Production of xylanase by a new strain of Thermoascus aurantiacus: obtainment of enzymatic extract with reduced cellulolytic activity for application in pulp and paper industries / Produção de xilanase por nova linhagem de Thermoascus aurantiacus: obtenção de extrato enzimático com reduzida atividade celulolítica para aplicação em indústria de papel e celulose

Xylanases are useful in several industrial segments, including pulp and paper bleaching, animal feed, and bread-making processes. However, the industrial use of these enzymes is closely related to its production cost and its catalytic properties. The process of solid state fermentation enables the use of agro-industrial residues as substrates for microbial cultivation and enzymes production, reducing costs. In the present study, different cultivation parameters were evaluated for the xylanase production by the thermophilic fungus Thermoascus aurantiacus, by solid state fermentation, using agro-industrial residues as substrates. High production of xylanase (1701.9 U g-1 of dry substrate) was obtained using wheat bran containing 65% of initial moisture, at 120 h of cultivation, and 45°C. The xylanase showed optimal activity at pH 5.0 and 75°C; its stability was maintained at pH 3.0­11.0. The enzyme retained its catalytic potential after 1 h, at 75°C. The enzymatic extract produced under optimized conditions showed reduced activities of endoglucanase and FPase. Our results, including the xylanase production by T. aurantiacus in low-cost cultivation medium, high structural stability of the enzyme, and reduced cellulolytic activity, encourage the application of this enzymatic extract in pulp and paper bleaching processes.

As xilanases apresentam aplicabilidade em diferentes segmentos industriais, como: branqueamento de papel e celulose, ração animal e panificação. No entanto, a utilização industrial dessas enzimas está intimamente relacionada com seu custo de produção e suas propriedades catalíticas. O processo de fermentação em estado sólido possibilita o uso de resíduos agroindustriais como substratos, para o cultivo microbiano e produção de enzimas, reduzindo o custo da produção enzimática. No presente trabalho, diferentes parâmetros de cultivo foram avaliados para produção de xilanase por cultivo em estado sólido do fungo termófilo Thermoascus aurantiacus, utilizando resíduos agroindustriais como substratos. A maior produção de xilanase, 1701,9 U g-1 de substrato seco, foi obtida no cultivo em farelo de trigo, contendo 65% de umidade inicial, em 120 horas de cultivo a 45°C. A xilanase produzida apresentou atividade ótima em pH 5,0 a 75°C, mantendo sua estabilidade em pH 3,0 a 11,0. A enzima manteve seu potencial catalítico após 1 h a 75°C. O extrato enzimático produzido nas condições otimizadas apresentou reduzida atividade de endoglucanase e FPase. Os resultados obtidos no presente trabalho (produção de xilanase pelo fungo em meios de cultivo de baixo custo, elevada estabilidade estrutural da enzima e reduzida atividade celulolítica) estimulam a aplicação desse complexo enzimático em processos de branqueamento de papel e celulose.

Production of beta-glucosidase on solid-state fermentation by Lichtheimia ramosa in agroindustrial residues: characterization and catalytic properties of the enzymatic extract

Background β-Glucosidases catalyze the hydrolysis of cellobiose and cellodextrins, releasing glucose as the main product. This enzyme is used in the food, pharmaceutical, and biofuel industries. The aim of this work is to improve the β-glucosidase production by the fungus Lichtheimia ramosa by solid-state fermentation (SSF) using various agroindustrial residues and to evaluate the catalytic properties of this enzyme. Results A high production of β-glucosidase, about 274 U/g of dry substrate (or 27.4 U/mL), was obtained by cultivating the fungus on wheat bran with 65% of initial substrate moisture, at 96 h of incubation at 35°C. The enzymatic extract also exhibited carboxymethylcellulase (CMCase), xylanase, and β-xylosidase activities. The optimal activity of β-glucosidase was observed at pH 5.5 and 65°C and was stable over a pH range of 3.5-10.5. The enzyme maintained its activity (about 98% residual activity) after 1 h at 55°C. The enzyme was subject to reversible competitive inhibition with glucose and showed high catalytic activity in solutions containing up to 10% of ethanol. Conclusions β-Glucosidase characteristics associated with its ability to hydrolyze cellobiose, underscore the utility of this enzyme in diverse industrial processes.

Production of enzymes from Lichtheimia ramosa using Brazilian savannah fruit wastes as substrate on solid state bioprocessess

Background: Enzyme production by solid state bioprocess (SSB) using residues as substrate for microorganisms is an alternative for costs reduction and to avoid their disposal into environment. The aim of this work was to evaluate the physiology of the fungus Lichtheimia ramosa in terms of microbial growth and production of amylases, β-glucosidases, carboxymethylcellulase (CMCase), and xylanases, via SSB, utilizing wastes of the Brazilian savannah fruits bocaiuva (Acrocomia aculeata), guavira (Campomanesia pubescens) and pequi (Caryocar brasiliense) as substrate at different temperatures (25, 30, and 35ºC) during 168 hrs. Results: Samples were taken every 24 hrs, which resulted in 8-points kinetic experiments to determine microbiological and enzymatic contents. The best substrate for β-glucosidase activity was pequi waste after 48 hrs at 30ºC (0.061 U/mL). For amylase activity, bocaiuva presented itself as the best substrate after 96 hrs at 30ºC (0.925 U/mL). CMCase activity was higher in guavira waste after 96 hrs at 35ºC (0.787 U/mL). However, the activity was more expressive for xylanase in substrate composed of bocaiuva residue after 144 hrs at 35ºC (1.802 U/mL). Conclusions: It was concluded that best growth condition for L. ramosa is at 35ºC for all substrates and that xylanase is the enzyme with more potential in SSB, considering the studied Brazilian savannah fruit wastes.