Yakult Central Institute for Microbiological Research, 1796 Yaho, Kunitachi-shi, Tokyo 186-8650, Japan.
J Biosci Bioeng. 2011 Jun;111(6):665-70. doi: 10.1016/j.jbiosc.2011.02.005. Epub 2011 Mar 2.
Generally recognized as safe, Streptococcus thermophilus was transformed using a plasmid expressing endogenous hyaluronic acid (HA) synthase genes. A single expression of hyaluronic acid synthase (hasA), uridine diphosphate-glucose dehydrogenase gene (hasB), or pyrophosphorylase gene (glmU) and double expression of hasA and hasB were attempted. A streptococcus-Escherichia coli shuttle vector, pBE31, was successfully transfected in S. thermophilus. The single expression of hasA or hasB allowed S. thermophilus to produce about 0.5-1.0 g/l HA. The strains coexpressing of hasA and hasB showed a markedly increased HA production (1.2g/l) which was six-fold increase compared with the wild-type strain. The maximum cell concentration and specific growth rate of each recombinant strain were lower than those of the wild-type strain; however, the specific production rate was more than 100-fold higher. Galactose concentration decreased in the coexpressing strain after depletion of lactose. The bacterial metabolism would be altered in order to achieve a higher production by changing the intracellular metabolism. The average molecular weight of HA (1.0 × 10(6) Da) was not affected by the expression of hasA and hasB. HA produced from recombinant strain could be an alternative material for medical, cosmetic and food utilization instead of HA from conventional pathogenic streptococci.
普遍认为安全的嗜热链球菌使用表达内源性透明质酸（HA）合酶基因的质粒进行转化。尝试了单表达透明质酸合酶（hasA）、尿苷二磷酸-葡萄糖脱氢酶基因（hasB）或焦磷酸化酶基因（glmU）和双表达 hasA 和 hasB。嗜热链球菌成功转染了穿梭质粒 pBE31。hasA 或 hasB 的单表达使嗜热链球菌能够产生约 0.5-1.0 g/l 的 HA。共表达 hasA 和 hasB 的菌株表现出明显增加的 HA 产量（1.2g/l），与野生型菌株相比增加了六倍。每个重组菌株的最大细胞浓度和比生长速率均低于野生型菌株；然而，特定生产率超过 100 倍。乳糖耗尽后，共表达菌株中的半乳糖浓度降低。为了通过改变细胞内代谢来实现更高的产量，细菌代谢将发生变化。HA（1.0×10^6Da）的平均分子量不受 hasA 和 hasB 表达的影响。重组菌株产生的 HA 可以替代传统致病性链球菌的 HA，用于医疗、美容和食品用途。
