Loofah Sponge Has a Potential Multifunctional Role for Enhanced Tetracycline Biodegradation: Carrier, Putative Nutrient Releaser and Solubilizer

The microbial removal of antibiotics is an environmentally friendly solution to antibiotic contamination in water. However, the main limitations for its application are the difficulty of direct utilization of antibiotics by bacteria and incomplete removal. In this study, a strain of Bacillus thuringiensis ZY that removed tetracycline (TC) as a sole carbon source was applied. Strain ZY was able to remove 50 mg/L TC at an efficiency higher than 70%, while the removal efficiency was increased to 100% after the immobilization by Loofah (Lfr). Meanwhile, the removal time was shortened from 6 to 4.5 d. Compared with the free ZY, the TC removal efficiency of Lfr-ZY was significantly improved under various conditions (temperature, pH and NaCl concentration). The removal efficiency of Lfr-ZY was still higher than 50% after 11 cycles, with strong removal ability and stability. In addition, the enhancement of TC bio-removal by Lfr-ZY involved the combination of the protection, adsorption, detoxification, putative nutrient release and solubilization effects of Lfr. The promising results suggest that the Lfr-based strategy has the potential for solving the problems of a lack of nutrient substrate for TC removal and the inability to remove it completely.