屎肠球菌M-2所产细菌素的分离纯化与特性研究

本文以前期从内蒙古传统干酪中分离到的一株产细菌素的屎肠球菌M-2为试材,对其所产细菌素进行提取纯化和理化特性研究。经80%硫酸铵盐析及SP Sepharose Fast Flow阳离子交换树脂层析得到纯化的细菌素,其比活力可达411.204AU/mg;Tricine SDS-PAGE电泳结果显示其分子量约为3400Da;特性研究发现该细菌素有很好耐热、耐酸碱、抗表面活性剂及蛋白酶敏感特性,且抑菌谱较广,不仅对李斯特氏菌、金黄色葡萄球菌、芽孢杆菌等革兰氏阳性菌有较强的抑制作用,还对大肠杆菌、假单胞菌等阴性菌表现出抑菌活性,有作为天然食品防腐剂的良好应用前景。     

蚯蚓粪中乳酸菌的分离及其在大肠杆菌O157：H7中的抗菌活性

本研究利用SL培养基从蚯蚓粪中分离到54株具有产酸性能的菌株,并以E.coli O157：H7（EDL933株）作为指示菌株,采用点种法检测分离菌株的抑菌活性。结果表明其中6个菌株对指示菌具有拮抗作用,通过形态特征,结合16S rDNA序列分析,初步鉴定该6个菌株分别为食物魏斯特菌（Listeria welshimeri）、乳酸片球菌（Pediococcus acidilactici）、短乳杆菌（Lactobacillus brevis）和格氏乳球菌（Lactococcus garvieae）。分离到的乳酸菌对E.coli O157：H7（EDL933株）具有显著的抑制作用,发酵温度和初始pH值影响发酵液的抑菌作用,优化环境因子可以促进拮抗菌对E.coli O157：H7的抑制作用。本研究为进一步分离抗菌产物用于人畜共患病的预防和治疗提供了理论依据。     

藜麦种子总黄酮的提取及体外抑菌作用

采用96孔板微量法和牛津杯法研究藜麦种子总黄酮对大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌、白色念珠菌、铜绿假单胞菌的抑制作用。结果表明,藜麦种子总黄酮对供试菌株的抑制效果由大到小顺序为大肠杆菌、枯草芽孢杆菌、白色念珠菌、铜绿假单胞菌,对金黄色葡萄球菌基本没有抑菌作用。最低抑菌浓度值分别为:大肠杆菌32 mg/mL、枯草芽孢杆菌64 mg/mL、白色念珠菌128 mg/mL、铜绿假单胞菌256 mg/mL、金黄色葡萄球菌512 mg/mL。说明藜麦种子总黄酮对大肠杆菌、枯草芽孢杆菌、白色念珠菌和铜绿假单胞菌有抑菌作用,对金黄色葡萄球菌不敏感。     

主成分分析法优选枸杞乳酸菌发酵饮品发酵剂

乳酸菌发酵作为果蔬汁的一种绿色加工技术,不仅可以赋予产品独特的风味,还可以转化其中的活性物质,提高产品的营养价值和保健功效。该研究以湖北杂交枸杞为原料,使用6种乳酸菌(植物乳杆菌、嗜热链球菌、嗜酸乳杆菌、鼠李糖乳杆菌、干酪乳杆菌及发酵乳杆菌)进行发酵,研究发酵前后枸杞果汁理化特性、主要活性成分及体外抗氧化变化,并利用主成分分析进行综合评价优选出理想的发酵菌株。结果表明,6种乳酸菌在枸杞果汁中生长良好,活菌数均能达到10.0 lg CFU/mL以上。发酵后的枸杞果汁中总糖和还原糖含量显著降低(P0.05),且植物乳杆菌和嗜热链球菌产酸能力更强,发酵后总酸含量达6.74、6.07g/kg。与未发酵枸杞果汁相比,经植物乳杆菌、嗜热链球菌、鼠李糖乳杆菌和发酵乳杆菌发酵的枸杞果汁中总酚含量增加了13.76%～28.07%,而嗜酸乳杆菌和干酪乳杆菌发酵后无显著性差异(P0.05)。6种乳酸菌发酵后枸杞果汁中总黄酮含量增加了55.80%～161.97%。发酵枸杞果汁的抗氧化活性与发酵前相比均有显著提高(P0.05)。基于主成分分析的综合评价函数显示经植物乳杆菌、发酵乳杆菌发酵的枸杞果汁品质更优,适宜作为开发枸杞高值化绿色加工饮品的发酵剂。     

