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The acidophilic and thermophilic pullulanases have many potential applications in the processes of starch liquefaction and saccharification. In this study, a gene encoding an amylopullulanase from Thermofilum pendens (TPApu) was heterologously expressed in Escherichia coli . Although TPApu possessed the same continuous GH57N_Apu domain and the succeeding α-helical region as other two amylopullulanases from Staphylothermus marinus (SMApu) and Caldivirga maquilingensis (CMApu), it only showed maximal amino acid identities of 25.7–28.7% with CMApu and SMApu. The purified TPApu appeared as a single band of SDS-PAGE with a molecular mass of 65.5 kDa and exhibited the maximal activity at pH 3.5 and 95–100 °C. TPApu had the highest catalytic efficiency towards pullulan (kcat/km, 8.79 s −1 mL mg −1 ) and α-cyclodextrin (kcat/km, 0.36 s −1 mM −1 ). In the initial stages, the ring-opening reactions of γ-cyclodextrin, 6- O -glucosyl-β-cyclodextrin, 6- O -maltosyl-β-cyclodextrin and the debranching reactions of 6- O -maltooctaosyl-β-cyclodextrin were firstly catalyzed. In the subsequent reactions, a serial of maltooligosaccharides were produced. As the most acidophilic amylopullulanase among thermophilic pullulanases reported to date, TPApu preferred to debranch the DP6–12 side chains of amylopectin at pH 4.5 and 100 °C. [ABSTRACT FROM AUTHOR]

Application of halophiles can decrease the cost of polyhydroxyalkanoate (PHA) production or bioplastic which are an alternative to the petroleum-derived plastic. Extremely halophilic archaeon, Natrinema ajinwuensis RM-G10 accumulated 61.02 ± 0.68% PHA of its cell dry mass at 72 h in repeated batch cultures yielding 0.210 ± 0.001 g L −1 h −1 volumetric productivity after selection of the best cultivation conditions. Transmission electron microscopy showed the presence of PHA granules inside the archaeal cells. Characterization by gas chromatographic analysis, gas chromatographic- mass spectrophotometric analysis, thermogravimetric analysis, differential scanning calorimetric analysis, X-ray diffraction analysis, Fourier transform infra red spectroscopy and nuclear magnetic resonance spectroscopy revealed the polymer to be poly(3-hydroxybutyrate- co -3-hydroxyvalerate) with 13.93 mol% 3-hydroxyvalerate content and having 35.45% crystallinity, −12.3 °C glass transition temperature, 143 °C and 157.5 °C melting temperatures and 284 °C degradation temperature. This is the first report on production enhancement (on a small scale) and characterization of the polyhydroxyalkanoate produced by Natrinema ajinwuensis (as synonym) ≡ Natrinema altunense strain RM-G10 and the Natrinema genus in general. [ABSTRACT FROM AUTHOR]

An extracellular halophilic alpha-amylase (AmyA) was produced by the haloarchaeon Haloterrigena turkmenica grown in medium enriched with 0.2% (w/v) starch. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography (SEC) analyses showed a major band at 66.0 kDa and a peak of 54.0 kDa, respectively. Analysis of tryptic fragments of the protein present in the major SDS-PAGE band by nano-LC-ESI–MS/MS led to identification of the alpha-amylase catalytic region, encoded by the htur2110 gene, as the protein possessing the described activity. Optimal values for activity were 55 °C, pH 8.5 and 2 M NaCl, and high thermostability was showed at 55 °C and 3 M NaCl. AmyA activity was enhanced by Triton X-100 and was not influenced by n -hexane and chloroform. Starch hydrolysis produced different oligomers with maltose as the smallest end-product. The efficiency of AmyA in degrading starch contained in agronomic residues was tested in grape cane chosen as model substrate. Preliminary results showed that starch was degraded making the enzyme a potential candidate for utilization of agro-industrial waste in fuel and chemicals production. AmyA is one of the few investigated amylases produced by haloarchaea, and the first alpha-amylase described among microorganisms belonging to the genus Haloterrigena . [ABSTRACT FROM AUTHOR]