Lactic Acid Bacteria Cells Research Articles

Experimental study of preservation of probiotic lactic acid bacteria in freeze-dried yogurts

This article presents research results on the relationship between the survival rate of lactic acid bacteria and the content of neurotransmitters in freeze-dried yogurt and yogurt with the addition of 15% pumpkin puree as a cryoprotectant. The decrease (p < 0.05) in the survival rate of lactic acid bacteria up to 52% and a predominance of norepinephrine (660–680 pmol/g) was noted in yogurt without cryoprotectant. In yogurt containing pumpkin puree, the survival rate of lactic acid bacteria was 25–28% higher. The content of serotonin and dopamine in freeze-dried yogurt with puree increased (p < 0.05) to 120–130 and 350–360 pmol/g, respectively. The use of pumpkin puree affects the content of neurotransmitters and allows the preservation of lactic acid bacteria cells if a sufficiently high primary drying temperature is used. The higher primary drying temperature and the use of cryoprotectant results in decreased (p < 0.05) drying time, energy savings, and an average of 20% in carbon footprint.

고초균-젖산균의 순차적 복합 발효를 통한 복합 기능성 물질 함유 황칠나무 추출물의 생산

The production of poly-γ-glutamic acid (γ-PGA) and γ-aminobutyric acid (GABA) was optimized by serial fermentation of Dendropanax morbiferus extract (DME) using Bacillus subtilis HA and Lactobacillus plantarum KS2020. The 1st alkaline fermentation was performed on 60% DME including 2% glucose and 10% monosodium ʟ-glutamate (MSG) as a precursor. The 1st fermented DME had 57 mg% tyrosine. Consequently, the 2nd lactic acid fermentation for 5 days increased the tyrosine content of 106 mg%. The mucilage containing γ-PGA showed a high content of 3.50% on the first day of alkaline fermentation and then increased to 4.10% after 2 days. The precursor (MSG) remaining in the 1st fermented DME was efficiently converted to GABA by the 2nd lactic acid fermentation in the presence of 5% skim milk, 1.5% glucose and 0.5% yeast extract, resulting in the production of 18.29 mg/mL GABA. The viable cells of lactic acid bacteria increased and indicated 9.49 log CFU/mL on the fermentation for 5 days, and the acidity of co-fermented DME indicated the highest value of 1.55%. Conclusively, the serial fermented DME has multi-functional ingredients containing γ-PGA, GABA, peptides and probiotics.

Production of lactic acid wort-based beverage with raspberry seed oil addition under static and dynamic conditions

Wort-based beverages produced by lactic acid fermentation showed high nutritional value and functional properties but their flavor was not well accepted by consumers. Therefore, raspberry (Rubus idaeus L) seed oil in concentration of 0.0375% (v/v) was used in order to improve beverage flavor and to increase its biological value. Fermentation was carried out in bottles (static conditions) and in a stirred tank bioreactor (dynamic conditions) at 25°C. The effect of raspberry seed oil addition was investigated by measuring the content of lactic acid bacteria cells, the pH, the phenolic compounds and the antioxidant activity of the beverages with raspberry seed oil addition and the control sample without oil addition. Results showed that stirring increased fermentation rate but led to a decrease in the phenolic compounds content and the antioxidant activity of the beverages produced. Nevertheless, all beverages can be classified as functional because the concentration of lactic acid bacteria was over 107 cells/mL. Our results indicated that functional lactic acid wort-based beverage with improved biological value and flavour can be produced in static fermentation by adding 0.0375% raspberry seed oil.

THE INFLUENCE OF NUTRIENTS AND LACTULOSE PREBIOTIC ON THE FERMENTATION PROCESSES IN THE TECHNOLOGY OF RECEIVING A FUNCTIONAL FOOD PRODUCT WITH AN INCREASED TITER OF VIABLE LACTIC ACID BACTERIA