西藏“灵菇”乳的发酵与抑菌机制研究（简报）

根据发酵过程中菌粒中主要微生物数量与发酵乳中主要营养物和产物含量间的关系,分析探讨了西藏"灵菇"乳的发酵机制;考察了不同发酵时期所得发酵乳对大肠杆菌、金黄色葡萄球菌、沙门氏菌的抑菌活性,结合化学物质模拟试验揭示了发酵乳的抑菌机制。结果显示,发酵前期,菌粒中的各微生物由于向乳中扩散及生长延滞,数量稍有减少;随着发酵的进行,菌粒中乳酸菌和酵母菌的数量一直处于相对稳定的水平,但醋酸菌含量呈明显的先升后降趋势;在整个发酵过程中,菌粒中的乳酸菌数量一直处于最高水平,其次为酵母菌,醋醋菌数量最少;乳酸是西藏“灵菇”发酵乳中的主要抑菌活性物质;乙酸和乙醇的存在对低浓度乳酸的抑菌活性有增效作用,但当乳酸浓度较高时,这种增效作用减弱。西藏“灵菇”发酵乳的总抑菌效果是微生物与其代谢产物的共同作用结果。     

腌制叶用芥菜发酵菌分离鉴定及应用研究

为获得发酵性能优良的菌株,生产优质的发酵叶用芥菜,本研究从自然发酵的芥菜中分离发酵用菌株,通过测定乳酸菌的生长、产酸和亚硝酸盐降解能力以及酵母菌的产气、产酯能力和蛋白酶活性等发酵特性进行筛选,并对筛选获得的优良发酵菌加以应用。结果表明,筛选获得的2株乳酸菌L8短乳杆菌(Lactobacillus brevis)、L9植物乳杆菌(Lactobacillus plantarum)和1株酵母菌Y9酿酒酵母菌(Saccharomyces cerevisiae)在腌制叶用芥菜中的发酵性能优良。与自然发酵的叶用芥菜相比,接菌发酵叶用芥菜的pH值和亚硝酸盐含量分别减少了2.22%和88.13%;总酸含量、氨基酸态氮含量分别增加了9.02%和28.09%。接菌发酵提高了腌制芥菜的营养品质和安全性。本研究丰富了叶用芥菜的发酵菌种,为蔬菜发酵加工产业奠定了技术基础。     

不同乳酸菌发酵甘薯渣产物组分分析

为提高甘薯淀粉加工副产物的高值化利用水平,本试验以植物乳杆菌(Lp)、干酪乳杆菌(Lc)、保加利亚乳杆菌(Lb)、戊糖片球菌(Pp)、嗜热链球菌(St)、商业植物乳杆菌(SZ)6种乳酸菌分别对甘薯渣进行发酵,系统分析不同发酵产物的pH值、总酸含量及营养功能成分,并采用灰色理论加权关联度对甘薯渣发酵产物进行综合营养评价,筛选适宜发酵甘薯渣的乳酸菌菌种。结果表明,6种乳酸菌的发酵能力存在显著差异,其中Lb组pH值最低(3.15),Lc组总酸含量最高(27.90);同时,不同乳酸菌对发酵产物中营养功能成分的影响存在显著差异,其中Lb组乳酸含量最高(11.60 mg·mL^-1),SZ组乙酸含量最高(66.99μg·mL^-1),Lb组可溶性膳食纤维含量最高(0.74 g·100 mL^-1),St组总酚含量最高(146.87μg GAE·mL^-1)。与未发酵样品相比,Lc组游离氨基酸总量提高了3.71倍;所有发酵产物中的Mg、Ca、Fe、Zn、Se等矿物质元素含量均显著提高。进一步通过灰色理论加权关联度分析发现...     

