A Lactic Acid Bacteria Consortium Impacted the Content of Casein-Derived Biopeptides in Dried Fresh Cheese

This study aimed to define a consortium of lactic acid bacteria (LAB) that will bring added value to dried fresh cheese through specific probiotic properties and the synthesis of bioactive peptides (biopeptides). The designed LAB consortium consisted of three Lactobacillus strains: S-layer carrying Levilactobacillus brevis D6, exopolysaccharides producing Limosilactobacillus fermentum D12 and plantaricin expressing Lactiplantibacillus plantarum D13, and one Enterococcus strain, Enterococcus faecium ZGZA7-10. Chosen autochthonous LAB strains exhibited efficient adherence to the Caco-2 cell line and impacted faecal microbiota biodiversity. The cheese produced by the LAB consortium showed better physicochemical, textural and sensory properties than the cheese produced by a commercial starter culture. Liquid chromatography coupled with matrix-assisted laser desorption/ionization-time of flight tandem mass spectrometry (LC-MALDI-TOF/TOF) showed the presence of 18 specific biopeptides in dried fresh cheeses. Their identification and relative quantification was confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using multiple reaction monitoring (MRM). The results also showed that their synthesis resulted mainly from β-casein and also α-S1 casein degradation by proteolytic activities of the LAB consortium. The designed LAB consortium enhanced the functional value of the final product through impact on biopeptide concentrations and specific probiotic properties.     

N-月桂酰基甲基丙氨酸钠三元复配体系的协同效应北大核心CSCD

将N‑月桂酰基甲基丙氨酸钠(SLMA)依次与月桂酰胺丙基甜菜碱(LAB)、烷基糖苷(APG1214)分别进行二元及三元复配,通过吊片法、稳态荧光探针法、动态光散射及稳态荧光猝灭法,对SLMA/LAB二元复配体系及SLMA/LAB/APG三元复配体系间的协同增效作用,以及溶液组成对其微极性、平均流体力学半径及胶束聚集数的影响进行了研究,并应用正规溶液理论计算二元及三元复配体系的相互作用参数。结果表明,SLMA/LAB二元复配体系及SLMA/LAB/APG三元复配体系均表现出全面增效的协同作用,其最佳物质的量比分别为n(SLMA)∶n(LAB)=3∶7,n(SLMA/LAB)∶n(APG1214)=3∶7,对应临界胶束浓度(CMC)分别为1.054×10^(−3)和1.595×10^(−4) mol/L,SLMA/LAB二元复配体系趋于形成分布集中的单一形态聚集体,且总体偏小;SLMA/LAB/APG三元复配体系的胶束大小比单一体系分布宽,且其胶束体积明显大于二元复配体系。两种复配体系所形成的胶束聚集数均小于单一体系,形成了更加紧密、稳定、较小的胶束结构。SLMA/LAB二元复配体系及SLMA/LAB/APG三元复配体系中表面活性剂分子间的相互作用力加快了稳定胶束的形成,胶束大小分布较宽,以球状及非球状胶束的形式存在,且复配体系形成了更加紧密的胶束结构。     

酸洗比色法在直链烷基苯生产质量控制中的应用

对于首次应用于大亚湾中微子物理实验的液体闪烁介质——直链烷基苯( LAB)的工业化生产,其最重要的质量控制指标为光衰减长度,这通常需要在实验室里利用专门仪器进行测量分析.经过对比研究,在LAB工业化生产流程的基础上,建立了相应的测试方法——酸洗比色分析方法,即使直链烷基苯和98.4％的发烟硫酸反应,在波长403 nm处...     

Preparative separation of lithospermic acid B from Salvia miltiorrhiza by polyamide resin and preparative high-performance liquid chromatography

Adsorption on polyamide resin was investigated as a means of separating lithospermic acid B (LAB) from a crude extract of the roots of the traditional Chinese medicine Salvia miltiorrhiza Bunge ("Danshen"). Variables affecting adsorption capacity (solution pH, contact time on resin, initial LAB concentration) were studied. Adsorption was strongly dependent upon the initial concentration of LAB and pH. In all conditions, the polyamide resin gave optimal adsorption of LAB at an initial concentration of 2.66 mg/mL and pH <3.0. The adsorption isotherm correlated well with the Langmuir-type adsorption isotherm. Maximal adsorption capacity was calculated to be 380 mg/g at pH 2.0 and 25°C. LAB purity of 85.30% could be obtained by polyamide resin adsorption followed by elution with 70% ethanol solution, and the recovery was 87.1%. After preparative HPLC, the maximum HPLC purity obtained was 99.28% with a recovery of 75.2%. This method provides an efficient and low-cost method for LAB purification for industrial applications.     

