Synergistic effect and application of xylanases as accessory enzymes to enhance the hydrolysis of pretreated bagasse

Abstract

Recently, the new trend in the second-generation ethanol industry is to use mild pretreatments, in order to reduce costs and to keep higher content of hemicellulose in the biomass. Nevertheless, a high enzyme dosage is still required in the conversion of (hemi)cellulose. The interaction between cellulases and xylanases seems to be an effective alternative to reduce enzyme loading in the saccharification process. At first, to evaluate the synergism of xylanases on bagasse degradation, we have produced two xylanases from glycoside hydrolase family 10 (GH10) and three xylanases from glycoside hydrolase family 11 (GH11), from two thermophilic organisms, Thermobifida fusca and Clostridium thermocellum, and one mesophilic organism, Streptomyces lividans. Peracetic acid (PAA) pretreated bagasse was used as substrate. The combination of XynZ-C (GH10, from C. thermocellum), and XlnB (GH11, from S. lividans) presented the highest degree of synergy after 6h (3.62). However, the combination of XynZ-C and Xyn11A (GH11, from T. fusca) resulted in the highest total yield of reducing sugars. To evaluate the synergism between xylanases and cellulases, commercial cellulase preparation from Trichoderma reesei was combined with the selected xylanases, XynZ-C and Xyn11A. About 2-fold increase was observed in the concentration of reducing sugars, when both xylanases, XynZ-C and Xyn11A, were added together with T. reesei cellulases in the reaction mixture.

Accessory enzymes influence cellulase hydrolysis of the model substrate and the realistic lignocellulosic biomass

“…The effect boosted by the simultaneous addition of accessory enzymes is far better than the overall that of their respective additions, implying a synergistic interaction of multiple accessory enzymes and cellulase enzymes [1,4,7]. With the simultaneous addition of 8.0 mg Htec, 8.0 mg Novozyme 188 and 2.0 mg AA9, the enzyme hydrolysis at 48 hr was 47%, which enhanced 47% as compare to that of the CTec1 loading alone.…”

“…Hemicellulases and pectinases can hydrolyze their respective non-cellulosic polysaccharide substrates that coat cellulose fibers, and thus assist in the hydrolysis of cellulose to boost a release of fermentable sugars from lignocellulosic biomass [4,12]. A xylanase-boosting effect has been observed on a range of pretreated lignocellulosic materials, regardless of their xylan content [7].…”

“…To improve the hydrolytic efficiency of cellulase enzyme preparations, considerable attempts have traditionally focused on their component cellulases because cellulose is the most abundant polysaccharide constituent in lignocellulose. However, it is now recognized that it is necessary to achieve an efficient enzymatic co-hydrolysis of the cellulose and hemicellulose present in pretreated lignocellulosic substrates to fermentable sugars, which requires a supplementation of the cellulases with some accessory enzymes [2][3][4].…”

Purification and Characterization of Xylanase from Spent Mushroom Compost and its Application in Saccharification of Biomass Wastes

“…Extracellular enzymes from SMC include cellulases, xylanases, and ligninases (Isikhuemhen and Mikiashvilli 2009;MayoloDeloisa et al 2009;Yang et al 2015), the activities and amounts of which depend on the mushroom species and its cultivation conditions. These extracellular enzymes have shown wide applications in the brewing, baking, leather, textile, and saccharification industries (Xin and He 2013;Goncalves et al 2015;Kocabas et al 2015). The extracellular enzymes extracted from these SMCs have broad potential applications.…”

Addition of β-galactosidase boosts the xyloglucan degradation capability of endoglucanase Cel9D from Clostridium thermocellum

“…The addition of non-cellulolytic enzymes, such as xylanases, can further enhance the hydrolytic potential of cellulase mixtures [10–12] and increase the hydrolytic efficiency of pretreated bagasse by enhancing cellulose accessibility [13]. Similarly, the degradation of xylans, particularly arabinoxylans, can be improved by exploiting the synergistic effects of β-xylanases, β-xylosidases, and α-arabinofuranosidases [14–16].…”