Effect of Oxygen-Supply Rates on Growth

McDANIEL, L. E. (Rutgers, The State University, New Brunswick, N.J.), E. G. BAILEY, AND A. ZIMMERL. Effect of oxygen-supply rates on growth of Escherichia coli. II. Comparison of results in shake flasks and 50-liter fermentor. Appl. Microbiol. 13: 115-119. 1965.-Growth of Escherichia coli and chemical changes in the medium were very similar in highly baffled flasks and in a 50-liter fermentor run under the same oxygen-supply conditions, based on sulfite-oxidation rates. Flasks with stainless-steel baffles (Biotech) gave growth patterns and rates of glucose and NH4-N utilization almost identical to those of the fermentor; results with Bellco 598 flasks (with 6 to 7 mm deep indentations) were quite similar. Unbaffled and Bellco 600 flasks (3 to 4 mm indentations) were similar to the fermentor at very high and very low oxygen-transfer rates, but gave much less growth than the fermentor at intermediate levels. Maximal oxygen-uptake rates occurred in the fermentor at the end of the logarithmic-growth phase when growth was 40 to 75% of maximum. In the fermentor, both sulfite-oxidation rates and rates of oxygen uptake correlated reasonably well with the total amount of growth produced. One of the problems in fermentation development is that of obtaining the same results in shake flasks and pilot-plant fermentors. The scale-up factor which has been most investigated is that of oxygen supply. Jensen, Schultz, and Shu (1961) reported fairly good scale-up of chlortetracycline yields from shake flasks to 100-gal fermentors by duplicating oxygen-uptake patterns. Good correlations in yeast growth have been reported when results were compared on oxygentransfer capacity of the equipment (Olson and Johnson, 1947; Strohm, Dale, and Peppler, 1959). However, Lockhart and Squires (1963) stated that different pieces of fermentation equipment, including shake flasks, with similar oxygentransfer rates may give entirely different results. Roxburgh, Spencer, and Sallans (1954) reported very different requirements for equal ustilagic acid production by Ustilago zeae in shake flasks and fermentors, on the basis of sulfite-oxidation rates. A wide range of oxygen-transfer rates can be obtained in commercially available shake flasks (Gaden, 1962; McDaniel, Bailey, and Zimmerli, 1965). It was shown in the latter paper that total yields of Escherichia coli cells depend on oxygensupply rates and on the type of flask used. In the work reported here, we studied the growth and fermentation characteristics of E. coli B in a 50liter fermentor, as compared with different types of shake flasks under conditions of high, intermediate, and low oxygen-supply rates. We wished, first, to find out which type of shake flask compared most closely with the fermentor, and, second, to gain some insight into factors influencing microbial behavior in shake flasks and fermentors which would permit good duplication of results between the two. MATERIALS AND METHODS Culture, media, and shake-fask procedures. The strain of E. coli B, the inoculum and growth media, the types of shake flasks, and shaking conditions were all as described by McDaniel et al. (1965). The shake-flask tests were run by removing medium from the fermentor after inoculation and dispensing it aseptically into sterile flasks in volumes to give the desired sulfite oxygen-absorption rates (OAR). One flask of each type was removed at each sampling time. Inoculum development. Quantities of 1 liter of inoculum were grown in 2-liter Erlenmeyer flasks. The cultures were incubated at 37 C on a shaker running at 220 rev/min; 10% inoculum was used, and the fermentor volumes were calculated so that the batch size would be 25 liters after removal of medium for shake flasks. Fermentor and accessories. The 50-liter fer115 on O cber 6, 2017 by gest ht://aem .sm .rg/ D ow nladed fom MCDANIEL, BAILEY, AND ZIMMERLI