Argyle J L, Baldwin R L
Department of Animal Science, University of California, Davis 95616.
J Dairy Sci. 1989 Aug;72(8):2017-27. doi: 10.3168/jds.S0022-0302(89)79325-5.
Experiments were conducted using mixed rumen bacterial cultures to determine which amino acids limited growth. Complete amino acid mixtures stimulated microbial growth alone and when added to casein. Amino acid subgroups did not stimulate growth alone or when added to casein or casein hydrolysates. Results were similar whether growth was limited by periodic addition of low amounts of carbohydrate or when higher amounts were added to batch cultures. Little growth occurred with ammonia as sole N source. Addition of 100 mg/L of amino acids and peptides quadrupled growth, peptides at 10 mg/L resulted in higher growth than the corresponding amount of free amino acids. Apparent saturation of growth occurred when 10 mg/L of a complete amino acid mixture or trypticase was added to cultures. The Michaelis constant values for amino acids and trypticase were determined to be .5 and 1.0 mg/L, respectively. Growth was a linear function of amount of carbohydrate fermented with the coefficient of slope increasing with increasing amino acid concentrations. These experiments demonstrate that growth stimulation from amino acids and proteins is due to the number of amino acids provided in a given mixture rather than specific growth limiting amino acids. Rumen bacterial growth is greatly stimulated by amino acids and peptides, with low affinity constant values, allowing good growth in the concentrations of amino acids and peptides found in vivo
使用混合瘤胃细菌培养物进行实验，以确定哪些氨基酸限制生长。完整氨基酸混合物单独以及添加到酪蛋白中时均能刺激微生物生长。氨基酸亚组单独或添加到酪蛋白或酪蛋白水解物中时均不能刺激生长。无论生长是通过定期添加少量碳水化合物来限制，还是在分批培养中添加较高量碳水化合物时，结果都是相似的。以氨作为唯一氮源时几乎不生长。添加100mg/L的氨基酸和肽可使生长增加四倍，10mg/L的肽比相应量的游离氨基酸导致更高的生长。当向培养物中添加10mg/L的完整氨基酸混合物或胰蛋白酶时，生长出现明显饱和。氨基酸和胰蛋白酶的米氏常数分别确定为0.5和1.0mg/L。生长是发酵碳水化合物量的线性函数，斜率系数随氨基酸浓度增加而增加。这些实验表明，氨基酸和蛋白质对生长的刺激是由于给定混合物中提供的氨基酸数量，而不是特定的生长限制氨基酸。瘤胃细菌生长受到氨基酸和肽的极大刺激，其亲和力常数较低，使得在体内发现的氨基酸和肽浓度下能够良好生长。
