Whole-cell bioreduction of aromatic α-keto esters using Candida tenuis xylose reductase and Candida boidinii formate dehydrogenase co-expressed in Escherichia coli

Table 3 Effect of additives and co-solvents on yield and enantiomeric excess of whole-cell bioreduction of ethyl 4-cyanobenzoylformate catalyzed by E. coli XR_FDH.

substrate conc. [mM]	org. co-solvent¹	additive^2,3	yield [mM]⁴/ee [%]⁵
100			82/97.2 R
100		NAD⁺	85/97.1 R
100		polymyxin B	75/97.0 R
100		NAD⁺, polymyxin B	77/97.2 R
100	ethyl acetate		1/> 99.9 R
100	ethyl acetate	NAD⁺	9/> 99.9 R
100	hexane		3/> 99.9 R
100	hexane	NAD⁺	7/> 99.9 R
500			134/> 99.9 R
500		NAD⁺	136/> 99.9 R
500		polymyxin B	125/> 99.9 R
500		NAD⁺, polymyxin B	126/> 99.9 R
500	butyl acetate		9/> 99.9 R
500	butyl acetate	NAD⁺	35/> 99.9 R
500	BMIMPF₆		74/> 99.9 R
500	BMIMPF₆	NAD⁺	108/> 99.9 R

Conditions: 40 g_CDW/L; 8.5 h reaction time. ¹Co-solvents were added in 1:1 volume ratio. ² [NAD⁺] = 490 μM. ³ [polymyxin B sulphate] = 144 μM. ⁴Standard errors ≤ 15%. ⁵Detection limit of ethyl 4-cyanomandelate is below 0.01 mM.

ISSN: 1475-2859