Produção e aplicação de extratos enzimáticos de fungos da podridão branca como pré-tratamento para sacarificação de resíduos agrícolas

Abstract

Ethanol derived from biomass is one of the most applied renewable sources of energy, however, in its production are used carbohydrate sources grown only for the alcoholic fermentation, diverting food production and rendering more expensive the land price. In the second generation of ethanol are employed lignocellulosic wastes from agroindustry. A bottleneck of this technique is the physical and chemical barrier formed by lignin which hinders the conversion of cellulose into simple sugars. In this work was studied the production of enzyme extracts rich in laccase, an important lignolitic enzyme which is present in the biodegradation of lignin by white rot fungi. Fungi Pleurotus ostreatus, Ganoderma lucidum and Trametes sp. were tested in static and shaken submerged culture, besides the addition of potential inducers of laccase, rice husks, milled eucalyptus and copper (II) sulfate. The cultivations were run in 7 days, at 28 °C and 120 rpm (shaken) and the medium contained glucose, monobasic potassium phosphate, magnesium sulfate and peptone. The enzymatic extracts were filtered through filter paper and the laccase activity was detected spectrophotometrically at 420 nm according to the degradation of 2,2'-Azino-bis (3- etilbenzetiazolino-6-sulfonic acid). The best results for each fungus were: 7182.81 ± 383.03 U/L, Pleurotus ostreatus with copper sulfate and eucalyptus; 2679.89 ± 369.58 U/L, Trametes sp. with copper sulfate and rice hulls; 217.95 ± 7.77 U/L, Ganoderma lucidum with copper sulfate and eucalyptus. Then the produced extracts were applied on rice husk and Eucalyptus Urophyla together with chemical mediators for laccase (syringaldazine, hydroalcoholic extract of grape and the acids vanillic, ferulic, gallic and 4-hydroxybenzoic). The products of this treatment were saccharificated with Cellic Ctec2 (Novozymes). The highest releases of sugars were obtained when the treatment with laccase was run with 4-hydroxybenzoic acid (2,93 g L-1 for rice husk and 1,07 g L-1 for Eucalyptus Urophyla).