Encapsulation of lactic acid bacteria in W1/O/W2 emulsions stabilized by mucilage:pectin complexes

Opuntia silvestri mucilage obtained from dried stems was explored as an emulsifier to prepare double emulsions aiming to encapsulate Lactiplantibacillus plantarum CIDCA 83114. W1/O/W2 emulsions were prepared using a two-step emulsification method. The aqueous phase (W1) consisted of L. plantarum CIDCA 83114, and the oil phase (O) of sunflower oil. The second emulsion was prepared by mixing the internal W1/O emulsion with the W2 phase, consisting of 4 % polysaccharides, formulated with different mucilage:(citric)pectin ratios. Their stability was assessed after preparation (day 0) and during storage at 4 °C (28 days). Determinations included creaming index, color, particle size, viscosity, turbidity, and bacterial viability, along with exposure to simulated gastrointestinal conditions. Significant differences were evaluated by analysis of variance (ANOVA) and Duncan's test (P < 0.05). After 28 days storage, bacterial viability in the W1/O/W2 emulsions was above 6 log CFU/mL for all the pectin:mucilage ratios. Emulsions containing mucilage and pectins showed lower creaming indices after 15 days, remaining stable until the end of the storage period. Formulations including 1:1 pectin:mucilage ratio exhibited the highest bacterial viability under simulated gastrointestinal conditions and were more homogeneous in terms of droplet size distributions at day 0, hinting at a synergistic effect between mucilage components (e.g., proteins, Ca2+) and pectin in stabilizing the emulsions. These results showed that Opuntia silvestri mucilage enhanced the stability of emulsions during refrigerated storage, highlighting its potential for encapsulating lactic acid bacteria. This presents an economical and natural alternative to traditional encapsulating materials.

Quantification of the environmental impact arising from the utilization of whole and defatted Okara in fermentative and dehydration processes

Okara is the insoluble pulp that remains after the grinding and filtration of soybeans during the production of soymilk and tofu. As it retains a noteworthy quantity of nutrients, there has been an increasing emphasis in the utilization of this residue for the development of sustainable processes. This study focused on assessing the environmental impact of employing okara as a medium for fermenting and dehydrating probiotic bacteria at laboratory scale. The evaluation was carried out using the Life Cycle Assessment (LCA) methodology, considering the entire process lifecycle. Whole okara and defatted okara were used as culture media for Lactiplantibacillus plantarum CIDCA 83114, followed by dehydration (either freeze-drying or spray-drying) and subsequent storage. For the purpose of comparison, both scenarios (whole and defatted okara) were evaluated using 1 kg of dehydrated final product for storage, as functional unit. Based on experimental results, the conservation of the received okara and the dehydration-storage (e.g., freezing and freeze-drying) phases were identified as the most significant environmental hotspots responsible for the most substantial impacts of the processes. The use of LCA facilitated the measurement of the environmental effects linked to the reutilization of okara as an agro-industrial residue, thus providing quantitative support when engineering its sustainable valorization.

Microfluidics potential for developing food-grade microstructures through emulsification processes and their application

The food sector continues to face challenges in developing techniques to increase the bioavailability of bioactive chemicals. Utilising microstructures capable of encapsulating diverse compounds has been proposed as a technological solution for their transport both in food and into the gastrointestinal tract. The present review discusses the primary elements that influence the emulsification process in microfluidic systems to form different microstructures for food applications. In microfluidic systems, reactions occur within small reaction channels (1-1000 μm), using small amounts of samples and reactants, ca. 102-103 times less than conventional assays. This geometry provides several advantages for emulsion and encapsulating structure production, like less waste generation, lower cost and gentle assays. Also, from a food application perspective, it allows the decrease in particle dispersion, resulting in a highly repeatable and efficient synthesis method that also improves the palatability of the food products into which the encapsulates are incorporated. However, it also entails some particular requirements. It is important to obtain a low Reynolds number (Re < approx. 250) for greater precision in droplet formation. Also, microfluidics requires fluid viscosity typically between 0.3 and 1400 mPa s at 20 °C. So, it is a challenge to find food-grade fluids that can operate at the micro-scale of these systems. Microfluidic systems can be used to synthesise different food-grade microstructures: microemulsions, solid lipid microparticles, microgels, or self-assembled structures like liposomes, niosomes, or polymersomes. Besides, microfluidics is particularly useful for accurately encapsulating bacterial cells to control their delivery and release on the action site. However, despite the significant advancement in these systems' development over the past several years, developing and implementing these systems on an industrial scale remains challenging for the food industry.