腊肉中有益微生物的分离筛选及鉴定

从湖南省张家界传统腊肉中分离到的4株乳酸菌,发酵产物均为乳酸,通过发酵特性试验,发现4株菌都具有较好的发酵特性,通过基本上符合发酵肉制品生产的要求。4株乳酸菌的生化鉴定结果表明,菌株LR17菌株LR65为戊糖片球菌,菌株LR28菌株LR89为清酒乳杆菌。     

优良乳酸菌的筛选及对腌制茭白品质的影响

为获得最适腌制茭白启动发酵剂,缩短腌制茭白生产周期、提高质量品质,从分离筛选保藏的4种乳酸菌菌株(植物乳杆菌、短乳杆菌、嗜柠檬酸明串球菌和戊糖片球菌)中优选出植物乳杆菌和戊糖片球菌2种优良乳酸菌,采用5种不同配比方式分别接种发酵,研究茭白腌制过程中p H、酸度、亚硝酸盐和微生物指标的变化,并对成品的色泽、质地和挥发性风味物质进行分析。结果表明,配比方式对茭白腌制过程中p H、酸度、乳酸菌数和细菌总数的影响不大;在不同配比方式接种中,接种1%植物乳杆菌和2%戊糖片球菌复合菌作为茭白腌制发酵剂,其腌制茭白的"亚硝峰"值最小,为1.62 mg·kg-1,色泽与鲜茭白最为接近,质地口感最好;不同配比方式接种茭白腌制共检测出挥发性风味物质118种,1%植物乳杆菌和2%戊糖片球菌腌制的茭白成品所含风味物质种类和相对含量均较高。因此,最终确定的最佳发酵剂为1%植物乳杆菌和2%戊糖片球菌。本研究结果为茭白的腌制及干制加工的工业化生产提供了理论依据。     

西藏"灵菇"乳的发酵与抑菌机制研究

根据发酵过程中菌粒中主要微生物数量与发酵乳中主要营养物和产物含量间的关系,分析探讨了西藏"灵菇"乳的发酵机制:考察了不同发酵时期所得发酵乳对人肠杆菌、金黄色葡萄球菌、沙门氏菌的抑菌活性,结合化学物质模拟试验揭示了发酵乳的抑菌机制.结果显示,发酵前期,菌粒中的各微生物由于向乳中扩散及生长延滞,数量稍有减少;随着发酵的进行,菌粒中乳酸菌和酵母菌的数量一直处于相对稳定的水平,但醋酸菌含量呈明显的先升后降趋势;在整个发酵过程中,菌粒中的乳酸菌数量一直处于最高水平,其次为酵母菌,醋醋菌数量最少:乳酸是西藏"灵菇"发酵乳中的主要抑菌活性物质;乙酸和乙醇的存在对低浓度乳酸的抑菌活性有增效作用,但当乳酸浓度较高时,这种增效作用减弱.西藏"灵菇"发酵乳的总抑菌效果是微生物与其代谢产物的共同作用结果.     

Phytate degradation by lactic acid bacteria and yeasts during the wholemeal dough fermentation: a 31P NMR study

myo-Inositol hexaphosphate (IP6) is the main source of phosphorus in cereal grains, and therefore, in bakery products. Different microorganisms such as yeasts and lactic acid bacteria have phytase enzymes able to hydrolyze IP6 during the wholemeal breadmaking. In this paper, the phytase activity of Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus curvatus, and Saccharomyces cerevisiae strains, isolated from southern Italian sourdoughs, is assayed using the (31)P NMR technique. The sourdough technology based on the use of lactic acid bacteria in the breadmaking is finally suggested.     

