Response of Vibrio parahaemolyticus to ethanol shock

In this study, the growth and survival of Vibrio parahaemolyticus in the presence of 0.0-8.0% ethanol was first examined. V. parahaemolyticus was then exposed to a sub-lethal dose of 5.0% ethanol for 30 and 60 min (ethanol shock). Morphological changes and alterations in cell leakage, thermal tolerance at 47 degrees C, and susceptibility to 8% ethanol and low temperature (4 and -18 degrees C) of V. parahaemolyticus caused by ethanol shock were investigated. In addition, recoveries of the ethanol-shocked cells of V. parahaemolyticus on thiosulfate-citrate-bile salts-sucrose agar (TCBS) and TSA-3.0% NaCl were also compared. The findings revealed that the presence of ethanol in TSB-3.0% NaCl at 6.0-8.0% and 5.0% or less, exerted bactericidal and partial growth inhibition effect, respectively, on V. parahaemolyticus. Recovery of ethanol-shocked cells of V. parahaemolyticus was significantly (P<0.05) less on TCBS than on TSA-3.0% NaCl. A significantly (P<0.05) marked increase of protein and nucleic acid material in the supernatant of cell suspension was found after cells of V. parahaemolyticus were exposed to ethanol shock. Extensive cell disruption, wrinkling and cell-wall pitting, indicative of cell-surface damage were also noted on the ethanol-shocked cells. Ethanol-shocked cells of V. parahaemolyticus exhibited a similar yet higher susceptibility at 4 and -18 degrees C compared with the control cells. Moreover, there was a marked increase in the thermal tolerance and resistance to 8.0% ethanol with cells of V. parahaemolyticus after ethanol shock. Finally, the duration of ethanol shock testing did not affect the extent of increased thermal tolerance. While cells of V. parahaemolyticus subjected to ethanol shock for 60 min showed an increase in their resistance to 8.0% ethanol, they also showed an increase in susceptibility at -18 degrees C, than those ethanol shocked for 30 min.     

Expression of superoxide dismutase, catalase and thermostable direct hemolysin by, and growth in the presence of various nitrogen and carbon sources of heat-shocked and ethanol-shocked Vibrio parahaemolyticus

Vibrio parahaemolyticus 690 was subjected either to heat shock at 42 degrees C or ethanol shock in the presence of 5% ethanol. The effects of those shocks on superoxide dismutase (SOD) and catalase (CAT) activities, and thermostable direct hemolysin (TDH) production were examined. In addition, the growth behaviors of the stressed and unstressed cells of V. parahaemolyticus in the presence of various nitrogen and carbon sources were compared. Both heat shock and ethanol shock reduced the levels of SOD and CAT activities in V. parahaemolyticus. Gel activity staining assay failed to detect the expression of CAT, while one SOD enzyme with an electrophoretic mobility greater than the [Mn]SOD and [Fe]SOD of Escherichia coli was detected in the unstressed, heat-shocked and ethanol-shocked cells of V. parahaemolyticus. Heat shock for 15-60 min and ethanol shock for 45-60 min were found to enhance the synthesis of TDH. Ethanol-shocked and unstressed cells of V. parahaemolyticus grew similarly and produced similar amounts of TDH when they were grown in TSB-3% NaCl, but slower growth and less production of TDH occurred with heat-shocked cells until after 200 min of cultivation. The growth rate and maximum growth of the unstressed, heat-shocked and ethanol-shocked cells varied with the nitrogen and carbon sources used. With the same nitrogen or carbon source, the growth patterns of the ethanol-shocked and unstressed cells were similar while the heat-shocked cells exhibited an extended lag period.     

