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In this paper, the production of biomass and ligninolytic enzymes by the white-rot fungus Pleurotus pulmonarius (Fr.) Quelet cultured on wheat bran at high initial moisture was evaluated. When the initial moisture was lower than 86%, the fungal hyphae penetrated into and bound tightly to the solid-substrate particles. When the moisture was equal or higher than 86%, the growth was characterized by formation of a large mycelial mass above the substrate (surface growth). In this case, the mycelial mass could be easily separated from the residual solid substrate and quantified by gravimetric analysis. The fungus produced 0.32 g of dry mycelial mass per g of dry substrate after 15 days of cultivation. Analysis of the residual substrate showed that growth was mainly due to the consumption of soluble proteins and carbohydrates. The condition of high initial moisture strongly promoted the expression of laccase (up to 24,000 U per g of substrate or 78,000 U per g of dry fungal biomass), while the production of manganese peroxidase was negatively affected. In fact, manganese peroxidase was maximally produced when the initial moisture was 75% (2,000 U per g of substrate). The production of other enzymes, such as polysaccharidases and proteases, was not significantly affected by the initial moisture. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A solid-state system to obtain rapid in vivo industrial dye decolourisation by the white-rot fungus Pleurotus pulmonarius is proposed. When cultivated on glucose\ammonium tartrate–corncob solid-state medium, P. pulmonarius decolourised structurally different synthetic dyes (including azo, triphenylmethane, heterocyclic and polymeric dyes). Amido black, congo red, trypan blue, methyl green, remazol brilliant blue R (RBB), methyl violet, ethyl violet and brilliant cresyl blue were completely decolourised after 6 days of cultivation, while methylene blue and Poly R-478 were partially decolourised. The capability of fungal culture to decolourise industrial dyes appears to be due to high titres of laccase (480 U/ml) produced in response to the presence of soluble phenolics.

The effect of several phenolic and aromatic monomers structurally-related to lignin on production of laccase by the white rot fungus P. pulmonarius (Fr.) Quelet has been studied. In the absence of an inducer, laccase was maximally produced after depletion of carbon and nitrogen sources. Among 15 phenolic and aromatic compounds tested, ferulic acid and vanillin were the most efficient inducers, increasing the production of laccase activity up to 10 times. A mixture of ferulic acid and vanillin was more efficient to induce the production of laccase than the isolated phenolics. At least three laccase isoforms designated as lcc1, lcc2 and lcc3 were identified by eletrophoretic analysis of P. pulmonarius culture filtrates. The lcc1 and lcc2 isoforms were produced by non-induced cultures, while lcc3 was found only in induced-culture filtrates.