Kombucha fermentation and its antimicrobial activity

Kombucha was prepared in a tea broth (0.5% w/v) supplemented with sucrose (10% w/v) by using a commercially available starter culture. The pH decreased steadily from 5 to 2.5 during the fermentation while the weight of the "tea fungus" and the OD of the tea broth increased through 4 days of the fermentation and remained fairly constant thereafter. The counts of acetic acid-producing bacteria and yeasts in the broth increased up to 4 days of fermentation and decreased afterward. The antimicrobial activity of Kombucha was investigated against a number of pathogenic microorganisms. Staphylococcus aureus, Shigella sonnei, Escherichia coli, Aeromonas hydrophila, Yersinia enterolitica, Pseudomonas aeruginosa, Enterobacter cloacae, Staphylococcus epidermis, Campylobacter jejuni, Salmonella enteritidis, Salmonella typhimurium, Bacillus cereus, Helicobacterpylori, and Listeria monocytogenes were found to be sensitive to Kombucha. According to the literature on Kombucha, acetic acid is considered to be responsible for the inhibitory effect toward a number of microbes tested, and this is also valid in the present study. However, in this study, Kombucha proved to exert antimicrobial activities against E. coli, Sh. sonnei, Sal. typhimurium, Sal. enteritidis, and Cm. jejuni, even at neutral pH and after thermal denaturation. This finding suggests the presence of antimicrobial compounds other than acetic acid and large proteins in Kombucha.     

Application of hexanal,E-2-hexenal,and hexyl acetate to improve the safety of fresh-sliced apples

The aims of this work were to evaluate the effects of different concentrations of hexanal, (E)-2-hexenal, hexyl acetate, and their mixtures on the fate of pathogenic species such as Escherichia coli, Salmonella enteritidis, and Listeria monocytogenes inoculated in model systems as well as the antimicrobial activity against the target species of the chosen molecules when added to the packaging atmosphere of inoculated fresh-sliced apples. The result obtained in this work pointed out the potential use of compounds such as hexanal, (E)-2-hexenal, and hexyl acetate for both the extension of shelf life and an improvement of hygienic safety of "minimally processed foods". In fact, hexanal, (E)-2-hexenal, and hexyl acetate had a significant inhibitory effect against pathogen microorganisms frequently isolated from raw materials (E. coli, S. enteritidis, and L. monocytogenes) when inoculated in both model and real systems. In this last condition, these compounds, at the levels used (150, 150, and 20 ppm for hexanal, hexyl acetate, and (E)-2-hexenal, respectively), displayed a bactericide effect on L. monocytogenes and they exhibited significant extensions of lag phase of E. coli and S. enteritidis inoculated at levels of 10(4)-10(5) CFU/g.     

Changes in membrane fatty acids composition of microbial cells induced by addiction of thymol, carvacrol, limonene, cinnamaldehyde, and eugenol in the growing media

Major active compounds from essential oils are well-known to possess antimicrobial activity against both pathogen and spoilage microorganisms. The aim of this work was to determine the alteration of the membrane fatty acid profile as an adaptive mechanism of the cells in the presence of a sublethal concentration of antimicrobial compound in response to a stress condition. Methanolic solutions of thymol, carvacrol, limonene, cinnamaldehyde, and eugenol were added into growth media of Escherichia coli O157:H7, Salmonella enterica serovar typhimurium, Pseudomonas fluorescens, Brochothrix thermosphacta, and Staphylococcus aureus strains. Fatty acid extraction and gas chromatographic analysis were performed to assess changes in membrane fatty acid composition. Substantial changes were observed on the long chain unsaturated fatty acids when the E. coli and Salmonella strains grew in the presence of limonene and cinnamaldehyde and carvacrol and eugenol, respectively. All compounds influenced the fatty acid profile of B. thermosphacta, while Pseudomonas and S. aureus strains did not show substantial changes in their fatty acid compositions.     

