Effect of moisture content in polyurethane foams as support for solid-substrate fermentation of Lecanicillium lecanii on the production profiles of chitinases

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, μ, and maximum biomass concentration, Xmax, there were significant differences in the enzyme production. Highest enzyme titers (emax) without glucose supplementation showed best results for >85% moisture content. emax, of exo-chitinase was 45-fold higher in CPUF than MPUF. Endochitinases, emax, 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, Ye/x, were higher with MPUF than with CPUF for endo-chitinases, but the reverse was found for exo-chitinases.