Monday, May 4, 2009
11-14
Production and toxicity of γ-decalactone and 4-hydroxydecanoic acid from R. aurantiaca
Mohamed Alchihab1, Jacqueline Destain1, Mario Aguedo2, Magali Masson1, Jean-Paul Wathelet2, and Philippe Thonart1. (1) Bio-Industry Unit, Gembloux Agricultural University, Passage des Déportés, 2, Gembloux, 5030, Belgium, (2) Organic Chemistry Unit, Gembloux Agricultural University, Passage des Déportés, 2, Gembloux, 5030, Belgium
The production of γ-decalactone by the psychrophilic yeast R. aurantiaca in a medium containing 2% castor oil was similar to that in medium containing 2% ricinoleic acid. No traces of lactones were detected by using olive oil as substrate. R. aurantiaca produced both γ-decalactone and its precursor 4-hydroxydecanoic acid. The production of γ-decalactone and 4-hydroxydecanoic acid was significantly higher when a 20-L bioreactor was used than when a 100-L bioreactor was used. The influence of pH on the extraction of γ-decalactone was also studied. By using 20 g/L of castor oil, 6.5 and 4.5 g/L of γ-decalactone were extracted after acidification at pH 2.0 and distillation at 100°C for 45 min in 20- and 100-L bioreactors, respectively. The effect of γ-decalactone and 4-hydroxydecanoic acid on the growth of R. aurantiaca was investigated. Our results show that γ-decalactone must be one of the limiting factors for its production. We confirmed that castor oil, besides being the substrate of bioconversion, acts as an extractant of the lactone. The addition of gum tragacanth to the fermentation medium at concentrations of 3 and 4 g/L seems to be an adequate strategy to enhance γ-decalactone production and to reduce its toxicity towards the cell. We propose a process at industrial scale using a psychrophilic yeast to produce naturally γ-decalactone from castor oil which acts also as a detoxifying agent; moreover the process was improved by adding a natural gum.