Characterization of macrophage-activating lactic acid bacteria isolated from Mukeunji

Food Science and Biotechnology - Lactic acid bacteria (LAB) were reported to comprise the majority of the bacterial population in mukeunji, a long-fermented kimchi. This current study investigated...     

Characterization and identification of lactic acid bacteria from freshwater fishes

This work reports on the characterization and identification of 249 strains of lactic acid bacteria (237 rods and 12 cocci) isolated from freshwater fish (mainly wild brown trout) and their surrounding environments. Approximately 90% (226 strains), not able to grow on Acetate (Rogosa) agar, exhibited a high degree of phenotypic homogeneity and were assigned to the genus Carnobacterium. Only a reduced number of strains (22) were allocated to the generaLactobacillus, Enterococcus, Lactococcus or Vagococcus. One strain remained unidentified at genus level. Most Carnobacteria were identified as C. piscicola (156), whereas the species C. divergens was represented only by 10 strains. A total of 59 carnobacteria remained unidentified at species level. After a numerical taxonomy classification based on phenotypic features, at a similarity level of 86% (S_SM), and with an average linkage algorithm (UPGMA) of clustering, 13 clusters were formed, seven of which contained three or more strains (regarded as significant clusters). Clusters I and II were labelled as Enterococcus durans and Lactobacillus spp, respectively. Clusters III to VI were assigned to C. piscicola, whereas cluster VII was adscribed to the species C. divergens. An accurate discrimination among Carnobacteria and Lactobacillus was achieved through the use of numerical taxonomy, although the separation betweenCarnobacterium species was not so clearly defined. Phenotypically, the distinction between both species relied only on a reduced number of tests (growth at 40°C and mannitol fermentation). The ability of Carnobacteria to degrade proteinaceous and lipidic compounds was scarce.     

两株降油菌株的分离及其降油特性

从华庆石油污染的仁壤rf-筛选出2株能够对原油进行高效降解的微生物菌株A1和A2。通过菌种降解特性的甲．因素实验可得菌种生长和降解的优化条件为：温度28℃、pH=8．0、盐度2g／L条件下,A1和A2菌株的石油降解率均达到95％以上。     

Characterization of lactic acid bacteria isolated from vacuum-packed cooked ring sausages

The bacterial populations of the surface layer and the centre of 15 spoiled vacuum-packed cooked ring sausages were characterized. About 95% of the total bacterial population in the surface layer and 55% at the centre were lactic acid bacteria. Another large bacterial group at the centre consisted of Bacillus spp. The lactic acid bacteria on the surface and at the centre were quite similar. Atypical streptobacteria, i.e. homofermentative psychrotrophic lactobacilli, were a major group of lactic acid bacteria in the surface layer of the spoiled sausages. Three main homofermentative groups could be observed on the basis of different carbohydrate patterns. Heterofermentative lactic acid bacteria belonged mainly to genus Leuconostoc. The proportion of leuconostocs in the spoiled sausages was also quite large. They could be divided into three main groups on the basis of different carbohydrate fermentation patterns. The lactic acid bacteria population of spoiled cooked ring sausages thus seemed to be heterogeneous. The strains isolated resembled strains observed by other workers in meat and meat products.     

Characterization of anti-listerial lactic acid bacteria isolated from Thai fermented fish products

Thai fermented fish products were screened for lactic acid bacteria capable of inhibitingListeriasp. (Listeria innocua). Of 4150 assumed lactic acid bacteria colonies from MRS agar plates that were screened by an agar-overlay method 58 (1.4%) were positive. Forty four of these strains were further characterized and 43 strains were inhibitory againstListeria monocytogenes. The strains were inhibitory to other Gram-positive (lactic acid) bacteria probably because of production of bacteriocins. All 44 strains inhibited bothVibrio choleraeandVibrio parahaemolyticusand 37 were inhibitory to a mesophilic fish spoilage bacterium (anAeromonassp.). Inhibition of Gram-negative bacteria was attributed to production of lactic acid. Most strains were identified asLactobacillusspp., and all grew well at ambient temperatures (25–37°C) and tolerated up to 6.5% NaCl. Glucose was fermented rapidly in laboratory media whereas pH decreased only very slowly in fish juice supplemented with 4% glucose and 3.5% NaCl or in a rice–fish mixture. Only four of 44 isolates could degrade and ferment complex carbohydrates such as rice, potatoes and maize starch. This indicates that other types of bacteria may be responsible for the rapid spontaneous fermentation of the products or that other yet-unknown factors ensure rapid fermentation. Overall anti-listerial lactic acid bacteria do occur in fermented fish products and the antibacterial activity against pathogenic bacteria indicates that they may be important in product safety.     

