Screening of Xylanolytic Aspergillus fumigatus for Prebiotic Xylooligosaccharide Production Using Bagasse

Abstract

Currently, lignocellulosic waste is a topic of global studies, given that fossil fuel reserves are diminishing, the new agricultural frontiers are limited and the demand for food and biofuels is increasing by the growing world population (1). For these reasons, technology must advance to improve the use of agricultural and agroindustrial residues to obtain food and biofuel.Xylans present in lignocellulosic materials have been studied for obtaining xylooligosaccharides (XOS) from waste materials such as corncobs, rice hulls, olive pits, barley straw (2), tobacco stalk, cott on stalk, sunfl ower stalk, wheat straw (3) and sugarcane bagasse (4-6). Sugarcane bagasse is inexpensive, renewable and abundant source of XOS especially in the countries that produce ethanol and sugar from sugarcane. However, more research is necessary to improve the use of this residue. SummarySugarcane bagasse is an important lignocellulosic material studied for the production of xylooligosaccharides (XOS). Some XOS are considered soluble dietary fi bre, with low caloric value and prebiotic eff ect, but they are expensive and not easily available. In a screening of 138 fungi, only nine were shortlisted, and just Aspergillus fumigatus M51 (35.6 U/mL) and A. fumigatus U2370 (28.5 U/mL) were selected as the most signifi cant producers of xylanases. These fungi had low β-xylosidase activity, which is desirable for the production of XOS. The xylanases from Trichoderma reesei CCT 2768, A. fumigatus M51 and A. fumigatus U2370 gave a signifi cantly higher XOS yield, 11.9, 14.7 and 7.9 % respectively, in a 3-hour reaction with hemicellulose from sugarcane bagasse. These enzymes are relatively thermostable at 40-50 °C and can be used in a wide range of pH values. Furthermore, these xylanases produced more prebiotic XOS (xylobiose and xylotriose) when compared with a commercial xylanase. The xylanases from A. fumigatus M51 reached a high level of XOS production (37.6 %) in 48-72 h using hemicellulose extracted from sugarcane bagasse. This yield represents 68.8 kg of prebiotic XOS per metric tonne of cane bagasse. In addition, in a biorefi nery, aft er hemicellulose extraction for XOS production, the residual cellulose could be used for the production of second-generation ethanol.

The potential of tailoring the conditions of steam explosion to produce xylo-oligosaccharides from sugarcane bagasse

“…2A). This was expected based on previous report with the Aspergilus fumigatus M51 endoxylanase used in this study (Carvalho et al, 2015). In fact, low DP XOS, predominantly xylobiose are known to be the typical products of endoxylanases (Qing and Wyman, 2011).…”

“…The EH of the extracted xylan was carried out at conditions previously optimized (Figueiredo et al, 2016). Briefly, 7% consistence (w/ v) xylan in an Erlenmeyer (125 mL) with 40 mL of acetate buffer (0.5 M, pH 5.0) was treated with an Aspergilus fumigatus M51endoxylanase (350 U/g of substrate) produced in Erlenmeyer as described elsewhere (Carvalho et al, 2015). The hydrolysis was incubated at 50°C for 48 h in shaker (model TE 405; Tecnal) at 130 rpm.…”

From lignocellulosic residues to market: Production and commercial potential of xylooligosaccharides

“…Chemical and auto-hydrolysis generate XOS with a wide range of polymerization (from DP2 to DP20) (Kaprelyants et al, 2017;Li et al, 2018), while enzymatic processes generate mostly low-DP XOS (from DP2 to DP4) (Carvalho et al, 2015;Kaprelyants et al, 2017;Sukri and Sakinah, 2018). It is well known that low-DP XOS present a higher prebiotic potential (Okazaki et al, 1990;Moura et al, 2007;Ho et al, 2018), hence being more suitable for food-related and pharmaceutical applications (Vázquez et al, 2000).…”

Production of Oligosaccharides from Agrofood Wastes

“…If the XOS recovery of commercial xylanase action is compared that due to microbial extracts, different results come forth when hydrolyzing the same substrate. In the work of Azevedo et al, different behaviors are appreciated when comparing the action of various microbial extracts that contain enzymes with xylanase activity and commercial preparations employing the same conditions (50 • C, pH 5, 1-96 h and hemicellulose from sugar cane bagasse) [116]. The concentrations reached with commercial enzymes are lower (0.50 g/L) than those obtained from the best microbial extract from Aspergillus fumigatus M51 (1.04 g/L).…”