Effect of growth rate and cultivation environments on cloned gene stability and the cloned gene product formation in Streptomyces lividans.
The growth rate and environmental effects on the stability of recombinant plasmid, pDML6 containing beta-lactamase gene, and the cloned gene product formation in Streptomyces lividans were studied. A maximum production rate of the cloned gene product was obtained at a specific growth rate 0.106 h-1 in glucose-limited chemostat cultivations without genetic selection pressure. Optimum environmental conditions for the recombinant plasmid stability and maximum formation rates of the cloned gene product were determined using continuous cultivations at the optimum specific growth rate. The fractions of plasmid harboring mycelium in prolonged cultivation up to 50 generations were varied from 77 to 95%. The recombinant plasmid was stably maintained in the host cells grown in different temperatures (24 to 36 degrees C) and pH (6.0 to 8.5). The formation of the cloned gene product was optimum at pH 7.0 and 27 degrees C, at which the maximum enzyme production rate was 0.82 kU g-1 h-1. Continuous cultivations varying the dissolved oxygen tension (10 to 80% air saturation) showed that the plasmids were maintained stably and the specific enzyme production rates were increased with increasing dissolved oxygen levels.
Lee
J H
JH
Department of Microbiology, Seoul National University, South Korea.
Lee
K J
KJ
D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000032:analysis; D010957:Plasmids; D011994:Recombinant Proteins / Q000096:biosynthesis*; D013302:Streptomyces / Q000254:growth & development* / Q000378:metabolism; D013696:Temperature; D001618:beta-Lactamases / Q000096:biosynthesis
D011994:Recombinant Proteins; D001618:beta-Lactamases; D010100:Oxygen