Production of three anti-listerial peptides by Lactobacillus curvatus in MRS broth

Three novel bioactive peptides (BAP1–3) from Lactobacillus curvatus CWBI-B28 were isolated and purified using de Man, Rogosa and Sharp (MRS) broth by a three-step protein purification protocol including ammonium sulfate precipitation, hydrophobic C₁₈ Sep-Pak column and reverse-phase high performance liquid chromatography (RP-HPLC). This procedure allowed the recovery of chromatographically pure antimicrobial peptides with the yields of 19%, 10% and 15% of BAP1, BAP2 and BAP3, respectively. The respective apparent molecular masses as determined by tricine-SDS-polyacrilamide gel electrophoresis were 6365, 3426 and 3496. N-terminal amino acid sequencing of the BAPs and comparison of their sequences with those of international data bases indicated that BAP1 is more likely to be a casein-derived bioactive protein produced upon hydrolysis of the tryptone present in MRS broth by Lb. curvatus CWBI-B28 during active growth. However, the identity of BAP2 and BAP3 could not be determined with certainty; yet, they would be novel bacteriocins not fitting in any of the known classes of bacteriocins. Therefore, this strain would have the ability to produce intrinsic antimicrobial substances and also release bioprotective peptides from milk-proteins upon cultivation in milk or casein-containing food products due to its proteolytic activity. Thus, Lb. curratus CWBI-B28 possesses a good potential to be used in food preservation and safety.     

三株人源干酪乳杆菌的益生特性

评价3株人源干酪乳杆菌的益生性能,为其在食品和保健品等行业中的应用提供理论支持。通过体外测定3株干酪乳杆菌的对模拟肠道的耐受性、黏附性、抑菌性及抗生素敏感性来评价其益生性能。3株干酪乳杆菌,特别是NCU011056,对高盐、酸和胆盐均具有高耐受性,NCU011056在100 g/L NaCl、pH 2. 0和3 g/L胆盐环境下存活率分别为95. 7%、87. 2%和80%; 3株干酪乳杆菌对Caco-2细胞系黏附能力各异,其中NCU011056黏附能力较强,黏附指数为60. 08%; 3株干酪乳杆菌对4种常见革兰氏阳性和革兰氏阴性致病菌均具有较强的抑菌能力; 3株干酪乳杆菌对青霉素、阿莫西林、头孢曲松、四环素、氯霉素、红霉素、利福平、环丙沙星均敏感。3株人源干酪乳杆菌,特别是NCU011056,具有良好的益生潜力,可考虑后期应用于食品、保健品等行业中。     

不同酵母与温度发酵的威代尔冰葡萄酒有机酸分析

以3个不同温度下5种酵母发酵的威代尔冰葡萄酒为实验样本,通过反相高效液相色谱对12种主要有机酸进行了定性定量分析。结果表明,在所有冰葡萄酒样品中均检测到了除甲酸和抗坏血酸外的10种有机酸,其中苹果酸含量最高,约占总有机酸的50%左右。酒石酸、柠檬酸、乙酸和琥珀酸的含量也比较高,马来酸含量最低。总有机酸含量随酿造温度升高而增加,而较低的发酵温度有利于对乙酸的控制,ST酵母在不同发酵温度下乙酸含量均较低。采用双因素方差分析的统计学方法,对不同酵母不同温度下发酵的冰葡萄酒中的乙酸含量进行分析发现,无论发酵温度还是酵母种类对冰酒发酵产生的乙酸都有极显著地影响。     

