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In this work, the protective effect of ectoines against pH stress and high temperature has been investigated using an alkaline active xylanase from Bacillus halodurans as a model. The disaccharide, trehalose—a well-known stabiliser for biomolecules (Kaushik and Bhat 2003), has also been included in the study. The enzyme was selected as a model because it is efficiently active at high pH and is highly stable in the pH range of 5.5–10.5 at 50 °C. | Appl Microbiol Biotechnol DOI 10.1007 s00253-012-4528-8 BIOTECHNOLOGICALLY RELEVANT ENZYMES AND PROTEINS Ectoine-mediated protection of enzyme from the effect of pH and temperature stress a study using Bacillus halodurans xylanase as a model Doan Van-Thuoc amp Suhaila O. Hashim amp Rajni Hatti-Kaul amp Gashaw Mamo Received 19 July 2012 Revised 5 October 2012 Accepted 18 October 2012 Springer-Verlag Berlin Heidelberg 2012 Abstract Compatible solutes are small soluble organic Keywords Compatible solutes . Ectoine . Hydroxyectoine . compounds that have the ability to stabilise proteins against Xylanase . Protein stabilisation various stress conditions. In this study the protective effect of ectoines against pH stress is examined using a recombi- nant xylanase from Bacillus halodurans as a model. Introduction Ectoines improved the enzyme stability at low 4.5 and 5.0 and high pH 11 and 12 stabilisation effect of hydrox- Organisms adapted to thrive in extreme environments have yectoine was superior to that of ectoine and trehalose. In the evolved strategies that allow them to survive and flourish in presence of hydroxyectoine residual activity after 10 h the harsh ecology they inhabit. Halophiles a group of extrem- heating at 50 C increased from about 45 to 86 at pH 5 ophiles growing in high salt environment have two adaptive and from 33 to 89 at pH 12. When the xylanase was strategies to cope with high external salt concentration one incubated at 65 C for 5 h with 50 mM hydroxyectoine at is the accumulation of inorganic ions used by members of the pH 10 about 40 of the original activity was retained extremely halophilic Archaea of family Halobacteriaceae and while no residual activity was detected in the absence of the Bacteria order Haloanaerobiales Empadinhas and da additives or in the presence of ectoine or trehalose. The Costa 2008 Oren 2002 and the other involving the accumu- xylanase activity was slightly stimulated in the presence of lation of small highly .