Dataset on the Life Cycle Assessment of fructo- and galacto-oligosaccharides (FOS and GOS) produced by synthesis or hydrolysis

The prebiotics like FOS and GOS are receiving special attention in the food industry due to their potential health benefits. They can be produced by enzymatic synthesis by using disaccharides or other substrates as raw materials or by extraction and hydrolysis from different natural sources (roots, legumes). However the environmental footprints of these different production schemes are lacking. This dataset presents Life Cycle Assessment (LCA) of the production of FOS and GOS by enzymatic synthesis from glucose (to get FOS) or lactose (to get GOS) and hydrolytic production from extraction of yacon potato (to get FOS) or chickpea (to get GOS). A cradle-to-gate approach was considered in the two scenarios under assessment (the phases of use and/or final disposal of FOS/GOS were not considered). The functional unit was defined as 100 g of FOS/GOS produced. LCAs were performed using data collected at the laboratory scale during experiments, supplemented with data from technical and scientific literature. Ecoinvent database provided background data. SimaPro was used for the LCA modeling with the midpoint impact EF2.0 characterization method to calculate environmental impacts. For each scenario (FOS produced by synthesis, FOS produced by hydrolysis, GOS produced by synthesis, GOS produced by hydrolysis), the Life Cycle Inventory (LCI) and the Life Cycle Impact Assessment (LCIA) are provided. These data can be used (i) to identify the main environmental hotspots of the production process, (ii) to compare the different process alternatives between them and (ii) to suggest eco-design options to upscale these processes. They could also be re-used in other LCA studies which would include FOS and/or GOS in the production system.

Fortification of water kefir with magnetite nanoparticles

The aim of this work was to evaluate the suitability of incorporating Fe₃O₄ (magnetite, M) NPs into water kefir (wKef) beverages. Magnetite NPs were synthesized and coated with pectins (cM), and incorporated into wKef beverages obtained by fermentation of a muscovado sugar solution with wKef grains. FeSO₄, usually employed as fortifier, was used as a control. Four different beverages were analyzed: wKef, wKef-cM, wKef-M, wKef-FeSO₄, indicating wKef beverages fortified with cM, M or FeSO₄, respectively. Their stability was assessed by determining the viability of total lactic acid bacteria and yeasts, and the composition of saccharides along storage at 4 °C for up to 30 days. The toxicity of M and cM was evaluated in an in vivo model of Artemia salina. The absorption of iron was quantified by determining ferritin values on intestinal Caco-2/TC7 cells, and its internalization mechanisms, by employing inhibitors of endocytic pathways and quantifying ferritin. M and cM were non-toxic on Artemia salina up to 500 µg/mL, a toxicity even lower than that of FeSO₄, which showed a LD50 of 304.08 µg/mL. After 30 days of storage, no significant decrease on yeasts viability was observed, and bacteria viability was above 6 log CFU/mL for the four beverages. In turn, sucrose decreased to undetectable values, concomitantly to an increase in the concentrations of glucose and fructose. Both wKef-M and wKef-cM led to a significant increase in the ferritin values (up to 2 folds) with regard to the basal state. The internalization of M NPs occurred via clathrins and caveolin pathways, whereas that of cM, by macropinocytosis. Safely incorporating M and cM NPs into wKef beverages appear as an innovative strategy for providing bioavailable iron aiming to ameliorate the nutritional status of populations at risk of iron deficiency (e.g., vegans).

Microencapsulation of Lactobacillus plantarum in W/O emulsions of okara oil and block-copolymers of poly(acrylic acid) and pluronic using microfluidic devices

Okara oil is a by-product remaining from defatting okara, the solid residue generated after extracting the aqueous fraction of grounded soybeans in the elaboration of soy beverages. The goal of this work was to encapsulate the probiotic Lactobacillus plantarum CIDCA 83114 into W/O emulsions composed of a block-copolymer constituted of pluronic® and acrylic acid (PPP12) and okara oil, prepared in microfluidic devices. For comparative purposes, alginate was also included as a second dispersed phase. Lactobacillus plantarum CIDCA 83114 was suspended in PPP12 or alginate giving rise to dispersed phases with different compositions, named I, II, III and IV. Controls were prepared by suspending microorganisms in water as dispersed phase. 6-carboxyfluorescein was added as bacterial marker in all the emulsions. The presence of green dyed bacteria in the dispersed phases, inside the droplets of the emulsions and the absence of fluorescence outside them, confirmed the complete encapsulation of bacteria in the dispersed phases. After being prepared, emulsions were freeze-dried. The exposure to gastric conditions did not lead to significant differences among the emulsions containing polymers. However, in all cases bacterial counts were significantly lower than those of the control. After exposing emulsions to the simulated intestinal environment, bacterial counts in assays I, II and III (emulsions composed of only one dispersed phase or of two dispersed phases with bacteria resuspended in the PPP12 one) were significantly greater than those of the control (p < 0.05) and no detectable microorganisms were observed for assay IV (emulsions composed of two dispersed phases with bacteria resuspended in the alginate one). In particular, bacterial cultivability in emulsions corresponding to assay I (only PPP12 as dispersed phase) exposed to the intestinal environment was 8.22 ± 0.02 log CFU/mL (2 log CFU higher than the values obtained after gastric digestion). These results support the role of PPP12 as an adequate co-polymer to protect probiotics from the gastric environment, enabling their release in the gut, with great potential for food or nutraceutical applications.

