Fifteen isolates of Aspergillus flavus, six isolates of Aspergillus niger and two isolates of Penicillium chrysogenum showing chitinolytic activity were isolated from chitin-rich soils of shrimp drying fields. Major process parameters affecting the production of chitinases by two isolates of P. chrysogenum, PPCS 1 and PPCS 2 have been optimised under solid substrate conditions. Maximum chitinase was recovered from mouldy bran with 1% sodium chloride solution, which showed temperature and pH optima at 40 degrees C and 4.0, respectively. MS-HCl as a moistening medium and 24 degrees C growth temperature were most suitable for chitinase production by both isolates. Isolate PPCS 1 yielded maximum chitinase (3809 units g(-1) (U g(-1)) initial dry substrate) at pH 5.0; inoculum size 1 x 106 spore ml(-1) and 80% initial moisture content, whereas isolate PPCS 2 yielded maximum chitinase (2516 U g(-1) initial dry substrate) at pH 4.0; inoculurn size 1 x 10(10) spore ml(-1) and 120% initial moisture content. (c) 2005 Elsevier Ltd. All rights reserved.