Characterization of a highly thermostable recombinant xylanase from Anoxybacillus ayderensis.

Xylanases are the main enzymes to hydrolyze xylan, the major hemicellulose found in lignocellulose. Xylanases also have a wide range of industrial applications. Therefore, the discovery of new xylanases has the potential to enhance efficiency and sustainability in many industries. Here, we report a xylanase with thermophilic character and superior biochemical properties for industrial use. The new xylanase is discovered in Anoxybacillus ayderensis as an intracellular xylanase (AAyXYN329) and recombinantly produced. While AAyXYN329 shows significant activity over a wide pH and temperature range, optimum activity conditions were determined as pH 6.5 and 65 °C. The half-life of the enzyme was calculated as 72 h at 65 °C. The enzyme did not lose activity between pH 6.0-9.0 at +4 °C for 75 days. Km, kcat and kcat/Km values of AAyXYN329 were calculated as 4.09824 ± 0.2245 µg/µL, 96.75 1/sec, and 23.61/L/g.s -1, respectively. In conclusion, the xylanase of A. ayderensis has an excellent potential to be utilized in many industrial processes.

Modeling and evaluation of the sucrose-degrading activity of recombinantly produced oligo-1,6-glucosidase from A. gonensis.

Fructose is the most preferred sugar to provide benefits for sweetening and health. As many industrial enzymes are used to produce High Fructose Syrup (HFS), it is vital to explore alternative enzymes for fructose production. Oligo-α-1,6-glucosidase (O-1-6-glucosidase) hydrolyzes non-reducing ends of isomaltooligosaccharides, panose, palatinose, and an a-limit dextrin by breaking α-1,6-glucoside bonds, although it generally has no activity on α-1,4-glucoside bonds of maltooligosaccharides. In this study, sucrose-hydrolyzing activity of O-1-6-glucosidase of thermophilic A. gonensis was evaluated. For this purpose, O-1-6-glucosidase gene region of A. gonensis was cloned in the pET28(a)+ expression vector, the expression product was purified, modeled, and biochemically characterized. The optimal activity of the enzyme was to be at pH 7.0 and 60 °C. The enzyme activity was halved at the end of the 276th h at 60 °C. The enzyme maintained its activity even after 300 h at pH 6.0-10.0. The values of Km, Vmax, kcat, and kcat/Km were determined as 44.69 ± 1.27 mM, 6.28 ± 0.05 µmoL/min/mg protein, 6.70 1/s and 0.15 1/mMs-1, respectively. While Zn2+, Cu2+, Pb2+, Ag2+, Fe3+, Hg2+, and Al2+ metal ions inhibited O-1-6-glucosidase, Mn2+, Fe2+, and Mg2+ ions activated the enzyme. Consequently, A. gonensis O-1-6-glucosidase (rAgoSuc2) has interesting properties, especially for HFS production.

Distribution of ß-lactamase genes among carbapenem-resistant Klebsiella pneumoniae strains isolated from patients in Turkey.

BACKGROUND: The emergence of carbapenem-resistant Klebsiella pneumoniae poses a serious problem to antibiotic management. We investigated the ß-lactamases in a group of carbapenem-resistant K. pneumoniae clinical isolates from Turkey. METHODS: Thirty-seven strains of K. pneumoniae isolated from various clinical specimens were analyzed by antimicrobial susceptibility testing, PCR for the detection of ß-lactamase genes, DNA sequencing, and repetitive extragenic palindronic (REP)-PCR analysis. RESULTS: All 37 isolates were resistant to ampicillin, ampicillin/sulbactam, piperacillin, piperacillin/tazobactam, ceftazidime, cefoperazone/sulbactam, cefepime, imipenem, and meropenem. The lowest resistance rates were observed for colistin (2.7%), tigecycline (11%), and amikacin (19%). According to PCR and sequencing results, 98% (36/37) of strains carried at least one carbapenemase gene, with 32 (86%) carrying OXA-48 and 7 (19%) carrying NDM-1. No other carbapenemase genes were identified. All strains carried a CTX-M-2-like ß-lactamase, and some carried SHV- (97%), TEM- (9%), and CTX-M-1-like (62%) ß-lactamases. Sequence analysis of bla(TEM) genes identified a bla(TEM-166) with an amino acid change at position 53 (Arg53Gly) from bla(TEM-1b), the first report of a mutation in this region. REP-PCR analysis revealed that there were seven different clonal groups, and temporo-spatial links were identified within these groups. CONCLUSIONS: Combinations of ß-lactamases were found in all strains, with the most common being OXA-48, SHV, TEM, and CTX-M-type (76% of strains). We have reported, for the first time, a high prevalence of the NDM-1 (19%) carbapenemase in carbapenem-resistant K. pneumoniae from Turkey. These enzymes often co-exist with other ß-lactamases, such as TEM, SHV, and CTX-M ß-lactamases.

Molecular analysis of the genus Anoxybacillus based on sequence similarity of the genes recN, flaA, and ftsY.

