雪莲菌中乳酸菌的益生特性

对分离自雪莲菌的乳酸菌进行益生特性评价。耐酸性和模拟胃肠液耐受性初筛结果表明,20株乳酸菌中有11株乳酸菌在pH 3.0和pH 2.5的培养基中具有耐受性,经过模拟胃肠液培养后有8株乳酸菌的活菌数大于10⁶ CFU/mL;疏水性、自凝聚性、抗氧化能力和抑菌实验结果表明,副干酪乳杆菌(Lactobacillus paracasei)KF2-5和鼠李糖乳杆菌(Lactobacillus rhamnosus)RG疏水性较高、抑菌性最强,菌株RG的自凝聚能力和抗氧化能力较强;耐药性实验结果显示,菌株KF2-5和RG对红霉素、卡那霉素、氯霉素和四环素敏感,对头孢噻肟和万古霉素具有耐药性;溶血性实验表明,2株菌均无溶血。本研究筛选得到2株具有益生特性的乳酸菌KF2-5和RG,在益生产品开发中具有潜在的应用前景。     

具有抑制肠道致病菌和黏附Caco-2细胞作用的益生性乳酸菌的筛选及鉴定

为了筛选具有肠道益生特性的乳酸菌,进一步开发益生菌资源,本文研究采用牛津杯、人工模拟胃肠液及体外黏附Caco-2细胞等方法,以鼠李糖乳杆菌GG(Lactobacillus rhamnosus GG,LGG)为对照菌株,对实验室保藏15株乳酸菌的益生特性进行筛选与评估。实验结果表明:15株乳酸菌对两株沙门氏菌都具有一定抑制效果,抑菌圈直径为10.95~22.06 mm;乳酸菌C174、D24、D599、C37、D512具有较好的耐酸耐胆盐能力,在人工胃液3 h内存活率达到60%以上,人工肠液4 h内存活率达到80%以上;在黏附试验中,C174对Caco-2细胞具有较强黏附能力,黏附数量为740 CFU/100细胞,略高于对照菌株鼠李糖乳杆菌(543 CFU/100细胞);通过对具有高黏附性的菌株C174进行生理生化和16S rRNA分子测序鉴定,结果表明菌株C174为植物乳杆菌(Lactobacillus plantarum),命名为Lactobacillus plantarum ZJ-174。Lactobacillus plantarum ZJ-174的抑菌能力强、能够耐酸耐胆盐,并具有很强的黏附能力,是一株潜在的益生菌,具有治疗或预防人和动物肠道疾病等应用价值。     

副干酪乳杆菌HCS17-040的筛选鉴定及其益生特性

目的：获得具有降甘油三酯功能的乳酸菌菌株。方法：从母乳及顺产的健康婴儿粪便中筛选分离乳酸菌菌株,采用单试剂法乳酸菌（GPO-PAP法）测定其甘油三酯去除能力。从中选择甘油三酯去除能力强的菌株进行形态学鉴定、生理生化及16S rDNA鉴定,并测定其耐受酸、胆盐和胃肠液的能力。结果：筛选分离出一株副干酪乳杆菌（Lactobacillus paracasei）,命名为HCS17-040（CGMCC No 19747）,其甘油三酯下降率达（42.80±1.79）%;该株菌在pH 3.0和pH 2.0的环境中培养17 h后存活率分别为89.39%和87.18%;在3 g/L和5 g/L的胆盐浓度环境中培养17 h后存活率分别为94.75%,92.97%;在人工胃液中作用3 h,存活率为93.93%;在人工肠液中作用4 h,存活率高达99.06%。结论：副干酪乳杆菌HCS17-040对甘油三酯具有一定的去除能力,且具有良好的耐酸、胆盐及人工胃肠液的能力。     