Characterization of the lactic acid bacteria in ewe's milk and cheese from northwest Argentina

Indigenous lactic acid bacteria in ewe's milk and artisanal cheese were studied in four samples of fresh raw milk and four 1-month-old cheeses from the provinces of northwest Argentina. Mean growth counts on M17, MRS, and MSE agar media did not show significant differences (P < 0.05) in raw milk and cheeses. Isolates of lactic acid bacteria from milk were identified as Enterococcus (48%), lactococci (14%), leuconostocs (8%), and lactobacilli (30%). All lactococci were identified as Lactococcus lactis (subsp. lactis and subsp. cremoris). Lactobacilli were identified as Lactobacillus plantarum (92%) and Lactobacillus acidophilus (8%). Enterococci (59%) and lactobacilli (41%) were isolated from cheeses. L. plantarum (93%), L. acidophilus (5%), and Lactobacillus casei (2%) were most frequently isolated. L. lactis subsp. lactis biovar diacetylactis strains were considered as fast acid producers. L. lactis subsp. cremoris strains were slow acid producers. L. plantarum and L. casei strains identified from the cheeses showed slow acid production. The majority of the lactobacilli and Lactococcus lactis strains utilized citrate and produced diacetyl and acetoin in milk. Enzyme activities (API-ZYM tests) of lactococci were low, but activities of L. plantarum strains were considerably higher. The predominance of L. plantarum in artisanal cheese is probably important in the ripening of these cheeses due to their physiological and biochemical characteristics.     

Characterization of PCB-degrading bacteria immobilized in polyurethane foam

This study is carried out to investigate (1) conditions for the synthesis of polyurethane foam to be used for immobilizing microorganisms, (2) the viability of microorganisms immobilized simultaneously into the pores of a polyurethane foam when the foam is synthesized, and (3) the difference in the ability to degrade PCBs between the immobilized and suspended microorganisms. The results of this study show that polyurethane foam is suitable for synthesizing 10% NCO-prepolymer, water and surfactant in the ratio of 100:2.6:1.2 (w/w), respectively, and the viability of microorganisms (input microbes) immobilized in the foam is high. The input microbes, designated as strain SY5, are isolated from a municipal sewage treatment plant. In addition, immobilized strain SY5 degrades 5-40% more PCB of a PCB mixture (Aroclor 1242) than the suspended strain SY5.     

Gene cloning and characterization of aldehyde dehydrogenase from a petroleum-degrading bacterium, strain HD-1

The hd-ald gene encoding aldehyde dehydrogenase (hd-ALDH) from an mixotrophic petroleum-degrading bacterium, strain HD-1 was cloned and sequenced. hd-ALDH (506 amino acids) is a member of the NAD+-dependent aldehyde dehydrogenase group. The hd-ald gene was expressed in Escherichia coli, and the recombinant enzyme was purified and characterized biochemically and enzymatically. The molecular weight of the enzyme was estimated to be 55,000 by SDS-PAGE, and 224,000 by gel filtration chromatography, suggesting that it acts as a tetramer. The CD spectrum suggests that the helical content of the enzyme is 10%. hd-ALDH was active on various aliphatic aldehyde substrates. The K(m) values of the enzyme were 6.4 microM for acetaldehyde, 4.2 microM for hexanal, 2.8 microM for octanal, and 0.84 microM for decanal, whereas the kcat values for these substrates were nearly equal (51-64 min(-1)). These results indicate that hd-ALDH acts preferentially on long-chain aliphatic aldehydes.     

