جستجوی مقالات مرتبط با کلیدواژه « exopolysaccharide » در نشریات گروه « صنایع غذایی »

Enterotoxigenic Escherichia coli is the most common bacterial agent causing diarrhea by binding to the intestinal mucosa and producing heat-labile enterotoxins. The aim of this study was to elucidate the interaction of two forms of dextran exopolysaccharides (molecular weights of (11-9 kDa) and (76-60 kDa)) produced by the probiotic bacterium Leuconostoc mesenteroides with the heat-labile enterotoxin ((B-pentamer) (LTB)) by using surface plasmon resonance (SPR). According to the results of interaction kinetics at 298 K, both low and high molecular weight dextran types exhibited high affinity (KA) (1.07×106 M-1 and 0.95×106 M-1, respectively) for LTB toxin in vitro. From a thermodynamic point of view, the values calculated of the Gibbs energy were negative (ΔG <0), and also enthalpy and entropy achieved both positive values (ΔH> 0 and ΔS> 0) via the van’t Hof equation, indicating that the interaction was spontaneous, endothermic, and disordered, respectively. With these findings, hydrophobic interactions appear to be important in the interaction between dextran and LTB toxins with hydrogenic bindings. Therefore, dextran molecules are capable of binding to LTB toxin and relatively displaying antitoxin effects. To sum up, these results could provide further insights for initiating extensive research with other lactic acid-derived exopolysaccharides in bacterial interactions and also with foodborne pathogen toxins.

One of the most important applications of biotechnology in the food industry is the production of various additives. Among the additives produced by biotechnology method is the production of exopolysaccharides produced by bacteria in dairy products.Diversity in the structure and chemical composition of microbial exopolysaccharides has made them superior to animal and plant polymers. Due to these cases, these compounds can be used as food additives with health effects. In the present study, Bacillus bacteria producing exopolysaccharides were isolated from the soils of desert areas and then, the structural and functional groups of exopolysaccharides were identified using FT-IR method. The presence of peaks in the frequency range 400-4000 (cm-1)indicates the polysaccharide and purity of the extracted material. Then, their effects on the quality of yogurt were investigated. Based on the results, the quality of yogurt samples containing exopolysaccharide of bacteria K, C, B, A and E significantly increased compared to the control group that did not contain exopolysaccharide.Exopolysaccharide from E bacterium significantly reduced hydration compared to other samples and control samples and also significantly increased the viscosity and water holding capacity and consistency of yogurt. Finally, based on the 16S rDNA sequence, the bacterium whose exopolysaccharide had the greatest effect on improving the quality of yogurt, Bacillus wiedmannii strain HBUM207173 was identified.

Lactic acid bacteria have been used as a starter culture to produce fermented dairy products. Identifying and studying the technological and antimicrobial properties of these bacteria can enable their industrial applications. The aim of this study was to investigate the technological and antimicrobial characteristics of Lactobacillus brevis isolated from Khikki cheese. For this purpose, after Gram-staining and catalase test, molecular identification of the desired strain was performed using FYM27 and R1492 universal primers. Various technological characteristics of this strain such as exopolysaccharide production, proteolytic activity, lipolytic activity, acid production, survival under refrigerator conditions and its autolytic activity were examined. The antimicrobial activity was measured using “Lawn on the spot” method on food borne pathogens. The results showed that the strain belongs to L. brevis gp104. This strain also had ability to produce exopolysaccharide as a secondary metabolite; although it did not show proteolytic and lipolytic activity. Lactobacillus brevis reached pH = 4.6 at 15 °C after 72 h. This time was 48 and 24 h for 24 and 37 °C, respectively. The results showed that on the seventh day of its storage in refrigerator, the survival of the strain was approximately equal to the initial inoculated amount, but after 14 days, 1.5 Log CFU/ml and after 21 days, about 2 Log CFU/ml decreased in its number. In addition, the autolytic activity of Lactobacillus brevis was calculated to be 53%. The inhibition zone diameter for Enterobacter aerogenes, Salmonella typhi, Staphylococcus epidermidis and Listeria innocua was 11.30, 10.10, 22.40 and 19.50 mm, respectively. Due to the favorable technological potential of L. brevis, this strain could be used in the production of probiotic products as well as adjunct culture in fermented products.

Yoghurt is one of the most popular fermented dairy product which affect by starter culture bacteria characteristics. In this study, isolated lactic acid strains from traditional Iranian yoghurt after passing morphology and safety evaluation steps were selected according to exopolysaccharide producing ability and apply as set yoghurt starter culture beside commercial starter without this ability, CH-1. During shelf life, rheological factors, syneresis amounts and organoleptic factors were determined. Results showed strong effects of exopolysaccharide on firmer structure, stronger rheological factors, decreased syneresis amounts and better sensory evaluation. Probably applied strains with exopolysaccharide production ability, due to trapped water in gel structure in high weight exopolysaccharide molecules, resulted in lower wheying off and firmer structure. we found that some Iranian lactic acid strains as our research strain have very good potential for stabilizer replacement and result in excellent structure and perfect sensory attribute.

In this study, exopolysaccharide production by Rhizubium radiobacter PTCC 1654 in Submergedfermentation to reduce waste sludge from dairy Industries as well as used as Beneficialmedium for the growth kind of microorganisms, were studied. Initial screening was used fractional factorial designs with 7 variables of time, temperature, concentration of calcium carbonate, ammonium sulfate concentration, Agitation rate, the percentage of dairy sludge and pH medium for the identification of variables affecting the growth of R. radiobacter Was performed. The results showed that three variables of dairy sludge, calcium carbonate concentration and time of incubation had positive effect on the growth of R.radiobacter(p<0/05). Moreover, that all variables, have a significant effect on the production of exopolysaccharideExopolysaccharides by R. radiobacter using response surface methodology(p<0/05).The maximum production of EPS was in concentration 1g/l calcium carbonate, 50% of dairy sludge and incubation time 101/69 hours, in which case exopolysaccharide production 0/686 g/100 ml and biomass production0/288 g/100 ml is. FTIR results showed that the exopolysaccharides produced in the dairy sludge has residues of carbohydrate, and carboxyl groups on its chain.

