Shimizu E, Oosumi T, Heima H, Tanaka T, Kurashige J, Enei H, Miwa K, Nakamori S
Central Research Laboratories of Ajinomoto Co., Inc., Kawasaki, Japan.
Biosci Biotechnol Biochem. 1995 Jun;59(6):1095-8. doi: 10.1271/bbb.59.1095.
We had constructed an L-threonine-hyperproducing strain of E. coli K-12 by recombinant DNA techniques. In this paper, culture conditions for the practical production of L-threonine were investigated using this strain. Cultivation temperature, concentration of required amino acids, and dissolved oxygen greatly influenced the yield of L-threonine. High production of L-threonine was obtained at a high level of dissolved oxygen for the recombinant strain, but not for the parent. This improved production was accompanied by a high copy number of recombinant plasmids and high activity of aspartokinase. Initial addition of L-threonine together with required amino acids greatly reduced the net production of L-threonine. To remove the reductive effect, methods for the addition of the required amino acids were tested. Lowering the required amino acids at a later stage of cultivation seemed to be effective to avoid the reductive effect of the accumulated L-threonine. By using the optimal conditions, the highest level of L-threonine production, 65 g/l, 48% yield, was achieved.
我们通过重组DNA技术构建了一株高产L-苏氨酸的大肠杆菌K-12菌株。本文利用该菌株研究了L-苏氨酸实际生产的培养条件。培养温度、所需氨基酸浓度和溶解氧对L-苏氨酸的产量有很大影响。对于重组菌株，在高溶解氧水平下可获得高产量的L-苏氨酸，但亲本菌株则不然。这种产量的提高伴随着重组质粒的高拷贝数和天冬氨酸激酶的高活性。初始添加L-苏氨酸和所需氨基酸会大大降低L-苏氨酸的净产量。为消除这种还原作用，测试了添加所需氨基酸的方法。在培养后期降低所需氨基酸的添加量似乎对避免积累的L-苏氨酸的还原作用有效。通过使用最佳条件，实现了L-苏氨酸的最高产量，即65 g/l，产率为48%。