Susceptibility of Vibrio parahaemolyticus to various environmental stresses after cold shock treatment

Vibrio parahaemolyticus was subjected to cold shock treatment at 20 or 15 degrees C for 2 or 4 h. The effect of cold shock on the survival of V. parahaemolyticus subjected to subsequent low temperature (5 and -18 degrees C) and other adverse conditions (47 degrees C, 6 ppm crystal violet, 1000 ppm H(2)O(2), 25 mM acetic acid and 25 mM lactic acid) was investigated. Regardless of the cold shock treatment, survival of V. parahaemolyticus increased when stored at 5 or -18 degrees C, while no increase in survival was noted for cells cold shocked in the presence of chloramphenicol. Cold shock treatment under the conditions tested, in general, enabled V. parahaemolyticus cells to survive better following subsequent challenge by crystal violet, while the cold-shocked organism was more susceptible to high temperature (47 degrees C), H(2)O(2) and organic acids (lactic and acetic acid) than the non-shocked cells. Furthermore, the temperature and time of the cold shock treatment affected the cold shock response of V. parahaemolyticus.     

Response of heat-shocked Vibrio parahaemolyticus to subsequent physical and chemical stresses

Vibrio parahaemolyticus foodborne strains 405, 556, and 690 and a V. parahaemolyticus chopping board isolate were heat shocked at 42 degrees C for 15, 30, or 45 min. Heat shock, regardless of heating periods tested, caused an increased demand for NaCl during recovery from heat injury. Further study with strain 690 and the chopping board isolate also revealed that heat shock generally increased the survival of the test organism during subsequent exposure to 47 degrees C, 20 ppm H202, and 8% ethanol and reduced the tolerance of the test organism to low temperatures (5 and -18 degrees C). The extent of the heat shock response of V. parahaemolyticus varied with strain and the duration of treatment. Furthermore, heat shock treatments in the present study caused the leakage of nucleic acids from V. parahaemolyticus cells. This effect was most pronounced with cells heat shocked at 42 degrees C for 45 min.     

Influence of growth conditions on pressure resistance of Vibrio parahaemolyticus in oysters and the optimization of postpressure treatment recovery conditions

Vibrio parahaemolyticus ATCC 43996 was grown at 15°C for 53 h, 20°C for 24 h, 25°C for 12 h, 30°C for 9 h, 35°C for 9 h, or 40°C for 6 h to early stationary phase. Oyster meats were blended, autoclaved at 121°C for 15 min, inoculated with V. parahaemolyticus, and pressure treated at 250 MPa for 2 and 3 min and at 300 MPa for 1 and 2 min at 21°C. Overall, growth temperatures of 20 and 40°C yielded the greatest pressure resistance in V. parahaemolyticus. The effects of salt concentration and H(2)O(2)-degrading compounds on the recovery of V. parahaemolyticus also were investigated. Sterile oyster meats were inoculated with V. parahaemolyticus and treated at 250 MPa for 1, 2, or 3 min at 21°C. These meats were then blended with 0.1% peptone water supplemented with 0.5 to 1.5% NaCl and plated on tryptic soy agar (TSA) supplemented with 0 to 3.5% NaCl. For recovery of pressure-injured cells, peptone water with 1% NaCl and TSA with 0.5% NaCl were the best diluent and plating medium, respectively. Addition of sodium pyruvate (0.05 to 0.2%) or catalase (8 to 32 U/ml) did not increase the recovery of V. parahaemolyticus after pressure treatment. The effect of incubation temperature and gas atmosphere on the recovery of V. parahaemolyticus after pressure treatment also was determined. Aerobic incubation at 30°C resulted in the highest recovery of V. parahaemolyticus in sterile oyster meats. The 30°C incubation temperature was also the optimum temperature for recovery of V. parahaemolyticus in pressure-treated live oysters. The results of this study indicate that the growth conditions for V. parahaemolyticus before and after high hydrostatic pressure treatment should be taken into consideration when assessing the efficacy of pressure inactivation.     

