Enhancing biodegradation of gaseous chlorobenzene by introducing micro-nano bubbles (MNBs): Performance and mechanisms

Chlorobenzene (CB) biodegradation is challenging due to its hydrophobic characteristics. Addition of silicone oil and surfactants are commonly used methods to enhance biodegradation efficiency by improve CB gas-liquid mass transfer efficiency. However, both approaches introduced new chemicals into the reactor, either as carbon sources for microorganisms or requiring regeneration. This study established a synergistic reactor by applying micro-nano bubbles (MNBs) with biodegradation process in a stirred tank bioreactor (STB) to purify CB waste gas. Experimental results demonstrate a reduction in start-up time by 2 days and a 13.5 % increase in overall degradation rate in synergistic reactor. The mass transfer fraction of CB ( β * s ) was increased by 13.33 %. Additionally, the synergistic reactor showed improved system stability and microbial activity, evidenced by the increased Zeta potential, extracellular polymer substances (EPS) secretion, and protein content. Notably, MNBs upregulate genes involved in aromatic ring hydroxylation and dehalogenation processes and promoted the enzyme SCACT (EC2.8.3.18) within the genus Acidovorax , which enhanced intracellular coenzyme A activity and facilitated chlorobenzene degradation in this genus, thereby enhancing CB degradation efficiency. These results indicate that MNBs can significantly improve the biodegradation performance of CB waste gas, offering a promising strategy for industrial applications.