A study of the influence of biologically active substances (fat-soluble vitamins, omega-3 fatty acids and vitamin D, as well as water-soluble vitamin C), prebiotic lactulose on the titer of viable cells of lactic acid bacteria was carried out for the further use of the obtained research results in the biotechnology of functional food products, obtained thanks to the successful course fermentation processes. Experiments have proven the expediency of using biologically active substances as stimulators of the growth of lactic acid bacteria, which contribute to the increase of biomass and support of their vital activity for 192 hours. Research has established that at the end of the experiment (192 hours), the highest titer of lactic acid bacteria was recorded in samples 1, 2, 3, 4, to which the prebiotic lactulose was added in the amount of 1, 3, 5 and 7 %, respectively. This is due to the fact that the prebiotic acts as a specific substrate that is used by the symbiosis of pure cultures of lactic acid bacteria for a long time, unlike milk sugar. Analyzing the obtained data, it is indicated that thanks to the addition of fat-soluble nutrients omega-3 fatty acids and vitamin D, as well as water-soluble vitamin C, there is a significant increase in the titer of viable cells of probiotic cultures at 6 and 24 hours of the experiment, although at the end of the experiment (by 192 hour) in these samples, an insignificant decrease of this indicator was recorded — from 10 to 8.9 log cells/ml. In the control sample (without the addition of biologically active substances and lactulose prebiotic), a significant decrease in the titer of viable cells of lactic acid bacteria was noted, compared to the test samples to which nutrients were added. The titer of lactic acid bacteria cells in the control sample was reduced by 192 hours from 8.5 to 5.5 log cells/ml. It is recommended to use the studied nutrients in the indicated concentrations to stimulate the growth and maintain the viability of lactic acid bacteria cultures in the technology of production of functional food products.

Aflatoxin M1 removal from milk using activated carbon and bentonite combined with lactic acid bacteria cells

This study was planned to explore the AFM1‐reducing potential of various heat and acid‐killed lactic acid bacteria (LAB), activated carbon and bentonite (BENT) in milk contaminated with 0.5 μg/L AFM1 and their impact on milk composition. A negligible impact was observed on milk composition with AC while exhibiting a higher AFM1 removal (78.2%) than bentonite (35.8%). Their combination with LAB cells increased AFM1 decontamination for most of the treatments, with highest AFM1 removal (97.6%) exhibited by a treatment involving 0.1% AC and acid‐killed cells of L. cremoris. The results of this study indicate that LAB cells associated with the adsorbents tested are highly effective in reducing milk AFM1 content.

Physicochemical, sensory, and antioxidant characteristics of stirred-type yogurt enriched with Lentinula edodes stipe powder.

The Lentinula edodes stipe (LES), a by-product of L. edodes fruiting body processing, is rich in dietary fiber, protein, and polysaccharides, which can be served as the functional ingredient in dairy products. In this study, stirred yogurts fortified with 1%, 2%, and 3% LES were prepared, and the effects of LES on the changes in color, pH, titratable acidity (TA), viable lactic acid bacteria (LAB) cells, syneresis, viscosity, texture, and antioxidant activity of the flavored yogurt were monitored at the beginning and the end of storage. The LES decreased the lightness, increased the red-green color values and yellow-blue color values, decreased the pH values, and increased the contents of TA, the viable LAB cells, and the antioxidant activity of yogurt samples in a dose-dependent manner. The addition of LES showed double-edged effects on the texture of yogurt, which significantly reduced firmness and viscosity but decreased the syneresis. Compared with plain yogurt, the 2% LES-fortified yogurt exhibited similar index values of texture parameters and higher scores of the appearance, fermented odor, taste quality, and overall acceptance, suggesting that this might be the optimal dose for industrial production. After cold storage for 28 days, pH values of all yogurt samples further decreased with increasing of TA. Interestingly, syneresis of LES-fortified yogurt decreased and the viable LAB cells and antioxidant activity of 3% LES-fortified yogurt slightly decreased. Therefore, LES is beneficial to improve physicochemical, sensory, and antioxidant properties of yogurt, which has the potential to be used in functional dairy products.

Profil gelatinisasi, karakteristik mikrobiologi dan sifat fungsional pati jagung ketan terfermentasi [Gelatinization profile, microbiological characteristics and funtional properties of fermented waxy corn starch

Waxy corn (AJU1) is widely cultivated in Gorontalo Province, but its utilization is limited to corn on cobs. A potential diversified product of processed waxy corn to be developed is waxy corn starch. One simple method to improve the functional properties of waxy corn starch is fermentation. This study aimed to determine the effect of different fermentation conditions and fermentation times on the gelatinization profile and functional properties of waxy corn starch. The research method used a completely randomized factorial design with two treatment factors namely fermentation conditions (aerobic and anaerobic) and fermentation time (3, 6, and 9 days). Results showed that the fermentation conditions significantly affected property of waxy corn starch. During fermentation, there was a change in the number of cells of lactic acid bacteria, yeast, and mold. The gelatinization profile of fermented waxy corn starch was to have resistant to stirring and high temperatures and reduced its retrogradation tendency. The fermentation process also changed the functional properties of glutinous corn starch, namely an increase in solubility, swelling, and acidity (decrease in pH).Keywords: aerobic, anaerobic, fermentation, starch, glutinous corn [AJU1]