Survival of Vibrio parahaemolyticus under environmental stresses as influenced by growth phase and pre-adaptation treatment

In this study, the susceptibility of Vibrio parahaemolyticus in different growth phases after exposure to lethal stresses including 47 °C and 8% ethanol was first investigated. The effect of a culture's growth phase on both the heat and ethanol shock response of V. parahaemolyticus was then examined. It was found that cells of V. parahaemolyticus in the mid-exponential phase, regardless of adaptation, were most susceptible to environmental stresses, while cells in the stationary phase were least susceptible to the lethal stresses examined. Adaptation with heat shock at 42 °C for 45 min or ethanol shock with 5% ethanol for 60 min induced an increased resistance of V. parahaemolyticus to subsequent lethal stresses at 47 °C and 8% ethanol. While the adaptation treatments resulted in a reduced resistance of the test organism to pH 4.4 and 20% NaCl. Generally, the extent of changes in the resistance of V. parahaemolyticus to lethal stresses between the adapted and control cells was found to be growth phase dependent. Compared with the respective control cells, the adapted late-exponential phase cells exhibited the greatest extent of change, while the adapted stationary phase cells showed the least change in their resistance to the lethal stresses examined.     

Characterization of low salinity stress in Vibrio parahaemolyticus

Vibrio parahaemolyticus is a marine foodborne pathogenic bacterium commonly found in seawater or seafood. This bacterium often encounters low salinity stress when the contaminated seafood is washed with fresh water during food processing. This study was conducted to investigate the response of exponential- and stationary-phase cells of V. parahaemolyticus ST550 to lethal or sublethal low salinity. Tolerance to lethal low salinity (0.25% NaCl) was enhanced in V. parahaemolyticus cells in the exponential phase by previous adaptation in sublethal low salinity (0.6% NaCl). Low salinity-adapted cells in the exponential phase were also cross-protected against the challenge of lethal low pH, indifferent to heat, and sensitized to bile, acetic acid, and lactic acid stress. The adapted cells in the stationary phase were significantly protected against heat treatment at 44°C for 10 and 15 min, sensitized to bile and acetic acid treatment, and indifferent to low pH and lactic acid.     

Effects of electrolyzed oxidizing water treatment on reducing Vibrio parahaemolyticus and Vibrio vulnificus in raw oysters

Contamination of Vibrio parahaemolyticus and Vibrio vulnificus in oysters is a food safety concern. This study investigated effects of electrolyzed oxidizing (EO) water treatment on reducing V. parahaemolyticus and V. vulnificus in laboratory-contaminated oysters. EO water exhibited strong antibacterial activity against V. parahaemolyticus and V. vulnificus in pure cultures. Populations of V. parahaemolyticus (8.74 x 10(7) CFU/ml) and V. vulnificus (8.69 x 10(7) CFU/ml) decreased quickly in EO water containing 0.5% NaCl to nondetectable levels (> 6.6 log reductions) within 15 s. Freshly harvested Pacific oysters were inoculated with a five-strain cocktail of V. parahaemolyticus or V. vulnificus at levels of 10(4) and 10(6) most probable number (MPN)/g and treated with EO water (chlorine, 30 ppm; pH 2.82; oxidation-reduction potential, 1131 mV) containing 1% NaCl at room temperature. Reductions of V. parahaemolyticus and V. vulnificus in oysters were determined at 0 (before treatment), 2, 4, 6, and 8 h of treatment. Holding oysters inoculated with V. parahaemolyticus or V. vulnificus in the EO water containing 1% NaCl for 4 to 6 h resulted in significant (P < 0.05) reductions of V. parahaemolyticus and V. vulnificus by 1.13 and 1.05 log MPN/g, respectively. Extended exposure (> 12 h) of oysters in EO water containing high levels of chlorine (> 30 ppm) was found to be detrimental to oysters. EO water could be used as a postharvest treatment to reduce Vibrio contamination in oysters. However, treatment should be limited to 4 to 6 h to avoid death of oysters. Further studies are needed to determine effects of EO water treatment on sensory characteristics of oysters.     

