BIOPRODUCTION AND CHARACTERIZATION OF SODIUM, POTASSIUM, AND CALCIUM LACTOBIONATES

Lactobionic acid and its salts are substances that have several applications in the pharmaceutical area. These products were obtained by bioconversion through the enzymatic complex glucose-fructose-oxidoreductase (GFOR)/gluconolactonase (GL) present in calcium alginate immobilized cells of Zymomonas mobilis. In the reactions catalyzed by this enzyme system, the medium pH must be controlled at slightly acid values. For this purpose, NaOH, KOH, or Ca(OH)2 were used, and as a result, the respective salts were formed. The kinetic study on the formation of sodium, potassium and calcium lactobionates was followed by the steps of purification and characterization aiming the potential use of these compounds in the pharmaceutical area. In the assays for the bioproduction of sodium, potassium or calcium lactobionates, yields of 74, 77 and 84% were obtained, respectively. In the salts purification step, purity levels of approximately 95% were achieved. The structural identities of the lactobionate salts were determined by high resolution mass spectrometry, in addition to the 13C and 1H NMR analysis. The characterization demonstrates the selectivity of the enzymatic reaction of GFOR/GL of Z. mobilis, in the production of lactobionic acid and its salts.乳糖酸及其盐类是一类在制药领域具备多种应用的物质。此类产物可通过生物转化手段制备：利用固定于海藻酸钙载体上的运动发酵单胞菌（Zymomonas mobilis）细胞所携带的复合酶系——葡萄糖-果糖氧化还原酶（glucose-fructose-oxidoreductase，GFOR）与葡萄糖酸内酯酶（gluoconolactonase，GL）完成催化反应。在该酶系催化的反应过程中，需将反应体系的pH值控制在弱酸性范围内；为此实验采用氢氧化钠、氢氧化钾或氢氧化钙调节pH，最终分别得到对应的乳糖酸钠、乳糖酸钾与乳糖酸钙产物。 本研究针对乳糖酸钠、乳糖酸钾及乳糖酸钙的合成过程开展动力学研究，随后对产物进行纯化与表征，旨在探索此类化合物在制药领域的应用潜力。在上述三种乳糖酸盐的生物合成实验中，分别获得了74%、77%与84%的产物得率；在盐类纯化步骤中，最终产物纯度可达约95%。 通过高分辨质谱（high resolution mass spectrometry）结合碳-13（¹³C）与氢-1（¹H）核磁共振分析，完成了各乳糖酸盐的结构确证。上述表征结果证实，运动发酵单胞菌所携带的GFOR/GL酶系在乳糖酸及其盐类的合成过程中具备良好的反应选择性。