Infrared spectroscopy with multivariate analysis to interrogate the interaction of whole cells and secreted soluble exopolimeric substances of Pseudomonas veronii 2E with Cd(II), Cu(II) and Zn(II)

Extracellular polymeric substances (EPS) are bacterial products associated to cell wall or secreted to the liquid media that form the framework of microbial mats. These EPS contain functional groups as carboxyl, amino, hydroxyl, phosphate and sulfhydryl, able to interact with cations. Thus, EPS may be considered natural detoxifying compounds of metal polluted waters and wastewaters. In this work Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) in combination with multivariate analysis (Principal Component Analysis-PCA-) were used to study the interaction of Cd(II), Cu(II) and Zn(II) and Pseudomonas veronii 2E cells, including bound EPS and cell wall, and its different soluble EPS fractions, previously characterized as Cd(II) ligands of moderate strength. Amino groups present in exopolysaccharide fraction were responsible for Zn(II) and Cu(II) complexation, while carboxylates chelated Cd(II). In lipopolysaccharide fraction, phosphoryl and carboxyl sites were involved in Cd(II) and Cu(II) binding, while Zn(II) interacted with amino groups. Similar results were obtained from cells. These studies confirmed that FTIR-PCA is a rapid analytical tool to provide valuable information regarding the functional groups in biomolecules related to metal interaction. Moreover, a discrimination and identification of functional groups present in both EPS and cells that interacted with Cd(II), Zn(II) and Cu(II) was demonstrated.

Release of health-related compounds during in vitro gastro-intestinal digestion of okara and okara fermented with Lactobacillus plantarum

Okara is a highly perishable by-product remaining after filtration of the smashed soybeans seeds in the production of soymilk. Due to its nutritional value, different approaches have been developed to use it as functional ingredient. Fermentation of okara appears as an interesting strategy to preclude spoilage, providing a more stable matrix to be incorporated in the formulation of functional foods. Okara has antioxidant compounds but the effect of fermentation, and their bioaccessibility still need to be investigated. To achieve this aim, the phenolic compounds (as determined by TPC and TFC assays) and the antioxidant properties (as determined by ABTS ^·+, DPPH ^· , O₂ ^·- assays) of okara and okara fermented with Lactobacillus plantarum CIDCA 83114 were assessed both before and after exposure to simulated gastro-intestinal conditions. Before digestion, okara showed higher values of TPC and TFC than the fermented counterpart. Although a decrease of TPC and TFC was observed after exposing okara to gastric conditions, no significant differences between okara and fermented okara were detected. No further decrease of TPC were observed in intestinal conditions. Okara showed higher antioxidant activity than fermented okara. There was a considerable decrease in the antioxidant activity for both samples when exposed to gastric and intestinal conditions. A good correlation between TFC and antioxidant activities was detected, suggesting that flavonoids play an important role as antioxidants. As a whole, this work provides a solid support for the stability of phytochemicals along the digestive process of both okara and fermented okara.

Pectin Hydrolysates from Different Cultivars of Pink/Red and White Grapefruits (Citrus Paradisi [macf.]) as Culture and Encapsulating Media for Lactobacillus Plantarum

Citrus pectin hydrolysates (Citrus paradisi [Mafc.]) from "Foster," "Red Shambar," "Tangelo Orlando," and "Citrumelo Swingle" cultivars were obtained by partial chemical hydrolysis and their properties as culture media (sole carbon/nutrient source) and encapsulating agents of Lactobacillus plantarum CIDCA 83114 were evaluated. The concentration of neutral sugars was maximal after 2-hour hydrolysis. All hydrolysates were rich in glucose >xylose >galactose >galacturonic acid >mannose >arabinose. "Citrumelo Swingle" cultivar was the one with the highest concentration of xylose. After 24 hr of fermentation with L. plantarum CIDCA 83114, bacterial viability increased from 6.76 ± 0.14 to almost 9 log CFU/mL, and lactic acid concentration, from 2.63 ± 0.41 to 7.82 ± 0.15 mmol/L in all hydrolysates. Afterwards, bacteria were entrapped in pectate-calcium beads by ionotropic gelation. Bacterial viability did not significantly decrease after freeze-drying and storage the beads at 4 °C for 45 days. PRACTICAL APPLICATION: Pectin hydrolysates were adequate culture media for microorganisms, as determined by the viabililty and lactic acid production. Considering that citrus peels are agro-wastes obtained in large quantities, their use as encapsulating materials provides a solution to overcome the environmental problem they entail.

