Increased availability of NADH in metabolically engineered baker’s yeast improves transaminase-oxidoreductase coupled asymmetric whole-cell bioconversion

Table 3 Initial growth rates, rates of substrate consumption, metabolite formation and calculated NADH balance during whole-cell reduction of acetophenone to (S)-1-phenylethanol

Strain	Growth rate (h⁻¹)	Glucose (mM/h)	Ethanol (mM/h)	Glycerol (mM/h)	Phenylethanol (mM/h)	NADH generation (mM/h)	NADH oxidation (mM/h)
Control, VAMT + SADH (TMB4162)	0.12 ± 0.02	−74 ± 9.92	105 ± 3.69	9.7 ± 4.52	0.5 ± 0.04	148 ± 19.8	115 ± 5.8
gpd1Δgpd2Δ, VAMT + SADH (TMB4163)	0.07 ± 0.03	−29 ± 9.20	35 ± 14.99	0.03 ± 0.02	1.4 ± 0.25	69 ± 18.4	36.4 ± 15

Rates were calculated for the first 4 h of reaction. NADH balance was calculated from the following assumptions: (i) under anaerobic conditions 2 mol of NADH are theoretically generated per mole glucose consumed. The value is in reality higher since NADH is also generated in anabolic reactions; (ii) 1 mol of NADH is oxidized per mole of ethanol, glycerol or (S)-1-phenylethanol being produced. During the initial phase of reaction there was also a low amount of oxygen in the bioreactor which also functioned as electron acceptor in respiration. Mean values and standard deviations are calculated from two different whole-cell bioconversions

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