Development and application of novel enzyme inhibitors for the preservation of freshness of marine products using a library of marine microorganisms

众所周知，适应低温的酶是导致海产品降级的原因。为了保持水产品的新鲜度，本研究旨在从天然来源中鉴定这些酶的性质并寻找其抑制剂。为了获得适应低温的酶，我们从日本不同地区的海洋动物的肠道内容物中纠正了3000多株海洋细菌。我们已经筛选出具有脂肪酶活性和磷脂降解酶活性(磷脂酶A1、磷脂酶C、溶磷脂酶C和鞘磷脂酶活性)的有价值的菌株。最后，我们确认了大约100株具有脂肪酶活性的菌株，以及大约10株具有磷脂降解酶活性的菌株。我们计划从以前分离的所有海洋微生物中同时鉴定这些酶的特性，并寻找它们对这些海洋脂肪降解酶的特异性抑制剂。在本研究中，还试图从不同地区的海水和海洋沉积物样本中分离出产生酪氨酸酶抑制剂的海洋微生物。从100m深的日本岛外海域分离到一株产酪氨酸酶抑制剂的菌株，并对其进行了进一步的鉴定和产生性研究。经分类鉴定，该菌株为木霉属。该菌株在海水介质中摇床培养时产生抑菌剂。该活性物质是一种低分子多肽。这种粗制的缓蚀剂可以防止虾等甲壳类动物的发黑反应，这表明该缓蚀剂可能适用于渔业。

Cold-adapted enzymes are known to be cause for debasement of marine products. To preserve freshness of marine products, our present study was designed to characterize the enzymes and to search their inhibitors from natural sources.In order to obtain the cold-adapted enzymes, we have corrected over 3,000 strains of marine bacteria from the intestinal contents of marine animals in various regions in Japan. We have screened valuable strains indicating lipase activity and phospholipid-degrading enzyme activities (phospholipase A1, phaspholipase C, lyzophospholipase C and sphingomyelinase activities). Finally, we have confirmed around 100 strains with lipase activity, and around 10 strains with phospholipids-degrading enzyme activities in the culture solution. We are planning to characterize these enzymes and to search their specific inhibitors for these marine lipid-degrading enzymes from all marine microorganisms isolated before at once.In the present study, an attempt was also made to isolate tyrosinase inhibitor-producing marine microorganisms from seawater and marine sediment samples of various areas. One strain which produced a tyrosinase inhibitor was isolated from Off-Niijima Islands at a depth of 100 m and was selected for further studies on the identification of it and production of the inhibitor. Base on the taxonomical characteristics, the strain was identified as Trichoderma sp. The strain produced the inhibitor when cultivated in seawater medium with shaking. The active substance was found to be a low molecular weight peptide. The crude inhibitor prevented the darkening reaction of crustaceans such as shrimp they are stored, suggesting that this inhibitor might be applicable to fisheries.