Pectin-decorated magnetite nanoparticles as both iron delivery systems and protective matrices for probiotic bacteria

The goal of this work was to investigate biophysical stability of iron-pectin nanoparticles and analyze the feasibility of using them as delivery systems for the probiotic strain Lactobacillus plantarum CIDCA 83114. Iron oxide (Fe₃O₄) nanoparticles were synthesized from 0.25M FeCl₂/0.5 M FeCl₃.6H₂O, and coated with citrus pectins. Their physico-chemical properties [FTIR, X-ray diffraction (XRD), ζ-potential, particle size, SEM, TEM] and their effect on bacterial stabilization (viability after freeze-drying/storage, stability when exposed to simulated gastro-intestinal conditions) were assessed. XRD indicated the almost exclusive presence of magnetite crystalline phases. FTIR spectra confirmed the adsorption of pectin on magnetite nanoparticles surface. SEM and TEM images evidenced agglomerated nanoparticles, and a morphological surface change after adsorption of pectin. DLS and ζ-potential results proved the solvation of the ionizable groups in the hydrophilic network which induced chain expansion and agglomeration. Iron from nanoparticles demonstrated to be non-toxic for microorganisms up to 1.00 mg/mL. Simulated saliva and gastric solutions prevented nanoparticles from dissolution. The higher pH of the intestinal conditions (solvated -COO- and Fe-O- groups) facilitated the dispersion and partial dissolution of nanoparticles. Pectins adsorption on magnetite nanoparticles significantly enhanced electrostatic repulsion, which aided the solvation of ionized iron forms. The soluble species diffused out from the aggregates, being detected in the simulated intestinal fluid. Regarding bacterial viability, no decays were observed neither when pectin-decorated nanoparticles were exposed to simulated fluids nor when stored at 4 °C for 60 days. The composites engineered in this work appear as adequate delivery systems for probiotic bacteria, whose target is the gut.

Characterization of Pectins Extracted from Different Varieties of Pink/Red and White Grapefruits [Citrus Paradisi (Macf.)] by Thermal Treatment and Thermosonication

The physical and chemical properties of pectin extracts obtained from different white and pink/red varieties of grapefruit [Citrus paradisi (Macf.)], using both conventional heating (CHE) and thermosonication (TS), were investigated. The content of galacturonic acid (GalA), degree of esterification (%DM), color and antioxidant capacity were analyzed. Fourier-Transform Infrared Spectroscopy (FTIR) associated with multivariate analysis enabled a structural comparison among the pectin extracts, and differential scanning calorimetry (DSC) completed a full landscape of the investigated extracts. Pectin extracts obtained by CHE showed mostly higher GalA than those obtained by TS. All the extracts had a high antioxidant capacity, as determined by 2,2 diphenyl 1-picrylhydrazyl (DPPH^* ) and 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS^* +) assays, and a high correlation with the GalA content. The main differences observed in the FTIR spectra occurred in the 1200 to 900 cm^-1 region (differences in GalA). The glass transition temperatures (Tgs) of all extracts were above 85 °C, making them interesting as stabilizing agents for the food industry.

PRACTICAL APPLICATION

A wide database for the characterization of pectin extracts from grapefruits was obtained. The relationship between the extraction method and the source of pectins, with the physicochemical and antioxidant properties provided great support for their application in the food industry.

Valorization of okara oil for the encapsulation of Lactobacillus plantarum

Oil-in-water (O/W) emulsions of okara oil-caseinate (1:2; 1:3 and 1:4 O/W ratios) were used to encapsulate Lactobacillus plantarum CIDCA 83114. Once encapsulated, microorganisms were freeze-dried or spray-dried, and observed by scanning electronic and confocal microscopies. A physical characterization of the dehydrated capsules was carried out by determining their moisture content, water activity, particle size, polydispersity index and zeta potential. Determining the induction times and peroxide values provided information about their susceptibility to oxidation. In turn, bacterial stability was analyzed by plate counting before and after freeze-drying and spray-drying, and during storage at 4°C. Spray-dried emulsions had lower Z-sizes and polydispersity indexes, higher induction times and lower peroxide values than the freeze-dried ones, thus resulting better systems to protect L. plantarum CIDCA 83114. In addition, the culturability of spray-dried bacteria did not decrease neither after spray-drying nor up to 60days of storage at 4°C. The results showed that the better physical-chemical stability of spray-dried capsules determined the greater stability of microorganisms. This demonstrates the importance of defining adequate emulsions' formulations for an efficient encapsulation of microorganisms, with promising applications in the development of novel functional foods.

