Published in Scientific Papers. Series B, Horticulture, Volume LXII
Written by Aglaia BURLACU, Florentina ISRAEL-ROMING, Călina Petruța CORNEA
Hemicellulose is a major component of the lignocellulosic biomass, located between lignin and cellulose fibers and is the second most abundant natural polymer on earth. The main constituent of hemicellulose is xylan, a polysaccharide comprised of β-1.4-linked xylopyranosyl residues. Due to its complex structure and heterogeneous nature, hydrolysis of xylan requires a synergic action of several enzymes generally named xylanases. Amongst them, acetyl xylan esterase (AXE) is an accessory enzyme that liberates acetyl groups from the side chains of the xylan backbone. These acetyl side-groups protect the backbone of xylan from the action of others enzymes, therefore their release facilitates the action of endoxylanases. Several microorganisms display acetyl xylan esterase activity, the main producers being fungi and bacteria. The aim of this study was to test different strains in regard to their ability to display acetyl xylan esterase activity. The microorganisms subjected to screening belonged to the genres: Aspergillus, Penicillium, Bacillus, Trichoderma and Fusarium. The strains subjected for screening were also studied for their xylanase activity, in order to compare their ability to produce both xylanase and acetyl xylan esterase. In addition, the microorganisms selected after the screening process were subjected to protein assay, in order to determine the specific enzymatic activities. The best acetyl xylan esterase activities were detected with Aspergillus brasiliensis ATCC 16404 UV 7, Aspergillus brasiliensis ATCC 16404 UV 5, Aspergillus niger UV 10 and Penicillium digitatum UV 11. These experimental results are significant for further studies related to hydrolysis of hemicellulose, regarding lignocellulosic biomass valorisation.
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