Fig. 2

Process optimization: (A) pH; (B) temperature; (C) substrate concentrations; (D) cell concentrations. General reaction conditions unless otherwise stated: 30 mM HMF, 1 equiv. glucose, 20 mg/mL cells, 4 mL Tris-HCl buffer (0.1 M, pH 8), 30 °C, 200 rpm, 3 h; (A) 0.1 M acetate buffer (AB, pH 4 and 5), phosphate buffer (PB, pH 5–8), and Tris-HCl buffer (pH 8 and 9); (B) 20–45 °C; (C) 50–200 mM HMF, 12 h; (D) 200 mM HMF, 20–60 mg/mL cells, 12 h