副干酪乳杆菌的分离鉴定及肠道耐受性研究

本研究对西藏传统乳制品中分离的35株乳酸菌进行16S rDNA序列分析,其中15株乳酸菌鉴定为干酪乳杆菌或副干酪乳杆菌群,通过recA基因序列分析后,进一步将其中5株归为副干酪乳杆菌。针对这5株副干酪乳杆菌进行耐受性评价,试验结果表明5株副干酪乳杆菌均具有较高的酸耐受性,其中副干酪乳杆菌KY1、KY2的耐受性最为突出。其在pH值为3.0的条件下处理3 h存活率可分别达到31.7%和30.9%,在高胆盐条件下处理4 h后存活率分别可达69.1%和64.9%,在人工胃液中3 h存活率可达15.1%和13.2%,人工肠液8 h存活率分别可达48.9%和48.3%,意味着这两株乳酸菌具有一定潜在的应用前景。     

具有抗氧化和抑菌能力的益生性乳酸菌筛选及鉴定

为筛选出具有抗氧化和抑菌能力的益生性乳酸菌菌株,对本实验室保存的18株乳酸菌进行耐酸耐胆盐、疏水性、自由基清除能力和抑菌能力分析,利用16S rDNA和管家基因pheS和rpoA序列同源性分析对筛选菌株进行鉴定。结果表明,菌株A1、A7、A13、A14、A15在pH 3.0时的存活率均大于70%,在牛胆盐质量分数为03%时的存活率均大于40%。菌株A15的产酸能力最强,24 h时的pH值为3.68。菌株A1、A7、A14、A15均具有高疏水性。菌株A15完整细胞悬液的羟自由基清除能力(39%)和DPPH自由基清除能力(51%)最强,菌株A14次之。此外,菌株A15对金黄色葡萄球菌和大肠杆菌的生长均有抑制作用。16S rDNA和管家基因pheS和rpoA序列同源性分析结果表明:A1为乳肠球菌、A7为副干酪乳杆菌、A14为副植物乳杆菌、A15为植物乳杆菌植物亚种,为开发新型营养健康乳酸菌发酵食品奠定基础。     

阿勒泰传统酸驼乳中乳酸菌发酵乳益生活性评价

为了探究乳酸菌对驼乳和牛乳益生活性的影响,用6株从新疆阿勒泰地区传统酸驼乳中筛选出的乳酸菌发酵驼乳和牛乳。通过模拟胃肠道环境耐受性、疏水性、抑菌能力、抗生素耐药性和溶血活性测定评价菌株的益生菌特性;通过抗氧化能力和α-葡萄糖苷酶抑制活性的评估比较其发酵驼乳和牛乳的益生活性。结果表明,6株乳酸菌具有一定的胃肠道定植能力和抑菌活性,对抗生素具有不同程度敏感性且不溶血。乳酸菌对驼乳和牛乳益生活性的影响与发酵时间有关,发酵36～48 h时具有较好降糖活性：副干酪乳杆菌(Lactobacillus paracasei)B1菌株发酵驼乳至36 h的ABTS⁺自由清除基能力最好(IC₅₀=14.99±0.09 mg/m L),粪肠球菌(Enterococcus faecium)A5和副干酪乳杆菌(Lactobacillus paracasei)B1发酵驼乳的DPPH自由基清除活性和α-葡萄糖苷酶的抑制活性最好,IC₅₀分别为23～38 mg/mL和IC₅₀在8～16 mg/mL。粪肠球菌A5和副干酪乳杆菌B1可作...     

不同剂量类干酪乳酪杆菌PC-01对葡聚糖硫酸钠(DSS)诱导小鼠结肠炎恢复的促进作用

类干酪乳酪杆菌(Lacticaseibacillus paracasei)PC-01是1株分离自西藏拉萨地区自然发酵酸牦牛乳中并具有潜在益生特性的菌株。通过葡聚糖硫酸钠诱导小鼠结肠炎模型，测定试验期间小鼠存活率、体重、疾病活动指数评分、结肠长度、组织切片、血清中髓过氧化物酶及细胞因子浓度、粪便中乳酸及短链脂肪酸含量，评价了不同剂量类干酪乳酪杆菌PC-01对结肠炎恢复的促进作用。结果表明，高剂量的菌株PC-01(1×10⁹ CFU/d)提高了小鼠的存活率，加快了小鼠体重的回升，明显改善了小鼠粪便形态及便血情况，促进小鼠结肠组织病变的恢复，减少了炎症范围，同时降低了血清中髓过氧化物酶及促炎因子IL-1β、IL-6的浓度，并显著提高了小鼠粪便中乳酸及短链脂肪酸的含量。当灌胃高剂量的菌株PC-01时，对小鼠结肠炎恢复的促进作用最为显著。     

