No abstract

A B S T R A C TThe use of microbial enzyme cocktails for the conversion of polysaccharides of plant origin into fermentable sugars is a global trend. The objectives of this study were to optimize the production of cellulases and hemicellulases by the fungus Lichtheimia ramosa, evaluate the catalytic properties of the produced enzymes, and apply these biocatalysts in the saccharification of sugarcane bagasse. The production of carboxymethylcellulase (CMCase), β-glucosidase, xylanase, and β-xylosidase by L. ramosa were 168.1 ± 2.2, 270.4 ± 8.9, 34 ± 0.8, and 199.2 ± 2.6 U/g of dry substrate, respectively. The optimum pH for the activity of the enzymes ranged between 4.5 and 5.5, and the optimum temperature varied between 55°C and 65°C. The enzymes were stable within a wide range of pH, and approximately 95% of their original activity was preserved when incubated for 1 h at 55°C. The half-lives (t 1/2 ) of CMCase, β-glucosidase, xylanase, and β-xylosidase were 68, 59, 52, and 54 min, respectively, when incubated at 60°C. The enzymes were stable in solutions containing ethanol (10%), and the kinetic parameters (K m and V max ) demonstrated that β-glucosidase from L. ramosa was competitively inhibited by glucose. The enzyme extract produced by L. ramosa was used for the saccharification of sugarcane bagasse pretreated with glycerol and the highest yield of glucose (10.66%) was obtained at 24 h of hydrolysis. The characteristics of the enzymes, combined with the efficiency in hydrolyzing sugarcane bagasse, allow for the application of this enzyme extract to processes of cellulose saccharification for the production of second-generation ethanol.

Invertases are used for several purposes; one among these is the production of fructooligosaccharides. The aim of this study was to biochemically characterize invertase from industrial Saccharomyces cerevisiae CAT-1 and Rhodotorula mucilaginosa isolated from Cerrado soil. The optimum pH and temperature were 4.0 and 70 °C for Rhodotorula mucilaginosa invertase and 4.5 and 50 °C for Saccharomyces cerevisiae invertase. The pH and thermal stability from 3.0 to 10.5 and 75 °C for R. mucilaginosa invertase, respectively. The pH and thermal stability for S. cerevisiae CAT-1 invertase from 3.0 to 7.0, and 50 °C, respectively. Both enzymes showed good catalytic activity with 10% of ethanol in reaction mixture. The hydrolysis by invertases occurs predominantly when sucrose concentrations are ≤5%. On the other hand, the increase in the concentration of sucrose to levels above 10% results in the highest transferase activity, reaching about 13.3 g/L of nystose by S. cerevisiae invertase and 12.6 g/L by R. mucilaginosa invertase. The results demonstrate the high structural stability of the enzyme produced by R. mucilaginosa, which is an extremely interesting feature that would enable the application of this enzyme in industrial processes.

Amylases catalyze the hydrolysis of starch, a vegetable polysaccharide abundant in nature. These enzymes can be utilized in the production of syrups, alcohol, detergent, pharmaceutical products, and animal feed formulations. The aim of this study was to optimize the production of amylases by the filamentous fungus Gongronella butleri by solid-state fermentation and to evaluate the catalytic properties of the obtained enzymatic extract. The highest amylase production, 63.25 U g−1 (or 6.32 U mL−1), was obtained by culturing the fungus in wheat bran with 55% of initial moisture, cultivated for 96 h at 25°C. The enzyme presented optimum activity at pH 5.0 and 55°C. The amylase produced was stable in a wide pH range (3.5–9.5) and maintained its catalytic activity for 1 h at 40°C. Furthermore, the enzymatic extract hydrolyzed starches from different vegetable sources, presenting predominant dextrinizing activity for all substrates evaluated. However, the presence of glucose was observed in a higher concentration during hydrolysis of corn starch, indicating the synergistic action of endo- and exoamylases, which enables the application of this enzymatic extract to produce syrups from different starch sources.