Levoglucosan (LG), 1,6-anhydro-beta -D-glucopyranose. was produced by pyrolysis of cellulose. A response surface method was used to optimize the reaction parameters: X-1, temperature; X-2, time required for heating cellulose from room temperature to the designed pyrolysis temperature; and X-3. vacuum, and a Box-Behnken design was employed for this purpose. The optimal temperature and time were found to be 388 degreesC and 26.2 min by fixing the vacuum at 1 mm HE. The levoglucosan prepared was fermented to citric acid by Aspergillus niger CBX-309, which was a mutant derived by gamma -ray mutagenesis of the parent strain CBX-2. The mutant could produce increasing citric acid with increasing LG purity and had a citric acid yield of 87.5% when using purified levoglucosan as the sole carbon source in a 5 day fermentation period.