Dairy products can be a rich source of diverse lactic acid bacteria (LAB) with high functional properties, such as exopolysaccharide (EPS) production. EPS are high molecular weight polymers that are composed of sugar units and are secreted by microorganisms into the surrounding environment. Produced EPS can be used as an additive by a health effect and texturing properties. In this study, exopolysaccharide producing LAB (ropy and mucoid colonies) were isolated and identified from raw sheep milk and sheep yogurt that made in rural areas of Urmia. For this purpose, lactic acid bacteria cultured on MRS agar and M17 agar media and then isolated on the basis of the ability to produce exopolysaccharides to study the diversity of species by phenotypic methods (Gram stain, biochemical and physiological tests) and then identified by polymerase chain reaction (PCR). The 4 strains of LAB isolated were Gram-positive as well as catalase negative and were able to produce large amounts of EPS. The amounts of bonded and abandoned exopolysaccharides which measured by phenol/sulfuric acid method, were 40.28±0.2 to 65.26±0.47 mg/L and 105.68±3.2 to 136.35±0.2 mg/L, respectively. Sheep yogurt which manufactured traditionally in West Azerbaijan province, contained exopolysaccharide producing strains that can have the potential to use in the dairy industry.

One of the most important points for yogurt production is the selection of starter culture, and also because of the necessity to preserve our natural starter cultures and to increase the availability of them for industrial use, the aim of this project was to determine the technological and organoleptic properties of yogurts producted by starter culture isolated from Iranian native yogurts. Eleven different yogurt samples were produced using 5 Lactobasillus delbruekii subsp.bulgaricus and 2 Streptococcus thermophiles isolates. Results showed there were no significant differences between acidifying activity of EPS-producing and non-EPS-producing starter cultures. Also isolates with a high proteolytic activity (isolates used in the examples H and I that proteolytic activity reaches during 28 days to 1 unit) have less the ability to produce acid during storage and viability of these isolates had been more than other strains. Samples that produced by EPS-producing starter culture exhibited better texture properties (consistency, syneresis and water holding capacity) than samples that produced using NEPS-producing starter culture. However, H and I samples due to high proteolytic activity and type of the exopolysaccharide is produced had less desirable textural properties. Syneresis reduced during storage and water holding capacity increased. But the synersis and water holding capacity of the samples produced using starters with high proteolytic activity, such as samples E, H, I similar to other samples until day 21, and in the fourth week the trend of changes has was reversed and the amount of synersis increased and water holding capacity is reduced.

SMP was substituted by WPC in four levels for preparing reconstituted milk. Two ropy and one nonropy starter cultures was used for Doogh preparation. Yield stress, viscosity, consistency index and pseudoplastic behavior of Doogh increased by increasing WPC content. Results showed that WPC increased colloidal particles dimension and constructed a network which led to a decrease in Doogh phase separation (%32 at the highest level of WPC) during storage. Starter type had no effect on the Doogh stabilization. It does not have any effect on the studied physical properties in the presence of WPC, as well. Adding WPC to milk leads to improve of physical properties and stability of Doogh but using EPS producing starter cultures requires further studies in this field.

The effect of exopolysaccharide producing (EPS+) starter culture on the proteolysis and lipolysis of the ultrafiltered white cheese was investigated. Four treatment of UF white cheese were produced: C1، with EPS-producing starter culture Y 8. 86 F، C2، with EPS-producing starter culture L904، C3، with EPS-producing starter cultures (L904 and Y 8. 86 F) and control samples with commercial starter culture DELVO-TEC. Cheese samples were ripened at 8-12°C for 60 days. Assessment of proteolysis in cheese samples was investigated by determination of soluble nitrogen (SN) at pH= 4. 6، tricholoracetic acid soluble nitrogen (TCA-SN) and urea-polyacrylamide gel electrophoresis and assessment of lipolysis were investigated by determining acidity index. The results showed that amount of SN، TCA-SN and acidity index in all cheeses increased progressively during ripening. The amounts of SN and TCA-SN in EPS+ cheeses were higher than control. The urea-PAGE electrophoresis showed that EPS producing starter culture was effective in the s1-casein break down in UF white cheese. The amount of acidity index content in cheese samples containing EPS-producing starter cultures and control cheese were not significantly different (P>0. 05).

Several strains of lactic acid bacteria, used as starter culture to produce yoghurt and other fermented products, produce exopolysaccharides which can improve textural properties of products. In this study, physical (syneresis), rheological (viscosity and firmness) and sensory properties of yoghurt samples produced with exopolysaccharide producing starter culture were investigated in comparison with nonexopolysaccharide producing starter culture CH-1 during 30 days of storage. Samples with exopolysaccharide producing starter culture had lower syneresis and were more viscous and firmer than those made with nonexopolysaccharide producing starter culture. Storage time had significant (P<0.001) effect on mentioned properties. Panelists expressed that yoghurts produced with YF-L811 were whiter, firmer and had lower syneresis before and after inserting spoon into them, stronger flavor and tended to be creaminess, more cohesive and adhesive than samples produced with CH-1. Difference between unpleasant sourness of samples produced with exopolysaccharide producing starter culture and nonexopolysaccharide producing starter culture was not significant (P>0.05).