Characterization and quantification of reversible redox sites in humic substances

Cyclic oxidation and reduction reactions using oxygen and palladium with H2, respectively, of dissolved humic and fulvic acids (HA and FA) and model quinone compounds were used to structurally characterize and quantify the electron-carrying capacity (ECC) of reversible redox sites present in humic substances. This technique was used to examine 8 quinone compounds and 14 HA and FA samples and identified 3 redox sites as a function of their stability against the Pd-catalyzed hydrogenolysis process. Six highly aliphatic HA and FA isolated from landfill leachate did not contain redox sites under any conditions; however, the other HA and FA demonstrated reversible redox properties characterized by a combination of three redox sites. On the basis of the model compound results, it is proposed that one site consists of a non-quinone structure (NQ) and the other two sites have quinone structures. The two quinone sites differ in that one group (Q1) has electron-withdrawing groups adjacent to the quinone functional group while the second group (Q2) contains either no substituents near the quinone or has nearby electron-donating groups with additional substitutents hindering hydrogenolysis through steric interactions. The reversible ECC of NQ sites ranged from 25 to 265 microequiv e- transferred/g HA or FA, representing 21-56% of the total ECC of the HA and FA when measured with the mildest reducing method (pH 8.0, pure Pd). Q1 redox sites resistant to hydrogenolysis at pH 8.0 using Pd/Al2O3 accounted for 13-58% of the total ECC and ranged from 40 to 120 microequiv e-/ g HA or FA. The most sensitive O2 reversible redox sites accounted for 8-50% of the total ECC (20-220 microequiv e-/ g HA or FA). These results directly demonstrate that HA and FA are capable of acting as reversible electron-transfer agents using different functional groups, some of which may not be quinones.     

Characterization of lactic acid bacteria isolated from Bukuljac, a homemade goat's milk cheese

The Bukuljac cheese is traditionally homemade cheese, produced from heat-treated goat's milk without the addition of any bacterial starter culture. The presence of lactic acid bacteria (LAB) in Bukuljac cheese has been analyzed by using a polyphasic approach including microbiological and molecular methods such as rep-PCR with (GTG)5 primer. Lactobacillus paracasei subsp. paracasei represents a dominant strain in the microflora of analyzed cheese. Out of 55 Gram-positive and catalase-negative isolates, 48 belonged to L. paracasei subsp. paracasei species. Besides lactobacilli, five Lactococcus lactis subsp. lactis and two Enterococcus faecalis were found. Results of PCR-denaturing gradient gel electrophoresis (DGGE) of DNA extracted directly from the fresh cheese revealed the presence of Leuconostoc mesenteroides. Only lactobacilli showed a high proteolytic activity and hydrolyzed alpha(s1)- and beta-caseins. They are also producers of diacetyl. In addition, 34 out of 55 isolates, all determined as lactobacilli, showed the ability of auto-aggregation. Among 55 isolates, 50 also exhibited antimicrobial activity.     

Characterization of bacteriocin-like inhibitory substances (BLIS) from lactic acid bacteria isolated from traditional Azerbaijani cheeses

The lactic acid bacteria (LAB) of southern Caucasus region present a special interest due to the diversity of lactic flora used for fermentations by various local populations during thousands of years. Four LAB strains, not identified previously, isolated from Motal and Brunza typical Azerbaijani cheeses were subjected to phenotypic identification and three of them could be identified as Lactobacillus paracasei subsp. paracasei and one as Lactobacillus rhamnosus. Test strains such as Lactobacillus bulgaricus 340 and Saccharomyces cerevisiae were inhibited by the four isolated strains. Antibacterial activity against Escherichia coli HB 101 was detected in Lactobacillus paracasei BN ATS 8w and L. rhamnosus FAZ 16m. L. paracasei BN ATS 5w and 8w, and L. rhamnosus FAZ 16m showed inhibitory effect on Staphylococcus aureus Cip 9973. The inhibition of Candida pseudotropicalis was detected only when using L. paracasei species BN ATS 5w and 7w. Culture of Listeria innocua was insensitive to the antimicrobial substances of all the studied strains. Complete inactivation or significant reduction in antibacterial activity was observed after treatment of cell-free supernatants with pronase E and proteinase K, but not with trypsin (except for L. rhamnosus FAZ 16m), indicating the protein nature of the active agents. Amylase treatment totally inactivated the substances of L. paracasei, what implies the importance of glycosylation for the activity. The activities of all the bacteriocin-like substances from studied LABs were stable over a wide pH range from 3 to 11.     