三种硅藻产多不饱和脂肪酸分析

采用f/2培养基,对3种硅藻:牟氏角毛藻(Chaetoceros mualleri)、三角褐指藻(Phaeoda-ctytuum tricornutum)、硅藻舟形藻(Navicala incerta)进行培养及脂肪酸组成研究。牟氏角毛藻和三角褐指藻的生长周期短,生物量较高。3种硅藻的脂肪酸组成相近,主要的脂肪酸是C14:0,C16:0,C16:1(n-7)和C20:5(n-3),多不饱和脂肪酸中C20:5(n-3)(EPA)含量最高,其中三角褐指藻中的EPA含量达到11.7%。3种硅藻的DHAC22:6(n-3)含量都较低。通过调整三角褐指藻和牟氏角毛藻的培养条件,可以提高EPA含量,作为优良的水产饵料。     

1株植物乳杆菌发酵豆粕产有机酸的研究

从发酵豆粕中筛选得到1株生长迅速产酸量大的乳酸菌,经鉴定为植物乳杆菌,命名为JUN-DY-6,利用该菌对豆粕进行固态发酵。通过高效液相色谱法(HPLC)对发酵豆粕中的有机酸组成进行了定性定量分析。结果显示:用JNU-DY-6生产的发酵豆粕中主要有6种有机酸,其中以乳酸、乙酸、丙酸和柠檬酸为主。且发酵豆粕工艺中糖蜜的添加与否对发酵豆粕中丙酸含量影响较大。碱性蛋白酶添加量0.5%,糖蜜添加量为3%的条件下发酵豆粕,产生有机酸含量峰值为14.646 g/L,比仅使用乳酸菌发酵的情况下提高了23.1%。SDS-PAGE凝胶电泳结果显示,发酵豆粕中的大豆蛋白基乎完全降解为小分子多肽。     

Bile salt hydrolase activity of three strains of Lactobacillus acidophilus

Three strains of Lactobacillus acidophilus, two from human intestinal origin (016 and L1) and one from porcine intestinal origin (ATCC 43121), were tested for their bile salt deconjugation activity. The L. acidophilus ATCC 43121 had more deconjugating activity of both sodium glycocholate and sodium taurocholate at pH 6.5 than did either L. acidophilus 016 or L1. The activity of intracellular bile salt hydrolase found in strain ATCC 43121 was 14-fold higher than that in either of the other two strains. The optimum pH for deconjugation of sodium glycocholate was between 4 and 5.5 for all three strains. For deconjugation of sodium taurocholate, the optimum pH was between 3.5 and 4.5 for strains L1 and ATCC 43121 and was between pH 5 and 6 for strain O16. The molecular mass of the enzyme in all three strains of L. acidophilus was estimated to be 126 kDa by Sephadex G-200 gel filtration. All three strains exhibited more bile salt hydrolase activity towards sodium glycocholate than towards sodium taurocholate.     

Growth of Campylobacter in media supplemented with organic acids

The growth of Campylobacter spp. in media supplemented with organic acids was examined. A Bioscreen C Microbiology Reader was used to measure growth of cultures incubated at 37 degrees C for 48 h in a tryptose-yeast extract basal broth medium and in basal broth supplemented with 10, 20, 30, 40, or 50 mM citric, fumaric, lactic, malic, or succinic acid. Growth of three of six isolates was significantly greater (P < or = 0.05) in media supplemented with 20 to 50 mM citric acid than in nonsupplemented media, growth of five of six isolates was significantly greater in media supplemented with 10 to 50 mM succinic acid than in nonsupplemented media, and growth of six of six isolates was significantly greater in media supplemented with 10 to 50 mM fumaric or malic acid or with 20 to 50 mM lactic acid than in nonsupplemented media. Isolates were also cultured in basal media supplemented with a mixture of 10, 20, 30, 40, or 50 mM fumaric, malic, lactic, and succinic acids. Results indicated that the growth of all Campylobacter isolates was significantly greater in media supplemented with mixtures containing each of these organic acids at 10 to 40 mM than in nonsupplemented media. These findings indicate that in vitro growth of Campylobacter spp. may be significantly enhancedin media supplemented with organic acids that support the growth of these bacteria.     

