Potential of endophytic fungus Phomopsis liquidambari for transformation and degradation of recalcitrant pollutant sinapic acid

• Phomopsis liquidambari degraded sinapic acid effectively in MSM and in soil.
• The possible biodegradation pathway by an endophytic fungus was first proposed.
• The expressions of PAD, laccase, and GAD genes were induced in degradation.
• P. liquidambari laccase improved the degradation rate of sinapic acid.
• P. liquidambari has potential for remediation of sinapic acid-contaminated sites.

The biodegradation potential of sinapic acid, one of the most representative methoxy phenolic pollutants presented in industrial wastewater, was first studied using an endophytic fungus called Phomopsis liquidambari. This strain can effectively degrade sinapic acid in flasks and in soil and the possible biodegradation pathway was first systematically proposed on the basis of the metabolite production patterns and the identification of the metabolites by GC-MS and HPLC-MS. Sinapic acid was first transformed to 2,6-dimethoxy-4-vinylphenol that was further degraded via 4-hydroxy-3,5-dimethoxybenzaldehyde, syringic acid, gallic acid, and citric acid which involved in the continuous catalysis by phenolic acid decarboxylase, laccase, and gallic acid dioxygenase. Moreover, their activities and gene expression levels exhibited a ‘cascade induction’ response with the changes in metabolic product concentrations and the generation of fungal laccase significantly improved the degradation process. This study is the first report of an endophytic fungus that has great potential to degrade xenobiotic sinapic acid, and also provide a basis for practical application of endophytic fungus in the bioremediation of sinapic acid-contaminated industrial wastewater and soils.