Effect of heat shock on the fatty acid and protein profiles of Cronobacter sakazakii BCRC 13988 as well as its growth and survival in the presence of various carbon,nitrogen sources and disinfectants

In the present study, Cronobacter sakazakii, a foodborne pathogen, was first subjected to heat shock at 47 °C for 15 min. Effect of heat shock on the fatty acid and protein profiles, carbon and nitrogen source requirements as well as the susceptibilities of C. sakazakii to Clidox-S, a chlorine-containing disinfectant and Quatricide, a quaternary ammonium compound were investigated. Results revealed that heat shock increased the proportion of myristic acid (14:0), palmitic acid (16:0) and the ratio of saturated fatty acid to unsaturated fatty acid, while reducing the proportion of palmitoleic acid (16:1) and cis-vacceric acid (18:1). In addition, eleven proteins showed enhanced expression, while one protein showed decreased expression in the heat-shocked compared to the non-heat-shocked cells. Non-heat-shocked cells in the medium supplemented with beef extract exhibited the highest maximum population. On the contrary, the highest maximum population of heat-shocked C. sakazakii was noted in the medium having either tryptone or yeast extract as the nitrogen source. Among the various carbon sources examined, the growth of the test organism, regardless of heat shock, was greatest in the medium having glucose as the carbon source. Furthermore, heat shock enhanced the resistance of C. sakazakii to Clidox-S or Quatricide.     

Effect of heat shock on thermal tolerance and susceptibility of Listeria monocytogenes to other environmental stresses

In the present study, Listeria monocytogenes Scott A, V7 and CCRC 14930 were first subjected to heat shock at 45°C for 1 h or at 48°C for 10 min. Thermal tolerance at 55°C and survival of the heat shocked as well as non-heat shocked cells of L. monocytogenes in the presence of 25% NaCl, 0.01% crystal violet, 0.1% H₂O₂, and 18% ethanol were examined.It was found that heat shock response of L. monocytogenes varied with strains, the condition of heat shock treatment and type of subsequent stress. Compared with the non-heat shocked cells, the 45°C-1 h heat shocked cells of strains Scott A and V7 showed an increased survival after exposure to 55°C for 60 min. Meanwhile, survival of the 48°C-10 min heat shocked L. monocytogenes cells, regardless of strain, exhibited no significant difference (p>0.05) with their respective control cells. Generally, heat shocking at 45°C for 1 h increased the tolerance of L. monocytogenes to NaCl, ethanol and crystal violet. On the other hand, heat shocking at 48°C for 10 min although increased the resistance of L. monocytogenes to NaCl reduced its resistance to H₂O₂ and crystal violet.     

Efficacy of the thin agar layer method for the recovery of stressed Cronobacter spp. (Enterobacter sakazakii)

Cronobacter spp. (Enterobacter sakazakii) are emerging opportunistic pathogens for all age groups, and are of particular concern when it comes to infants. Prior to contaminating food, the organism may be exposed to a variety of stresses, leading to a generation of sublethally injured cells that may not be detected by selective media unless a protracted recovery period is included in the isolation procedure. This study evaluated the efficacy of the thin agar layer (TAL) method for the recovery of Cronobacter cells that had been exposed to various stress conditions. Five strains of C. sakazakii and C. muytjensii were exposed to starvation, heat, cold, acid, alkaline, chlorine, or ethanol, with or without further exposure to desiccation stress. The recovery of the stressed cells was determined on tryptone soy agar (TSA; nonselective control medium), violet red bile glucose agar (VRBGA; selective agar), Druggan-Forsythe-Iversen (DFI; selective agar), and TAL media (viz., VRBGA overlaid with TSA, and DFI overlaid with TSA). Regardless of stress type, there were no significant differences among the recoveries of stressed desiccated Cronobacter spp. cultures on TSA, DFI+TSA, and VRBGA+TSA, but there was significantly less recovery on VRBGA. The recovery of prestressed desiccated Cronobacter spp. on DFI+TSA was similar to that on TSA, whereas the recovery on VRBGA+TSA was lower. DFI+TSA performed better than VRBGA+TSA did in differentiating Cronobacter spp. within mixed bacterial cultures. The results of this study suggest the use of the TAL method DFI+TSA as an improved method for the direct recovery of stressed Cronobacter spp.     

