The utilization of gum tragacanth to improve the growth of Rhodotorula aurantiaca and the production of γ-decalactone in large scale

The production of γ-decalactone and 4-hydroxydecanoic acid by the
psychrophilic yeast R. aurantiaca was studied. The effect of both compounds
on the growth of R. aurantiaca was also investigated and our results show that
γ-decalactone must be one of the limiting factors for its production. The addition
of gum tragacanth to the 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. The production of γ-decalactone and 4-
hydroxydecanoic acid was significantly higher in 20-l bioreactor than in 100-l
bioreactor. 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. 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.