Using valonia tannin (an ellagitannin) as the substrate, factors influencing the yield of ellagic acid and biosynthesis of valonia tannin hydrolase by Aspergillus SHL 6 are investigated. Valonia tannin concentration, pH, temperature, carbon and nitrogen sources during the fermentation are identified as important hydrolysis parameters. The yield of ellagic acid and the hydrolase activity of valonia tannin both have maximum values (within the range of the tests) when 100 ml of culture medium containing 5.0 g 1(-1) of valonia tannin in a 250 ml conical beaker is incubated at 28 degreesC and initial pH from 4.5 to 5.0 using a rotary shaker at 120 rpm for 72 h. (C) 2004 Elsevier Ltd. All rights reserved.