Preparation Of Bacillus Subtilis Antibacterial Substance And Its Application In The Preservation Of Aquatic Products

The fermentation product of Bacillus subtilis can effectively inhibit a variety of pathogens.Because of its antibacterial activity and biosurfactant characteristics,it has been widely used in many fields such as agriculture,animal husbandry,food,and oil extraction.It has broad market prospects.In this paper,the fermentation products of Bacillus subtilis were firstly separated and the antibacterial substances in the fermentation products were determined.Then,a preliminary study was conducted on the solid-state fermentation process of Bacillus subtilis,and the optimal fermentation process combination was determined through response surface optimization design.Secondly,taking the sea prawn as the research object,the dominant spoilage bacteria in the shrimp meat were isolated and purified,and the antibacterial substance produced by Bacillus subtilis was used to explore its antibacterial effect on the dominant spoilage bacteria.Finally,the produced antibacterial substances are further applied to the refrigerated preservation of sea prawns,in order to provide theoretical guidance for the application of antibacterial substances produced by Bacillus subtilis in the preservation of aquatic products.The specific research work and conclusions of this paper are as follows:1.The fermentation product of Bacillus subtilis was obtained by LB liquid fermentation,and the product was separated and identified.The experimental results showed that the antibacterial substance produced by Bacillus subtilis was preliminarily speculated to be a surfactin lipopeptide compound,and its liquid fermentation yield was 196mg/L.2.Through the single factor experiment of fermentation conditions,the optimal level of each influencing factor in the solid-state fermentation process was obtained,which were fermentation temperature 31 ?,fermentation time 48 h,inoculation amount 10%,and material-liquid ratio 3:7.Based on the analysis of the fermentation process composition,Box-Behnken was used to obtain the optimal level and interaction of the influencing factors,and the optimal fermentation technology combination was determined by regression model:inoculum amount 11.36%,fermentation temperature 31.41 ?,fermentation time 37.21 h,the predicted output is 6.145 g/kg.Under laboratory conditions,the specific process parameters are as follows: inoculum amount 11%,temperature 31 ?,fermentation time 38 h,the actual fermentation yield is 6.08 g/kg.The above experiments provide a theoretical basis for the large-scale production of Bacillus subtilis antibacterial substances.3.In order to realize the rational use of Bacillus subtilis antibacterial substances in food preservation,the inhibitory effect of antibacterial substances on spoilage bacteria was explored.The dominant spoilage bacteria were isolated and purified from the shrimp meat of sea prawns,and 16 Sr DNA molecular identification and morphological observation were performed on them.The experimental results show that the dominant strains of shrimp meat in the spoilage process are Shewanella,Vibrio alginolyticus,Psychrophilus,and Zoococcus citrus.4.The experiment took Shewanella and Vibrio alginolyticus as the research objects,and explored the antibacterial mechanism of antibacterial substances on spoilage bacteria.The experimental results show that its antibacterial method is to destroy the cell membrane structure of bacteria,and its minimum inhibitory concentration is 20 mg/m L.The experimental results provide a certain theoretical support for fully understanding the antibacterial mechanism of Bacillus subtilis antibacterial substances against spoilage bacteria.5.The experiment took shrimp meat as the research object,and explored the changes in the freshness index of shrimp meat during the cold storage process.The experimental results show that after the antibacterial substance solution treats shrimp meat,the p H change of shrimp meat can be slowed down to 7.4 for two days,and the time for shrimp meat TVBN to reach 30 mg/100 g is prolonged by about 2 days,which can effectively inhibit spoilage.The growth and reproduction of bacteria in the process of refrigerating shrimp meat.Compared with the control group,the antibacterial substance solution treatment can increase the shelf life of shrimp meat in cold storage for 2 to 3 days,which provides theoretical support for the application of the antibacterial substance in the direction of antiseptic and fresh-keeping.