A Combined Approach of Infrared Spectroscopy and Multivariate Analysis for the Simultaneous Determination of Sugars and Fructans in Strawberry Juices During Storage

In this work, a Fourier transform mid-infrared spectroscopy (FTIR)-based method was developed for simultaneously quantifying simple sugars and exogenously added fructooligosaccharides (FOS) in strawberry juices preserved for up to 14 d using nonthermal techniques (geraniol and vanillin+ultrasound). The main spectral differences were observed in the 1200 to 900 cm^-1 region. The presence of FOS was identified by the typical bands at 1134, 1034, and 935 cm^-1 . During storage, a significant decrease of sucrose was concomitant to an increase of glucose and fructose in juices stored without any previous preservation treatment, as determined by high-performance liquid chromatography (HPLC). A principal component analysis was performed on the FTIR spectra corresponding to the different treatments. The groups observed explained more than 94% of the variance and were related to changes in the carbohydrate composition during storage. Then, different partial least square models (PLS) were defined to determine the concentrations of glucose, sucrose, fructose, and those of exogenously added FOS with degrees of polymerization within 3 and 5. The carbohydrates' concentrations determined by HPLC were used as reference method. The models were validated with independent sets of data. The mean of predicted values fitted nicely those obtained by HPLC (correlation and R²  > 0.97), thus supporting the use of the PLS models to monitor the quality of strawberry juices in unknown samples. In conclusion, FTIR spectroscopy appears as an adequate analytical tool to quick assess whether juice formulations meet specifications in terms of authenticity, contamination and/or deterioration.

PRACTICAL APPLICATION

FTIR spectroscopy provided a method potentially transferable to the food industry when associated with the multivariate analysis. The robust 21 PLS models defined in this work provided reliable tools for the rapid monitoring of juices' authenticity and/or deterioration. In this regard, FTIR associated to multivariate analysis enabled the determination of different sugars in a single measurement without the need of pure sugars as standards. This experimental simplicity supports the use of FTIR at the production line, and also contributes to save time in determining carbohydrates' composition and stability, in an environmentally friendly way.

Okara: A Nutritionally Valuable By-product Able to Stabilize Lactobacillus plantarum during Freeze-drying, Spray-drying, and Storage

Okara is a nutritionally valuable by-product produced in large quantities as result of soymilk elaboration. This work proposes its use as both culture and dehydration medium during freeze-drying, spray-drying, and storage of Lactobacillus plantarum CIDCA 83114. Whole and defatted okara were employed as culture media for L. plantarum CIDCA 83114. The growth kinetics were followed by plate counting and compared with those of bacteria grown in MRS broth (control). No significant differences in plate counting were observed in the three media. The fatty acid composition of bacteria grown in whole and defatted okara showed a noticeable increase in the unsaturated/saturated (U/S) fatty acid ratio, with regard to bacteria grown in MRS. This change was mainly due to the increase in polyunsaturated fatty acids, namely C18:2. For dehydration assays, cultures in the stationary phase were neutralized and freeze-dried (with or without the addition of 250 mM sucrose) or spray-dried. Bacteria were plate counted immediately after freeze-drying or spray-drying and during storage at 4°C for 90 days. Freeze-drying in whole okara conducted to the highest bacterial recovery. Regarding storage, spray-dried bacteria previously grown in whole and defatted okara showed higher plate counts than those grown in MRS. On the contrary, freeze-dried bacteria previously grown in all the three culture media were those with the lowest plate counts. The addition of sucrose to the dehydration media improved their recovery. The higher recovery of microorganisms grown in okara after freeze-drying and spray-drying processes and during storage was ascribed to both the presence of fiber and proteins in the dehydration media, and the increase in U/S fatty acids ratio in bacterial membranes. The obtained results support for the first time the use of okara as an innovative matrix to deliver L. plantarum. Considering that okara is an agro-waste obtained in large quantities, these results represent an innovative strategy to add it value, providing a symbiotic ingredient with promising industrial applications in the development of novel functional foods and feeds.

Effect of Galacto-Oligosaccharides: Maltodextrin Matrices on the Recovery of Lactobacillus plantarum after Spray-Drying

