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Stability of an alkaline protease from a microbial species isolated from an alkaline soda lake Shahrzad
Bakhtiar Maria Andersson Amare Gessesse* Bo Mattiasson Rajni Hatti-Kaul *Corresponding author Keywords: hyperthermophilic proteins, thermostability, enzyme, structure analysis
Alkaline proteases for use in detergents account for the largest world market among bulk enzymes. A microbial species AL-20 related to Nesterenkonia halobia isolated from an alkaline soda lake in Ethiopia, and grown on chicken feather was used as a source of an alkaline protease. The enzyme was purified and characterized with respect to stability using differential scanning calorimetry and circular dichroism. The secondary structure of the enzyme was preserved after overnight storage at 50ºC, pH 10, also in the presence of 1% SDS. In contrast, subtilisin showed loss of conformation under similar conditions of pH and temperature. The activity and stability of the enzyme was independent of the calcium ions, unlike the other enzymes belonging to this group. Even the use of chelating agents did not affect the protease activity. The presence of SDS (0.1% w/v), commercial detergent (0.1% w/v),10 mM Ca2+ and 5 mM EDTA, respectively, did not influence the denaturation profile of the enzyme. |
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