الفهرس 
Growth yieldOnly 14 pages are availabe for public view
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Abstract
The ability of anumber of micro-organisms to excrete enzymes for the degradation of macromolecules is a well established fact. Among those enzymes is glucoarnyulase, which converts starch and related polysaccharides into glucose for application in food processing and preparation. In fermentation industry it is of great interest to perform production of exocellular enzymes cheap and efficient. This thesis tries to throw some light on bioenergetic consequences of the extracellular enzyme glucoarnylase production by some Aspergillus niger strains. In a preliminary screening, all the selected Aspergillus niger strains were able to hydrolyse starch. In liquid shake flask cultures maximal enzyme production was shown by the wild type Asperg illus niger ATCC 101 5 and overproducing A-niger DS 15835 strain. Both A-niger wild type and over-producing strains have been grown in maltose-and glucose-limited continuous cultures. The glucoamylase production under maltose-limitation is signcantly higher than under glucose-limitation Acomparison between both A-niger strains showed that the overproducing strain most probably is a regulatory mutant. Maximal molar growth yields on substrate (Y submax) and on oxygen (’02~~~w)e re very high indicating that growth was very efficient and protein production for biomass was not exceedingly energy consuming. The maintenance coefficient (!%) was higher than for some other fungi. It has been found that the energy costs for the production of exocellular enzyme glucoamylase is very high. Dependin~onth e efficiency of energy conservation the glucoamylase protein yield n on ATP is between 1.4 and 2.6 gram protein per mol ATP, which is equal or less than 10% of the theoretical maximum of 25.5.