Applications of Lactic Acid Bacteria and Their Bacteriocins against Food Spoilage Microorganisms and Foodborne Pathogens

Lactic acid bacteria (LAB) are Gram-positive and catalase-negative microorganisms used to produce fermented foods. They appear morphologically as cocci or rods and they do not form spores. LAB used in food fermentation are from the Lactobacillus and Bifidobacterium genera and are useful in controlling spoilage and pathogenic microbes, due to the bacteriocins and acids that they produce. Consequently, LAB and their bacteriocins have emerged as viable alternatives to chemical food preservatives, curtesy of their qualified presumption of safety (QPS) status. There is growing interest regarding updated literature on the applications of LAB and their products in food safety, inhibition of the proliferation of food spoilage microbes and foodborne pathogens, and the mitigation of viral infections associated with food, as well as in the development of creative food packaging materials. Therefore, this review explores empirical studies, documenting applications and the extent to which LAB isolates and their bacteriocins have been used in the food industry against food spoilage microorganisms and foodborne pathogens including viruses; as well as to highlight the prospects of their numerous novel applications as components of hurdle technology to provide safe and quality food products.     

Lactic acid bacteria used in inoculants for silage as probiotics for ruminants

Many studies have shown the beneficial effects on ruminant performance of feeding them with silages inoculated with lactic acid bacteria (LAB). These benefits might derive from probiotic effects. The purpose of the current study was to determine whether LAB included in inoculants for silage can survive in rumen fluid (RF), as the first step in studying their probiotic effects. Experiments were conducted in the United States and Israel with clarified (CRF) and strained RF (SRF) that were inoculated at 10⁶–10⁸ microorganisms/mL with and without glucose at 5 g/L. RF with no inoculants served as control. Ten commercial inoculants were used. The RF was incubated at 39°C and sampled in duplicates at 6, 12, 24, 48, 72, and 96 h for pH and LAB counts. The results indicate that with glucose the pH of the RF decreased during the incubation period. In the SRF, the pH of the inoculated samples was higher than that of the controls in most cases. This might be a clue to the mechanism by which LAB elicit the enhancement in animal performance. LAB counts revealed that the inoculants survived in the RF during the incubation period. The addition of glucose resulted in higher LAB counts.     

Alkylation of benzene with 1-octene over titania pillared montmorillonite

Linear alkylbenzene sulfonic acid, the largest-volume synthetic surfactant, in addition to its excellent performance, is important due to its biodegradable environmental friendliness, as it has a straight chain and is prepared by the sulphonation of linear alkylbenzenes (LAB). To ensure environmental protection, the commercial benzene alkylation catalysts HF or AlCl₃ are replaced and we have developed a clean LAB production process using a pillared clay catalyst capable of not only replacing the conventional homogeneous catalysts, but also having high selectivity for the best biodegradable 2-phenyl LAB isomer. Pillared clay catalysts having high Br?nsted acidity show efficient conversion in gas phase alkylation of benzene with 1-octene with a good 2-phenyl octane selectivity.     

Characteristics of the Proteolytic Enzymes Produced by Lactic Acid Bacteria

Over the past several decades, we have observed a very rapid development in the biotechnological use of lactic acid bacteria (LAB) in various branches of the food industry. All such areas of activity of these bacteria are very important and promise enormous economic and industrial successes. LAB are a numerous group of microorganisms that have the ability to ferment sugars into lactic acid and to produce proteolytic enzymes. LAB proteolytic enzymes play an important role in supplying cells with the nitrogen compounds necessary for their growth. Their nutritional requirements in this regard are very high. Lactic acid bacteria require many free amino acids to grow. The available amount of such compounds in the natural environment is usually small, hence the main function of these enzymes is the hydrolysis of proteins to components absorbed by bacterial cells. Enzymes are synthesized inside bacterial cells and are mostly secreted outside the cell. This type of proteinase remains linked to the cell wall structure by covalent bonds. Thanks to advances in enzymology, it is possible to obtain and design new enzymes and their preparations that can be widely used in various biotechnological processes. This article characterizes the proteolytic activity, describes LAB nitrogen metabolism and details the characteristics of the peptide transport system. Potential applications of proteolytic enzymes in many industries are also presented, including the food industry.     