In this work maltodextrins were added to commercial galacto-oligosaccharides (GOS) in a 1:1 ratio and their thermophysical characteristics were analyzed. GOS:MD solutions were then used as matrices during spray-drying of Lactobacillus plantarum CIDCA 83114. The obtained powders were equilibrated at different relative humidities (RH) and stored at 5 and 20°C for 12 weeks, or at 30°C for 6 weeks. The Tgs of GOS:MD matrices were about 20-30°C higher than those of GOS at RH within 11 and 52%. A linear relation between the spin-spin relaxation time (T2) and T-Tg parameter was observed for GOS:MD matrices equilibrated at 11, 22, 33, and 44% RH at 5, 20, and 30°C. Spray-drying of L. plantarum CIDCA 83114 in GOS:MD matrices allowed the recovery of 93% microorganisms. In contrast, only 64% microorganisms were recovered when no GOS were included in the dehydration medium. Survival of L. plantarum CIDCA 83114 during storage showed the best performance for bacteria stored at 5°C. In a further step, the slopes of the linear regressions provided information about the rate of microbial inactivation for each storage condition (k values). This information can be useful to calculate the shelf-life of spray-dried starters stored at different temperatures and RH. Using GOS:MD matrices as a dehydration medium enhanced the recovery of L. plantarum CIDCA 83114 after spray-drying. This strategy allowed for the first time the spray-drying stabilization of a potentially probiotic strain in the presence of GOS.

Effect of protective agents and previous acclimation on ethanol resistance of frozen and freeze-dried Lactobacillus plantarum strains

The aim of this work was to study the protective effect of sucrose, trehalose and glutamate during freezing and freeze-drying of three oenological Lactobacillus plantarum strains previously acclimated in the presence of ethanol. The efficiency of protective agents was assessed by analyses of membrane integrity and bacterial cultivability in a synthetic wine after the preservation processes. No significant differences in the cultivability, with respect to the controls cells, were observed after freezing at -80 °C and -20 °C, and pre-acclimated cells were more resistant to freeze-drying than non-acclimated ones. The results of multiparametric flow cytometry showed a significant level of membrane damage after freeze-drying in two of the three strains. The cultivability was determined after incubation in wine-like medium containing 13 or 14% v/v ethanol at 21 °C for 24 h and the results were interpreted using principal component analysis (PCA). Acclimation was the most important factor for preservation, increasing the bacterial resistance to ethanol after freezing and freeze-drying. Freeze-drying was the most drastic method of preservation, followed by freezing at -20 °C. The increase of ethanol concentration from 6 to 10% v/v in the acclimation medium improved the recovery of two of the three strains. In turn, the increase of ethanol content in the synthetic wine led to a dramatic decrease of viable cells in the three strains investigated. The results of this study indicate that a successful inoculation of dehydrated L. plantarum in wine depends not only on the use of protective agents, but also on the cell acclimation process prior to preservation, and on the ethanol content of wine.

Applications of Infrared and Raman Spectroscopies to Probiotic Investigation

In this review, we overview the most important contributions of vibrational spectroscopy based techniques in the study of probiotics and lactic acid bacteria. First, we briefly introduce the fundamentals of these techniques, together with the main multivariate analytical tools used for spectral interpretation. Then, four main groups of applications are reported: (a) bacterial taxonomy (Subsection 4.1); (b) bacterial preservation (Subsection 4.2); (c) monitoring processes involving lactic acid bacteria and probiotics (Subsection 4.3); (d) imaging-based applications (Subsection 4.4). A final conclusion, underlying the potentialities of these techniques, is presented.

Role of S-layer proteins in the biosorption capacity of lead by Lactobacillus kefir

The role of S-layer proteins (SLP) on the Pb(2+) sequestrant capacity by Lactobacillus kefir CIDCA 8348 and JCM 5818 was investigated. Cultures in the stationary phase were treated with proteinase K. A dot blot assay was carried out to assess the removal of SLP. Strains with and without SLP were exposed to 0-0.5 mM Pb(NO3)2. The maximum binding capacity (q max ) and the affinity coefficient (b) were calculated using the Langmuir equation. The structural effect of Pb(2+) on microorganisms with and without SLP was determined using Raman spectroscopy. The bacterial interaction with Pb(2+) led to a broadening in the phosphate bands (1,300-1,200 cm(-1) region) and strong alterations on amide and carboxylate-related bands (νCOO(-) as and νCOO(-) s). Microorganisms without SLP removed higher percentages of Pb(2+) and had higher q max than those bearing SLP. Isolated SLP had much lower q max and also removed lower percentages of Pb(2+) than the corresponding whole microorganisms. The hydrofobicity of both strains dramatically dropped when removing SLP. When bearing SLP, strains do not expose a large amount of charged groups on their surfaces, thus making less efficient the Pb(2+) removal. On the contrary, the extremely low hydrofobicity of microorganisms without SLP (and consequently, their higher capacity to remove Pb(2+)) can be explained on the basis of a greater exposure of charged chemical groups for the interaction with Pb(2+). The viability of bacteria without SLP was not significantly lower than that of bacteria bearing SLP. However, microorganisms without SLP were more prone to the detrimental effect of Pb(2+), thus suggesting that SLP acts as a protective rather than as a sequestrant layer.

