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Rezumat articol ediţie STUDIA UNIVERSITATIS BABEŞ-BOLYAI
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Rezumat: Isolate GUVSC8 was obtained from commercial salt crystals of Vedaranyam, Tamil Nadu, India and categorized as an extreme halophile based on its requirement of 25% (w/v) NaCl for growth. Morphological, chemotaxonomic and 16S rRNA gene sequences revealed the cells to be coccus, producing bright orange C-50 bacterioruberin pigmentation with 95.95% similarity to Halococcus hamelinensis DQ017835. Culture was grown in minimal medium containing 1% (w/v) starch, the cell-free supernatant was used to extract amylase using cold acetone whereas, the cell pellet was used to extract polyhydroxyalkanoates. The polymer was extracted using sodium hypochlorite-chloroform and characterized to be a co-polymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) using crotonic acid assay, FT-IR, DSC, 1H NMR analysis. Up on incubation of the crude enzyme with starch, produced numerous pores on the starch granules, indicating vigorous starch degradation and confirming the amylolytic activity. TLC and LC-ESI-MS analysis revealed, the major end product of starch hydrolysis to be glucose, maltose, maltotriose, maltotetrose, maltopentose and other maltooligosaccharides, thus confirming it to be an alpha-amylase. Effects of NaCl, pH and temperature, on activity of partially purified amylase, revealed best amylase activity at 2M NaCl, pH6 and 45°C. The amylase was stable and active in presence of divalent cations such as Mg2+, Ni2+, Zn2+, Ca2+ and Co2+. The activity increased in presence of Mn2+ and it lost 87% of its activity in presence of EDTA. To the best of our knowledge, this is the first report on coproduction of alpha amylase and PHAs by a salt crystal isolate belonging to the genus Halococcus.
Keywords: alpha-amylase, Archaea, Halococcus, halophiles, polyhydroxyalkanoates. |
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