No abstract

Bacillus subtilis JM‐3 was isolated from anchovy sauce naturally fermented in an underground cellar at 15 ± 3C for 3 years. The activity of the B. subtilis protease was highest in the 40–60% ammonium sulfate fraction. The yield of the purified protease was 5.3%, and its purification ratio was 35.6 folds. The molecular weight of the B. subtilis protease was 17.1 kDa, and its Km and Vmaxvalues were 1.75 μg/mL and 318 μM 1/min, respectively. The optimal temperature for protease activity was 60C, but optimal stability temperature was 30C. The optimal pH for protease activity and stability was 5.5. Therefore, the B. subtilis JM‐3 protease was classified as an acid protease. The relative activities of the B. subtilis JM‐3 protease were 69, 21 and 1.3% at 10, 20 and 30% NaCl concentrations, respectively. The best substrate for the B. subtilis JM‐3 protease was benzyloxycarbonyl‐glycine‐p‐nitrophenyl ester followed by bovine serum albumin. p‐Toluene‐sulfonyl‐L‐lysine chloromethylketone was the strongest inhibitor followed by soybean trypsin inhibitor, but N‐ethylmaleimide did not inhibit this enzyme. The B. subtilis JM‐3 protease was therefore presumed to be a trypsin‐like serine protease.

A lysozyme was purified from the viscera of scallops by ion exchange, gel permeation and affinity chromatographies. The yield of the purified lysozyme was 1.52%, and its purification ratio was 411.9 folds. The molecular weight of the scallop lysozyme was about 14.5 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optimal temperature for lysozyme activity was 20C, but the optimal stability temperature was between 20 and 30C. The optimal pH for lysozyme activity was 5.0, but the optimal stability pH was between 5.0 and 6.0. Scallop lysozyme had antibacterial activities against both gram‐positive and gram‐negative bacteria in which gram‐negative bacteria, Escherichia coli and Vibrio vulnificus, were inhibited more effectively than gram‐positive bacteria. Egg white lysozyme inhibited gram‐positive bacteria better than the scallop lysozyme, whereas the reverse was true for gram‐negative bacteria. The N‐terminal sequence of the scallop lysozyme consisted of 10 amino acids: proline, cysteine, valine, tyrosine, alanine, phenylalanine, methionine, asparagine, glutamic acid and aspartic acid. PRACTICAL APPLICATIONS Egg white lysozyme (EWL) has been used as a preservative or antibacterial agent in the pharmaceutical and food industry, but is limited to broaden its application because of poor antibacterial activity against gram‐negative bacteria. Scallop viscera lysozyme has two times higher antibacterial activity against gram‐negative bacteria (Escherichia coli and Vibrio vulnificus) than EWL. Therefore, scallop viscera lysozyme shows a promise as a bacteriostatic or prophylactic agent in food preservation and specialty product.