Effect of physical properties on the stability of Lactobacillus bulgaricus in a freeze-dried galacto-oligosaccharides matrix

The ability of galacto-oligosaccharides (GOS) to protect Lactobacillus delbrueckii subsp. bulgaricus upon freeze drying was analyzed on the basis of their capacity to form glassy structures. Glass transition temperatures (T(g)) of a GOS matrix at various relative humidities (RH) were determined by DSC. Survival of L. bulgaricus in a glassy GOS matrix was investigated after freezing, freeze drying, equilibration at different RHs and storage at different temperatures. At 32 °C, a drastic viability loss was observed. At 20 °C, the survival was affected by the water content, having the samples stored at lower RHs, the highest survival percentages. At 4°C, no decay in the cells count was observed after 45 days of storage. The correlation between molecular mobility [as measured by Proton nuclear magnetic resonance (¹H NMR)] and loss of viability explained the efficiency of GOS as cryoprotectants. The preservation of microorganisms was improved at low molecular mobility and this condition was obtained at low water contents and low storage temperatures. These results are important in the developing of new functional foods containing pre and probiotics.

Lipid hydroperoxide and markers of renal disease susceptibility in African-Caribbean and Caucasian patients with Type 2 diabetes mellitus

AIMS

The reasons for the increased incidence of diabetic nephropathy in African-Caribbean compared with Caucasian subjects are poorly understood. Increased oxidative stress is linked to the development of endothelial dysfunction and histological abnormalities associated with diabetic renal disease. Therefore, it was assessed whether a marker of oxidative stress, lipid hydroperoxide (LOOH) and endothelial damage, von Willebrand factor (vWF) varied according to ethnic origin in the presence or absence of early diabetic nephropathy.

METHODS

Eighty-eight patients with Type 2 diabetes mellitus of African-Caribbean or Caucasian origin without a history of cardiovascular disease or clinical proteinuria were studied. Patients were classified as having microalbuminuria or normal albumin excretion. Fasting plasma vWF and LOOH were measured by an inhouse enzyme-linked immunoassay and ferrous oxidation with xylenol orange (FOX) assay, respectively. The relationship of LOOH to urinary albumin status, the metabolic disturbances of diabetes, blood pressure and ethnic origin were assessed using multivariate analysis.

RESULTS

Compared with Caucasian patients those of African-Caribbean origin had higher systolic blood pressure and HDL-cholesterol (157.8 +/- 17.0 vs. 147.8 +/- 24.4, P = 0.041 and 1.6 +/- 0.4 vs. 1.3 +/- 0.5, P = 0.018) but lower total triglycerides (1.3 +/- 0.8 vs. 1.9 +/- 1.1, P = 0.008). LOOH was significantly higher in the African-Caribbean patients compared with Caucasians (5.98 +/- 2.49 vs. 4.49 +/- 2.19, P = 0.006). vWF tended to be higher in microalbuminuric patients but showed no variation with ethnicity. In logistic regression analysis, LOOH was the only independent predictor of a raised albumin excretion rate (P = 0.008). In multiple regression analysis, African-Caribbean ethnicity (P = 0.020) HDL-cholesterol (P = 0.036), total triglycerides (P = 0.002) and a raised albumin excretion rate (P = 0.002) were independent predictors of LOOH.

CONCLUSIONS

In this group of Type 2 diabetic patients an increase in LOOH is associated with abnormal urinary albumin excretion. African-Caribbean origin was a determinant of LOOH independently of microalbuminuria. It is postulated that increased oxidative stress is of pathophysiological significance in accelerating the development of renal disease in African-Caribbean patients.

Functional link between ataxia-telangiectasia and Nijmegen breakage syndrome gene products

Ataxia-telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) are recessive genetic disorders with susceptibility to cancer and similar cellular phenotypes. The protein product of the gene responsible for A-T, designated ATM, is a member of a family of kinases characterized by a carboxy-terminal phosphatidylinositol 3-kinase-like domain. The NBS1 protein is specifically mutated in patients with Nijmegen breakage syndrome and forms a complex with the DNA repair proteins Rad50 and Mrel1. Here we show that phosphorylation of NBS1, induced by ionizing radiation, requires catalytically active ATM. Complexes containing ATM and NBS1 exist in vivo in both untreated cells and cells treated with ionizing radiation. We have identified two residues of NBS1, Ser 278 and Ser 343 that are phosphorylated in vitro by ATM and whose modification in vivo is essential for the cellular response to DNA damage. This response includes S-phase checkpoint activation, formation of the NBS1/Mrel1/Rad50 nuclear foci and rescue of hypersensitivity to ionizing radiation. Together, these results demonstrate a biochemical link between cell-cycle checkpoints activated by DNA damage and DNA repair in two genetic diseases with overlapping phenotypes.

