxime,cefotaxime,cefpirome)and the potential biodegradation pathways under pure cultue and co-culture were investigated.The main findings are as follows:1)Based on the specific tolerance levels of each strain to specific antibiotics,four strains of Bacillus clausii(Bacillus clausii SIN,Bacillus clausii T,Bacillus clausii N/R and Bacillus clausii O/C)were obtained from the probiotic preparation Enterogenima through resistance screening and 16 S RNA identification.2)Results of the biodegradation experiments showed that pure culture of B.clausii T could completely remove the mixture of cefuroxime,cefotaxime and cefpirome within 8 h.And degradation ability of the co-culture of B.clausii T and B.clausii O/C to the mixture of cefuroxime,cefotaxime and cefpirome was stronger than that of the pure culture of B.clausii O/C,indicating that B.clausii T was the dominant bacteria that degrade the above cephalosporin antibiotics.Real-time quantitative PCR analysis showed that cefuroxime or cefpirome enhanced the expression level of ?-lactamase encoding gene bcl1,suggesting that gene bcl1 might be involved in the hydrolysis of cefuroxime and cefotaxime.However,cefotaxime led to the down-regulation of the gene bcl1,suggesting that expression product of this gene did not play the main role in biotransformation of cefotaxime.3)Seven possible biotansfomation products of cefotaxime were detected by LC-MS.It was concluded that the potential biotransformation pathways of cefotaxime by B.clausii included deacetylation,hydrolysis,and decarboxylation.At the same time,it was found that for a single cefuroxime and cefpirome,the biological toxicity of the degradation products under the co-culture of B.clausii T and B.clausii O/C was significantly lower than that under the pure culture.In summary,the results of this study provided a new and environmentally-friendly degradation strategy for efficient removal of cephalosporin antibiotics,laying a certain theoretical foundation and experimental support for revealing the biotransformation mechanism of cephalosporin antibiotics.