Comparative study of removal of ciprofloxacin from synthetic wastewater by two strains of saccharomyces cerevisiae yeast spores

Abstract

Among the developing countries in the world, Bangladesh is suspected to be one of the major contributors to regional and global antibiotic resistance because of the widespread misuse of antibiotics in human healthcare, agriculture and farming. The indiscriminate use of antibiotics and lack of sufficient wastewater treatment plants have resulted in the presence of antibiotics in Bangladesh surface waters and ciprofloxacin is among the highest detected antibiotics. Saccharomyces cerevisiae has been employed as an adsorbent and a microbial agent in wastewater treatment technologies and also its chitosan rich spores has the potential of performing better as an adsorbent. The main objective of the study is to compare the removal capacity and investigate the removal of ciprofloxacin by cells and spores of three different strains of Saccharomyces cerevisiae yeast- strain S-5, strain R and strain SWPN. In this study, the best pre-sporulation and sporulation media for maximum yield of spores were established by monitoring six combinations of media for every strain. The best pre-sporulation media for the three strains were determined to be- a) 0.8% yeast extract, 0.3% peptone and 10% dextrose for strain S-5, b) 1% yeast extract, 2% peptone and 2% potassium acetate for strain R and c) 0.8% yeast extract, 0.3% peptone and 5% potassium acetate for strain SWPN. 1% potassium acetate was the best sporulation medium for strain S-5 and R while 0.5% potassium acetate was the most suitable sporulation medium for strain SWPN. The adsorption capacity and degradation ability of the cells and spores of the three strains of Saccharomyces cerevisiae yeast were also studied. The adsorption experiments revealed that the maximum adsorption capacities of strain S-5, strain R and strain SWPN cells were 1.77±0.09 mg/g, 1.58±0.13 mg/g and 1.90±0.18 mg/g respectively. Additionally, the maximum adsorption capacities of strain S-5, strain R and strain SWPN spores were 6.20±0.22 mg/g, 4.57±0.22 mg/g and 5.40±0.08 mg/g respectively. The adsorption capacity increased by 3.5, 3 and 2.8 times by strain S-5, R and SWPN respectively in their spore forms. Degradation studies of ciprofloxacin by the yeast cells and spores showed that the organism was not able to degrade the antibiotic. Furthermore, Langmuir isotherm and Temkin isotherm were found to be the best fit for yeast cells and spores respectively through adsorption isotherm experiments. From the study it can be concluded that chitosan rich yeast spores can perform better that yeast cells in removing ciprofloxacin from synthetic wastewater.