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Title: Biotransformation of Ferulic acid to 4-Vinylguaiacol by Enterobacter soli and E. aerogenes

Author
item Hunter, William
item Manter, Daniel
item VAN DE LELIE, D - Rti International, Usa

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2012
Publication Date: 9/18/2012
Citation: Hunter, W.J., Manter, D.K., Van De Lelie 2012. Biotransformation of Ferulic acid to 4-Vinylguaiacol by Enterobacter soli and E. aerogenes. Current Microbiology. 65:752-757.

Interpretive Summary: The conversion of ferulic acid to 4-vinylguaiacol (4-VG), vanillin, vanillyl alcohol and vanillic acid by five different bacteria, all Enterobacter species was investigated. Ferulic acid is a relatively inexpensive component that is common in agricultural crops and crop residues. While 4-vinylguaiacol (4-VG), vanillin, vanillyl alcohol and vanillic acid are compounds with much higher values than ferulic acid. Two of the bacteria, E. soli and E. aerogenes, accumulated 550-600 ppm amounts of 4-VG when grown in media containing 1000 ppm ferulic acid; no accumulations were observed with the other strains. Decreasing the amount of ferulic acid present in the media increased the conversion efficiency. When ferulic acid was supplied in 500, 250 or 125 ppm amounts E. aerogenes converted ~ 72 % of the ferulic acid present to 4-VG while E. soli converted ~ 100% of the ferulic acid to 4-VG when supplied with 250 or 125 ppm amounts of ferulic acid. Also, increasing the acidity of the growth media improved the conversion efficiency. At pH 5.0 E. aerogenes converted ~ 84 % of 1000 ppm ferulic acid to 4-VG and E. soli converted ~100%. Only small, 1 to 5 ppm, accumulations of vanillin, vanillyl alcohol and vanillic acid were observed. E. soli has a putative phenolic acid decarboxylase (PAD) that is 168 amino acids long and is similar to PADs in other Enterobacteriales; this enzyme is likely involved in the conversion of ferulic acid to 4-VG by these bacteria. E. soli or E. aerogenes might be useful as a means of biotransforming ferulic acid to 4-VG, a value added product.

Technical Abstract: We investigated the conversion of ferulic acid to 4-vinylguaiacol (4-VG), vanillin, vanillyl alcohol and vanillic acid by five Enterobacter strains. These high-value chemicals are usually synthesized using chemical methods but biological synthesis adds value. Ferulic acid, a relatively inexpensive component of agricultural crops, is plentiful in corn hulls, cereal bran and sugar-beet pulp. Two Enterobacter strains, E. soli and E. aerogenes, accumulated 550-600 ppm amounts of 4-VG when grown in media containing 1000 ppm ferulic acid; no accumulations were observed with the other strains. Decreasing the amount of ferulic acid present in the media increased the conversion efficiency. When ferulic acid was supplied in 500, 250 or 125 ppm amounts E. aerogenes converted ~ 72 % of the ferulic acid present to 4-VG while E. soli converted ~ 100% of the ferulic acid to 4-VG when supplied with 250 or 125 ppm amounts of ferulic acid. Also, lowering the pH improved the conversion efficiency. At pH 5.0 E. aerogenes converted ~ 84 % of 1000 ppm ferulic acid to 4-VG and E. soli converted ~100%. Only small, 1 to 5 ppm, accumulations of vanillin, vanillyl alcohol and vanillic acid were observed. E. soli has a putative phenolic acid decarboxylase (PAD) that is 168 amino acids long and is similar to PADs in other Enterobacteriales; this protein is likely involved in the bioconversion of ferulic acid to 4-VG. E. soli or E. aerogenes might be useful as a means of biotransforming ferulic acid to 4-VG, a value added product.