副干酪乳杆菌HD1.7微胶囊制备及质量评价

为提高益生菌副干酪乳杆菌HD1.7对环境的抗性,采用实用性强的喷雾干燥法,将菌株包埋在壁材中制成长货架期、高保护性的微胶囊制剂。通过正交试验优化了进风速度、脱脂乳粉含量、进料速度、低聚果糖含量对微胶囊细菌存活率的影响,探讨了副干酪乳杆菌HD1.7微胶囊在模拟胃肠道以及不同温度储存条件下的菌体存活率。结果表明:进风温度115℃、脱脂乳粉含量4%、进料速度6.5 mL/min、低聚果糖含量0.8%时可显著提高微胶囊化副干酪乳杆菌HD1.7的存活率,达到48.37%。副干酪乳杆菌HD1.7微胶囊在模拟人工胃液和人工肠液处理2 h分别仍有40.9%和86.77%的存活率;模拟胃液1 h转至肠液2 h后微胶囊基本崩解完全;常温封闭储存45 d时副干酪乳杆菌HD1.7微胶囊仍有94.87%的存活率,说明HD1.7微胶囊常温封闭储存时的稳定性较高。     

脱脂牛乳体系中美拉德反应产物对乳酸菌的增殖作用

为探究脱脂牛乳体系(skim milk system, SMS)中美拉德反应产物(Maillard reaction products, MRPs)对乳酸菌体外增殖的影响。以脱脂牛乳为原料,通过单因素和响应面试验优化SMS-MRPs的制备工艺条件,研究不同浓度的SMS-MRPs对副干酪乳杆菌L9、鼠李糖乳杆菌G5、罗伊氏乳杆菌G8和嗜热链球菌Q2这4株乳酸菌生长曲线、活菌数、菌体干重和产酸能力的影响。结果表明,当葡萄糖质量浓度60.0 g/L、反应时间120 min、反应温度95℃时,SMS-MRPs积累最多。SMS-MRPs质量浓度为15.0 g/L时,4株菌的OD₆₅₀峰值较对照组均显著提高(P<0.05),副干酪乳杆菌L9的活菌数为1.076×10⁹ CFU/mL;鼠李糖乳杆菌G5的活菌数为1.240×10⁹ CFU/mL;罗伊氏乳杆菌G8的活菌数为1.313×10⁹ CFU/mL;嗜热链球菌Q2的活菌数为1.386×10⁹ CFU/mL。此外,SMS-MRPs处理...     

副干酪乳杆菌NCU622耐酸耐胆盐及其黏附性能

通过体外实验研究副干酪乳杆菌NCU622的耐酸、耐胆盐性能;采用体外细胞模型（人体结肠腺癌细胞系Caco-2细胞）测定副干酪乳杆菌NCU622的黏附性能,考察了菌体浓度、作用时间及生长阶段对其黏附性能的影响,并对该菌株进行细胞毒性检测。结果表明：副干酪乳杆菌NCU622在pH 2.5的MRS液体培养基中作用3 h,存活率为98.21%;在胆盐质量浓度为0.3、0.5 g/100 mL的MRS液体培养基中作用4 h,存活率分别为95.14%和85.07%。副干酪乳杆菌NCU622对Caco-2细胞的黏附能力较强,为（21.19±0.94）CFU/Caco-2细胞,且菌体浓度、作用时间及生长阶段对其黏附性能均有影响。副干酪乳杆菌NCU622与Caco-2单层细胞共培养24 h后,对其无裂解作用。这表明副干酪乳杆菌NCU622具有良好的耐酸耐胆盐能力及较强的黏附性能,且对Caco-2细胞无裂解作用,符合微生态制剂和乳酸菌发酵功能食品的菌种要求。     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Assessment of the microbiological safety of salad vegetables and sauces from kebab take-away restaurants in the United Kingdom

