PRODUCTION OF GAMMA-DECALACTONE AND 4-HYDROXY-DECANOIC ACID IN THE GENUS SPORIDIOBOLUS

Within the genus Sporidiobolus, S. odorus has been widely reported as having the ability to convert castor oil or its derivatives to gamma-d ecalactone, but other species have also shown potential for lactone pr oduction. In this work, the bioconversion of ricinoleic acid methyl es ter to gamma-decalactone was studied with four species of Sporidiobolu s: S. salmonicolor, S. ruinenii, S. johnsonii, and S. pararoseus. With 4.1 g/l of ricinoleic acid methyl ester, only S. salmonicolor and S. ruinenii were able to produce gamma-decalactone (12 and 40 mg/l respec tively). S. johnsonii and S. pararoseus did not produce any lactone in spite of consuming the precursor. The four strains showed different s ensitivities to lactone. Between S. salmonicolor and S. ruinenii, the latter was the best biocatalyst. During four successive batch cultivat ions in a 7-l bioreactor, 5.5 g/l of gamma-decalactone was produced wi th S. ruinenii in each 10-d run. This was essentially due to its abili ty to produce the open form of gamma-decalactone (i.e., 4-hydroxy-deca noic acid), which is far less toxic than the lactone.