Bildung von α-Mannosidase durch Arthrobacter

The production of yeast cell wall mannan degrading -mannosidase was studied in shake flask experiments as well as in a highly instrumented, computer-coupled bioreactor. The enzyme is predominantly excreted into the culture liquid upon submerged cultivation on yeast mannan. Only low activities were detected with mannose or glucose as carbon source whereas the enzyme formation was totally repressed by glycerol. The amount of enzyme produced is proportional to the microbial biomass formed.Carbon-unlimited cultivation on mannose, the primary product of enzymic digestion, resulted in a specific growth rate of 0.10h^–1, a specific oxygen uptake rate ·h and a respiratory quotient ofRQ=1.0. Addition of yeast mannan (0.5%) to nutrient-depleted bacterial cells resulted in an almost complete utilization of this substrate, with 55% of substrate carbon being converted to biomass and 37% to carbon dioxide. The yield coefficient on mannan wasY _x/s =0.51 (g/g). Enzyme formation started with a delay of 30–40 min and stopped with termination of growth. Due to the increased production of mannose by the action of the enzyme the specific growth rate increased from 0.05 to 0.10 h^–1, thus enabling computations of maintenance and yield coefficients for oxygen and carbon dioxide metabolism.