The purpose of this study was to establish the microbiological safety of salad vegetables and sauces served in kebab take-away restaurants. Comparison with published microbiological guidelines revealed that 4.7% of 1213 salad vegetable samples were of unsatisfactory microbiological quality due to Escherichia coli and/or Staphylococcus aureus levels at ≥10² cfu g⁻¹. Another 0.3% of salad samples were of unacceptable quality due to S. aureus at ≥10⁴ cfu g⁻¹ (2 samples) or the presence of Salmonella Kentucky (1 sample). Cucumber was the most contaminated salad vegetable with regards to unsatisfactory levels of E. coli (6.0%) or S. aureus (4.5%). Five percent of 1208 sauce samples were of unsatisfactory microbiological quality due to E. coli, S. aureus at ≥10² cfu g⁻¹ and/or Bacillus cereus and other Bacillus spp. at ≥10⁴ cfu g⁻¹. A further 0.6% of sauce samples were of unacceptable quality due to Bacillus spp. (Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis) at ≥10⁵ cfu g⁻¹ or the presence of Salmonella Agbeni (1 sample). More samples of chilli sauce (8.7%) were of unsatisfactory or unacceptable microbiological quality than any other sauce types. The results emphasize the need for good hygiene practices in kebab take-away restaurants handling these types of ready-to-eat products.     

Investigations of the natural microflora of poppy seeds (<Emphasis Type="Italic">Papaver somniferum</Emphasis>) and hazelnut kernels (<Emphasis Type="Italic">Corylus avellana</Emphasis>) including microbiological decomposition

Fatty seeds of Papaver somniferum and Corylus avellana undergo a rapid microbial degradation after being ground. Those bacteria and fungi which are mainly responsible for the microbial decay were identified, and the most important growth and death processes were documented using crucial indicator-organisms. Additionally, an aflatoxin-screening was carried out in order to assess the possible risk-potential of food intoxication. The acid value (indicator for free fatty acids) of poppy seeds and hazelnut kernels was determined during their fermentation in order to document the decomposition of triglycerides.In this study it could be proved that initially a natural decay of oil seeds is caused by bacteria, yeasts and mould fungi. After the bacteria died in the course of time, yeasts and mould fungi dominated the germ spectrum. Bacteria taking part in the degradation were identified as varieties of Staphylococcus xylosus, Enterobacteriaceae and coliforms. Yeasts were identified as Pichia burtonii, and the mould fungi are associated with the genus Alternaria.On account of the absence of the genus Aspergillus in the spectrum of mould fungi, no aflatoxin was produced.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Control of meatborne Listeria monocytogenes and Brochothrix thermosphacta by a bacteriocinogenic Brochothrix campestris ATCC 43754

The effect of a bacteriocinogenic Brochothrix campestris ATCC 43754 upon the growth of Brochothrix thermosphacta and a 4 strain mixture of Listeria monocytogenes was determined in All Purpose Tween (APT) broth and on pork adipose tissue discs at 4 degrees C. Inocula were prepared to give initial numbers of B. campestris of 6-7 log cfu/ml or cm(2) and 3-4 log cfu/ml or cm(2) of B. thermosphacta and L. monocytogenes. Adipose tissue discs were evaluated by a sensory panel to determine the intensity and acceptability of any off-odours produced during the growth of B. campestris. During co-culture in APT broth with B. campestris the growth of B. thermosphacta or L. monocytogenes was 4 log cycles less than growth in its absence. B. campestris showed limited growth on inoculated pork adipose tissue, increasing from initial numbers of about 6 log cfu/cm(2) to a maximum of 7 log cfu/cm(2) within 7d. B. campestris at numbers of 7 log cfu/cm(2) produced slight off-odours but these were not perceived by the panel as unacceptable. When co-inoculated on adipose tissue discs with B. campestris the numbers of B. thermosphacta or L. monocytogenes was limited to about 2-3 log units less than the numbers attained in its absence. B. campestris ATCC 43754 may be useful for meat preservation because it can inhibit B. thermosphacta and L. monocytogenes in situ while producing little change in the sensory properties of the product.