Bioprocessamento de resíduo agroindustrial e madeireiro da Amazônia via fermentação em estado sólido utilizando Ganoderma spp. para a produção de enzimas lignocelulolíticas

Abstract

Ganoderma species are reported to produce lignocellulolytic enzymes. These enzymes have high added value and can be obtained through solid mushroom cultivation in lignocellulosic residues. In this sense, this work aimed to evaluate the production of lignocellulolytic enzymes produced by Ganoderma lucidum and G. tropicum in solid fermentation using açaí seeds (Euterpe sp.) and marupá sawdust (Simarouba amara Aublet). The residues before and after the fermentation process were characterized in terms of proximate composition, macro and micronutrients, as well as structural changes. The enzymes were extracted in distilled water (ligninases) and in 0.1 M sodium acetate buffer (pH 5.0) (cellulases) every 2 days, for a total period of 30 days. Enzyme stability was evaluated against variations in pH and temperature, and in the presence of metal ions. After the fermentation of the fungi, in general, there was an increase in the content of proteins and available carbohydrates and a reduction of lipids and fibers, as well as signs of degradation of lignocellulosic fiber, mainly in the marupá-based residue after fermentation of G. tropicum. Acai seeds were the most efficient substrate in inducing enzyme synthesis. The highest activity of carboxymethylcellulases (CMCases) was observed on the 14th day of fermentation for G. tropicum (2.37 U/g) and on the 8th day for G. lucidum (1.92 U/g), when cultivated in açaí. While in marupá, the maximum activities of CMCases were observed on the 12th day of fermentation, both for G. tropicum (1.42 U/g) and for G. lucidum (0.48 U/g). The peaks of activity of FPases (total cellulases), in the fermentation in açaí, were of 0.04 U/g for G. tropicum and 0.21 U/g for G. lucidum, while in marupá, the maximum activity was of 0 .09 U/g for G. tropicum and 0.15 U/g for G. lucidum. As for laccases, fermentations in açaí showed maximum activity on the 8th day, with values of 29 U/mL for G. tropicum and 128 U/mL for G. lucidum. In contrast, in the marupá-based substrate, the maximum laccase activity was observed on the 8th day of fermentation for G. lucidum (23 U/mL) and on the 16th day for G. tropicum (7 U/mL). In the açaí based substrate, the highest concentrations of total peroxidases were observed on the 12th day for G. tropicum (37 U/mL) and G. lucidum (78 U/mL), while in marupá, the maximum activities were verified on the 16th day of fermentation for G. tropicum (12 U/mL) and on the 8th day for G. lucidum (25 U/mL). The optimal temperature for CMCases activity ranged between 30, 50 and 60 °C, while for FPases it was around 30 and 70 °C. Laccases showed greater stability up to an average temperature of 50 °C, compared to cellulases. CMCases obtained from fermentation in marupá sawdust were stable to ions, while FPases were strongly inhibited. G. tropicum produced more ion-stable ligninases. Ligninolytic enzymes were stable in different pH ranges. In general, both residues were good inducers of the synthesis of lignocellulolytic enzymes by G. lucidum and G. tropicum, with emphasis on açaí seeds.