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用大肠桿菌测定维生素B12,培养基简单,方法易於掌握,但蛋氨酸有干摄作用。豆类发酵食品中游离的蛋氨酸含量很高,不能使用以碱破壞维生素B12来改正结果的方法。本实验利用活性炭吸附作用,以pH4.5的醋酸纳缓(?)液洗脱去蛋氨酸,最後用热的65％酒精洗脱吸附在活性炭上的维生素B_12,其回收率平均为98.8％。由於酒精洗脱液含有极微量的蛋氨酸,在测定时仍应与碱破壤法结合使用。 利用此种方法分析了9种发酵食品,其中以臭豆腐乳含量最高,每百克合有1.88—9.800微克的稚生素B_12活性。
Determination of vitamin B12 with Escherichia coli, medium simple, easy to grasp the method, but methionine dry shoot. Legume fermented foods free of methionine content is high, can not be used to destroy vitamin B12 alkali to correct the results of the method. In this experiment, the removal of methionine was eluted with sodium acetate buffer (pH4.5) at pH4.5 by using activated carbon adsorption. Finally, vitamin B12 adsorbed on activated carbon was eluted with hot 65% ethanol, and the average recoveries were 98.8%. As the alcohol eluate contains a trace of methionine, the determination should be combined with the alkali broken soil method. Nine kinds of fermented foods were analyzed by this method, of which the highest content of stinky fermented milk was 1.88-9.800 micrograms of biotin-B_12 activity per hundred grams.