Effect of different Bacillus strains on the profile of organic acids in a liquid culture of Daqu

A reversed‐phase high‐performance liquid chromatography method for the analysis of malic, lactic, acetic, citric, succinic, propionic and butyric acids, during the incubation of Bacillus spp., was developed. All samples taken from cultivation were centrifuged (20 min, 11,500g at 5°C) and filtered through a 0.45 µm membrane filter before injection. A programme pumping phosphate buffer at pH 2.50 and acetonitrile was used to separate the compounds on a C₁₈ column. Various parameters affecting analysis were optimized to take less than 30 min with a good linearity (R > 0.999). Bacillus licheniformis or B. subtilis, isolated from Daqu, was inoculated to ferment a liquid culture of Daqu. Growth of bacteria and organic acid production during the fermentation were investigated. Although there were no significant differences in the production of organic acids between B. licheniformis and B. subtilis during the first 8 h, significant differences in the production rates of organic acids, except for citric acid, were observed between B. licheniformis and B. subtilis from 8 to 48 h, with the final concentration of each organic acid varying. Copyright © 2013 The Institute of Brewing & Distilling     

Bile salt deconjugation and cholesterol removal from media by Lactobacillus strains used as probiotics in chickens

BACKGROUND: Bile salt deconjugation by Lactobacillus strains is often closely linked to bile tolerance and survival of the strains in the gut and lowering of cholesterol in the host. The present study investigated the deconjugation of bile salts and removal of cholesterol by 12 Lactobacillus strains in vitro. The 12 strains were previously isolated from the gastrointestinal tract of chickens. RESULTS: The 12 Lactobacillus strains could deconjugate sodium glycocholate (GCA, 16.87–100%) and sodium taurocholate (TCA, 1.69–57.43%) bile salts to varying degrees, with all strains except L. salivarius I 24 having a higher affinity for GCA. The 12 Lactobacillus strains also showed significant (P < 0.05) differences in their ability to remove cholesterol from the growth medium (26.74–85.41%). Significant (P < 0.05) correlations were observed between cholesterol removal and deconjugation of TCA (r = 0.83) among the L. reuteri strains (C1, C10 and C16) and between cholesterol removal and deconjugation of TCA (r = 0.38) and GCA (r = 0.70) among the L. brevis strains (I 12, I 23, I 25, I 211 and I 218). In contrast, although L. gallinarum I 16 and I 26 and L. panis C 17 showed high deconjugating activity, there was no correlation between cholesterol removal and deconjugation of bile salts in these strains. CONCLUSION: The results showed that the 12 Lactobacillus strains were able to deconjugate bile salts and remove cholesterol in vitro, but not all strains with high deconjugating activity removed cholesterol effectively. Copyright © 2009 Society of Chemical Industry     

Production of antimicrobial metabolites by strains of Lactobacillus or Lactococcus co-cultured with Bacillus cereus in milk

During co-culture of Lactobacillus (five strains) or Lactococcus (two strains) with Bacillus cereus, organic acids and other potentially antimicrobial metabolites are produced. Lactic acid was produced at very different rates by the lactic acid bacteria (LAB) and the final concentrations varied much, however, the crucial point of rapid pH reduction during the initial hours of fermentation coincides with lactic acid production. Moderate amounts of acetic acid were produced during fermentation and the final concentrations were much smaller compared to lactic acid. According to these experiments, production of diacetyl, carbon dioxide and ethanol was considered too small to contribute to inhibition of B. cereus. The inhibitory substance produced by the LAB strains was not sensitive to proteinase K, trypsin or pepsin, so it was not likely that the LAB strains produced bacteriocins antagonistic against B. cereus. The strains that produced lactic acid fastest inhibited B. cereus best. Increased concentrations of lactic and acetic acid and carbon dioxide were also observed after co-culture with B. cereus compared to growth of the LAB strains alone, which indicates that B. cereus stimulates the biosynthetic capacities of the LAB strains.     

