INSIGHTS INTO THE XYLAN DEGRADATION SYSTEM OF CELLULOMONAS sp. B6: BIOCHEMICAL CHARACTERIZATION OF XYLANASE CsXyn10A AND ARABINOFURANOSIDASE CsAbf62A

GARRIDO, MERCEDES; LANDONI, MALENA; PEÑA, MARIA JESUS; TOPALIAN, JULIANA; WIRTH, SONIA; URBANOWICZ, BREEANNA; CAMPOS, ELEONORA

Buzios

Simposio; XXIII SIMPÓSIO NACIONAL DE BIOPROCESSOS ? SINAFERM XIV SEMINÁRIO DE HIDRÓLISE ENZIMÁTICA DE BIOMASSAS ? SHEB XIV SEMINÁRIO BRASILEIRO DE TECNOLOGIA ENZIMÁTICA ? ENZITEC; 2022

Valorization of the hemicellulose fraction of plant biomass is crucial for the sustainability oflignocellulosic biorefineries (Qaseem et al., 2021). The Cellulomonas genus comprises Gram-positive actinobacteria that degrade cellulose and other polysaccharides by secreting a complexarray of enzymes, under appropriate culture conditions. In this work, we studied the specificity andsynergy of two enzymes, CsXyn10A and CsAbf62A, which were identified as highly abundant in theextracellular proteome of Cellulomonas sp. B6 when grown on wheat bran as carbon source,suggesting they have a relevant role in arabinoxylan degradation (Piccinni et al., 2019; Ontañon etal,.2020). To understand their contribution to xylan utilization and explore their potential forbioprocessing, recombinant enzymes were heterologously expressed in E. coli and their activitieswere thoroughly characterized. rCsXyn10A is active across a broad pH range (5 to 9) attemperatures up to 55 °C, with a specific activity of almost 450 IU/mg (as xylose equivalents) and aKM of 7.9 mg/mL (on beechwood xylan). It cleaves the backbone of glucuronoxylan andarabinoxylan, releasing short xylo-oligosaccharides, xylobiose and xylose. rCsAbf62A specificallyremoves α-1,2 and α-1,3-L-arabinosyl substituents attached to monosubstituted xylose andarabinose in xylan and arabinan backbone, respectively, but it cannot act on double substitutedresidues. It has a specific activity of 17.0 IU/mg and of 0.2 IU/mg with a KM of 2.5 μM, onarabinoxylan and pNPA, respectively. The amount of xylobiose released from either wheatarabinoxylan or arabino-xylo-oligosaccharides increased significantly when rCsXyn10A wassupplemented with rCsAbf62A, indicating that the removal of arabinosyl residues by rCsAbf62Aimproved rCsXyn10A accessibility to β-1,4-xylose linkages. Although both enzymes have activity onwheat bran, confirming their potential to act on complex biomass, no synergy was observed,indicating that additional enzymes are necessary for full xylan hydrolysis from this feedstock. Theseresults contribute to designing tailor-made, substrate specific enzymatic cocktails for xylanvalorization.