| Preservative is one of the most important additive in the food industry. Nowdays Sodium Benzoate and sorbic acid Potassium are the widely used chemical preservative. However, studies reveal that these chemical preservatives may lead to some problems inducing carcinogenic effect., it will become a trend that bio-preservative replace the chemical preservative in the food industry gradually for the safety reason. As a newly developed bio-preservative, propionicin has been studied intensively now by the foreign researcher, however, it has no report China to our knowledge, especially on the microbiol inhibition activity. In this paper we study the metabolites inhibitory activity of a Propionibacterium.shermann using the spoilage organism Pseudomnas.putida as indicator strain.In this thesis the main research include following parts: the primary investigate of the inhibitory effect of propionibactium metabolite on spoilage organism Pseudomnas.putida; Single Factor Design, Plackett-Burman design and Response Surface Analysis have been employed for the optimization of fermertation conditions and the composition of the fermentation medium; the properties of the metabolite including inhibitory spectrum; the concentration of the organic acid; the antimicrobial sensitivity to heat and protolytic enzymes were studied in detail.The thesis investigated the main characters of the propionbacteria, including the observation of it's micrograph, physiology, biochemistry and study the inhibitory activity of the metabolite .The results showed that the bacteria was pleomorphic rods that frequently formed irrrgular clumps with "Chinese -character" arrangements; the metabolite had strong inhibitory effect at low pH(5.0) by measuring the turbidity value, Result of agar diffusion method showed that metabolite also had strong inhibitory effect on indicator organism at pH5.3 when the plate contain 2.0 × 3~6cfu/ml of the indicator organism.This thesis established the optimized cluture contidions as follow: the inoculant which stored at -70℃ was inoculated in SLB lipid medium. After incubating for 48 hours in SLB, the culture strains were inoculated in fermention medium with 5% incoculation volume. After incubating for 72 hours at 30℃, we measured the inhibitory activity of the metabolite. Single Factor Design experiment sesults showed that the optimization fermentation medium is 1.0% corn steep powder, 2% Glucose and 0.1% Tween 80. on the base of primary medium.The study found that the corn steep powder, glucose and yeast extract powder are the most important factors in the primarily optimized fermention medium by the Plackett-Burman design. The farther optimization level of three important factors were studied by Response Surface Analysis, and the optimization composition of the fermentation medium was as follow: 10g corn steep powder, 25g Glucose, 7g yeast extract powder, 0.1% Tween 80, 0.25g monopotassium phosphate, 0.005g manganous sulfate and 1000 ml distilled water, pH 7.0 beforeautoclaving. The final inhibitory activity of the metabolite was 34AU/ml when fermented with the optimization condition and medium. Inhibitory activity increased 0.79 time than that of the primary fermentation medium.The properties of the metabolite were studied in detail. Results showed that it can inhibit the growth of gram negative bacteria and some yeast, but it can not inhibit the growth of the gram positive bacteria. The organic acid was measured by the reverse HPLC method, the concentration of the acetic acid and the propionic are all about 0.31%. Antimicrobial activity of the metabolite is stable in the temperature range of 60°C~121°C for 20 minutes at the acid condition(pH5.3). The metabolite is sensitive to pepsin, however it is not sensitive to trypsin and protease K.In this thesis we have studied the inhibitory activity of the metabolite of the Propionibacterium, the optimization of culture condition and the examination of partial properties of the metabolite. This has great value on the further use of the metabolite as food preservative in China. Furt...
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