Immobilized Bakers Yeast

The use of immobilized yeast allows the use of solvents different from water [81, 339]—for example, hexane [MO, 341], while the use of a water-miscible solvent (THF, DMSO, or 1,4-dioxane) or of a nonpolar solvent saturated with water sometimes deactivated the cells [321,322,342,343] as an exception to this rule, fluorenones have been bioreduced in DMSO/water mixtures to fluorenols with good to excellent enan-tioselectivity [344]. 

Calcium alginate [345-347] as well as K-carrageenan [348-350] has been used for immobilizing baker s yeast, and a sodium alginate/calcium chloride-immobilized baker s yeast has been used during the synthesis of d- and L-armentomycin [351]. This system has also been used for tiie reduction of several p-keto esters [352], and the antiselectivity as well as the yields was improved compared to reductions using classical conditions [217,353-355]. Calcium alginate-immobilized cells of S. cerevisiae were pretreated at 50 °C for 30 min, and tiien the cells showed an increased performance (80%) and an excellent selectivity (ee 99%) in the reduction of 3-chloropropiophenone 

8 WHOLE-CELL BIOCATALYSIS IN IONIC LIQUIDS AND DEEP EUTEaiC SOLVENTS 

Despite many efforts the use of classical organic solvents for biocatalytic transformations using whole cells remains limited. Water as a natural reaction medium limits the number of applications, since only a small number of substrates are sufficiently water soluble. As an alternative the use of an ionic liquid may be considered. A very early example for such a reaction has been reported by Cull in 2000 [360]. 

The use of certain anions, for example [BFJ, decreases the biocompatibility (obviously by forming hydrofluoric acid due to the presence of water) [365, 366]. Effects of residual water content [367-370], pH value [371], miscibility with water [372], as well as the kind of microorganism must not be neglected. 

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K Nakamura, K Inoue, K Ushio, S Oka, A Ohno. Stereochemical control on yeast reduction of a-keto esters. Reduction by immobilized bakers yeast in hexane. J Org Chem 53 2589-2593, 1988. 

Naoshima, Y. Maeda, J. Munakata, Y. Control of the Enantioselectivity of Bioreduction with Immobilized Bakers Yeast in a Hexane Solvent System. J. Chem. Soc. Perkin Trans. 1 1992,... 

Ionic liquid [bmimJPFg can be used as a solvent in yeast reduction [21]. The reduction ofketones with immobilized baker s yeast (alginate) in a 100 10 2 [bmimjPFfi ionic liquid water MeOH mix affords chiral alcohols (Figure 8.28). 

Bahrami K, Khodaei MM, Farrokhi A (2009) Highly efficient solvent-free synthesis of dihydropyrimidinones catalyzed by zinc oxide. Synth Commun 39 1801-1808 74. Gross GA, Wurziger H, Schober A (2006) Solid-phase synthesis of 4,6-diaryl-3,4-dihydro-pyrimidine-2(lH)-one-5-carboxylic acid amide derivatives a Biginelli three-component-condensation protocol based on immobilized beta-ketoamides. J Comb Chem 8 153-155 Desai B, Dallinger D, Kappe CO (2006) Microwave-assisted solution phase synthesis of dihydropyrimidine C5 amides and esters. Tetrahedron 62 4651 664 Kumar A, Maurya RA (2007) An efficient bakers yeast catalyzed synthesis of 3,4-dihydro-pyrimidin-2-(lH)-ones. Tetrahedron Lett 48 4569-4571 77. Zalavadiya P, Tala S, Akbari J, Joshi H (2009) Multi-component synthesis of dihydropyrimidines by iodine catalyst at ambient temperature and in-vitro anti mycobacterial activity. Arch Pharm 342 469-475... 

Y Naoshima, J Maeda, Y Munakata, T Nishiyama, M Kamezawa, H Tachibana. Bioreduction with immobilized baker s yeast in hexane using alcohols as an energy source. J Chem Soc Chem Commun 964-965, 1990. 

Howarth J, James P, Dai J (2001) Immobilized baker s yeast reduction of ketones in an ionic liquid, [bmim]PF and water mix. Tetrahedron Lett 42 7517-7519... 

Kotorman, M. et ah, Coenzyme production using immobilized enzymes. III. Immobilization of glu-cose-6-phosphate dehydrogenase from bakers yeast. Enzyme Microb. TechnoL, 16, 974, 1994. 

A detailed recipe has been given for the reduction of ethyl acetoacetate to ethyl-(S)-3-hydroxybutanoate (118) by Baker s yeast.Various forms of immobilized Baker s yeast can also be used,117 resulting in improved optical yields in some cases. 

Evidence for the involvement of salt links in the stabilization of bakers yeast jS-o-fructofuranosidase has been obtained from studies of immobilization of the enzyme on cellulose, derivatives of Sephadex and insolubilized con-canavalin A, and modification with citraconic anhydride, methyl acetimidate, or ethylene diamine. The general stability to such treatments was offered as the evidence, since modification of either amino- or carboxy-groups would result in loss of conformational stability, unless the stabilizing salt linkages were present. 

Schemel2.12 Immobilized baker s yeast reduction of hydroxy keto ester 25.

Only a few studies in the literature reported malate production from fumarate using immobilized baker s yeast, Saccharomyces cerevisiae. Nevertheless, only one-third of the specific activity of yeast conversion is achieved as compared with the bacterial system (Oliveira et al., 1994). Neufeld et al. (1991) studied L-malate formation by immobilized S. cerevisiae that was amplified for fumarase in the presence of a surfactant. The highest specific activity... 

Yajima A, Naka K, Yabuta G. Immobilized baker s yeast reduction in fluorous media. Tetrahedron Lett. 2004 45 4577-4579. 

The reduction of acefylfrimethylsilane [387, 388] by immobilized baker s yeast using two different ionic liquid buffer sysfems was studied in more detail, and the effects of temperature and pH were investigated. Finally high )delds (>99%) and superior enantioselectivity (ee>99.9%) could be obtained [382]. 

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