Effect of organic acid on lauroamide propyl betaine surface dilatational modulus and foam performance in a porous medium

The purpose of this work was to study the effect of surface tension and surface dilatational modulus on foam performance in high-salinity water in a porous medium. In order to clarify the role of the surface dilatational property in foam flow in a porous medium, three systems were established: a system with low surface dilatational modulus and high surface tension, a system with low surface dilatational modulus and low surface tension, and a system with high surface dilatational modulus and low surface tension. Measurement of dilatational modulus and surface tension showed that lauroamide propyl betaine (LAB) could not reduce surface tension and that surface dilatational modulus was low. The addition of lauric acid (LCOOH) to LAB could not achieve high surface dilatational modulus; however, it could reach lower surface tension. The addition of myristic acid (MCOOH) to LAB could achieve high surface dilatational modulus and lower surface tension. Unlike the other two systems, the results of a dilatational modulus comprised of a mixture of MCOOH and LAB were not a constant, as demonstrated by varied surface area deformation outcomes. With the increase of deformation, surface dilatational modulus decreased. Results of foam flow tests showed that among the two lower surface dilatational modulus systems, LAB foam had higher flow resistance regardless of flow rate. Among the two systems of similar lower surface tension, the mixture of LAB and MCOOH showed higher flow resistance than the mixture of LAB and LCOOH. However, with the increase of flow rate, pressure differences between the two systems became smaller, which corresponded to the decrease of surface dilatational modulus with an increase of deformation.     

二氧化硅担载Preyssler杂多酸上苯和1-癸烯的烷基化反应:利用表面响应方法进行统计设计(英文)

The response surface method (RSM) was applied to study the liquid phase alkylation of benzene with 1-decene catalyzed by means of silica supported Preyssler heteropoly acid. A three step experimental design was developed based on the central composite design (CCD). Catalyst loading, catalyst mass percent, and benzene to 1-decene molar ratio were used to optimize 1-decene conversion and linear alkylbenzene (LAB) yield. The results indicated that the quadratic model was significant for these two responses. The experimental results revealed that all variables had positive effect on 1-decene conversion. While increasing the catalyst loading tends to decrease LAB yield. Benzene to 1-decene molar ratio was found to be the most important factor that influenced LAB yield with a positive effect. Design expert software suggested several optimized solutions, among them the best choice was to use 31% catalyst loading, benzene to 1-decene molar ratio of 13, and catalyst percent of 3.6 wt% for obtaining 100% conversion and 88% LAB production yield.     

Aminoborohydrides. 12. Novel tandem S(N)Ar amination-reduction reactions of 2-halobenzonitriles with lithium N,N-dialkylaminoborohydrides

A novel tandem amination-reduction reaction has been developed in which 2-(N,N-dialkylamino)benzylamines are generated from 2-halobenzonitriles and lithium N,N-dialkylaminoborohydride (LAB) reagents. These reactions are believed to occur through a tandem S(N)Ar amination-reduction mechanism wherein the LAB reagent promotes halide displacement by the N,N-dialkylamino group, and the nitrile is subsequently reduced. This one-pot procedure is complimentary to existing synthetic methods and is an attractive synthetic tool for the nucleophilic aromatic substitution of halobenzenes with less nucleophilic amines. The (N,N-dialkylamino)benzylamine products of this reaction are easily isolated after a simple aqueous workup procedure in very good to excellent yields.     

