Efficient biotransformation of d-fructose to d-mannose by a thermostable d-lyxose isomerase from Thermosediminibacter oceani

Abstract

Abstract d -Mannose has prebiotic effect and potential medical application. Besides, it can be used as substrate to produce mannitol, a functional polyol widely used in food industry. As this result, it has attracted many researchers’ attention. In this work, a thermostable d -mannose-producing d -lyxose isomerase (D-LI) was characterized from a hyperthermophile, Thermosediminibacter oceani. The recombinant D-LI could be remarkably activated by Mn2+. It displayed maximal activity in presence of 1 mM Mn2+ at pH 6.5 and 65 °C, and was determined to be highly thermostable at 80 °C. The half-life was calculated to be 5.64, 2.82, 0.77, and 0.2 h at 70, 75, 80, and 85 °C, respectively. The enzyme showed the optimum activity using d -lyxose as substrate and could also effectively catalyze the isomerization between d -fructose and d -mannose. Under optimum conditions, 101.6 g/L d -mannose was produced from 400 g/L d -fructose after reaction for 9 h, giving a conversion yield of 25.4%.