Growth inhibition of Vibrio parahaemolyticus in seafood by tabletop dry ice cooler

Tabletop dry ice coolers (three types; dome model, cap model and tripod model), which are used in kitchens and hotel banquet halls to refrigerate fresh seafood, were investigated to determine whether growth of Vibrio parahaemolyticus was inhibited by their use. On TSA plates containing 1.8% NaCl and fresh seafood (fillets of squid, pink shrimp and yellowtail), V. parahaemolyticus (O3:K6, TDH+) inoculated at 4 to 5 log CFU/sample and left at ambient temperature (25 degrees C) grew by 1.0 to 2.8 orders in 4 hours. In contrast, with tabletop coolers no significant increase in viable count occurred in 3 to 4 hours, confirming that tabletop coolers inhibited the growth of V. parahaemolyticus. The temperature in each tabletop cooler was kept below 10 degrees C for 80 to 135 min, though the CO2 gas concentration in them remained high for only a short time (0 to 75 min). It was presumed that the refrigeration function mainly contributed to growth inhibition. Our results indicate that tabletop dry ice coolers are helpful for prevention of food-borne disease due to V. parahaemolyticus in food-service locations, such as kitchens and banquet halls.     

Biochemical and virulence characterization of viable but nonculturable cells of Vibrio parahaemolyticus

Vibrio parahaemolyticus is a common foodborne pathogen frequently causing outbreaks in summer. Maintenance of virulence by the viable but nonculturable (VBNC) state of this pathogen would allow its threat to human health to persist. This study reports on the change in virulence and concomitant changes in activity of two enzymes and fatty acid profiles when V. parahaemolyticus ST550 entered the VBNC state in the modified Morita mineral salt-0.5% NaCl medium incubated at 4 degrees C. The major change in fatty acid composition occurred in the first week, with a rapid increase in C15:0 fatty acid and saturated/unsaturated ratio while a rapid decrease in C16:1 was observed. The activity level of the inducible protective enzyme superoxide dismutase became undetectable in the VBNC state, whereas that of constitutive glucose-6-phosphate dehydrogenase did not change in either the exponential phase or the VBNC state. Cytotoxicity against HEp-2 cells and a suckling mouse assay showed that virulence was lowered in the VBNC state compared with exponential-phase cells. Longer incubation times were required by the VBNC cells to achieve the same level of virulence as seen in exponential-phase cells. Culturable cells were recovered on selective agar medium from the VBNC cultures injected into suckling mice, probably as the result of in vivo resuscitation. Results of this study add to our understanding of the biochemical and physiological changes that have not been reported when V. parahaemolyticus enters into the VBNC state.     

几种天然食用成分对副溶血性弧菌抑菌作用研究

副溶血性弧菌是引起我国特别是沿海地区细菌性食物中毒危害的首要食源性致病菌。本实验通过单因素试验和正交试验研究醋酸、酒精与茶多酚3 种天然食用成分对菌悬液中副溶血性弧菌存活率的影响。单因素试验结果表明：经体积分数高于50%酒精或质量浓度为0.5mg/mL的茶多酚处理5min能完全杀灭菌悬液中的副溶血性弧菌;经pH2 的醋酸溶液处理也能使菌悬液中副溶血性弧菌降低4.79lg(CFU/mL)。正交试验结果表明：酒精体积分数、茶多酚质量浓度和酸度对副溶血性弧菌的抑制效果具有明显的协同作用;pH2.8、酒精体积分数20% 及茶多酚质量浓度0.125mg/mL 或pH2.4、酒精体积分数12% 及茶多酚质量浓度0.125mg/mL 的混合体系均能有效抑制副溶血性弧菌的生长。这些研究结果说明食用酒精、醋酸和茶叶提取物的适当配合将有可能作为复合杀菌剂用于水产食品中,从而降低副溶血性弧菌感染的风险。     

