Production of L‐Arabinose from Corn Hull Arabinoxylan by Arthrobacter aurescens MK5 α‐L‐Arabinofuranosidase

Abstract

Arabinoxylans, which are comprised of a xylan backbone to which are attached glycosyl units that are primarily L-arabinofuranosyl units, are ubiquitous among plant species where it is a constituent of the cell wall. Arabinoxylan has attracted much attention as a potential biomass resource and L-arabinose has recently been reported to possess functional properties that are effective in the treatment of diabetes. Here, we report an α-L-arabinofuranohydrolase, isolated from the soil microbe Arthrobacter aurescens strain MK5, effective in releasing L-arabinose from corn hull arabinoxylan. When A. aurescens strain MK5 was grown in a liquid medium, corn hull arabinoxylan, which has a higher arabinose content (Ara/Xyl = 0.6) than oat spelts xylan (Ara/Xyl = 0.12), induced more efficient arabinoxylan hydrolase production. Analysis of enzyme activity in the culture broth revealed that arabinoxylan hydrolase activity was high, and α-L-arabinofuranosidase and β-xylosidase activities were low. The optimum pH of the MK5 arabinoxylan hydrolase at 40 °C was around 7 and enzyme activity was relatively stable at an alkaline pH up to 9.5. The optimum temperature at pH 7 was around 50 °C and enzyme activity was stable under 50 °C. During the hydrolysis of corn hull arabinoxylan, only L-arabinose was released and 45.1% maximum sugar recovery was achieved. The A. aurescens MK5 enzyme was a typical arabinoxylan α-L-arabinofuranohydrolase and was most effective at releasing L-arabinose from corn hull arabinoxylan, which has a high arabinose content. This enzyme may have important industrial applications.

Investigation of commercial enzyme preparations for selective release of arabinose from corn fibre

“…The highest yield of monomer arabinose (36%) was obtained in the case of hydrolysis of 6 h SAA pretreated destarched corn fibre with Hemicellulase NS22002 at pH 6. This yield of monomer arabinose is comparable with the yields achieved on purified corn hull arabioxylan by Kurakake et al 30 The results of the investigation of enzymatic activities (xylanase and AX-AFH) and hydrolysis of corn fibre imply that Hemicellulase NS22002 has high endo-xylanase activity over a broad pH range, negligible -xylosidase activity at pH 3 and 4, and its -L-arabinofuranosidase is hypothesized to act only on solubilised substrates. During the enzymatic hydrolysis of 6 h SAA pretreated destarched corn fibre at pH 6, negligible amounts of monomer OHS were released indicating the recalcitrance of the solubilised oligosaccharides against enzymatic decompositions.…”

“…30 The enzyme released only arabinose from the arabinoxylan, and an arabinose yield of 45% was achieved in the case of a substrate concentration of 2% (w/w). 30 The advantages of these methods are the mild reaction conditions applied, and the pure arabinose solution obtained regarding the solubilised monosaccharides. The drawbacks are that the production of the starting materials investigated (purified arabinan and arabinoxylan) and the purification of the applied enzymes require complex and expensive processes.…”

“…Activity of α‐L‐arabinofuranosidases is influenced by the degree of substitution of the hemicellulose polymers with arabinosyl residues, the position of the arabinose moieties and the presence of other substitutions . Utilization of α‐L‐arabinofuranosidases and endo‐arabinanases to produce arabinose from lignocellulose‐ or pectin‐derived materials is of growing importance in the field of biotechnology . L‐arabinose has been reported to have beneficial properties regarding blood sugar reduction and for the treatment of human diabetes .…”

“…investigated arabinose production from corn hull arabinoxylan using α‐L‐arabinofuranosidase purified from Arthobacter aurescens MK5 . The enzyme released only arabinose from the arabinoxylan, and an arabinose yield of 45% was achieved in the case of a substrate concentration of 2% (w/w) . The advantages of these methods are the mild reaction conditions applied, and the pure arabinose solution obtained regarding the solubilised monosaccharides.…”

Integrated Process of Arabinose Biopurification and Xylitol Fermentation Based on the Diverse Action of Candida boidinii

“…10 Commercial production of L-arabinose is a complex process consisting of acid hydrolysis of gum arabic, followed by multiple procedures of purification. 6 The relatively high cost of gum arabic and the expensive purification steps result in the high cost of pure arabinose, 11 which has evoked an increasing research effort to develop new cost-effective methods of arabinose production from agro-residues rich in hemicellulose or pectin, for example from sugar beet pulp, 11 corn hull, 12 xylose-mother liquor, 6 wheat bran 13 and corn fibre. 14 Biopurification of hemicellulosic hydrolysate is an interesting and inexpensive strategy to produce a pure arabinose solution through the depletion of other sugars (e.g.…”