Water properties in cream cheeses with variations in pH, fat, and salt content and correlation to microbial survival

Water mobility and distribution in cream cheeses with variations in fat (4, 15, and 26%), added salt (0, 0.625, and 1.25%), and pH (4.2, 4.7, and 5.2) were studied using (1)H NMR relaxometry. The cheese samples were inoculated with a mixture of Listeria innocua, Escherichia coli O157 and Staphylococcus aureus, and partial least-squares regression revealed that (1)H T(2) relaxation decay data were able to explain a large part of the variation in the survival of E. coli O157 (64-83%). However, the predictions of L. innocua and S. aureus survival were strongly dependent on the fat/water content of the samples. Consequently, the present results indicate that NMR relaxometry is a promising technique for predicting the survival of these bacteria; however, the characteristics of the sample matrix are substantial.     

Lingonberry (Vaccinium vitis-idaea) and European cranberry (Vaccinium microcarpon) proanthocyanidins: isolation, identification, and bioactivities

European, small-fruited cranberries (Vaccinium microcarpon) and lingonberries (Vaccinium vitis-idaea) were characterized for their phenolic compounds and tested for antioxidant, antimicrobial, antiadhesive, and antiinflammatory effects. The main phenolic compounds in both lingonberries and cranberries were proanthocyanidins comprising 63-71% of the total phenolic content, but anthocyanins, hydroxycinnamic acids, hydroxybenzoic acids, and flavonols were also found. Proanthocyanidins are polymeric phenolic compounds consisting mainly of catechin, epicatechin, gallocatechin, and epigallocatechin units. In the present study, proanthocyanidins were divided into three groups: dimers and trimers, oligomers (mDP 4-10), and polymers (mDP > 10). Catechin, epicatechin, A-type dimers and trimers were found to be the terminal units of isolated proanthocyanidin fractions. Inhibitions of lipid oxidation in liposomes were over 70% and in emulsions over 85%, and in most cases the oligomeric or polymeric fraction was the most effective. Polymeric proanthocyanidin extracts of lingonberries and cranberries were strongly antimicrobial against Staphylococcus aureus, whereas they had no effect on other bacterial strains such as Salmonella enterica sv. Typhimurium, Lactobacillus rhamnosus and Escherichia coli. Polymeric fraction of cranberries and oligomeric fractions of both lingonberries and cranberries showed an inhibitory effect on hemagglutination of E. coli, which expresses the M hemagglutin. Cranberry phenolic extract inhibited LPS-induced NO production in a dose-dependent manner, but it had no major effect on iNOS of COX-2 expression. At a concentration of 100 μg/mL cranberry phenolic extract inhibited LPS-induced IL-6, IL-1β and TNF-α production. Lingonberry phenolics had no significant effect on IL-1β production but inhibited IL-6 and TNF-α production at a concentration of 100 μg/mL similarly to cranberry phenolic extract. In conclusion the phenolics, notably proanthocyanidins (oligomers and polymers), in both lingonberries and cranberries exert multiple bioactivities that may be exploited in food development.     

Vapor-phase activities of cinnamon, thyme, and oregano essential oils and key constituents against foodborne microorganisms

