Pleurotus pulmonarius (Fr)

The effect of several phenolic and aromatic monomers structurally-related to lignin on production of laccase by the white rot fungus P. pulmonarius (Fr.) Quélet 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.

The production of ligninolytic enzymes (laccase and Mn-dependent peroxidase) by the white-rot fungus Pleurotus pulmonarius (FR.) Quélet was studied in solid-state cultures using agricultural and food wastes as substrate. The highest activities of laccase were found in wheat bran (2,860 ± 250 U/L), pineapple peel (2,450 ± 230 U/L), and orange bagasse (2,100 ± 270 U/L) cultures, all of them at an initial moisture level of 85 %. The highest activities of Mn peroxidase were obtained in pineapple peel cultures (2,200 ± 205 U/L) at an initial moisture level of 75 %. In general, the condition of high initial moisture level (80-90 %) was the best condition for laccase activity, while the best condition for Mn peroxidase activity was cultivation at low initial moisture (50-70 %). Cultures containing high Mn peroxidase activities were more efficient in the decolorization of the industrial dyes remazol brilliant blue R (RBBR), Congo red, methylene blue, and ethyl violet than those containing high laccase activity. Also, crude enzymatic extracts with high Mn peroxidase activity were more efficient in the in vitro decolorization of methylene blue, ethyl violet, and Congo red. The dye RBBR was efficiently decolorized by both crude extracts, rich in Mn peroxidase activity or rich in laccase activity.

In this paper, the production of biomass and ligninolytic enzymes by the white-rot fungus Pleurotus pulmonarius (Fr.) Quélet 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.

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