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Pectinase is an important enzyme that finds application in many food processing industries and solid-state fermentation (SSF) is an attractive technology for enzyme production. In this work, a SSF process is described for the production of pectinase by Aspergillus niger Aa-20 and lemon peel pomace (LPP) as support and carbon source in a solid-state bioreactor. The process consists of three steps. (1) Selection of microorganism for SSF. Eight different fungal strains from the genus Aspergillus and Penicillium were screened for invasion ability on LPP; (2) Selection of particle size. Invasion ability of selected fungal strain was analyzed on four particle sizes of LPP; (3) SSF process was operated in a column-tray bioreactor at 30 degrees C and 70% moisture content, 194 mL/min of air flow rate and substrate particle size (2-0.7 mm) of LPP for 96 h. Results showed, that high levels of pectinase activities were obtained. The maximum pectinase activity obtained was 2181 U/L Maximum biomass and maximum specific growth rate of A. niger Aa-20 were X-max = 8 mg glucosamine/g of LPP and mu(max) = 0.1271/h. The LPP and the use of A. niger Aa-20 in SSF suggest as a very promising process for pectinase production. (c) 2012 Elsevier B.V. All rights reserved.