Characterization of acetic acid bacteria in "traditional balsamic vinegar"

This study evaluated the glucose tolerance of acetic acid bacteria strains isolated from Traditional Balsamic Vinegar. The results showed that the greatest hurdle to acetic acid bacteria growth is the high sugar concentration, since the majority of the isolated strains are inhibited by 25% of glucose. Sugar tolerance is an important technological trait because Traditional Balsamic Vinegar is made with concentrated cooked must. On the contrary, ethanol concentration of the cooked and fermented must is less significant for acetic acid bacteria growth. A tentative identification of the isolated strains was done by 16S-23S-5S rDNA PCR/RFLP technique and the isolated strains were clustered: 32 strains belong to Gluconacetobacter xylinus group, two strains to Acetobacter pasteurianus group and one to Acetobacter aceti.     

Tobacco and poverty: evidence from Vietnam

This review examined existing evidence to investigate the link between tobacco and poverty in Vietnam, to assess the impact of tobacco control policies on employment related to tobacco consumption and to identify information gaps that require further research for the purposes of advocating stronger tobacco control policies. A Medline, PubMed and Google Scholar search identified studies addressing the tobacco and poverty association in Vietnam using extensive criteria. In all, 22 articles related either to tobacco and health or economics, or to the potential impact of tobacco control policies, were identified from titles, abstracts or the full text. 28 additional publications were identified by other means. PHA, LTT and LTTH reviewed the publications and prepared the initial literature review. There is extensive evidence that tobacco use contributes to poverty and inequality in Vietnam and that tobacco control policies would not have a negative impact on overall employment. Tobacco use wastes household and national financial resources and widens social inequality. The implementation and enforcement of a range of tobacco control measures could prove beneficial not only to improve public health but also to alleviate poverty.     

Characterization of charcoal adsorption sites for aromatic compounds: insights drawn from single-solute and bi-solute competitive experiments

Charcoal, the residue of incomplete biomass burning that is found in many soils and sediments, is considered a high affinity sorbent for organic pollutants. However, little is known about the microscopic processes controlling sorption. The purpose of this study was to gain molecular-scale insight into the sorption on a charcoal of three weakly soluble aromatic compounds [benzene (BEN), toluene (TOL), and nitrobenzene (NBZ)] by conducting both single-solute and bi-solute experiments. The charcoal (420 m2 g(-1)) was produced from maple wood shavings by oxygen-limited pyrolysis at 673 K. Solute affinity for charcoal followed the order NBZ > TOL > BEN. Commonly employed sorption models did not adequately describe the single-solute isotherms. Competition in both TOL-BEN and the TOL-NBZ bi-solute systems was strong. Normalization of the isotherms for the hydrophobic driving force by using an existing free energy correlation between sorption and partitioning to an inert solvent (benzene or n-hexadecane) with a nonpolar aromatic compound calibration set resulted in a finding of enhanced sorption of NBZ relative to the coalesced BEN and TOL isotherms, indicating some specificity in the interaction of NBZ. The competitive data indicated 1:1 molar competition between BEN and TOL and between NBZ and TOL, showing conclusively that this specificity was not due to a subpopulation of sorption sites unique to NBZ. H-bonding was ruled out, as the relative affinity for the sorbent among the solutes did not change at all when increasing the solution pH from 6.5 to 11. 1H NMR experiments showed molecular complexation in chloroform between NBZ and model graphene polycyclic aromatic units (naphthalene, phenanthrene, and pyrene) which was absentfor BEN and TOL. This result, in combination with the results of a companion study (Zhu and Pignatello, Environ. Sci. Technol. (in press)), is used to support the existence of pi-pi electron donor-acceptor interactions between NBZ (electron acceptor) and the polycyclic aromatic charcoal surface (electron donor) as the cause of enhanced NBZ sorption.     

