Levoglucosan kinase involved in citric acid fermentation by Aspergillus niger CBX-209 using levoglucosan as sole carbon and energy source

Abstract

Conditions were optimized for the production of citric acid by a mutant A. niger CBX-209 using levoglucosan derived from pyrolysis of wastepaper as a sole carbon and energy source in a simple medium. The optimum concentration of levoglucosan and wheat bran in the medium was 8% and 3%, respectively, at an optimum initial pH between 5.5 and 6.0 at 35°C. During fermentation, direct formation of glucose 6-phosphate from levoglucosan in the presence of ATP and Mg 2+ as observed by HPLC in the reaction with both cell extracts and partially purified enzyme, suggested that the enzyme acting on levoglucosan is a kinase. Time-course changes in the levels of this special levoglucosan kinase in A. niger CBX-209 grown on levoglucosan and glucose revealed that levoglucosan kinase was an inductive enzyme.