(The) effects of culture conditions on genetic parameters in batch culture of a recombinant bacillus megaterium producing carboxymethylcellulase

Abstract

For the analysis of the effects of culture conditions such as temperature, pH and dissolved oxygen level, on cell growth, production of carboxymethylcellulase, plasmid stability, plasmid content and gene expression efficiency in recombinant cell fermentation system, batch culture was performed using a recombinant $\underline{Bacillus}$ $\underline{megaterium}$ ATCC 14945(pCK 108). As culture temperature increased from 30$^\circ$C to 44$^\circ$C, maximum cell concentration and plasmid stability tended to decline but plasmid content, gene expression efficiency and specific production of carboxymethylcellulase increased. And expression of cloned gene was more efficient at higher plasmid content. At acidic and basic pHs, production of carboxymethylcellulase, plasmid content and plasmid stability were showed lower value than those obtained in the vicinity of neutral pH. At higher level of dissolved oxygen, maximum cell concentration, plasmid content and gene expression efficiency were higher, but plasmid stability was less affected by low level of dissolved oxygen. From the analyses of phenotypic expression of the recombinant cells and electrophoretic analyses of plasmid isolated, it was found that the instability of the plasmid was caused by segregation rather than modification of plasmid itself.