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Journal of Chemistry
Volume 2015, Article ID 798304, 8 pages
Research Article

Production and Characterization of Alkaline Protease from a High Yielding and Moderately Halophilic Strain of SD11 Marine Bacteria

1College of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
2Hebei Province Key Laboratory of Applied Chemistry, Qinhuangdao, Hebei 066004, China
3Sansom Institute for Health Research, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA 5001, Australia
4Flinders Centre for Nanoscale Science & Technology, School of Computer Science, Engineering and Mathematics, Flinders University, Adelaide, SA 5042, Australia

Received 16 December 2014; Revised 5 May 2015; Accepted 6 May 2015

Academic Editor: Murat Senturk

Copyright © 2015 Hongxia Cui et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A marine bacterium SD11, which was isolated from sea muds (Geziwo Qinhuangdao Sea area, China), was used to produce thermostable alkaline serine nonmetal protease in the skim milk agar plate medium with 10% NaCl. The optimal temperature about the manufacture of the extracellular protease was ~60°C. The crude enzyme was stable at 20–50°C. The activity was retained to 60% and 45% after heating for 1 h at 60 and 70°C, respectively. The protease was highly active in a wide pH scope (8.0–10.0) and maximum protease activity exhibited at pH 10.0. The activity was restrained by phenylmethylsulfonyl fluoride (PMSF) but mildly increased (~107%) in the presence of ethylenediaminetetraacetic acid (EDTA), indicating that the production contains serine-protease(s) and nonmetal protease(s). Moreover, the crude alkaline protease was active with the 5 mM Ca2+, Mn2+, Zn2+, Cu2+, Na+, and K+ that existed separately. In addition, the protease showed superduper stability when exposed to an anionic surfactant (5 mM SDS), an oxidizing agent (1% H2O2), and several organic solvents (methanol, isopropanol, and acetone). These results suggest that the marine bacterium SD11 is significant in the industry from the prospects of its ability to produce thermally stable alkaline protease.