The aim of the study presented here was to gain knowledge about the vapor-phase antimicrobial activity of selected essential oils and their major putatively active constituents against a range of foodborne bacterial and fungal strains. In a first step, the vapor-phase antimicrobial activities of three commercially available essential oils (EOs)-cinnamon (Cinnamomum zeylanicum), thyme (Thymus vulgaris), and oregano (Origanum vulgare)-were evaluated against a wide range of microorganisms, including Gram-negative bacteria (Escherichia coli, Yersinia enterocolitica, Pseudomonas aeruginosa, and Salmonella choleraesuis), Gram-positive bacteria (Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, and Enterococcus faecalis), molds (Penicillium islandicum and Aspergillus flavus), and a yeast (Candida albicans). The minimum inhibitory concentrations (MICs) were generally lower for oregano EO than for the thyme and cinnamon EOs, especially against the relatively resistant Gram-negative. The persistence of the EOs' antimicrobial activities over time was assessed, and changes in the composition of the atmosphere they generated over time were determined using single-drop microextraction (SDME) in combination with gas chromatography-mass spectrometry (GC-MS) and subsequent analysis of the data by principal component analysis (PCA). More relevant chemicals were selected. In addition, the vapor-phase activities of putatively key constituents of the oils were screened against representative Gram-positive (L. monocytogenes) and Gram-negative (S. choleraesuis) bacteria, a mold (A. flavus), and a yeast (C. albicans). Of the tested compounds, cinnamaldehyde, thymol, and carvacrol showed the strongest antimicrobial effectiveness, so their MICs, defined as the minimum vapor concentrations that completely inhibited detectable growth of the microorganisms, were calculated. To check for possible interactions between components present in the EOs, cinnamon EO was fortified with cinnamaldehyde and thyme EO with thymol, and then the antimicrobial activities of the fortified oils were compared to those of the respective unfortified EOs using fractional inhibitory concentration (FIC) indices and by plotting inhibition curves as functions of the vapor-phase concentrations. Synergistic effects were detected for cinnamaldehyde on A. flavus and for thymol on L. monocytogenes, S. choleraesuis, and A. flavus. In all other cases the fortification had additive effects, except for cinnamaldehyde's activity against S. choleraesuis, for which the effect was antagonistic. Finally, various microorganisms were found to cause slight changes over time to the atmospheres generated by all of the EOs (fortified and unfortified) except the fortified cinnamon EO.     

Green-leaf-derived C6-aroma compounds with potent antibacterial action that act on both Gram-negative and Gram-positive bacteria

All eight C6-aliphatic alcohol and aldehyde compounds in naturally occurring green leaves showed bacteriostatic effects against Staphylococcus aureus IFO 12732, methicillin-resistant S. aureus, Escherichia coli IFO 3301, E. coli O157:H7, and Salmonella enteritidis, with bacteriostatic activities of less than 12.5 microg mL(-1). In this study, the susceptibility of Gram-positive bacteria tested was observed to be greater than that of Gram-negative bacteria. The bactericidal action of the aldehyde compounds was found to be much stronger than that of the alcohol compounds under both liquid and gaseous conditions. The most effective compound was (3E)-hexenal at concentrations of 0.1 and 1 microg mL(-1), which killed 2.1 x 10(5) cfu mL(-1) of S. aureus IFO 12732 and 1.4 x 10(5) cfu mL(-1) of E. coli IFO 3301, respectively, by direct contact with the compound. Lethality of (3E)-hexenal against S. aureus IFO 12732 and E. coli IFO 3301 was also observed as a result of gaseous contact at concentrations of 3 and 30 microg mL(-1), respectively. The bactericidal effects of 30 microg mL(-1) (3E)-hexenal were thoroughly maintained throughout periods of 2 days and 1 day against S. aureus IFO 12732 and E. coli IFO 3301, respectively, by a complex formation with alpha-cyclodextrin.     

Inhibition of pathogenic bacterial adhesion by acidic polysaccharide from green tea (Camellia sinensis)

An acidic polysaccharide CS-F2 from Camellia sinensis was examined to characterize its anti-adhesive effects against pathogenic bacteria, most notably Helicobacter pylori, Propionibacterium acnes, and Staphylococcus aureus. CS-F2 showed marked inhibitory activity against the pathogen-mediated hemagglutination with a minimum inhibitory concentration (MIC) between 0.01 and 0.1 mg/mL, which is lower than the previously reported MIC values for Panax ginseng and Artemisia capillaris. The inhibitory effects of CS-F2 on the adhesion of H. pylori to AGS adenocarcinoma gastric epithelial cells, or P. acnes and S. aureus to NIH 3T3 fibroblast cells, were further assessed resulting in MIC values between 0.063 and 0.13 mg/mL. Importantly, CS-F2 showed no inhibitory effects against Lactobacillus acidophilus, Escherichia coli, or Staphylococcus epidermidis. Our results suggest that CS-F2, which is a pectin-type polysaccharide with a molecular weight of approximately 8.0 x 10(4) Da, may exert a selective anti-adhesive effect against certain pathogenic bacteria, while exerting no effects against beneficial and commensal bacteria.