INFLUENCE OF BIOLOGICALLY ACTIVE SUBSTANCES AND LACTULOSE PREBIOTICS ON THE FERMENTATION PROCESSES WITH THE PARTICIPATION OF LACTIC ACID BACTERIA

A study of the influence of biologically active substances (fat-soluble vitamins, omega-3 fatty acids and vitamin D, as well as water-soluble vitamin C), prebiotic lactulose on the titer of viable cells of lactic acid bacteria was carried out for the further use of the obtained research results in the biotechnology of functional food products, obtained thanks to the successful course fermentation processes. Experiments have proven the expediency of using biologically active substances as stimulators of the growth of lactic acid bacteria, which contribute to the increase of biomass and support of their vital activity for 192 hours. Research has established that at the end of the experiment (192 hours), the highest titer of lactic acid bacteria was recorded in samples 1, 2, 3, 4, to which the prebiotic lactulose was added in the amount of 1, 3, 5 and 7 %, respectively. This is due to the fact that the prebiotic acts as a specific substrate that is used by the symbiosis of pure cultures of lactic acid bacteria for a long time, unlike milk sugar. Analyzing the obtained data, it is indicated that thanks to the addition of fat-soluble nutrients omega-3 fatty acids and vitamin D, as well as water-soluble vitamin C, there is a significant increase in the titer of viable cells of probiotic cultures at 6 and 24 hours of the experiment, although at the end of the experiment (by 192 hour) in these samples, an insignificant decrease of this indicator was recorded — from 10 to 8.9 log cells/ml. In the control sample (without the addition of biologically active substances and lactulose prebiotic), a significant decrease in the titer of viable cells of lactic acid bacteria was noted, compared to the test samples to which nutrients were added. The titer of lactic acid bacteria cells in the control sample was reduced by 192 hours from 8.5 to 5.5 log cells/ml. It is recommended to use the studied nutrients in the indicated concentrations to stimulate the growth and maintain the viability of lactic acid bacteria cultures in the technology of production of functional food products.

Metabolites changes of a low-temperature and low-salt fermented Chinese kohlrabi during fermentation based on non-targeted metabolomic analysis

A low-temperature and low-salt industrially fermented Chinese kohlrabi (LSCK) was developed in this study, with the salt usage decreased by approximately 70% compared to the traditional high-salt fermented Chinese kohlrabi (HSCK). The differences in physicochemical properties, metabolites and overall flavors during LSCK fermented for 0, 45 and 90 days (d) were analyzed by gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS), electronic nose (E-nose) and other techniques. The results showed that the total acid content increased significantly from 3.68 to 8.59 g/kg. However, the protein content significantly decreased from 2.52/100 to 0.66 g/100 g. The number of lactic acid bacteria cells increased significantly from 3.69 to 4.46 log10CFU/g. Based on multivariate statistical analysis, 21, 14, and 15 differential metabolites were identified in the three treatment groups A1 (0 and 45 days), A2 (45 and 90 days), and A3 (0 and 90 days) respectively (VIP &amp;gt; 1, p &amp;lt; 0.05, |log2FC| ≥ 1.1). Carbohydrates, sugar alcohols, amino acids and their derivatives were the main differential metabolites in the LSCKs fermented for different periods. Aminoacyl−tRNA biosynthesis and glycine, serine and threonine metabolism pathways significantly correlated with the differential metabolites based on Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis (p &amp;lt; 0.05). Furthermore, the overall odors were significantly different among the LSCKs with different fermentation periods, as detected by E-nose. The present study describes the change trend of metabolites during LSCK fermentation and elucidates important metabolic pathways in LSCK, providing a theoretical basis for the target regulation of functional metabolites in kohlrabi and the optimization of LSCK processing.

