초록
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 Mn<SUP>2+</SUP>. It displayed maximal activity in presence of 1mM Mn<SUP>2+</SUP> at pH 6.5 and 65<SUP>o</SUP>C, and was determined to be highly thermostable at 80<SUP>o</SUP>C. The half-life was calculated to be 5.64, 2.82, 0.77, and 0.2h at 70, 75, 80, and 85<SUP>o</SUP>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, 101.6g/L d-mannose was produced from 400g/L d-fructose after reaction for 9h, giving a conversion yield of 25.4%.