Aspergillus terreus CCT 3320 immobilized on chrysotile or cellulose/TiO2 for sulfide oxidation

The increasing interest in applying chiral sulfoxides in asymmetric syntheses requires their preparation on a large scale, which can be obtained by enantioselective enzymatic oxidation of sulfides. We have focused on the preparation of sulfoxides 1–6 using Aspergillus terreus CCT 3320 cells to oxidize the precursor sulfides. These biotransformations lead to enantiomeric excesses (ee) better than 95%. In order to improve the biocatalytic process, the cells were immobilized on two supports, chrysotile and on cellulose/TiO2. The immobilized cells showed a similar biocatalytic behavior in the conversion rate and in the sulfoxide enantiomeric excess. Scanning electron microscopy (SEM) micrographs show that the cells are intertwined with the fibers of both supports, allowing fast separation from the reaction media and easing the biocatalyst reuse. Supported cells stored for at least 3 months showed no loss of activity.