Investigation of the biochemical activity of starter compositions enriched with propionic acid bacteria on various raw materials

Currently, there is a need to develop an assortment of low-lactose or lactose-free dairy products and plant-based products due to an increase in the number of consumers with lactase deficiency, allergic to cow's milk components, cholesterol problems, etc. For the development of plant and lactose-free bioproducts, it is possible to use various starter cultures enriched with probiotics. Various starter cultures were used in the work, propionic acid bacteria were used as a probiotic. The objects were lactose-free milk and vegetable bases: rice milk, oat milk and coconut milk; the control was selected milk. A comparative analysis of the fermentation process of various compositions of starter cultures enriched with propionic acid bacteria on various raw materials was carried out. The duration of fermentation of vegetable raw materials is 8-10 hours, the acid-forming activity of combined starter cultures is quite high. The number of viable cells of lactic acid and propionic acid bacteria in the obtained bioproducts has a high value and amounts to 107-108 K.O.E. /cm3. This confirms that the nutrient medium for the cultivation of selected starter compositions is favorable, the microflora of the starter composition develops harmoniously. Lactic acid microorganisms and propionic acid bacteria make it possible to obtain fermented biological products with a variety of taste characteristics inherent in a certain type of raw material. According to the results of the research, the developed starter compositions meet the requirements for starter cultures, have valuable technological properties that allow expanding the range of plant and lactose-free biological products.

Exopolysaccharides from Lactic Acid Bacteria: A Review on Functions, Biosynthesis and Applications in Food Industry

Lactic acid bacteria are the substantial source for producing polysaccharides used in technological applications as thickeners and viscosifiers in the food industry. A broad variety of lactic acid bacteria species secrete structurally diverse exopolysaccharides that contribute to their surface attachment, protection against abiotic or biotic stress factors and nutrient uptake. The exopolysaccharides are produced naturally during fermentation process by living lactic acid bacteria cells and accepted as postbiotic for these metabolites having various physiological health-promoting effects. Exopolysaccharide producer lactic acid bacteria encode a great number of enzymes and regulatory proteins involved exopolysaccharide biosynthesis process. This process is a complex and occurs through presence of multiple genes. However, it is crucial the understanding of structure, composition, function, chemical, and physical properties of exopolysaccharides which vary from one type of bacteria to another via chemical analysis methods. In this review, the use of lactic acid bacteria exopolysaccharides, their structures, genetic modules and biosynthesis, and the use of exopolysaccharides derived from lactic acid bacteria in the food industry are described, discussed and focused on recent developments.

Mitigation of aflatoxin M1 in milk by the magnetized Fe3O4 lactic acid bacteria cells: a response surface methodology (RSM) study

ABSTRACT The current work aimed to optimise aflatoxin M1 (AFM1) removal from milk by magnetic inactivated lactic acid bacteria (LAB) adsorbent using response surface methodology (RSM). In this research, the ability of 5 strains of LAB was evaluated for AFM1 removal. Lactobacillus rhamnosus, which indicated the highest adsorption efficiency compared to other strains (p < 0.05), was selected. The obtained LAB was modified using Fe3O4 particles for the generation of magnetic inactivated LAB adsorbent, which was further characterised by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometer. The results indicated that L. rhamnosus cells were successfully functionalised and modified by Fe3O4 particles. A central composite design (CCD) was applied to investigate the effect of variables including time (5–125 min), temperature (3–23°C), initial AFM1 concentration (0.1–2.1 μg L-1), and fat (0–3.6%) on AFM1 removal from milk using synthesised adsorbent. According to the RSM model, the optimal adsorption conditions for the second-order model were observed at 73.60 min, the temperature of 17.82°C, AFM1 concentration of 1.598 µg L−1, and fat content of 0.9% leading to the maximum removal efficiency of 56.92%. Hence, the magnetic inactivated LAB adsorbent synthesised using this approach can be an efficient easy-to-separate adsorbent in removing AFM1 from milk. The main functional groups involved in AFM1 removal were carboxyl, amide, and hydroxyl/amino groups. Moreover, the synthesised adsorbent had superparamagnetic behaviour and could be rapidly separated from aqueous solutions. In conclusion, the current study presented a novel method for the efficient adsorption of AFM1 to improve the safety figures of milk.

Taxonomic structure of bacterial communities in sourdoughs of spontaneous fermentation.

