Abstract
The possibility of using Aspergillus terreus protease in detergent formulations was investigated. Sodium dodecyl sulfate (SDS) and native polyacrylamide gel electrophoresis indicated that the purified alkaline protease (148.9 U/mg) is a monomeric enzyme with a molecular mass of 16 ± 1 kDa. This was confirmed by liquid chromatography–mass spectrometry. The active enzyme degraded the co-polymerized gelatin. The protease demonstrated excellent stability at pH range 8.0–12.0 with optimum at pH 11.0. It was almost 100 % stable at 50 °C for 24 h, enhanced by Ca2+ and Mg2+, but inhibited by Hg2+, and strongly inhibited by phenylmethyl sulfonyl fluoride. It showed maximum activity against casein followed by gelatin; its Vmax was 12.8 U/ml with its corresponding KM of 5.4 mg/ml. The proteolytic activity was activated by Tween-80, Triton-100 and SDS, and remained unaltered in the presence of H2O2 and NaClO. The enzyme exhibited higher storage stability at 4, 28 and −20 °C. It was stable and compatible to the desired level in the local detergents. The addition of the protease to the Super wheel improved its blood stain removal. The isolated protease can thus be a choice option in detergent industry.
Highlights
Proteases (EC 3.4.21–24 and 99) are hydrolytic enzymes that cleave peptide bonds of proteins
Sodium dodecyl sulfate (SDS) and native polyacrylamide gel electrophoresis indicated that the purified alkaline protease (148.9 U/mg) is a monomeric enzyme with a molecular mass of 16 ± 1 kDa
The enzyme preparation (30 mg/ml) was stored at the corresponding temperature and the residual activity was recorded by the standard assay procedure as described previously after exactly 10 days for a period of 40 days
Summary
Proteases (EC 3.4.21–24 and 99) are hydrolytic enzymes that cleave peptide bonds of proteins. The study of alkaline protease properties is important from the point of view of its practical applicability. Alkaline proteases used in detergent preparations must have higher activity at alkaline pH, broad temperature range, broad substrate specificity, stability in the presence of surfactants, oxidizing agents, and compatibility with detergents (Kumar and Takagi 1999; Adinarayana et al 2003; Choudhary and Jain 2012). Usually increased the activity and stabilized the enzyme (Sharma et al 2006; Anandan et al 2007; Kalpana devi et al 2008; Dubey et al 2010). The nature of the enzyme and its active site as well as its cofactor requirements can be deduced from inhibition studies (Sigma and Mooser 1975).
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