Object of study: Lactococus lactis; L-Lactic acid; plasmid PK18mob; plasmid PNZ8150 Mission: Construct the genetic engineering strain- Lactococus lactis to get the high-efficiency, high purity and low-cost production of L-lactate. Knockout gene D-lactate dehydrogenase (ldhA) in genome of Lactococus lactis, with suicide vector PK18mob, with the method of homologous recombination. ...