ΠΜΣ Μικροβιακή ΒιοτεχνολογίαLibrary of the School of Science
Δημήτρης Χατζηνικολάου Επικ. Καθηγ. (Επιβλέπων), Αμαλία Καραγκούνη-Κύρτσου Καθηγ., Γιώργος Διαλλινάς Αναπλ. Καθηγ.
Καθαρισμός, βιοχημιός και κινητικός χαρακτηρισμός μίας β-ξυλοζιδάσης από ένα θερμόφιλο βακτηριακό στέλεχος Geobacillus sp. απομονωμένο από το ηφαιστειακό σύμπλεγμα της Σαντορίνης
beta-Xylosidases play an important role in xylan degradation, hydrolyzing
xylobiose and short length xylo-oligosaccharides to xylose units. The interest
in biomass degrading enzymes for biorefinery applications has steadily
increased during the last decades and as a result, several relevant enzymes
including beta-xylosidases have been studied although only a few of them could
function at elevated temperatures and harsh process conditions. In the present
study, we describe the production, purification and biochemical
characterization of a novel beta-xylosidase from a thermophilic Geobacillus sp.
strain isolated from Santorini volcanic area, Aegean Sea, Greece. For the β-
xylosidase production, the bacterial strain was cultivated in liquid cultures,
with wheat bran and ammonium sulfate as carbon and nitrogen source
respectively.The enzyme was subsequently purified to electrophoretic
homogeneity from the optimized extracellular culture medium through a two step
chromatographic process (DEAE Sephacel και Sephacryl S-200 HR). According to
gel filtration and SDS-PAGE, the purified beta-xylosidase revealed a dimeric
structure with a subunit MW of 55 kDa. It was highly active against
para-NitroPhenyl Xylopyranoside (pNPX) showing maximum activity at pH 6 and 65o
C (Km 0.26 mM). The enzyme proved to be very stable at temperatures below 65 oC
with more than 2 hours half-life at 70 oC, while it was stable at pH range from
5 to 10. The effect of metal ions on enzyme activity and various
monosaccharides were additionally studied. Finally, we couldn’t detect any
transglycosylation activity against pnpX. All the above results indicate that
this novel beta-xylosidase, probably belongs to GH43 family and is a highly
promising candidate for the beta-xylosidase activity and the bioconversion of
lignocellulosic biomass in general.
Beta-xylosidase, Enzyme purification, Biodegradation, Geobacillus, Xylan
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