不同黄酒中有机酸的测定

采用HPLC法对客家娘酒及绍兴黄酒中10种有机酸草酸、酒石酸、丙酮酸、乳酸、乙酸、富马酸、柠檬酸、琥珀酸、苹果酸、莽草酸进行定性、定量分析。结果表明:不同酒种不同品牌的酒中所含有机酸的种类和数量存在一定的差异。     

短乳杆菌发酵苹果汁工艺优化及有机酸变化

该研究利用短乳杆菌发酵苹果汁,生产能够调节人体肠道功能的乳酸菌苹果汁。通过单因素实验确定最适碳源、氮源以及缓冲因子;并以总酸、还原糖的变化为依据,进行响应面优化,确定最适发酵工艺条件,采用高效液相色谱法测定苹果汁发酵过程中有机酸组成及含量变化。结果表明,优化后发酵苹果汁的最佳培养基条件为:葡萄糖质量浓度50 g/L,蛋白胨质量浓度9 g/L,K₂HPO₄质量浓度4 g/L;菌种接种量为8%,发酵温度为36℃,发酵时间为6 d。在该条件下测得苹果汁的总酸为2. 61 g/100 g、还原糖为5. 027 g/100 g;经短乳杆菌发酵后苹果汁的品质明显优于发酵前。发酵后乳酸、富马酸、乙酸、奎宁酸含量显著增多;苹果酸、琥珀酸含量均持续减少,酒石酸含量无明显变化。     

Utilization of sugars by Lactobacillus acidophilus strains

Utilization of various carbohydrates viz., glucose, fructose, sucrose, lactose and galactose by Lactobacillus acidophilus strains was investigated in Lactobacillus Selection Broth. Maximum viable counts, acid production and sugar utilization by different test strains were in the order: glucose greater than or equal to fructose greater than sucrose greater than or equal to lactose greater than galactose. The generation time of the tested strains was shorter in glucose medium as compared to sucrose or lactose medium.     

Dry sausage fermented by Lactobacillus rhamnosus strains

The ability of three probiotic Lactobacillus rhamnosus strains GG, E-97800 and LC-705 and one commercial Pediococcus pentosaceus starter strain (control) to produce dry sausage was studied. During the fermentation process the numbers of inoculated lactic acid bacteria increased from approx. 7 log10 to 8-9 log10 cfu/g and the pH values decreased from 5.6 to 4.9-5.0. The sensory test indicated that the dry sausages fermented by L. rhamnosus LC-705 were inferior to the control sausages. The presence of inoculated experimental strains as predominant organisms in the dry sausages was recognised on the basis of their genetic fingerprints by ribotyping. The concentrations of biogenic amines remained low during the ripening process. These results indicated that the studied Lactobacillus rhamnosus strains, especially strains GG and E-97800, are suitable for use as probiotic starter cultures in fermenting dry sausage.     

Production of salami from ostrich meat with strains of Lactobacillus sake, Lactobacillus curvatus and Micrococcus sp

The aim of this study was to produce Italian-type salami from ostrich meat using different combinations of Lactobacillus sake, Lactobacillus curvatus and Micrococcus sp., and to compare the sensory characteristics of these products to that of salami produced with glucono-delta-lactone (GdL). Meat inoculated with starter cultures was fermented for four days (20-22 °C, 97-99% RH) and ripened for a further 11 days (16-18 °C, 40-60% RH). Cell counts of lactic acid bacteria and micrococci, and changes in pH were determined daily during fermentation. According to texture and sensory evaluation, the best salami was produced by a starter culture containing L. curvatus DF 38 and Micrococcus sp. MC 50.     

