副干酪乳杆菌对甘薯浆液中淀粉絮凝机理研究

为探讨酸浆法分离甘薯淀粉传统工艺中的淀粉沉降分离机理,进一步制备高效生物絮凝剂。本实验采用Zeta 电位测定、粒度分析及离子键检测研究副干酪乳杆菌对甘薯淀粉絮凝沉淀的作用。结果表明：絮凝过程基于“架桥”机理,淀粉颗粒与菌体间靠离子键结合,絮凝作用使悬浊液中淀粉平均粒径减小,密度增大,导致淀粉颗粒凝聚沉降;通过热处理和酶处理实验分析菌体起絮凝作用的活性成分组成,表明副干酪乳杆菌活性成分为蛋白类物质。     

The effect of treating alfalfa with Lactobacillus buchneri 40788 on silage fermentation,aerobic stability,and nutritive value for lactating dairy cows

Lactobacillus buchneri 40788 and enzymes (beta-glucanase, alpha-amylase, xylanase, and galactomannase) were applied to chopped alfalfa (39% DM) to study their effects on the fermentation and nutritive value of the silage. Alfalfa was treated with nothing, or L. buchneri 40788, for a final application rate of 1 x 10(5), 5 x 10(5), or 1 x 10(6) cfu/g of fresh forage and ensiled in laboratory silos for 2, 4, 8, and 56 d. Treatment with L. buchneri 40788 had few effects on the end products of fermentation through 8 d of ensiling. However, after 56 d of ensiling, treated silages had a higher pH (4.55 vs. 4.38) and higher concentrations of acetic acid (6.40 vs. 4.24%), propionic acid (0.18 vs. 0.06%), and ammonia-N (0.35 vs. 0.29%) when compared to untreated silage. Lactic acid was also numerically lower in treated (3.51%) than untreated (4.12%). Silages treated with the moderate and highest dose of L. buchneri 40788 also resulted in greater recoveries of DM than did untreated silage. Alfalfa (43% DM) was also untreated or treated with a commercial application of L. buchneri 40788 (4 x 10(5) cfu/g, a commercial dose) in farm-scale bag silo. Holstein cows were fed a diet comprised of 32% untreated or treated alfalfa silage, 11% corn silage, 5% chopped alfalfa hay, and 52% of concentrate (DMB) for a 6-wk treatment period. Dry matter intake and milk composition were unaffected by treatment, but cows fed silage treated with L. buchneri 40788 produced 0.8 kg more milk than did cows fed untreated silage. Treated silage had a higher concentration of acetic acid (5.67 vs. 3.35%) but lower lactic acid (3.50 vs. 4.39%) than untreated silage. When exposed to air, the total mixed ration containing treated alfalfa silage remained stable for 100 h, whereas the ration containing untreated silage spoiled after 68 h. Treating alfalfa silage with L. buchneri 40788 increased the concentration of acetic acid, and when the silage was combined into a total mixed ration and fed to lactating cows, it improved the aerobic stability of the ration and increased milk production.     

Binding of Bile Salts by Soluble Fibers and Its Effect on Deconjugation of Glycocholate by Lactobacillus acidophilus and Lactobacillus casei.

ABSTRACT: Binding of sodium cholate, sodium taurocholate, and sodium glycocholate by guar gum, soluble oat fiber, xanthan gum, and inulin was studied. All soluble fibers were able to bind sodium cholate, sodium taurocholate, and sodium glycocholate from a mixture of the three, but when tested individually, the fibers bound little or no sodium cholate. In general, the fibers bound higher concentrations of conjugated bile salts than they did free bile salts. Soluble oat fiber, which bound as much or more sodium cholate and sodium glycocholate as did the other 3 fibers, was tested for its effect on deconjugation of glycocholate by Lactobacillus acidophilus and Lactobacillus casei. The presence of the fiber significantly increased (P < 0.05) deconjugation by all cultures.     

Reduction of Escherichia Coli O157:H7 and Lactobacillus Plantarum Numbers on Fresh Beef by Polylactic Acid and Vacuum Packaging

ABSTRACT: The efficacy of 2% molecular weight 240, 2% molecular weight 360 polylactic acid (PLA), and an equal mix of both at reducing numbers of Escherichia coli O157:H7 and Lactobacillus plantarum on raw beef was determined. Fresh beef cubes inoculated with either organism were dipped in PLA solutions or wrapped in PLA-sprayed films. Samples were vacuum packaged and stored at 4°C for 42 d. Treated samples maintained a significantly lower pH than controls. Growth of E. coli O157:H7 was totally inhibited by both PLA treatments by up to 7.29 log₁₀ CFU/cm² when the spray method was used. However, PLA treatments against L. plantarum were not very effective.     