Involvement of radical species in inactivation of Vibrio parahaemolyticus in saline solutions by direct-current electric treatment

The effect of pulsed low-direct-current (DC) electric treatment on the viability of Vibrio parahaemolyticus in artificial seawater and 3.0% (w/v) NaCl solution was studied as a function of available chlorine (AC) concentration. The amount of AC generated during the DC electric treatment increased in proportion to the amount of passed DC. The survival fraction of V. parahaemolyticus cells decreased depending on AC concentration. When the generated AC components were completely reduced in the presence of sufficient sodium thiosulfate, no inactivation of V. parahaemolyticus in the NaCl solution was observed during the DC electric treatment. Based on the AC concentration, the inactivation efficacies of the DC electric treatment of the seawater and NaCl solution were approximately 4-fold and 30-fold that of the exogenous addition of sodium hypochlorite, respectively. Fluorometric analysis using 2-[6-(4'-hydroxy)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid showed that the generation of highly reactive radical species such as hydroxyl radical in the seawater and NaCl solution occurred during the DC electric treatment. The amount of generated radical species depended on the amount of passed DC. It is concluded that pulsed low-DC electric treatment of saline solutions exerts superior inactivation efficacy against V. parahaemolyticus to sodium hypochlorite owing to the generation of radical species.     

耐超高压胁迫副溶血性弧菌的逆境耐受性

目的：探讨水产品中耐超高压胁迫的副溶血性弧菌对高压及其他逆境环境的耐受性。方法：以80～250 MPa超高压处理原始敏感菌株（Vibrio. parahaemolyticus ZJGSMC001）,筛选得到耐高压菌株（V. parahaemolyticus ZJGSPR001）,以其他逆境处理,分析二者对高压和其他逆境的耐受性差异。结果：以250 MPa压力胁迫处理,耐压菌株存活量比原始菌株高2（lg（CFU/mL））。3 ℃以下原始菌株生长速率为负值,45 ℃以上原始菌株不能存活,耐压菌株则生长良好,1 ℃和48 ℃时仍可存活。在NaCl质量浓度高达11.5 g/100 mL时,原始菌株为负生长,耐压菌株仍能生长。耐压菌株对有机溶剂和有机酸的耐受性增强,其中乙醇体积分数12%、丙酮体积分数9%、甲苯体积分数0.75%、柠檬酸3 mg/mL和乳酸体积分数1.5%时,原始菌株全部致死,耐压菌株仍存活。结论：原始菌株对压力较敏感,而耐压菌株经超高压胁迫处理后,除对高压的耐受能力提高外,对其他逆境（如温度、氯化钠、有机溶剂、有机酸）的耐受性也有所增强。     

The susceptibility of Streptococcus thermophilus 14085 to organic acid,simulated gastric juice,bile salt and disinfectant as influenced by cold shock treatment

Streptococcus thermophilus is a thermophilic lactic acid bacterium which is used as the starter organism for the fermentation of yoghurt and some cheese. In the present study, S. thermophilus BCRC 14085 was subjected to cold shock treatment by exposure at 10 °C for 2 h. The effect of cold shock on the susceptibility of S. thermophilus in subsequent lethal stress environments such as simulated gastric juice (pH 2.0–3.0), bile solution (2.0%) and various organic acids (0.75 M, pH 3.5) including propionic, lactic, acetic, citric and tartaric acid was investigated. In addition, the survival of cold-shocked and non-shocked S. thermophilus exposed to disinfectants, Clidox-S and Quatricide, were compared. Results revealed that cold shock enhanced the tolerance of S. thermophilus in the presence of simulated gastric juice (pH 2.5 and 2.8), while in bile solution, the population increase of cold-shocked cells is higher than that of non-shocked cells after 12 h of incubation. Furthermore, the susceptibility of S. thermophilus, regardless of cold shock, to organic acid varied with the kinds of organic acid examined. The cold-shocked S. thermophilus showed a significantly less survival (P < 0.05) than that of the non-shocked cells when exposed to lactic or acetic acid. Furthermore, cold shock reduced the survival of S. thermophilus when exposed to Quatricide but not Clidox-S.     