Determination of the relationship between oxalate degradation and exopolysaccharide production by different Lactobacillus probiotic strains

The aim of this study was to evaluate the protective effects of exopolysaccharide (EPS) production on resistance to gastrointestinal digestive conditions and oxalate by probiotic strains of the species Lactobacillus rhamnosus, Lactobacillus fermentum and Lactobacillus brevis. The oxalate‐degrading ability of the strains was determined using an enzymatic assay. The correlation between oxalate degradation rate and EPS production was not significant (P > 0.05); however, the high‐EPS‐producing L. fermentumIP5 and L. brevisYG7 strains showed high oxalate‐degrading activity, whereas the low‐EPS‐producing strain L. fermentumBP5 demonstrated low oxalate‐degrading activity. The present findings suggest that dietary supplementation with the probiotic strain L. fermentumIP5 could be a promising strategy for the prevention of oxalate stone disease.     

Analysis of trans fatty acids in deep frying oils by three different approaches

Simulated frying experiments were performed on three different types of oils with French fries as the fried food. Comparison of frying oil samples was then made with their control counterparts (i.e. oil samples heated without food). Three different methods, gas chromatography (GC), attenuated total reflection (ATR) AOCS method Cd 14d-99 and attenuated total reflection negative second derivative absorbance (−2D ATR), were applied to quantify total trans fats. The total trans fats were found to be higher in the frying oil samples as compared to the control samples, which might be due to the presence of a high amount of trans fats in the pre-fried and frozen French fries. In general, the ATR AOCS method Cd 14d-99 produced lower amounts of trans fatty acids and the −2D ATR absorbance method produced higher amounts when compared with those obtained by gas chromatography.     

Lactobacillus kefiranofaciens发酵生产Kefiran多糖的初步研究

研究了发酵条件(温度、起始pH、接种量等)对乳酸菌Lactobacillus kefiranofaciens发酵产Kefiran多糖的影响,并对菌体的形态及发酵特性进行了研究。研究结果表明,菌体形态在生长期间会发生改变,为短杆状-链杆状-短杆状;胞外多糖是从菌体生长期开始合成的;接种量为10%、起始pH为5.3、培养温度为25℃时有利于多糖的合成;CaCO3、Tween80和NaCl的添加量分别为1.2%、4%和0.25%时,胞外多糖的产量可达1.50g/L。     

罗伊氏乳杆菌酸奶的研制

本文初步研究了罗伊氏乳杆菌的生长特性,并利用其发酵生产酸奶。通过单因素实验探讨了白砂糖的添加量、菌种间的配例以及发酵时间三个因素对酸奶的感官品质的影响,通过正交实验确定了最佳生产工艺。结果表明,罗伊氏乳杆菌的产酸量和活菌数量均在发酵28h达到最高。生产酸奶生产的最佳工艺条件为:接种量为1%,接种比例[c(罗伊氏乳杆菌):c(嗜热链球菌+保加利亚乳杆菌)]为1:1,糖添加量为9%,发酵时间为16h。该酸奶内活菌数量为4.2×108cfu/g。     

乳杆菌脱除伏马毒素的研究

为了探究植物乳杆菌(Lactobacillus plantarum)B7和戊糖乳杆菌(L.pentosus)X8对伏马毒素FB1和FB2脱除作用及影响因素。本文采用高效液相荧光检测的方法研究菌体细胞的伏马毒素脱除率。结果表明植物乳杆菌B7和戊糖乳杆菌X8在37℃吸附1h后对FB1的脱除率分别为52.9%和58.0%,对FB2的脱除率分别达到了85.2%和86.5%。p H、温度、酶影响菌株B7和X8结合伏马毒素FB1和FB2的效果,并且两株菌脱除伏马毒素的作用与其活力无关。两株菌体结合伏马毒素的效率随p H升高而降低。当p H>7时,无法检测到两株乳杆菌具有结合伏马毒素的能力。经100℃沸水浴处理后,菌体细胞脱除伏马毒素的效率上升;经溶菌酶处理后,菌体脱除伏马毒素的效率降低。两株乳杆菌具有以吸附方式脱除伏马毒素FB1和FB2的能力,但吸附FB2的效果高于吸附FB1的效果。