title: Guaiacol production from ferulic acid, vanillin and vanillic acid by Alicyclobacillus acidoterrestris.
abstract: Alicyclobacilli are thermophilic, acidophilic bacteria (TAB) that spoil fruit juice products by producing guaiacol. It is currently believed that guaiacol is formed by Alicyclobacillus in fruit juices as a product of ferulic acid metabolism. The aim of this study was to identify the precursors that can be metabolised by Alicyclobacillus acidoterrestris to produce guaiacol and to evaluate the pathway of guaiacol production. A. acidoterrestris FB2 was incubated at 45°C for 7days in Bacillus acidoterrestris (BAT) broth supplemented with ferulic acid, vanillin or vanillic acid, respectively. The samples were analysed every day to determine the cell concentration, the supplement concentration using high performance liquid chromatography with UV-diode array detection (HPLC-DAD) and the guaiacol concentration, using both the peroxidase enzyme colourimetric assay (PECA) and HPLC-DAD. The cell concentration of A. acidoterrestris FB2 during the 7days in all samples were above the critical cell concentration of 10(5)cfu/mL reportedly required for guaiacol production. The guaiacol produced by A. acidoterrestris FB2 increased with an increase in vanillin or vanillic acid concentration and a metabolic pathway of A. acidoterrestris FB2 directly from vanillin to guaiacol was established. The high concentration of vanillic acid (1000mg/L) resulted in an initial inhibitory effect on the cells, but the cell concentration increased after day 2. Guaiacol production did not occur in the absence of either a precursor or A. acidoterrestris FB2 and guaiacol was not produced by A. acidoterrestris FB2 in the samples supplemented with ferulic acid. The presence of Alicyclobacillus spp. that has the ability to produce guaiacol, as well as the substrates vanillin or vanillic acid is prerequisite for production of guaiacol.
authors.affiliation: Department of Food Science, Stellenbosch University, Private Bag X1, Matieland (Stellenbosch) 7602, South Africa. witthuhnrc@ufs.ac.za
authors.forename: R Corli
authors.initials: RC
authors.lastname: Witthuhn
authors.forename: Enette
authors.initials: E
authors.lastname: van der Merwe
authors.forename: Pierre
authors.initials: P
authors.lastname: Venter
authors.forename: Michelle
authors.initials: M
authors.lastname: Cameron
mesh_terms: D056450:Alicyclobacillus / Q000378:metabolism*; D001547:Benzaldehydes; D001628:Beverages / Q000382:microbiology*; D003373:Coumaric Acids / Q000378:metabolism; D005519:Food Preservation; D005638:Fruit; D006139:Guaiacol / Q000378:metabolism*; D014641:Vanillic Acid / Q000378:metabolism
chemical_list: D001547:Benzaldehydes; D003373:Coumaric Acids; D006139:Guaiacol; C004999:ferulic acid; C100058:vanillin; D014641:Vanillic Acid