Poster 2-18

Hugh G. Lawford and Joyce D. Rousseau

Bioengineering Laboratory
Department of Biochemistry
University of Toronto
Toronto, Ontario, Canada M5S 1A8

Telephone: (416) 978-7096; Fax: (416) 978-8548; E-mail: hugh.lawford@utoronto.ca

We have previously described environmental conditions that promote the synthesis of lactic acid from glucose by Zymomonas mobilis [Appl. Biochem. Biotechnol. 70–72, 173 (1998)]. In a glucose-limited chemostat operating at a low dilution rate, the decreased ethanol yield was attributed to the pH-dependent shift in pyruvate metabolism from ethanol to lactic acid. Complex nutritional elements in the medium were also implicated in lactic acid production since very little lactic acid was produced with a defined salts medium. In this study we have explored the role of a putative d-specific lactic acid dehydrogenase (ldh) using a d-ldh(-) mutant. The role of glycolytic flux was also investigated by altering the rate of feeding nongrowing batch cultures and by using a condition of nitrogen limitation in continuous cultures. The performance of the d-ldh(-) mutant was compared with that of the parent strain, namely Z. mobilis ATCC 39676.

ABSTRACT WITHDRAWN