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NITROGEN LIMITATION FOR ENHANCED CITRIC ACID PRODUCTIVITY BY A 2-DEOXY D-GLUCOSE RESISTANT CULTURE OF ASPERGILLUS NIGER NG^D-280

SIKANDER ALI, IKRAM-UL-HAQ, M.A. QADEER AND ¹ JAVED IQBAL

Abstract: The present investigation is concerned with the nitrogen limitation for enhanced citrate productivity by a 2-deoxy D-glucose resistant culture of Aspergillus niger NGd-280 in 15-L stirred tank bioreactor. Nutrients especially nitrogen source have a marked influence on citrate productivity because it is an essential constituent of basal cell proteins. Ammonium nitrate at various concentrations was used as a nitrogen source. The specific growth rate was inhibited and the biosynthesis of citric acid was delayed at higher concentration of ammonium nitrate. The specific citric acid production rate was highest when intracellular ammonium ion concentration was between 2.0-3.0 mmol/g cells. However, citrate production was stopped when intracellular ammonium ion concentration decreased below 1.0 mmol/g cell.

Biotechnology Research Laboratory, Department of Botany, Government College, Lahore, Pakistan.
Department of Botany, Quaid-e-Azam Campus, University of the Punjab, Lahore, Pakistan.