Endo-xylanases from Cohnella sp. AR92 aimed at xylan and arabinoxylan conversion into value-added products

HERO, JOHAN S.; PISA, JOSÉ H.; ROMERO, CINTIA M.; NORDBERG KARLSSON, EVA; LINARES-PASTÉN, JAVIER A.; MARTINEZ, M. ALEJANDRA

APPLIED MICROBIOLOGY AND BIOTECHNOLOGY

SPRINGER

Año: 2021

0175-7598

The genus Cohnella belongs to a group of Gram-positive endospore-forming bacteria within Paenibacillaceae family. Although most species were described as xylanolytic bacteria, the literature still lacks some key information regarding their repertoire of xylan degrading enzymes. The whole genome sequence of an isolated xylan degrading bacterium Cohnella sp. strain AR92 was found to contain five genes encoding putative endo-1,4-β-xylanases, of which four were cloned, expressed and characterized to better understand the contribution of the individual endo-xylanases to the overall xylanolytic properties of strain AR92. Three of the enzymes, CoXyn10A, CoXyn10C and CoXyn11A, were shown to be effective at hydrolysing xylans derived from agro-industrial by-products, producing oligosaccharides with substrate conversion values of 32.5%, 24.7%, and 10.6%, respectively, using sugarcane bagasse glucurono-arabinoxylan and of 29.9%, 19.1%, and 8.0%, respectively, using wheat bran derived arabinoxylan. The main reaction products from GH10 enzymes were xylobiose and xylotriose, whereas CoXyn11A produced mostly xylooligosaccharides (XOS) with 2 to 5 units of xylose, often substituted, resulting in potentially prebiotic arabinoxylooligosaccharides (AXOS). The endo-xylanases assayed displayed operational features (temperature optima from 49.9 ºC to 50.4 ºC and pH optima from 6.01 to 6.31) fitting simultaneous xylan utilization. Homology modelling confirmed the typical folds of the GH10 and GH11 enzymes, substrate docking studies allowed prediction of subsites (-2 to +1 in GH10, and -3 to +1 in GH11), and identification of residues involved in ligand interactions, supporting the experimental data. Overall, the Cohnella sp. AR92 endo-xylanases presented significant potential for enzymatic conversion of agro-industrial by-products into high-value products.