Staphylococcal Enterotoxin B and Nuclease Production Under Controlled Dissolved Oxygen Conditions

Abstract

Enterotoxin B, nuclease, and total exoprotein production by Staphylococcus aureus strain S-6 was studied in a 0.5-liter fermentor system. While these extracellular products were elaborated over a wide range of aeration rates, maximal production occurred within the very narrow range of 125 to 150 cm3 of air per min. The levels attained at the optimal aeration rate were not increased by maintaining a constant pH, although yield of enterotoxin:cell mass was highest at a constant pH of 7.0. During the growth cycle of the cultures, when aeration rate alone or aeration rate and pH were held constant, the dissolved oxygen (DO) levels, initially set at 100% of saturation, decreased to 5 to 10% 4 to 5 h after inoculation. The oxygen demand of the culture then maintained this level for an additional 4 to 6 h. This interval of low DO was characterized by maximal growth and exoprotein production. When the DO was controlled at a constant value throughout growth (by increasing or decreasing the airflow rate as appropriate), the culture demonstrated different optima for maximal growth and exoprotein production. A constant DO of 100% stimulated growth to extremely high densities, but the accumulation of toxin and nuclease was not observed. On the other hand, maintaining constant DO levels at 50 or 10% raised exoprotein levels higher than those achieved in a culture grown at the optimal aeration rate. Compared to the optimal aeration rate culture, the 10% DO culture yielded 20% more nuclease, 25% more toxin, and 40 to 50% more total exoprotein. These results indicate that it is the DO and not the aeration rate, per se, that is influential in controlling growth, toxin, nuclease, and total exoprotein production.

The Effect of Medium Volume and Yeast Extract Diffusate on δ–Hemolysin Production by Five Strains of Staphylococcus aureus

“…aureus 100 and Staph. aureus 56, respectively (Carpenter & Silverman 1974;Carpenter & Silverman 1976;Jarvis et al 1973) where both aeration rate and dissolved oxygen concentration were found to affect the formation of each toxin as well as nuclease and total extracellular protein.…”

“…1) or whether some other factor such as the accumulation of a particular metabolite in response to certain aeration conditions, or a volatile inhibitor (such as carbon dioxide) was responsible for the effects observed. It is interesting to note, however, that the observations of Dietrich et al (1972) on the effect of shaking speed on the secretion of enterotoxin B were explained by the discovery that both an optimum aeration rate and dissolved oxygen concentration were required for enterotoxin B production (Carpenter & Silverman 1974).…”

Heterogeneity of Staphylococcus aureus enterotoxin B as a function of growth stage: implications for surveillance of foods

“…1. The fermentor, with attendant equipment for temperature and aeration regulation has been previously described (4).…”

Effect of environmental conditions on production of toxic shock syndrome toxin 1 by Staphylococcus aureus

“…The degree of aeration and DO level have been shown to influence the production of other staphylococcal products. Carpenter and Silverman (5) observed that maximal enterotoxin B (SEB) production occurred within a narrow range of aeration rates (125 to 150 cm3/min). A constant DO of 100% resulted in profuse growth but no SEB or nuclease was produced, whereas 10% stimulated synthesis of both products.…”