RESUMO
The purpose of this study was first to examine the electrochemical oxidation of two antibiotics, tetracycline (TC) and tylosin (Tylo), considered separately or in mixture, on a glassy carbon electrode in aqueous solutions; and then to assess the relevance of such electrochemical process as a pre-treatment prior to a biological treatment (activated sludge) for the removal of these antibiotics. The influence of the working potential and the initial concentration of TC and Tylo on the electrochemical pre-treatment process was also investigated. It was noticed that antibiotics degradation was favoured at high potential (2.4â V/ saturated calomel electrode (SCE)), achieving total degradation after 50â min for TC and 40â min for Tylo for 50â mgâ L(-1) initial concentration, with a higher mineralization efficiency in the case of TC. The biological oxygen demand in 5 days (BOD5)/Chemical oxygen demand (COD) ratio increased substantially, from 0.033 to 0.39 and from 0.038 to 0.50 for TC and Tylo, respectively. Regarding the mixture (TC and Tylo), the mineralization yield increased from 10.6% to 30.0% within 60â min of reaction time when the potential increased from 1.5 to 2.4â V/SCE and the BOD5/COD ratio increased substantially from 0.010 initially to 0.29 after 6â h of electrochemical pre-treatment. A biological treatment was, therefore, performed aerobically during 30 days, leading to an overall decrease of 72% of the dissolved organic carbon by means of the combined process.
Assuntos
Eletrólise/instrumentação , Esgotos/química , Tetraciclina/isolamento & purificação , Tilosina/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/instrumentação , Carbono , Misturas Complexas/química , Misturas Complexas/isolamento & purificação , Misturas Complexas/efeitos da radiação , Eletroquímica/instrumentação , Eletrodos , Campos Eletromagnéticos , Desenho de Equipamento , Análise de Falha de Equipamento , Vidro , Esgotos/análise , Tetraciclina/química , Tetraciclina/efeitos da radiação , Tilosina/química , Tilosina/efeitos da radiação , Água/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/efeitos da radiação , Purificação da Água/métodosRESUMO
Tylosin is a macrolide antibiotic used as veterinary drug and growth promoter. Attempts were made for hyper production of tylosin by a strain of Streptomyces fradiae NRRL-2702 through irradiation mutagenesis. Ultraviolet (UV) irradiation of wild-type strain caused development of six morphologically altered colony types on agar plates. After screening using Bacillus subtilis bioassay only morphological mutants indicated the production of tylosin. An increase of 2.7+/-0.22-fold in tylosin production (1500mg/l) in case of mutant UV-2 in complex medium was achieved as compared to wild-type strain (550mg/l). Gamma irradiation of mutant UV-2 using (60)Co gave one morphologically altered colony type gamma-1, which gave 2500mg/l tylosin yield in complex medium. Chemically defined media promoted tylosin production upto 3800mg/l. Maximum value of q(p) (3.34mg/gh) was observed by mutant gamma-1 as compared to wild strain (0.81mg/gh). Moreover, UV irradiation associated changes were unstable with loss of tylosin activity whereas mutant gamma-1 displayed high stability on subsequent culturing.