| Aquatic products become people’s favorite food for its rich nutrition and taste. However, because of its high nutrients and moisture content, the neutral pH value, less connective tissue in the muscular and easy to become alkaline, if not immediately taken effective measures to keep fresh after harvest, they will be easy to breed bacteria and spoiled soon. Marine bacteria have huge potential of producing a variety of novel bioactive substances, so they have much important research value. In this paper, marine bacteria in shrimp and scallops were the object of research, and the bacteria had the antibacterial activity were selected and identified and its antibacterial activity was studied. Furthermore, it was applied in aquatic products processing and fresh-keeping. And the effectiveness of inhibit the growth of pathogenic bacteria in aquatic products was studied in order to effectively improve the quality of aquatic products. The main results were as follows:1. The bacteria separated and purified from aquatic products were studied by using spot inoculation and their antibacterial activity for preserved bacteria was researched. Finally, the strain S2with high antibacterial activity was screened. The results showed that it had different degrees of inhibition effect on17of21indicators, especially on V8. This indicated that the strain S2had broad antibacterial spectrum and its antibacterial effect is relatively good. According to its morphological, physiological and biochemical properties together with phylogenetic analysis of its16S rRNA sequence, the strain S2was identified. The results showed that the16S rRNA sequence of S2shared the highest identity with Pseudoalteromonas peptidolytic. Hence, S2was preliminary identified to be Pseudoalteromonas peptidolytic with morphology, physiological and biochemical properties and16S rRNA gene sequence and it was named Pseudoalteromonas peptidolytic S2.2. The strain S2with antibacterial activity was cultivated and its growth curve was determined. The results showed that its lag phase (0～15h), exponential phase (15～60h), stationary phase (60～105h) and decline phase (after105h). Antibacterial activity was detected after26h and peaked in the stationary phase. S2had stronger sensitivity to most antibiotics, and had stronger resistance to some antibiotics (such as penicillin G, azithromycin, kanamycin, cefalexin, nalidixic acid, norfloxacin, erythromycin and so on).3. Based on the basis of existing research, the antimicrobial activity of SA10extracellular products was studied. The antibacterial substances of SA10extracellular products had strong adaptability to the temperature, only at low temperature (～0℃) and high temperature condition (above80℃) would its antibacterial activity decrease. However, they were easy to be influenced by pH value. The ethanol precipitation experiments showed that S2fermented liquid contains most antibacterial substances could be precipitatd by ethanol, and the antibacterial substances have significant inhibition to the growth of Vibrio parahaemolyticus. The toxicology studies showed that antimicrobial substances had no obvious side effects on mice.4. The extracellular antimicrobial substances were applied into the aquatic products processing such as seedling and processing of scallop. The results show that the extracellular products of S2improved breeding water microbial environment of aquatic products and effectively reduce drug dosage and improve product quality. Furthermore, it improved quality of aquatic products in the process of low temperature storage, inhibited bacteria breeding and extended the shelf life of products. |
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