Improved production of l-asparaginase by Bacillus brevis cultivated in the presence of oxygen-vectors

The efficiency of three oxygen-vectors liquid paraffin, silicone oil and n-dodecane in the production of l-asparaginase by Bacillus brevis was evaluated at 4% (v/v) concentration. All of the three oxygen-vectors were found to exhibit a stimulatory effect on l-asparaginase activity. Liquid paraffin at 6% (v/v) resulted in 34% increase in the l-asparaginase activity accompanied by a 48% increase in the production of cell mass at a 10 L scale. This improvement in l-asparaginase activity and cell mass production in the presence of liquid paraffin can be related to the fact that liquid paraffin was capable of maintaining dissolved O2 concentration above 28% through out the course of the fermentation. Maintenance of the dissolved O2 concentration above 28% could be viewed in terms of an adequate oxygen supply to the rapidly dividing cells of the bacterium, which in turn resulted in enhancement in cell mass production and l-asparaginase activity.