Fitopatógenos de cana-de-açúcar: caracterização do potencial de produção de enzimas lignocelulolíticas

Abstract

The production of second generation ethanol from lignocellulosic biomasses depends on physical, chemical and enzymatic pretreatment steps, in which simple sugars are released from the constituents of cellulose and hemicellulose. However, these processes require optimization in order to avoid the production of inhibitory molecules of fermentation and increase the concentration of fermentable sugars, an alternative to achieve this objective is by diversifying the existing lignocellulolytic enzyme pool. Thus, the present study aimed to analyze the potential of sugarcane pathogens Sporisorium scitamineum, Colletotrichum falcatum and Thielaviopsis paradoxa in the production of lignocellulolytic enzymes. Initially, qualitative assays indicated the production of cellulases and phenoloxidases in vitro by C. falcatum and T. paradoxa, and were further submitted to solid-state fermentation using sugarcane bagasse as a substrate. A complete factorial design was used to determine the influence of the addition of yeast extract (0-5%), moisture (85-95%) and culture time (4-12 days) on the enzymatic activity of endoglucanase, total cellulase, laccase and lignin peroxidase. For T. paradoxa, the operational condition of 95% moisture, 5% yeast extract and 4 days of cultivation, maximized the production of endoglucanase and total cellulase, being (U mL-1) 0.690 and 0.307 the maximum activities achieved, respectively. For C. falcatum, 90% moisture and 5% yeast extract, without influence of the culture time, generated better endoglucanase and total cellulase activity, with the maximum yields obtained (U mL-1) being 2,754 and 0,183, respectively. Laccase activity was verified only in the extract of C. falcatum (95% moisture, 5% yeast extract, 12 days), reaching 473.85 IU L-1. Lignin peroxidase activity was not observed in any analyzed extract. In addition, an in silico analysis of the set of proteins encoded by the three pathogens was compared to that of Trichoderma reesei, in order to identify the CAZy domain proteins. The data show that C. falcatum has the highest number of proteins active in carbohydrates and can supplement the enzymatic extracts of T. reesei with activities related to the pectin and lignin break, mainly.