Improvement of xylanase production by thermophilic fungus Thermomyces lanuginosus SDYKY-1 using response surface methodology

Xylanase production by Aureobasidium pullulans on globe artichoke stem: Bioprocess optimization, enzyme characterization and application in saccharification of lignocellulosic biomass

Statistical optimization of the factors affecting xylanase production by Aureobasidium pullulans NRRL Y-2311-1 on globe artichoke stem was performed for the first time. The optimization strategies used resulted in almost six-fold enhancement of xylanase production (66.48 U/ml). Biochemical and thermal characterization of the crude xylanase preparation was performed to elucidate its feasibility for different industrial applications. The optimum conditions for xylanase activity were pH 4.0 and 30-50°C. The enzyme was very stable over a wide pH range of 3.0-8.0. The thermal stability studies revealed an inactivation energy of 183 kJ/mol. Thermodynamic parameters (enthalpy, entropy, and Gibbs free energy) for thermal inactivation were also determined. Primary application of the crude xylanase preparation in saccharification of corn cob subjected to different pretreatment techniques has been evaluated. The crude xylanase preparation was very promising for saccharification of corn cob pretreated with aqueous ammonia. The maximum yield of reducing sugar was 357 mg/g dry substrate, which revealed that the crude xylanase from A. pullulans could be a very good alternative in saccharification of lignocellulosic biomass for biological fuel generation. This study also provides a basis for further exploitation of globe artichoke by-products in microbial production of several other industrially significant metabolites.

High levels of β-xylosidase in Thermomyces lanuginosus: potential use for saccharification

A new strain of Thermomyces lanuginosus was isolated from the Atlantic Forest biome, and its β-xylosidases optimization in response to agro-industrial residues was performed. Using statistical approach as a strategy for optimization, the induction of β-xylosidases activity was evaluated in residual corn straw, and improved so that the optimum condition achieved high β-xylosidases activities 1003 U/mL. According our known, this study is the first to show so high levels of β-xylosidases activities induction. In addition, the application of an experimental design with this microorganism to induce β-xylosidases has not been reported until the present work. The optimal conditions for the crude enzyme extract were pH 5.5 and 60 °C showing better thermostability at 55 °C. The saccharification ability of β-xylosidase in the presence of hemicellulose obtained from corn straw raw and xylan from beechwood substrates showed a xylo-oligosaccharide to xylose conversion yield of 80 and 50%, respectively, at 50 °C. Our data strongly indicated that the β-xylosidases activities was not subjected to the effects of potential enzyme inhibitors often produced during fermentation process. These data suggest the application of this enzyme studied for saccharification of hemicellulose, an abundant residue in the American continents, thus providing an interesting alternative for future tests for energy production.

Production of Biomass-Degrading Multienzyme Complexes under Solid-State Fermentation of Soybean Meal Using a Bioreactor

Biomass-degrading enzymes are one of the most costly inputs affecting the economic viability of the biochemical route for biomass conversion into biofuels. This work evaluates the effects of operational conditions on biomass-degrading multienzyme production by a selected strain of Aspergillus niger. The fungus was cultivated under solid-state fermentation (SSF) of soybean meal, using an instrumented lab-scale bioreactor equipped with an on-line automated monitoring and control system. The effects of air flow rate, inlet air relative humidity, and initial substrate moisture content on multienzyme (FPase, endoglucanase, and xylanase) production were evaluated using a statistical design methodology. Highest production of FPase (0.55 IU/g), endoglucanase (35.1 IU/g), and xylanase (47.7 IU/g) was achieved using an initial substrate moisture content of 84%, an inlet air humidity of 70%, and a flow rate of 24 mL/min. The enzymatic complex was then used to hydrolyze a lignocellulosic biomass, releasing 4.4 g/L of glucose after 36 hours of saccharification of 50 g/L pretreated sugar cane bagasse. These results demonstrate the potential application of enzymes produced under SSF, thus contributing to generate the necessary technological advances to increase the efficiency of the use of biomass as a renewable energy source.