Omana D A, Wu J
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada, T6G 2P5.
Poult Sci. 2009 Oct;88(10):2224-34. doi: 10.3382/ps.2008-00485.
The effect of various concentrations of CaCl2 and KCl on egg white proteins during isoelectric precipitation of ovomucin was investigated in this study. At low concentrations of CaCl2 (<50 mM), lysozyme was the major contaminant in the precipitated ovomucin, whereas ovalbumin was the predominant one at high concentrations (>or=100 mM). At 50 mM CaCl2 concentration, the concentrations of both lysozyme and ovalbumin were moderate. Ovomucin with a purity of 97.3% was prepared using a 2-step method: egg white was first precipitated in the presence of 50 mM CaCl2 followed by a second 500 mM CaCl2 extraction. The concentrations of other proteins in the precipitate were 1.3% of ovalbumin, 1.1% of lysozyme, and 0.4% of ovomucoid. Unlike CaCl2-treated samples, ovotransferrin was found to be the second major contaminant in all KCl-treated precipitates. Compared with the control, adding KCl at the lowest concentration of 2.5 mM increased significantly the content of ovalbumin (from 7.6 to 68.0%) and reduced significantly the content of lysozyme (from 25.5 to 6.4%) in the precipitates; however, increasing the concentrations of KCl up to 500 mM did not affect the content of ovalbumin, but the content of lysozyme showed a general reduction trend. Although KCl was used widely in literature as the last step of ovomucin washing, our results show that KCl is not an efficient salt in purifying ovomucin.
本研究考察了在卵粘蛋白等电沉淀过程中，不同浓度的氯化钙（CaCl₂）和氯化钾（KCl）对蛋清蛋白的影响。在低浓度CaCl₂（<50 mM）时，溶菌酶是沉淀的卵粘蛋白中的主要污染物，而在高浓度（≥100 mM）时，卵白蛋白是主要污染物。在CaCl₂浓度为50 mM时，溶菌酶和卵白蛋白的浓度适中。采用两步法制备了纯度为97.3%的卵粘蛋白：首先在50 mM CaCl₂存在下沉淀蛋清，然后用500 mM CaCl₂进行二次提取。沉淀物中其他蛋白质的浓度分别为：卵白蛋白1.3%、溶菌酶1.1%、卵类粘蛋白0.4%。与CaCl₂处理的样品不同，在所有KCl处理的沉淀物中，转铁蛋白是第二主要污染物。与对照组相比，添加最低浓度为2.5 mM的KCl可显著增加沉淀物中卵白蛋白的含量（从7.6%增至68.0%），并显著降低溶菌酶的含量（从25.5%降至6.4%）；然而，将KCl浓度提高至500 mM并不影响卵白蛋白的含量，但溶菌酶的含量总体呈下降趋势。尽管在文献中KCl被广泛用作卵粘蛋白洗涤的最后一步，但我们的结果表明，KCl在纯化卵粘蛋白方面并非有效盐类。
