氮源对克雷伯氏菌NⅢ2分泌絮凝剂特性的影响

实验研究了蔗糖为碳源,硝酸钠、脲、蛋白胨、硫酸铵和氯化铵等氮源对NⅢ2发酵产絮凝剂的影响。结果表明,发酵液起始pH值为7.50,以硝酸钠为氮源,发酵液pH会上升,升至7.60～8.34时,NⅢ2菌株开始大量分泌微生物絮凝剂,发酵72 h,产量可达7.5 g/L,该产量是目前报道的克雷伯氏菌产絮凝剂的最高值。脲为氮源,pH则下降,降至5.04～6.49时,大量分泌絮凝剂,发酵72 h产量达5.2 g/L。蛋白胨、氯化铵和硫酸铵等为氮源时,pH下降十分明显,pH小于3.71时有絮凝剂分泌,发酵72 h产量约2.0 g/L或更小。以硝酸钠和脲为氮源时,发酵液中有黄色物质分泌,该黄色物质出现或黄色逐渐加深,是NⅢ2菌高产絮凝剂的标志。除硫酸铵外,其他氮源发酵所产絮凝剂为O-糖蛋白。当以硝酸钠、脲、蛋白胨、硫酸铵和氯化铵为氮源时,絮凝剂中蛋白的含量分别为9.55%、33.28%、19.39%、13.81%和15.51%,且蛋白含量越高,絮凝剂活性越大。

Effect of nitrogen sources on characterization of bioflocculant production by Klebsiella sp. NⅢ2

Effects of nitrogen sources on bioflocculant production by Klebsiella sp. NⅢ2 were studied when sucrose was used as the carbon source. By using sodium nitrate as nitrogen source, and the original pH value was 7.5, the bioflocculant was largely secreted by Klebsiella sp. NⅢ2 when pH values of fermentation fluids reached to 7.60 - 8.34. And after 72 hours＇ fermentation, the bioflocculant yield could be 7.5 g/L, which is the high- est for Klebsiella so far reported. By using urea as nitrogen source, and the original pH value was also 7.5, the pH values of fermentation fluids decreased at early stage. When they kept within 5.04 - 6.49, biofloeculant was largely produced, and the corresponding highest yield reached 5.2 g/L. When peptone, ammonium sulfate and ammonium chloride were used as the nitrogen sources, some acidic substances were secreted, which made the pH values of cultures obviously dropped. Then some amount of bioflocculant was produced when pH value was less than 3.7. And the corresponding production of bioflocculant could be 2 g/L or less. Some yellowish sub-strate which can be a mark for high bioflocculant yield could only be secreted when sodium nitrate or urea using as nitrogen source. Apart from ammonium sulfate, the bioflocculant produced by other four nitrogen sources was O-glycoprotein. When used sodium nitrate, urea, peptone, ammonium sulfate and ammonium chloride as the ni-trogen sources, the protein contents in the bioflocculant were 9.55%, 33.28%, 19.39%, 13.81%, and 15.51% , respectively. And the high the protein content, the higher the activity of bioflocculant was.