Within the genus Sporidiobolus, S. odorus has been widely reported as having the ability to convert castor oil or its derivatives to gamma-decalactone, but other species have also shown potential for lactone production. In this work, the bioconversion of ricinoleic acid methyl ester to gamma-decalactone was studied with four species of Sporidiobolus : 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 respectively). S. johnsonii and S. pararoseus did not produce any lactone in spite of consuming the precursor. The four strains showed different sensitivities to lactone. Between S. salmonicolor and S. ruinenii, the latter was the best biocatalyst. During four successive batch cultivations in a 7-l bioreactor, 5.5 g/l of gamma-decalactone was produced with S. ruinenii in each 10-d run. This was essentially due to its ability to produce the open form of gamma-decalactone (i.e., 4-hydroxy-decanoic acid), which is far less toxic than the lactone.