Fig. 4

Optimization of EM2. a Time courses of the initial conditions: wet biomass of S-selective whole-cell catalyst (20 g L⁻¹) in KP buffer (50 mM, pH 6.5, 1 mM NAD⁺) containing the KMTB (90 g L⁻¹) and sodium formate (125 g L⁻¹), at 200 rpm and 25 °C. b Effects of different pH on (S)-HMTBA production. c Effects of different temperatures on (S)-HMTBA production. d Effects of NAD⁺ concentration on (S)-HMTBA production. e Time course of the optimized conditions: wet biomass of S-selective whole-cell catalyst (20 g L⁻¹) in KP buffer (50 mM, pH 7.0, 0.4 mM NAD⁺) containing the KMTB (90 g L⁻¹) and sodium formate (125 g L⁻¹), at 200 rpm and 30 °C at 20-mL scale. f Time course of the optimized conditions at 1-L scale