Synergic effect of adsorption and biodegradation by microsphere immobilizing Bacillus velezensis for enhanced removal organics in slaughter wastewater

Abstract

Bacterial cell immobilization offers considerable advantages over traditional biotreatment methods using free bacteria. Bacillus velezensis was underwented isolation and genetic identification as COD-degrading bacteria in slaughter wastewaterand immobilized on the surface of polyvinyl alcohol (PVA) microsphere with the adhesion to bio-carrier through direct physical adsorption. The removal CODMn rates of microsphere (PVA) immobilized cells were 16.99%, increased 9.38% from a 50% concentration of slaughter wastewater within 24 h at 37 °C, pH 7.0, and 120 rpm, which was about 2.2 times that of the free bacteria. A significant difference was found in two groups (p < 0.01 p value less than 0.01 means statistical significance), and the COD degradation rate of the micro-sphere immobilized Bacillus velezensis strain was higher than the control group (PVA: control vs 20.08: 10.81), with the processing time reaching 36 h (p < 0.05). Additionally, similar results were obtained from a 20% concentration of slaughter wastewater within 24 h and 36 h. Moreover, the starch and protein digestibility of the immobilized Bacillus velezensis strain was higher than that of the free bacteria (20.1%: 42.2% vs. 17.5%: 37.2%). These findings revealed that the PVA-bacteria system was a simple, green, and inexpensive process, as well as a promising method. The research goal is aimed to synergize the effects of adsorption and biodegradation, as it can enhance organic removal by immobilized Bacillus velezensis in slaughter wastewater. Moreover, it may be possible that more potential materials can be used as biological carriers for the immobilization of bacterial cells later, which is beneficial for the recycling of resources.