Insulin and IGFs induce apoptosis in chick embryo retinas deprived of L-glutamine

In chick embryo retinas, cultured in serum-free medium lacking L-glutamine, IGF-I, IGF-II and insulin induced apoptotic DNA fragmentation and cell death, IGF-I being the most efficacious compound. The apoptotic effect, which was particularly evident in retinas removed from 7-day-old chick embryos, declined with the age of the embryos and disappeared after day 11. Apoptosis appeared after a time lag of 8 h and then increased with time up to 16 h. Cycloheximide, an inhibitor of protein synthesis, was capable of entirely abolishing apoptotic cell death. The effect induced by IGFs or insulin was suppressed by the addition of glutamine. Cytokine-mediated apoptosis was also observed after withdrawal of phosphate. We suggest that IGFs or insulin may produce, in retinas cultured in medium lacking L-glutamine or phosphate, a conflict of signals that could be lethal for retinal cells.

The effects of TGF-beta1 on chick embryo retina development in vitro

This paper studies the effect exerted by TGF-beta1 on the development of chick embryo retina cultured in vitro. The addition of TGF-beta1 to retinal explants inhibited DNA synthesis, measured as 3H-thymidine incorporation into trichloroacetic acid-insoluble fraction, while it increased both wet weight and protein content, in particular that of extracellular matrix proteins. Lastly, in explants treated with TGF-beta1 an increment in the level of fibronectin was demonstrated by means of Western blotting analysis.

Differentiation of Y79 cells induced by prolonged exposure to insulin

Y79 human retinoblastoma cells are known to contain receptors for both insulin and insulin-like growth factors (IGFs), to produce these cytokines and release them in the culture medium. Previously we have demonstrated that IGFs and insulin stimulate Y79 cell proliferation through the involvement of type I IGF receptor and Insulin Receptor Substrate 1 (IRS-1). This paper studies the effect of prolonged exposure to insulin on Y79 cells. Cells grown for 10 days in the presence of insulin were reseeded and incubated once more with insulin. In the reseeded cells proliferation lowered and morphological changes appeared. After 10 days of reseeding, cells stopped proliferating and showed long ramifying neurite processes and varicosities consistent with neuronal differentiation. Morphological differentiation was accompanied by a marked increase in the content of total protein and in that of tubulin, the major protein constituent of microtubules, a marked increase in the content of specialized protein markers of dopaminergic and cholinergic differentiation (dopamine beta-hydroxylase and choline acetyltransferase activities, respectively); a contemporaneous decrease in the content of glial fibrillary acidic protein (GFAP), a specific marker of glial cells, was also observed. Our results demonstrate that prolonged exposure to insulin induces Y79 cells to differentiate into a neuronal-like phenotype. At this moment it is not possible to establish the mechanism by which insulin induces this differentiative effect.

Changes in protein composition during chick embryo retina development

Two dimensional gel electrophoresis was employed to analyse the protein composition of chick embryo retina during "in ovo" development in order to individuate some components which are typical of different stages of growth. The study of protein composition of 7-day-old chick embryo retinas revealed the presence of about eighty different soluble components. In four of these proteins the staining intensity decreased during retina development. One of these components, of 35 KD with an isoelectric point of about 5.15, was partially purified by means of preparative isoelectric focusing. Other components, which were absent at day 7 appeared during the second week of development and were clearly visualised at day 16. These results were also compared with those obtained by means of 2DGE performed on liver and brain of chick embryo at day 7 and 16 of development.

Insulin-like growth factors in chick embryo retina during development

Evidence exists supporting an important role for insulin-like growth factors (IGFs) during fetal growth. In the present report we performed studies to define whether developing chick retina contains IGFs and whether IGFs play a role in the growth of this tissue. We have shown that both IGF-I and IGF-II are present in chick embryo retina throughout development (7th-18th day). The highest values, when expressed as ng/g of tissue, were found in the youngest retinas studied (7th-9th day) and at 16th-18th day of development. During whole development the content of IGF-II was about two to three times higher than that ascertained for IGF-I. The tissue also contains cell-surface binding for IGFs. However, the developmental pattern of IGF-I binding was quite different from that found for IGFs, showing the highest values during the second week of development. Competitive studies showed that this receptor has a high affinity for IGF-I, a lower affinity for IGF-II, and a very much lower affinity for insulin. Also anti-IGF-I receptor antibody (alpha IR3) inhibited 125I-labeled IGF-I binding to the receptor. Such results indicate the presence of type I IGF receptor in chick embryo retina. Affinity labeling experiments have confirmed this hypothesis. We have also shown that cultured retinal explants contain, synthesize and release into the medium appreciable amounts of IGFs. Both exogenous IGF-I and IGF-II added to the culture medium stimulated DNA synthesis of retinal explants. Evidence that the retinas produce IGFs and possess IGF-IR together with the growth-promoting effect of IGFs suggests that these factors play an important role as regulators of retinal growth.