TABLE 4.

Effect of initial oxygen addition on fermentation characteristics of wild-type V5 and UV9 and UV9/ure2::kan mutant strains in MS80 synthetic medium

Strain	Initial oxygen concentration (mg liter−1)	Maximum CO2 production rate (g of CO2 liter−1 h−1)	Final cell population (108 cells ml−1)	Assimilated nitrogena (mg of N liter−1)	Assimilated prolineb (mg of N liter−1)	Nitrogen assimilation efficiencyc (mg of N/10−12 cells)
V5	0	1.1	1.1	71	5.6	6.8
	3	1.1	1.2	73	5.5	6.8
	6	1.1	1.2	75	5.4	7.0
	9	1.1	1.2	79	6.6	7.2
	12	1.1	1.2	79	9.0	7.2
UV9	0	1.1	1.1	78	7.3	7.6
	3	1.1	1.2	79	7.6	7.5
	6	1.2	1.2	79	13	7.6
	9	1.2	1.4	80	20	7.1
	12	1.2	1.4	80	20	7.1
V5/ure2::kan	0	1.1	1.1	79	7.0	7.8
	3	1.1	1.2	79	7.8	7.6
	6	1.1	1.2	79	12	7.6
	9	1.2	1.4	80	20	7.1
	12	1.2	1.4	80	20	7.0

^aAmmonium salts and α-amino acids (all amino acids except proline) in the medium were considered residual assimilable nitrogen (initial values: ammonium salts, 32 mg of N liter⁻¹; α-amino acids, 48 mg of N liter⁻¹). 

^bThe residual proline concentration was determined by spectrophotometry at 460 nm after reaction with ninhydrin (initial value, 19.9 mg of N liter⁻¹). 

^cNitrogen assimilation efficiency was calculated by dividing the total amount of degraded nitrogen by the final cell population.