Characteristics of thermostable endoxylanase and β-xylosidase of the extremely thermophilic bacterium Geobacillus thermodenitrificans TSAA1 and its applicability in generating xylooligosaccharides and xylose from agro-residues

Abstract

An extremely thermophilic bacterial isolate that produces a high titer of thermostable endoxylanase and β-xylosidase extracellularly in an inducible manner was identified as Geobacillus thermodenitrificans TSAA1. The distinctive features of this strain are alkalitolerance and halotolerance. The endoxylanase is active over a broad range of pH (5.0-10.0) and temperatures (30-100 °C) with optima at pH 7.5 and 70 °C, while β-xylosidase is optimally active at pH 7.0 and 60 °C. The T 1/2 values of the endoxylanase and β-xylosidase are 30 min at 80 °C, and 180 min at 70 °C, respectively. The endoxylanase activity is stimulated by dithiothreitol, but inhibited strongly by EDAC and Woodward's reagent K. N-BS and DEPC strongly inhibited β-xylosidase. MALDI-ToF (MS/MS) analysis of tryptic digest of β-xylosidase revealed similarity with that of G. thermodenitrificans NG 80-2, and suggested that this belongs to the GH 52 glycosyl hydrolase super family. The action of endoxylanase on birch wood xylan and agro-residues such as wheat bran and wheat straw liberated xylooligosaccharides similar to endoxylanases of the family 10 glycoside hydrolases, while the enzyme preparation having both endoxylanase and β-xylosidase liberated xylose as main hydrolysis product.

Secretion of recombinant thermo-alkali-stable endoxylanase of polyextremophilic Bacillus halodurans TSEV1 and its utility in generating xylooligosaccharides from renewable agro-residues

“…The pH optimum and alkalistability in the range between pH 8.0 and 11.0 suggest its applicability in biotechnological processes operating at elevated pH. The pH optimum is similar to the endogenous xylanase [20] and better than other extremophilic bacterial xylanases [33,34]. The temperature optimum of 70 • C is lower than that of endogenous enzyme, but similar to that reported by Mamo et al [29].…”

“…The homogeneously purified xylanase has similar molecular mass (42 kDa) to that of the endogenous xylanase of B. halodurans TSEV1 [20] and close to other extremophilic bacterial xylanases [33,34]. The pH optimum and alkalistability in the range between pH 8.0 and 11.0 suggest its applicability in biotechnological processes operating at elevated pH.…”

“…The difference in the temperature optimum of endogenous and recombinant xylanases could be attributed to the reducing environment of E. coli cytoplasm. The thermostability of the recombinant xylanase is similar to the endogenous enzyme, but better than that of other extremophilic bacteria [20,29,34]. The reports on higher stability of enzymes expressed from genes having similar nucleotide sequence are not uncommon in Bacillus xylanases [29,35].…”

Endoglucanase and Xylanase Production by Chryseobacterium Species Isolated from Decaying Biomass

“…B. subtilis BS04 showed highest enzyme production at 35ºC. Higher incubation temperature also is 50-60ºC, which has been reported by other researchers in the literature [44][45][46][47][48][49].…”

Biological Activities of Xylooligosaccharides Generated from Garlic Straw Xylan by Purified Xylanase from Bacillus mojavensis UEB-FK

“…One of the exciting applications of xylanases is the production of xylan oligosaccharides (XOS) from many agro-wastes [12][13][14]. Among such underutilized hemicellulose resources, garlic straw is one of the promising materials.…”