Alain Latrasse

Production of 6-pentyl-α-pyrone by Trichoderma sp. from vegetable oils

Abstract A total of 108 strains of Trichoderma sp. were compared for their ability to produce 6-pentyl-α-pyrone (6PP), a coconut-like aroma. Among them, one strain, Trichoderma viride TSP2, demonstrated a good ability to produce 6PP from several commercial vegetable oils including castor oil (C18:1, OH n-7=89.3%), hazelnut oil (C18:1=78.6%), grapeseed oil (C18:2=66%) and linseed oil (α-C18:3=46.6%). By increasing the oil concentration from 5 to 20%, 1.2 g l−1 of 6PP was achieved after 6 days of cultivation. In comparison, 80 mg l−1 of 6PP were produced when glucose (30 g l−1) was used as the carbon source.

In Situ Detoxification of the Fermentation Medium during γ-Decalactone Production with the Yeast Sporidiobolus salmonicolor

γ‐Decalactone (γ‐C10) is known to be highly toxic for the microorganims used for its production. In this work, three techniques were studied in order to overcome this toxicity during a bioconversion process using ricinoleic acid as precursor of the lactone: in situ trapping in oily phases, in porous hydrophobic sorbents and in β‐cyclodextrins. Oily phases added to the media (olive, Miglyol, tributyrin, and paraffin) had a protective effect on Sp. salmonicolor, and they improved the lactone production. β‐cyclodextrins, which have a hydrophobic cavity that can trap molecules such as γ‐C10, have been used to protect the yeasts. The results showed insufficient preservation of cell viability. Some sorbents (activated carbon and polystyrene‐based sorbents) were successfully tested during bioconversion. In all cases viability exceeded the reference one. Nevertheless the aroma production was 30% lower than the reference. All of these solutions led to some enhancement of the cell viability during bioconversion of methyl ricinoleate to γ‐C10. For improvement of the lactone production, the oil trapping method seemed to be the best with the experimental conditions tested.

Conversion of oleic acid to 10-hydroxystearic acid by Nocardia paraffinae

Resting cells of Nocardia paraffinaeCBS 255 58 anaerobically converted oleic acid to 10-hydroxystearic acid (optimum activity at 35°C and pH 7). Addition of oleic acid (0.22 mg/ml of medium), as an inducer, improved the hydroxylating activity. The biocatalyst was inactivated by sonication, lyophilization and heating, but kept 65% of its initial activity after five freeze-thawing treatments. This activity appeared to be located either in the cells or bound to the plasmic membrane.