Conversion and upgrading of syringate by Acinetobacter baylyi ADP1

Area of Science:

• Microbiology
• Biotechnology
• Synthetic Biology

Background:

• Lignin is a sustainable source of aromatic compounds, offering an alternative to fossil fuels.
• Biological upgrading of lignin derivatives enhances lignocellulose utilization.
• Efficient conversion of S-lignin aromatics like syringate requires further research into microbial hosts and pathways.

Purpose of the Study:

• Investigate the conversion of S-lignin-related syringate in Acinetobacter baylyi ADP1.
• Exploit the native vanillate demethylase (VanAB) for syringate O-demethylation.
• Develop microbial strains for converting lignin-derived aromatics into valuable chemicals.

Main Methods:

• Utilized wild-type and engineered Acinetobacter baylyi ADP1 strains.
• Characterized the activity of the native vanillate demethylase (VanAB) on syringate and 3-O-methylgallate (3MGA).
• Constructed a strain with heterologous expression of Pseudomonas putida KT2440's gallate dioxygenase (galA) for further conversion.

Main Results:

• Discovered native VanAB in A. baylyi ADP1 efficiently O-demethylates syringate to 3MGA and then to gallate.
• VanAB showed higher preference for syringate over 3MGA.
• Overexpression of vanAB led to simultaneous conversion but impaired growth; native expression caused 3MGA accumulation.
• Engineered strain successfully converted 3MGA into 2-pyrone-4,6,-dicarboxylate (PDC) using heterologous galA.

Conclusions:

• A. baylyi ADP1 possesses a novel syringate conversion pathway via VanAB.
• Adjusting vanAB expression levels allows controlled conversion of syringate to gallate or 3MGA.
• Heterologous expression of galA enables further conversion of 3MGA to PDC, a polyester precursor.
• A. baylyi ADP1 demonstrates significant potential for lignin-derived aromatic compound upgrading.