Application of xylanases and debranching enzymes of Cellulomonas sp. B6 for plant polysaccharides deconstruction into compounds with prebiotic and biopharmaceutical potential

ONTAÑON, ORNELLA; GARRIDO, MERCEDES M; LANDONI, MALENA; TOPALIAN, JULIANA ; LAURA NAVAS; CAMPOS, ELEONORA

Mendoza

Congreso; Congreso SAIB 2022; 2022

Xylan is the most abundant hemicellulose in nature, composed by a backbone of β 1-4 xylose unites anda diversity of substituent groups (arabinose, acetyl groups, glucuronic acids, feruloyl acids). The efficientdegradation of xylan is of particular biotechnological interest since the hydrolysis products are desirablefor a broad range of applications: short xylo-oligosaccharides (XOS) are emerging prebiotics, withdemonstrated beneficial effects on health. Xylose, arabinose and glucuronic acids are precursors ofbiopharmaceuticals, food additives and biofuels.Cellulomonas sp. B6 is a soil bacterium with high xylanolytic potential, since it secretes a repertoire ofxylanases by growth on biomass and encodes for diverse debranching enzymes active on hemicellulose.In this work we describe the catalytic potential of two xylanases from glycosode hydrolases (GH) families10 and 11 (rCsXyn10A, rCsXyn11A), a GH62 α-L- arabinofuranosidase (rCsAbf62A) and a GH67 αglucuronidase (rCsAgu67A), expressed and purified as recombinant enzymes. Additionally, we studiedthe effect of combining these xylanases and debranching enzymes on biomass conversion to XOS andmonomeric sugars. The hydrolysis products were analyzed by thin layer chromatography (TLC), highperformance anion-exchange chromatography/pulsed amperometric detection (HPAEC-PAD) andmass spectrometry (Maldi-TOF).The two recombinant xylanases showed different performance on commercial arabino- andglucuronoxylan, the main hemicelluloses present in plant biomass. The most active and thermostablewas rCsXyn10A, which achieved a maximal activity above 400 U/mg on arabinoxylan at pH6 and 50°C,releasing short xylooligosaccharides (XOS) and xylose. Meanwhile, rCsXyn11A hydrolyzed xylans to xylosefree XOS reaching 65 U/mg in glucuronoxylan at 30°C, pH6. Debranching enzymes showed the expectedactivity: rCsAbf62A released arabinose from monosubstituted (α-1,2 and α-1,3) side-groups inarabinoxylooligosaccharides (AXOS) and arabinoxylan while rCsAgu67A was only active on externalsubstitutions of glucuronic acid from glucuronoxylooligosaccharides (GXOS) but was not active onglucuronoxylan.Combined activity of each xylanase with rCsAbf62A improved the deconstruction of wheat arabinoxylanand wheat bran (a complex biomass composed of glucans, arabinoxylan, and lignin) to shorter XOS andxylobiose (X2). Besides, there was also a slight increase in the yield of xylose released by rCsXyn10A.rCsAgu67A was only active on oligosaccharides released by rCsXyn10A from glucuronoxylan-richbiomasses, obtaining glucuronic acid and unsubstituted XOS as products.Therefore, the individual or concerted activity of the tested enzymes has biotechnological potential forbiomass hydrolysis into value added products. We will keep working in the combination of them and otherenzymes in order to produce an enzyme cocktail with high activity and selectivity on hemicellulose.