Abstract
Problem statement: The production of hydrolytic enzymes by T. aurantiacus has been performed under solid-state fermentations using lignocellulosic materials. The influences of the inoculum size and of the fermentation medium on the production of hemicellulases and cellulases were studied. Filtrates from the cultures were used to hydrolyze a pulp of sugarcane bagasse and the produced enzymes were shown to be candidates for use as co-adjuvants in plant saccharification. Aproach: The present study focuses on the effect of different culture conditions on production of cellulases and hemicellulases by T. aurantiacus. It is also provides a possible application of T. aurantiacus enzymes in the degradation of sugarcane bagasse pulp, considering that this thermophilic fungus is a potential source of thermostable enzymes. Results: T. aurantiacus was cultivated on four different agricultural residues: sugarcane bagasse, sugarcane straw, wheat straw and corn cob. Xylanase was produced with much more expressive activity than cellulases. The highest titre of xylanase was obtained on sugarcane straw at 9 days (1679.8 IU g−1); the same was observed for β- glucosidase (29.9 IU g−1) at 6 days. With an inoculum load of 108 spores g−1, the amount of exoglucanase produced by the fungus considerably exceeds that produced with 104 spores g−1. Xylanases and cellulases purified from filtrates of the cultures were investigated to hydrolyze a bagasse pulp prepared with alkaline peroxide. Xylanase or sulphuric acid were used as pretreatments for xylan removal, increasing the cellulase performance on pulp bagasse. However, results revealed that the removal of hemicellulose is not the only main factor limiting the cellulose hydrolysis. Conclusion: Results indicate that the xylanase action on alkaline-pretreated sugar cane bagasse enhances the cellulolytic effect promoted by a commercial cellulase. This study thus presents an evaluation of the applicability of enzymes from Thermoascus aurantiacus to potentially improve the enzymatic cellulose hydrolysis.
Highlights
The study of sugarcane as a feedstock for the production of biofuel is a significant endeavor (Kuo and Lee, 2009; Lee and Breessan, 2006; Baudel et al, 2005; Adsul et al, 2005)
An alkaline peroxide to treat bagasse was reported by Brienzo et al (2009), resulting in a pulp with 5.9% lignin, 16.1% hemicellulose and 61% cellulose
We examined the extracellular hydrolysis of p-nitropheny l-β-1, 4-O-glucoside. βenzymes produced by T. aurantiacus in various culture xylosidase activity was determined using p-nitrophenylconditions
Summary
The study of sugarcane as a feedstock for the production of biofuel is a significant endeavor (Kuo and Lee, 2009; Lee and Breessan, 2006; Baudel et al, 2005; Adsul et al, 2005). Counted in a Neubauer chamber and a standardized Some filamentous fungi produce cellulases that suspension (104 or 108 spores −1g substrate) was retain relatively high cellulose-degrading activity at inoculated into Erlenmeyer flasks of 300 mL with 15 g temperatures of 50-70°C, species such as of the different agroindustrial residues: sugarcane. Different T. aurantiacus strains show endoglucanases with acid pI (around 3.5-3.7) Enzymatic activities: The xylanase activity was (Hong et al, 2007; Parry et al, 2001) that display high determined in a mixture containing 800 μL of stability (at 70°C half live of 98 h)
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