Rapid identification, by use of the LTQ Orbitrap hybrid FT mass spectrometer, of antifungal compounds produced by lactic acid bacteria

Fungal contamination of food causes health and economic concerns. Several species of lactic acid bacteria (LAB) have antifungal activity which may inhibit food spoilage fungi. LAB have GRAS (generally recognised as safe) status, allowing them to be safely integrated into food systems as natural food preservatives. A method is described herein that enables rapid screening of LAB cultures for 25 known antifungal compounds associated with LAB. This is the first chromatographic method developed which enables the rapid identification of a wide range of antifungal compounds by a single method with a short analysis time (23 min). Chromatographic separation was achieved on a Phenomenex Gemini C18 100A column (150 mm?×?2.0 mm; 5 μm) by use of a mobile-phase gradient prepared from (A) water containing acetic acid (0.1%) and (B) acetonitrile containing acetic acid (0.1%), at a flow rate of 0.3 µL min^?1. The gradient involved a progressive ramp from 10–95% acetonitrile over 13 min. The LC was coupled to a hybrid LTQ Orbitrap XL fourier-transform mass spectrometer (FTMS) operated in negative ionisation mode. High mass accuracy data (<3 ppm) obtained by use of high resolution (30,000 K) enabled unequivocal identification of the target compounds. This method allows comprehensive profiling and comparison of different LAB strains and is also capable of the identification of additional compounds produced by these bacteria.     

In vitro assessment of pediococci- and lactobacilli-induced cholesterol-lowering effect using digitally enhanced high-performance thin-layer chromatography and confocal microscopy

The cholesterol-lowering properties of 12 lactic acid bacteria (LAB) in the absence or presence of 0.3% bile salts were assessed and compared quantitatively and qualitatively in vitro. A new, more sensitive and cost-effective high-performance thin-layer chromatography method combined with digital image evaluation of derivatised chromatographic plates was developed and validated to quantify cholesterol in LAB culture media. The performance of the method was compared with that of the o-phthalaldehyde method. For qualitative assessment, assimilated fluorescently tagged cholesterol was visualised by confocal microscopy. All LAB strains exhibited a cholesterol-lowering effect of various degrees (19–59% in the absence and 14–69% in the presence of bile salts). Lactobacillus plantarum LAB12 and Pentosaceus pentosaceus LAB6 were the two best strains of lactobacilli and pediococci. They lowered cholesterol levels by 59% and 54%, respectively, in the absence and by 69% and 58%, respectively, in the presence of bile salts. Confocal microscopy showed that cholesterol was localised at the outermost cell membranes of LAB12 and LAB6. The present findings warrant in-depth in vivo study.

(A) 3D plots based on scan at 525 nm of (B) derivatized HPTLC plate of separated cholesterol and (C) confocal microscopic image showing the localisation of NBD-cholesterol assimilated by LAB

     

Lactic acid bacteria production from whey

The main purpose of this work was to isolate and characterize lactic acid bacteria (LAB) strains to be used for biomass production using a whey-based medium supplemented with an ammonium salt and with very low levels of yeast extract (0.25 g/L). Five strains of LAB were isolated from naturally soured milk after enrichment in whey-based medium. One bacterial isolate, designated MNM2, exhibited a remarkable capability to utilize whey lactose and give a high biomass yield on lactose. This strain was identified as Lactobacillus casei by its 16S rDNA sequence. A kinetic study of cell growth, lactose consumption, and titratable acidity production of this bacterial strain was performed in a bioreactor. The biomass yield on lactose, the percentage of lactose consumption, and the maximum increase in cell mass obtained in the bioreactor were 0.165 g of biomass/g of lactose, 100%, and 2.0 g/L, respectively, which were 1.44, 1.11, and 2.35 times higher than those found in flask cultures. The results suggest that it is possible to produce LAB biomass from a whey-based medium supplemented with minimal amounts of yeast extract.     

Novel theoretical studies of the dehydrogenation of LiBH2NH3

It is believed that the dehydrogenation of LiNH₂BH₃ (LAB) proceeds through a combination of the decomposition of the LiBH₂NH₃ (LBA) and LAB isomers. The dehydrogenation of LBA, an isomer of LAB, is discussed in this article. It is demonstrated that the loss of H₂ from LBA takes place in a two‐step reaction. Studies of the dehydrogenation process were performed using Møller–Plesset second‐order perturbation theory with a 6‐311++G(3df,2pd) basis set. The intrinsic reaction coordinate was calculated to determine the minimum energy paths. Finally, the rate constants were obtained using the transition‐state theory (TST), TST/Eckart, canonical variational transition‐state theory (CVT), CVT/small‐curvature tunneling correction, and CVT/zero‐curvature tunneling correction methods from 200 to 2500 K. This is the first report on a different dehydrogenation mechanism for an alkali‐metal amidoborane, and the energy barrier of LBA is much lower than that of the traditionally studied LAB. © 2012 Wiley Periodicals, Inc.     

