In this investigation, the isolate S. halophilum strain LY20 was selected for further study because it appeared to be the best selleck screening library producer of extracellular amylase and protease. To date, there are no reports for amylase and protease production at the same time from one isolate, because the protease can hydrolyze other proteins such as amylase. However, maximal production of both enzymes was observed simultaneously during the stationary growth
phase of LY20 (Fig. 2). This particular phenomenon could be explained that the amylase was not the substrate of the protease, which was confirmed by SDS-PAGE after incubating the two enzyme solutions (80 °C and pH 10.0) for 30 min (data not shown). There are many reports on isolation of amylases from halophiles (Mellado et al., 2004; Litchfield, 2011), but pure preparation of halophilic β-amylase has not been obtained. In this study, purification of an β-amylase from LY20 was reported. Similar enzyme was previously described from Halobacillus sp. LY9 (Li
& Yu, 2011), but its enzymatic properties were mostly obtained from crude extracts. Molecular weight of the β-amylase was determined to be 81 kDa (Fig. 3, lane 2). selleck chemicals The value was higher than other β-amylases from nonhalophiles (Shen et al., 1988; Young et al., 2001). The enzyme showed an optimal activity at 70 °C and excellent thermostability under high temperatures. These characteristics made it obviously different from other β-amylases, which were neither
active nor stable at temperatures above 65 °C (Shen et al., 1988; Young et al., 2001). It is desirable that amylases check details should be active at high temperature for gelanization (100–110 °C), liquefaction (80–90 °C), and saccharification (60–65 °C) for the application in the starch industry. Until today, amylases from bacteria belonging to genus Bacillus are heavily used in the starch-processing industry (Mamo & Gessesse, 1999; Demirkan et al., 2005). As thermostability is an important feature for amylolytic enzymes, the β-amylase from LY20 might be industrially exploited for starch liquefaction and saccharification. Molecular weight of the purified protease was estimated to be 30 kDa on SDS-PAGE. Similar values presented other halophilic proteases previously characterized (Karbalaei-Heidari et al., 2007a, b; Xiong et al., 2007). The enzyme showed the optimal activity at 80 °C. In contrast to other proteases from halophiles (Amoozegar et al., 2007; Karbalaei-Heidari et al., 2009), it required relatively higher temperature to maintain the maximum activity. Moreover, high thermostability over a wide temperature range (30–80 °C) was observed. These properties made it potential use in industrial applications that require high temperatures. The amylase and protease from LY20 were found to be highly active and stable in the presence of higher concentrations of NaCl.