Effect of moisture content in polyurethane foams as support for solid-substrate fermentation of Lecanicillium lecanii on the production profiles of chitinases Marı ´a del Carmen Marin-Cervantes, Yoyi Matsumoto, Laura Ramı ´rez-Coutin ˜o, Zaizy Rocha-Pino, Gustavo Viniegra, Keiko Shirai * Universidad Autonoma Metropolitana, Biotechnology Department, Laboratory of Biopolymers, Avenue San Rafael Atlixco No. 186. Col. Vicentina, C.P. 09340, Mexico City, Mexico Received 26 January 2007; received in revised form 31 August 2007; accepted 15 October 2007 Abstract Finely minced (MPUF) and roughly cut (CPUF) polyurethane foam was used as inert support for the growth and chitinases production of Lecanicillium lecanii by solid-substrate fermentation. L. lecanii growths on CPUF produced loose and disperse mycelia throughout the polymer honeycomb, but MPUF resulted in dense aggregates at the ends of the polymer branches. Despite similar growth rates, m, and maximum biomass concentration, X max , there were significant differences in the enzyme production. Highest enzyme titers (e max ) without glucose supplementation showed best results for >85% moisture content. e max , of exo-chitinase was 45-fold higher in CPUF than MPUF. Endochitinases, e max , were similar for CPUF and MPUF. Catabolic repression of enzyme production depended on moisture level, being stronger for lower moisture contents for exo- chitinases and milder or insignificant for endo-chitinases. Biomass yield coefficients of enzymes, Y e/x , were higher with MPUF than with CPUF for endo-chitinases, but the reverse was found for exo-chitinases. # 2007 Elsevier Ltd. All rights reserved. Keywords: Lecanicillium lecanii; Polyurethane foam; Chitinases; Entomopathogenic fungi 1. Introduction Verticillium are gathered mycoparasitic and entomopatho- genic species that produce extracelullar enzymes, such as chitinases. Several strains of Lecanicillium lecanii and Verticillium fungicola were evaluated as chitinase producers, and it is reported the activity to induce morphological changes in phytopathogen fungi [1]. The strains of Verticillium fungicola USDA 4519 and those of Lecanicillium lecanii USDA 974, USDA 2460, and ATCC 26854 showed the highest activities. Natural polymeric substrates, such as chitin, have been used to support growth of Lecanicillium lecanii as source of nutrients as well as inducer [2]. Chitin is not degraded inside the cell due to its insolubility, size, molecular complexity and heterogeneous composition but fungi secrete chitinases with different specificity, endochiti- nases and exochitinases, which are able to transform or hydrolyse chitin [3]. Verticillium lecanii (Lecanicillium lecanii) has been culti- vated in solid substrate fermentation (SSF) using chitin as carbon source. SSF produced a highly concentrated enzymatic extract with very active chitinases [2]. The readily available sugar cane bagasse was used as support for fungal growth in that study; however, such SSF showed problems of substrate sterilization, temperature and pH control, as well contamination of the system, which was mainly detected at long process time. Besides, the enzymatic extracts carried impureness from the organic support, which involved a harder purification process. The substrates in SSF, which are usually by products of agro- industry, have some disadvantages, such as excessive thickness of the substrate layer, low porosity, or inadequate internal structures that disturbed the aeration, heat removal and inefficient nutrient uptake. In most of these systems it is not possible to separate residual solid substrate from biomass, www.elsevier.com/locate/procbio Process Biochemistry 43 (2008) 24–32 * Corresponding author. Tel.: +52 5 5804 49 21; fax: +52 5 5804 47 12. E-mail address: smk@xanum.uam.mx (K. Shirai). 1359-5113/$ – see front matter # 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.procbio.2007.10.009