Z. mobilis was cultivated anaerobically for 27 h at 30 ◦C, 130 rpm at pH 6.2 in an automatically controlled fermenter (30 L) fitted with a pH electrode (Applikon®, The Netherlands).
pH was adjusted with 5 M KOH.
10 L of medium containing 200 g L−1 glucose, 5 g L−1 yeast extract, 0.5 g L−1 KH2PO4, 0.02 g L−1 MgSO4·7H2O, 0.02 g L−1 Fe(NH4)2(SO4)2·6H2O, 0.001 g L−1 biotin and 0.002 g L−1 calcium panthotenate were inoculated with 1 L preculture grown on the same medium.
Rhodotorula mucilaginosa, a producer of the auxiliary enzyme gluconolactonase (GL; EC 3.1.1.17) needed for the enzyme activity assay, was grown in 1 L flasks in a shaker at 30 ◦C, 300 rpm in a medium containing 150 g L−1 glucose, 30 g L−1 malt extract and 3 g L−1 soya
peptone for 48 h