Earlier, empirical findings helped to produce procedures to improve the selectivity of yeast entire cell biotransformations. These procedures incorporated substrate modification, alterations in cultiva tion ailments or the application of different carbon sources, the usage of inhibitors or the utilization of two phase systems. Just lately, also water immiscible ionic liquids have been used as biocompatible solvents for yeast full cell biocatalysis so as to supply a substrate reservoir and an in situ extracting agent to increase chemical yields. If these techniques were not effective, substitute microorganisms needed to be screened. Furthermore to Saccharomyces cerevisiae also different yeasts have been uncovered which supplied useful biocatalysts for asymmetric carbonyl reduction. Some had been efficient adequate to become employed for industrial applications by diverse com panies.
Some recent advances selleck chemical within the biocatalytic reduction of carbonyl containing compounds are summarized in Table one and involve by way of example the discovering of new activities for Yarrowia lipolytica. Lagos et al. screened various yeast strains for the enantioselective production of the halohydrin precursor for propranolol synthesis. Yarrowia lipolytica 1240 resting cells gave the anti Prelog enantiomer one chloro three propan two ol with 87% yield and 99% ee. In addition, Pichia mexicana 11015 resting cells have been found to give 85% yield and 95% ee for the enantiomer. Dehli and Gotor discovered that resting cells of Saccharomyces montanus CBS 6772 carried out the bioreduction of 2 oxo cyclopentane carbonitriles on the corresponding cis hydroxynitriles in 93% ee, and higher de and chemical yields. As inexpensive alternative, Saccharomyces cerevisiae is still fairly often employed for laboratory scale bioreductions. Enders et al.
described the effective asymmetric total synthesis of callystatin A, a potent cytotoxic polyke tide from a marine sponge, employing selleck a blend of chemical and biocatalytic procedures. Consequently, tert butyl six chloro three,5 dioxohexanoate was subjected to dried bakers yeast in the biphasic method and was regio and enantioselectively diminished to your hydroxy keto ester in 94% enantiomeric excess. Moreover, Bertau and Burli reported the application of Saccharomyces cerevisiae cells for the synthesis of hexanediol. Glucose was used as auxiliary substrate for cofactor regeneration and with 25 mmol of hexanedione as substrate full conver sion with 99% ee, 96% de and 75% yield was accomplished. Servi and coworkers showed that full cells of Geotrichum candidum CBS 233. 76 and Rhodotorula mucillaginosa CBS 2378 reduced three,four dichlorophenacyl chloride on the and alcohol, respectively. Matsuyama et al. screened quite a few yeast strains for the big scale manufacturing of one,three butanediol, as the productivity of already reported asymmetric microbial reduction processes was not satisfactory.