Integrated whole genome sequencing and transcriptomic analysis reveal the biodegradation mechanism of vanillic acid in Herbaspirillum aquaticum KLS-1

Abstract

Vanillic acid (VA) is a phenolic compound frequently present in wastewater and agricultural soil. High concentrations of VA will increase the burden of sewage treatment and pose toxicity to crop plants. Although advanced oxidation has been successfully used to remove VA, green and sustainable treatments for VA pollution with efficient VA-degrading microbes, especially about the full pathways of VA degradation, are not well documented. In this study, a full investigation of VA degradation ability and associated metabolic mechanisms in the new VA-degrading bacterium Herbaspirillum aquaticum KLS-1 was performed. Results showed that strain KLS-1 completely removed 500 mg/L VA within 36 h following a zero-order degradation kinetic model with a degradation half-time of 15.01 h. An efficient VA degradation occurred under the conditions with pH values of 7–9, temperatures of 30–40 °C, and shaking speeds of 150–200 rpm. A fed-batch experiment and SEM analysis showed that strain KLS-1 exhibited a good ability to remove up to 46.8 mg VA without cellular damage. The protocatechuate ortho-cleavage pathway was probably associated with efficient VA degradation in strain KLS-1 according to the whole genome sequencing and transcriptomic analysis. This study has offered a comprehensive understanding of full VA degradation mechanisms in microbes by using genomic sequencing coupled with transcriptomic analysis and provided a new VA-degrading bacterium for potential bioremediation of VA pollution.