CHARACTERIZATION OF DesR-DEPENDED VANILLIC AND SYRINGIC ACIDS-INDUCIBLE SYSTEM FROM SPHINGOBIUM SP.SYK-6

Phenolic acids are bioactive compounds commonly found in seeds, fruit peels, and leafy vegetables, were they exist as conjugates or in a free form. Syringic acid, a derivative of hydroxybenzoic acid, exhibits a range of bioactivities including antioxidant, anti-inflammatory, antimicrobial, and even anticancer properties, highlighting its significance in biomedical and industrial applications. Furthermore, syringic acid acts as a precursor for syringyl derivatives, important in food and pharmaceutical industries. Over the past decades, the aerobic alphaproteobacterium Sphingobium sp. SYK-6 has emerged as a model system for lignin-derived aromatic compound catabolism [1,2]. This Gram-negative bacterium, originally isolated from kraft pulp mill effluent, utilizes diverse biaryl and monoaryl lignin derivatives as sole carbon and energy sources. Syringic acid is converted to 3-methylgallic acid by gallate dioxygenase, and which is metabolized via gallate cleavage pathway. Inducible gene expression systems, composed of transcription factors (TFs) and inducible promoters, regulate gene expression in response to environmental conditions, including small molecules. These systems regulate gene expression by either repressing or activating transcription, depending on whether the TF inhibits or promotes RNA polymerase binding to the promoter. Genetically encoded biosensors, based on these systems, are powerful analytical tools for detecting specific chemical compounds in biological samples. TF-based whole-cell biosensors have been applied in synthetic biology for strain screening, target molecule detection, or monitoring biopolymer degradation processes. Although biosensors for various phenolic acids have been developed, a syringic acid-specific biosensor remains a challenge [3]. In this study, we characterized and parameterized the DesR-depended vanillic and syringic acids-inducible gene expression system from Sphingobium sp. SYK-6 that can potentially be used for developing transcription factor-based biosensor. This work was supported by the EU funds investment programme 2021–2027 [Project No. 10-038-T-0062] under grant agreement with the Central Project Management Agency.