Abstract - The gas balance technique applied to batch cultures of the aerobic microorganism Aspergillus awamori NRRL3112 results in respiratory coefficient,RQ, values as high as 1.4 for glucose concentrations around 50g/L and no nutrients or oxygen concentration limitation. RQ decreases during the culture to values around 1.0 for glucose concentrations lower than 10g/L. Besides of an indication of drastic metabolic changes, these data suggest the need for some care when utilizing the RQ value for process control purposes. This RQ variability also has influence on the determination mode of the specific oxygen uptake rate, qO2 (mmol/gh). If the RQ value is constant, qO2 can be determined through a carbon dioxide (CO2) gas balance. This determination mode gives more reliable results than the one based on the oxygen gas balance since CO2 determination via a spectrophotometer of infrared gives accurate results and is a fast response relative to fluctuations in the CO2. In the case of this process however, reliable values of specific oxygen uptake rate, qO2, can be obtained only through the oxygen gas balance
Gas balance technique; catabolic metabolism; respiratory quotient; Aspergillus sp.