Influence of Fermentation Beetroot Juice Process on the Physico-Chemical Properties of Spray Dried Powder

Picking vegetables is, along with salting and drying, one of the oldest ways to preserve food in the world. This is the process of decomposition of simple sugars into lactic acid with the participation of lactic bacteria. The aim of the study was to obtain powders from fermented red beet juice with the highest possible amount of lactic acid bacteria (LAB) and active ingredients. For the analysis, juices were squeezed from the vegetables and two types of fermentation were used: a spontaneous fermentation and a dedicated one. After inoculation, samples were taken for analysis on a daily basis. Extract, pH, total acidity, pigments, and color were measured. In addition, microbiological tests were also carried out. The juices from the fifth day of fermentation was also spray dried, to obtain fermented beetroot powder. Juices from 3–5th day were characterized by a high content of LAB and betanin, had also a low pH, which proves that the lactic fermentation is working properly. The exception was the juice from spontaneous fermentation. According to the observations, the fermentation process did not run properly, and further analysis is needed. The powders were stable; however, results obtained from the pigment content and the LAB content are not satisfactory and require further analysis.     

Production of Functional Buttermilk and Soymilk Using Pediococcus acidilactici BD16 (alaD+)

Functional foods or drinks prepared using lactic acid bacteria (LAB) have recently gained considerable attention because they can offer additional nutritional and health benefits. The present study aimed to develop functional drinks by the fermentation of buttermilk and soymilk preparations using the Pediococcus acidilactici BD16 (alaD⁺) strain expressing the L-alanine dehydrogenase enzyme. LAB fermentation was carried out for 24 h and its impact on the physicochemical and quality attributes of the fermented drinks was evaluated. Levels of total antioxidants, phenolics, flavonoids, and especially L-alanine enhanced significantly after LAB fermentation. Further, GC-MS-based metabolomic fingerprinting was performed to identify the presence of bioactive metabolites such as 1,2-benzenedicarboxylic acid, 1-dodecene, 2-aminononadecane, 3-octadecene, 4-octen-3-one, acetic acid, azanonane, benzaldehyde, benzoic acid, chloroacetic acid, colchicine, heptadecanenitrile, hexadecanal, quercetin, and triacontane, which could be accountable for the improvement of organoleptic attributes and health benefits of the drinks. Meanwhile, the levels of certain undesirable metabolites such as 1-pentadecene, 2-bromopropionic acid, 8-heptadecene, formic acid, and propionic acid, which impart bitterness, rancidity, and unpleasant odor to the fermented drinks, were reduced considerably after LAB fermentation. This study is probably the first of its kind that highlights the application of P. acidilactici BD16 (alaD⁺) as a starter culture candidate for the production of functional buttermilk and soymilk.     

Aminoborohydrides. 11. Facile reduction of N-alkyl lactams to the corresponding amines using lithium aminoborohydrides

[reaction: see text] Various five- and six-membered N-alkyl lactams were reduced to the corresponding cyclic amines using lithium N,N-dialkylaminoborohydrides (LAB). Most of the reductions were essentially complete after refluxing in THF for 2 h. The cyclic amine products were easily isolated after an aqueous workup in very good to excellent yields. It is possible to selectively reduce most functional groups, such as esters, in the presence of a lactam using LAB reagents.     

High-performance liquid chromatography determination of phenyllactic acid in MRS broth

Phenyllactic acid (PLA) is an organic acid produced by some strains of lactic acid bacteria (LAB) and concentrations higher than 7.5 mg/ml inhibit growth of moulds and yeasts. Since PLA can be used to select LAB, a rapid, simple and cheap method for its determination is desirable. Typical methods for its analysis in broth are time-consuming, analytically complicated, and have poor recoveries. Herein we propose a simple and rapid method that does not require extraction, but only microfiltration of broth before injection in HPLC. The improved chromatographic conditions allow separation and quantification of PLA with a recovery of 98.7%. The method is highly reproducible with an intraday repeatability of the total peak area of 2.00%, while an interday repeatability of 2.69%.