Genome predictions based on selected genes would be a very welcome approach for taxonomic studies. We analyzed three genes, recN, flaA, and ftsY, for determining if these genes are useful tools for systematic analyses in the genus Anoxybacillus. The genes encoding a DNA repair and genetic recombination protein (recN), the flagellin protein (flaA), and GTPase signal docking protein (ftsY) were sequenced for ten Anoxybacillus species. The sequence comparisons revealed that recN sequence similarities range between 61% and 99% in the genus Anoxybacillus. Comparisons to other bacterial recN genes indicated that levels of similarity did not differ from the levels within genus Anoxybacillus. These data showed that recN is not a useful marker for the genus Anoxybacillus. A 550-600-bp region of the flagellin gene was amplified for all Anoxybacillus strains except for Anoxybacillus contaminans. The sequence similarity of flaA gene varies between 61% and 76%. Comparisons to other bacterial flagellin genes obtained from GenBank (Bacillus, Pectinatus, Proteus, and Vibrio) indicated that the levels of similarity were lower (3-42%). Based on these data, we concluded that the variability in this single gene makes it a particularly useful marker. Another housekeeping gene ftsY suggested to reflect the G+C (mol/mol) content of whole genome was analyzed for Anoxybacillus strains. A mean difference of 1.4% was observed between the G+C content of the gene ftsY and the G+C content of the whole genome. These results showed that the gene ftsY can be used to represent whole G+C content of the Anoxybacillus species.

The ATPase activity of the G2alt gene encoding an aluminium tolerance protein from Anoxybacillus gonensis G2.

The G2ALT gene was cloned and sequenced from the thermophilic bacterium Anoxybacillus gonensis G2. The gene is 666 bp long and encodes a protein 221 amino acids in length. The gene was overexpressed in E. coli and purified to homogeneity and biochemically characterized. The enzyme has a molecular mass of 24.5 kDa and it could be classified as a member of the family of bacterial aluminium resistance proteins based on homology searches. When this fragment was expressed in E. coli, it endowed E. coli with Al tolerance to 500 µM. The purified G2ALT protein is active at a broad pH range (pH 4.0-10.0) and temperature range (25°C-80°C) with optima of 6.0 and the apparent optimal temperature of 73°C respectively. Under optimal conditions, G2ALT exhibited a low ATPase activity with K (m) (-) and V (max) (-) values of 10±0.55 µM and 26.81±0.13 mg Pi released/min/mg enzyme, respectively. The ATPase activity of G2ALT requires Mg(2+) and Na(+) ions, while Zn(2+) and Al(3+) stimulate the activity. Cd(2+) and Ag(+) reduced the activity and Li(+), Cu(2+), and Co(2+) inhibited the activity. Known inhibitors of most ATPases, like such as ß-mercaptoethanol and ouabain, also inhibited the activity of the G2ALT. These biochemical characterizations suggested that G2ALT belongs to the PP-loop ATPase superfamily and it can be responsible for aluminium tolerance in A. gonensis G2.

Cloning, purification and characterization of a thermostable carboxylesterase from Anoxybacillus sp. PDF1.

The gene encoding a carboxylesterase from Anoxybacillus sp., PDF1, was cloned and sequenced. The recombinant protein was expressed in Escherichia coli BL21, under the control of isopropyl-ß-D-thiogalactopyranoside-inducible T7 promoter. The enzyme, designated as PDF1Est, was purified by heat shock and ion-exchange column chromatography. The molecular mass of the native protein, as determined by SDS-PAGE, was about 26 kDa. PDF1Est was active under a broad pH range (pH 5.0-10.0) and a broad temperature range (25-90 °C), and it had an optimum pH of 8.0 and an optimum temperature of 60 °C. The enzyme was thermostable carboxylesterase, and did not lose any activity after 30 min of incubation at 60 °C. The enzyme exhibited a high level of activity with p-nitrophenyl butyrate with apparent K(m), V(max), and K(cat) values of 0.348 ± 0.030 mM, 3725.8 U/mg, and 1500 ± 54.50/s, respectively. The effect of some chemicals on the esterase activity indicated that Anoxybacillus sp. PDF1 produce an carboxylesterase having serine residue in active site and -SH groups in specific sites, which are required for its activity.

Cloning, expression, purification and characterization of fructose-1,6-bisphosphate aldolase from Anoxybacillus gonensis G2.

The fructose-1,6-bisphosphate aldolase gene from the thermophilic bacterium, Anoxybacillus gonensis G2, was cloned and sequenced. Nucleotide sequence analysis revealed an open reading frame coding for a 30.9 kDa protein of 286 amino acids. The amino acid sequence shared approximately 80-90% similarity to the Bacillus sp. class II aldolases. The motifs that are responsible for the binding of a divalent metal ion and catalytic activity completely conserved. The gene encoding aldolase was overexpressed under T7 promoter control in Escherichia coli and the recombinant protein purified by nickel affinity chromatography. Kinetic characterization of the enzyme was performed at 60 degrees C, and K(m) and V(max) were found to be 576 microM and 2.4 microM min(-1) mg protein(-1), respectively. Enzyme exhibits maximal activity at pH 8.5. The activity of enzyme was completely inhibited by EDTA.