In the HA fermentation by Streptococcus zooepidemicus
ATCC 39920, several important features were found. This strain
is an aerotolerant anaerobe; it grows as well under both aerobic
and anaerobic cultures. HA is a capsular biopolymer shedding
to the medium, and the amount of unreleased HA capsule is
relatively insignificant. Dissolved oxygen is a stimulant for the
cells to over-synthesize HA, and 5% air saturation is the critical
DO level. The critical level does not change with changing
cell concentration and type of impeller. The primary function
of agitation is to mix the broth. Vigorous agitation favors oxygen
absorption, but is not helpful directly to the HA production;
in contrast, vigorous agitation would result in a longer operation
time. Accordingly, when practicing the scaleup of HA
fermentation, the criteria relevant to aeration and agitation can
be proposed as follows: keep DO level above the critical value,
choose an impeller suitable for viscous liquids, and set a mild
agitator speed to achieve homogeneity.
In the HA fermentation by Streptococcus zooepidemicusATCC 39920, several important features were found. This strainis an aerotolerant anaerobe; it grows as well under both aerobicand anaerobic cultures. HA is a capsular biopolymer sheddingto the medium, and the amount of unreleased HA capsule isrelatively insignificant. Dissolved oxygen is a stimulant for thecells to over-synthesize HA, and 5% air saturation is the criticalDO level. The critical level does not change with changingcell concentration and type of impeller. The primary functionof agitation is to mix the broth. Vigorous agitation favors oxygenabsorption, but is not helpful directly to the HA production;in contrast, vigorous agitation would result in a longer operationtime. Accordingly, when practicing the scaleup of HAfermentation, the criteria relevant to aeration and agitation canbe proposed as follows: keep DO level above the critical value,choose an impeller suitable for viscous liquids, and set a mildagitator speed to achieve homogeneity.
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