本研究是利用超過濾系統，移除玻尿酸醱酵液之微量蛋白質。藉由透析降低醱酵液離子強度，促使醱酵液中微量蛋白質凝集析出，再以微過濾加以濾除。將去除菌體的醱酵液進行蛋白質電泳實驗，可得知醱酵液中殘存蛋白質之分子量均低於11 kDa以下。將醱酵液在10 kDa超過濾膜下進行透析，當溶液導電度降低至1.247 ms/cm時，會有白色蛋白質顆粒凝集析出。我們進一步以IR鑑定此凝集物，發現在1567 cm-1具有蛋白質之胜鍵特徵吸收。此結果顯示蛋白質析出是由於鹽溶現象 (Salting-in) 所造成。利用此鹽溶現象進行純化，玻尿酸中蛋白質含量可由1.39 % 降低至0.102 % (g protein/g HA)，達到化妝品級之水準，而且製程回收率可達83%。相較於傳統耗費大量酒精同時需額外添加界面活性劑製程相比，本製程極具競爭力。

The removal of trace protein from broth of hyaluronic acid fermentation by ultrafiltration was studied. The decrease of ion strength in the broth resulted in protein coagulation. The coagulated particles were removed by microfiltration. With SDS-PAGE electrophoresis, it was found that the molecular weight of contaminant proteins were below 11 kDa. Accordingly, a ultrafiltration membrane of 10 kDa MWCO was used to dialyze the broth. When the conductivity of the broth was lower than 1.247 ms/cm, some insoluble material appeared. The insoluble has a strong absorbance at 1567 cm-1,which is the characteristic absorbance of peptide bond. This fact suggests that the appearance of the insoluble is due to protein coagulation, a phenomenon known as salting-in. Taking advantage of the salting-in method, the protein content in HA could be reduced from 1.39 % to 0.102 % (g protein/g HA), with a recovery up to 83% . The purity of hyaluronic acid is within cosmetic grade. Compared to traditional, processes which use large amounts of ethanol and surfactant, the present process is highly competitive.

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