副溶血弧菌在玻璃表面生物菌膜的生长特性及超声波法解离作用

本文研究了副溶血弧菌(Vibrio parahaemolyticus)在玻璃表面生物菌膜(biofilm,BF)的生长特性,生长过程中环境因素的影响及超声波对其的解离作用。采用结晶紫染色法观察生物菌膜在玻璃表面的生长形态;酶标仪在595 nm波长处测量不同培养条件下生物菌膜的生物量;平板菌落计数法衡量超声波对菌膜的解离效果。结果表明:结晶紫染色法可直观清晰观察副溶血弧菌在玻璃表面形成的生物菌膜,且随着培养时间的延长,副溶血弧菌生物菌膜形成的网状结构越来越致密。根据酶标仪测得的生物菌膜生物量的大小可得到在玻璃表面菌膜生长的最佳条件,当培养基盐度为3%,培养时间为24 h,培养时转速为70 r/min得到的副溶血弧菌生物菌膜已经成熟且菌体个数达到2.56×107 CFU/cm2。用50 k Hz超声波,采用间歇式超声波处理方法(每作用30 s间隔30 s)作用总时间4 min在保持菌体活性的同时能达到最佳解离效果。     

原儿茶酸对副溶血弧菌的抑菌和减毒作用

该研究旨在探讨原儿茶酸对副溶血弧菌的抑菌活性和减毒作用,揭示原儿茶酸抑菌的作用机制。通过测定最小抑菌浓度（Minimal Inhibitory Concentration,MIC）、生长曲线、核酸与蛋白质泄漏量、丙二醛（MDA）含量,利用扫描电镜观察副溶血弧菌形态的变化,来评估原儿茶酸对副溶血弧菌的抑菌活性及其对细胞膜完整性和通透性的影响。同时,通过检测亚抑菌浓度（Sub-inhibitory Concentrations,SICs）下原儿茶酸对副溶血弧菌毒力因子合成的影响,研究原儿茶酸对副溶血弧菌的毒力衰减作用。实验结果表明,原儿茶酸的MIC为2 mg/mL,经MIC浓度原儿茶酸处理后,副溶血弧菌发生严重内陷和破裂,上清液中核酸、蛋白质、MDA含量分别是对照组的2.65倍、1.94倍和10.05倍。此外,原儿茶酸在浓度为1/4 MIC时对胞外多糖、胞外蛋白酶、生物被膜的抑制率分别为40.57%、19.79%和26.04%,在浓度为1/2 MIC时的抑制率分别为52.85%、28.38%和34.69%。原儿茶酸主要作用于细胞膜,通过影响细胞膜的完整性和通透性抑制副溶血弧菌的生长,在亚抑菌浓度下便可有效减弱副溶血弧菌毒力。     

玉米胚芽油脂肪酸衍生化工艺

以玉米胚芽油为原料,对其中亚油酸进行酯化衍生化,实现亚油酸的富集。分别考察碱用量、反应时间、反应温度及酸化程度对水解反应和H2SO4-甲醇溶液体积分数、用量、反应时间和温度对酯化反应的影响。结果表明：醇油比(95%乙醇-玉米胚芽油,mL/g)为2:1,KOH用量为玉米胚芽油皂化当量的1.1倍、80℃水浴回流100min时,水解反应最完全,酸值最大为207.85mg KOH/g,所得脂肪酸在催化剂5% H2SO4-甲醇溶液用量为5mL/g、70℃水浴30min条件下甲酯化反应最完全,气相色谱检测甲酯化程度为100%。经尿素包合进行富集得到纯度为96.98%的亚油酸。