Isolation and enzyme determination of Candida tropicalis mutants for DCA production.

Techniques, named two-step enrichment and double-time replica-plating method (TEDR), are described that allow a mutated population of Candida tropicalis to be enriched efficiently for mutants deficient in the alkane degradation pathway (Alk(-)) and to be selected easily for mutants increasing in the DCA (dicarboxylic acids) excretion pathway. After C. tropicalis was mutated with ethyl methane sulphonate and ultraviolet, the Alk(-) mutants were enriched (the first step enrichment, up to eightfold in one round of enrichment) by treatment with nystatin in medium SEL1-1.

Electron impact mass spectral fragmentation of chiral bisbenzoxazole, bisbenzothiazole and biscarbamide derivatives of 2,2-dimethyl-1,3-dioxolane.

The mass spectrometric fragmentation behaviour of five pairs of (R,R)- and (S,S)-4,5-bis(benzoxazol-2-yl)-2,2-dimethyl-1,3-dioxolane derivatives, one pair of (R,R)- and (S,S)-4,5-bis(benzothiazol-2-yl)-2,2-dimethyl-1,3-dioxolanes, and three pairs of (R,R)- and (S,S)-N,N'-bis(2-hydroxyaryl)-2,2-dimethyl-1,3-dioxolane-4,5-dicarbamides, all important compounds for asymmetric catalysis (P. Jiao et al., Tetrahedron Asymmetry 2001; 12: 3081), has been studied with the aid of mass-analyzed ion kinetic energy spectrometry and accurate mass measurements under electron impact ionization conditions.