Influence of dilution rate on enzyme synthesis in Aspergillus niger in continuous culture.

Abstract

Summary: Aspergillus niger was grown in continuous culture under steady-state conditions in citrate-limiting or glucose-limiting medium. The specific activities of hexokinase, phosphofructokinase, pyruvate kinase, fructose diphosphatase, 6-phosphogluconate dehydrogenase and, to a limited extent, citrate synthase under citrate limitation remained at a relatively constant steady-state level irrespective of the dilution rate (0.01 to 0.5 h-1). Increase in dilution rate led to an increase in the specific activities of aconitase, NAD(P) isocitrate dehydrogenase, malate dehydrogenase, and glucose-6-phosphate dehydrogenase in both citrate and glucose limiting culture, and to an increase in citrate synthase, hexokinase, phosphofructokinase, pyruvate kinase, and 6-phosphogluconate dehydrogenase only in glucose limitation. A decrease in specific activity with increasing dilution rate occurred with isocitrate lyase in both citrate and glucose limitation and for fructose diphosphatase only in glucose limitation. The specific activity of malate synthetase showed a peak activity in the middle range of dilution rates.