一株嗜酸乳杆菌突变株转化亚油酸为共轭亚油酸条件的研究

以嗜酸乳杆菌为出发菌株，用紫外诱变方法，得到一株共轭亚油酸转化量较高的突变株，其转化亚油酸为共轭亚油酸的最佳条件为：反应温度35℃，pH值4．0，保温时间48h，亚油酸与培养液的比例为1000mg：100ml，在此条件下共轭亚油酸的产率达38．1％。在1mmol／L浓度下，Na^ 、Fe^2 、Mg^2 有助于提高共轭亚油酸的产量，而Hg^2 、Co^2 、Cu^2 、Mn^2 、Fe^3 不利于共轭亚油酸的合成。用超声波处理细胞后，共轭亚油酸的产率显著提高。     

益力多对小鼠的急性毒性及遗传毒性的影响

实验用SPF级NIH种健康小白鼠,对广州益力多乳品有限公司生产的益力多牌活性乳酸菌乳饮品在急性毒性及遗传毒性方面进行了研究.结果表明,用5倍于原样品的浓缩液,在相当于原液推荐量的150倍的剂量即100.0g/kg.BW灌胃时,未观察到动物有任何不良反应.在5.00-40.00g/kg. BW (5倍浓缩液) 的剂量,微核试验结果为阴性,在10.00-40.00g/kg.BW (5倍浓缩液) 的剂量,精子畸变试验结果为阴性.提示益力多对小鼠无急性毒性作用,并在体细胞水平和生殖细胞水平均无诱变作用.     

Study of the Lactobacillus sakei protective effect towards spoilage bacteria in vacuum packed cooked ham analyzed by PCR-DGGE

The effectiveness of Lactobacillus sakei B-2 inoculated as a protective culture on the inhibition of spoilage bacteria on sliced vacuum packed cooked ham was investigated by using culture-dependent and -independent approaches. Total microbial DNA was directly extracted from both control and treatment samples, and subjected to a nested PCR protocol, PCR–DGGE analysis was used to identify and monitor the dynamic changes in the microbial population, followed by partial 16S rDNA sequencing. The DGGE profile demonstrated that the protective culture effectively suppressed growth of predominant spoilage bacteria L. sakei, Lactobacillus curvatus and Leuconostoc mesenteroides in cooked ham during storage at 4 °C, however, growth of uncultured Leuconostoc was not inhibited. The shelf-life of this product inoculated with L. sakei B-2, at levels of 5.91 ± 0.04 log₁₀ CFU g⁻¹ was 35 days, compared to 15 days of control samples, when the ham was stored at 4 °C.     

益生菌豆酸乳发酵条件的优化

豆酸乳是将大豆磨浆后与牛乳混合经乳酸菌发酵而赋予特殊风味的产品,但尚未有仅用嗜酸乳杆菌和两歧双歧杆菌2株菌来发酵益生菌豆酸乳的报道。对碳源、生长促进因子、稳定剂和温度等发酵条件进行优化,实验结果表明:在豆水比为1:8、牛乳含量为30%的豆浆牛乳混合物中添加4.0%的蔗糖、0.3%的葡萄糖、0.6%的低聚果糖、0.8%的BY-H-260,在无菌条件下添加0.005%的嗜酸乳杆菌菌粉和0.015%的两歧双歧杆菌菌粉,在42℃条件下发酵5～5.5 h,酸度可达70～75°T(pH为4.0左右),活菌数可达108cfu/mL级,组织状态良好。     

Effects of inulin and oligofructose on the rheological characteristics and probiotic culture survival in low-fat probiotic ice cream

ABSTRACT:  The effects of supplementation of oligofructose or inulin on the rheological characteristics and survival of Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 in low-fat ice cream stored at –18 °C for 90 d were studied. Addition of oligofructose or inulin to ice cream mix significantly increased apparent viscosity and overrun and developed the melting properties in ice cream during storage ( P < 0.05). However, the highest increase in firmness, the lowest change in melting properties, and the longest 1st dripping time were obtained in probiotic ice cream containing inulin ( P < 0.05). Some textural properties have also improved especially by the end of storage. Freezing process caused a significant decrease in the viability of Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 ( P < 0.05). Oligofructose significantly improved the viability of L. acidophilus La-5 and B. animalis Bb-12 in ice cream mix ( P < 0.05). Although the viable numbers for both bacteria decreased throughout the storage, the minimum level of 10⁶ CFU/g was maintained for B. animalis Bb-12 in only ice cream with oligofructose during storage.     

Sake and Beer Spoilage Lactic Acid Bacteria — A Review

Japanese rice wine, sake, is a traditional alcoholic beverage in Japan. Similar to the case with beer, sake is known to be microbiologically stable and most microorganisms fail to grow in sake. This is principally due to its high ethanol concentration that reaches approximately 20% (v/v) in undiluted sake products and 15% (v/v) in finished products. Despite the high level of ethanol content, spoilage incidents occasionally occur in sake, due to the presence of highly ethanol‐tolerant lactobacilli, known as hiochi‐bacteria. Hiochi‐bacteria are generally composed of two groups of lactobacilli, hiochi‐lactobacilli and true hiochi‐bacilli. The former group of lactobacilli is less ethanol‐and heat‐tolerant, and therefore rarely poses a problem to sake products. In contrast, the true hiochi‐bacilli exhibit extraordinarily high ethanol tolerance and cause spoilage incidents in sake, conferring acidity and off‐flavors, such as diacetyl, in spoiled products. From a taxonomic standpoint, the true hiochi‐bacilli mainly consist of two Lactobacillus species, L. fructivorans and L. homohiochi. The strains of true hiochi‐bacilli prefer sake‐like environments, and the presence of ethanol and mevalonic acid, in combination with low pH milieu, is essential or stimulatory for the growth of these bacteria. Interestingly, the type strain of L. fructivorans does not show such characteristics, suggesting the true hiochi‐bacilli are profoundly adapted to sake environments. Although beer spoilage lactic acid bacteria do not have close taxonomic relationships with true hiochi‐bacilli, there are striking similarities between these two groups of spoilage lactic acid bacteria. In this review, unique features of sake and beer spoilage lactic acid bacteria are discussed in comparative terms.