Characterization of lactic acid bacteria isolated from a Greek dry-fermented sausage in respect of their technological and probiotic properties

A total of 147 lactic acid bacteria was isolated from two types of naturally fermented dry sausages at four different stages of the ripening process studied in order to select the most suitable strains according to their technological characteristics including probiotic properties and antimicrobial activity against food-borne pathogens. Identification of the isolates revealed that 90% were lactobacilli, 4% enterococci, 3% Pediococcus sp. and sporadic isolates of Weissella viridescens, Leuconostoc pseudomesenteroides, and Leuconostoc sp. The isolated strains of Lactobacillus sakei (49 isolates), Lactobacillus curvatus (24 isolates) and Lactobacillus plantarum (7 isolates) were further characterized. All strains could grow at 15?°C, whereas the majority of the strains was able to grow in the presence of 6.5% NaCl and on acetate agar. The enzymatic potential of the strains was evaluated using the API ZYM system. During in vitro investigations all strains exhibited high leucine and valine aminopeptidase activities and moderate acid phosphatase and phosphohydrolase activities. Some strains showed very weak lipolytic activity. The enzyme profiling is an important factor for selection of strains as starter cultures. A large majority of the strains tolerated 0.1% bile salts whereas 58% of Lactobacillus curvatus strains and all Lactobacillus plantarum strains were resistant to 0.3% bile salts. All Lactobacillus sakei strains and the majority of Lactobacillus curvatus and Lactobacillus plantarum strains exhibited an anti-listerial activity against three Listeria monocytogenes strains. A percentage of 75, 50 and 29% of Lactobacillus sakei, L. curvatus and L. plantarum strains, respectively, could inhibit two Staphylococcus aureus strains. The contribution of the selected strains to a possible inhibition of Listeria monocytogenes and S. aureus in situ on fermented meats would be of considerable interest to enhance the hygienic quality of these products.     

Molecular characterization of antibiotic-resistant salmonella isolates from retail meat from markets in northern Vietnam

A total of 118 Salmonella isolates were detected from 283 retail meat samples (135 pork and 148 chicken meat) purchased at retail markets in Northern Vietnam. Thirteen serovars, including Infantis, Anatum, Rissen, Reading, Emek, Typhimurium, Blockley, London, Newport, Derby, Weltevreden, Albany, and Hadar, were determined. Resistance to tetracycline (54.2%), sulfonamides (52.5%), streptomycin (41.5%), trimethoprim (36.4%), chloramphenicol (35.6%), and ampicillin (33.1%) was commonly seen in the Salmonella isolates. Fourteen [bla(TEM), bla(OXA-1), bla(PSE-1), aadA1, sul1, tetA, tetB, tetG, cmlA1, floR, dfrA1, dfrA12, aac(3)-IV, and aphA1-1AB ] of 17 resistance genes were detected from the isolates demonstrating resistance. Genes for plasmid-mediated quinolone resistance, such as qnrA, qnrB, qnrS, qepA, and acc(6')-1b-cr, were not detected in 23 quinoloneresistant isolates. The substitution TCC to TTC at codon 83 of gyrA was found in the 18 quinolone-resistant isolates. The data revealed that resistant Salmonella strains were widely distributed in Northern Vietnam via the food chain and that they might contain multiple genes specifying identical resistance phenotypes. Thus, further studies are necessary to clarify the mechanisms of antibiotic resistance in Salmonella strains and their spread in the livestock market.     

Characterization of lactic acid bacteria isolated from raw cows’ milk cheeses currently produced in Galicia (NW Spain)

Twenty cheeses belonging to the four Protected Designations of Origin manufactured in Galicia (NW Spain) (6 Arzúa-Ulloa, 4 Tetilla, 6 Cebreiro and 4 San Simón da Costa) were selected from a total of 60 cheeses on basis of their (typical) sensorial profiles. A total of 218 lactic acid bacteria (LAB) isolates were obtained from the predominant microflora of the selected cheeses and were identified as Lactococci (98 isolates), Leuconostocs (56), Mesophilic Lactobacilli (54), Pediococci (8) and Enterococci (2). Eighty-four of the isolates produced mainly malty, spicy or sulfide flavours in pasteurised whole milk, and were not characterized further. Some good producers of diacetyl-acetoin in milk (>100 mg/L) were found among a total of 129 LAB selected, although the isolates were generally less acidifying and less proteolytic than many of those obtained 10-15 years ago. The results suggest that the microflora in cheese-making environments have undergone changes, with the most evident difference being the practical absence of Enterococcal strains among the current isolates.