The article is devoted to the study of the microbiome of spontaneously fermented sourdoughs. The aim of the work was to study the inf luence of the technological parameters of sourdough propagations on the taxonomic structure of the microbiome of spontaneously fermented sourdoughs. Two spontaneously fermented sourdoughs were studied: dense rye sourdough and liquid rye sourdough, both prepared using the same batch of peeled rye f lour. To study the taxonomic structure of the sourdough microbiome in dynamics, the method of high-throughput sequencing of 16S rRNA gene fragments of microorganisms was used. It was shown that the technological parameters of sourdough (humidity, temperature) do not affect the taxonomic composition of the microbiome of dense rye or liquid rye sourdough at the phylum/class/genus level. It was found that during the f irst three days of propagations, bacteria from the phyla Proteobacteria and Firmicutes dominated in the microbial community. In the phylum Proteobacteria, microorganisms from the order Enterobacterales took a large share, which persisted for three days of backslopping. The phylum Firmicutes was represented by lactic acid bacteria of the genera Weissella, Lactobacillus, Leuconostoc, Pediococcus, Lactococcus. It was established by classical microbiological methods that after a day of fermentation, the number of lactic acid bacteria cells was signif icantly higher in liquid rye sourdough compared to dense one. However, with further propagation of sourdoughs, the number of cells was comparable, while signif icant changes occurred at the level of genera and species. It was shown that as the relative number of lactic acid bacteria of the genus Lactobacillus increased, a gradual displacement of the coccal forms of Lactococcus, Leuconostoc, Weissella, Pediococcus happened. With further propagation of sourdough after 10 days, the position of the dominant groups of bacteria was occupied by representatives of the phylum Firmicutes, lactic acid bacteria of the genus Lactobacillus. The inf luence of the mode and parameters of the sourdough on the species composition of lactobacilli, which demonstrated a low bacterial diversity, is shown. In the f irst three days of propagations, lactobacilli L. curvatus, L. brevis, and Lactiplantibacil- lus sp. dominated in both sourdoughs. After a month of backslopping, Fructilactobacillus sanfranciscensis and Companilactobacillus sp. dominated in dense rye sourdough, and L. pontis dominated in liquid rye sourdough

IMPROVEMENT OF BRUSH CHEESE RECIPES BRYNZA TYPE WITH HIGH TITER OF LACTIC BACTERIA

Fermented milk products made by fermenting milk with lactic acid bacteria play an important role in children's nutrition. In particular, brine cheese type "Brynza" has other advantages, including efficient use of raw materials, the ability to sell cheese without maturation or with a short maturation period (not more than 14 days), rapid return on investment. Optimization of the recipe and selection of raw materials for the production of young pickled cheeses with high titers of lactic acid bacteria is an urgent task today in the development of medium-sized businesses and craft industries in Ukraine. It was found that the increase in acidity of the product is influenced by the addition of different composition of starter cultures (Lactococcus lactis subsp. Lactis; Lactococcus lactis subsp. Cremoris; Lactococcus lactis subsp. Lactis (bio diacetylactis); Leuconostoc mesenteroides subsp. effects on acid shift. It was found that organoleptic parameters do not significantly depend on the use of milk pasteurization process, so the use of an additional stage of milk preparation will contribute not only to the profitability of the recipe and raw materials, but also to potential demand for brine cheese "Brynza". It was found that the largest number of living cells of lactic acid bacteria is characteristic of cheese samples made with additional inoculation of starter cultures. Recommendations are given for the use of recipes and the choice of raw materials for the production of brine cheese type "Brynza" with a high titer of lactic acid bacteria.

Production of a Potentially Probiotic Product for Animal Feed and Evaluation of Some of Its Probiotic Properties.

Nowadays, probiotics have been proposed for substituting antibiotics in animal feed since the European Union banned the latter compounds in 2006 to avoid serious side effects on human health. Therefore, this work aimed to produce a probiotic product for use in animal feed by fed-batch fermentation of whey with a combination of kefir grains, AGK1, and the fermented whole milk used to activate these kefir grains. The probiotic culture obtained was characterized by high levels of biomass (8.03 g/L), total viability (3.6 × 108 CFU/mL) and antibacterial activity (28.26 Activity Units/mL). Some probiotic properties of the probiotic culture were investigated in vitro, including its survival at low pH values, under simulated gastrointestinal conditions, after freezing in skim milk at −20 °C, and in the commercial feed during storage at room temperature. The viable cells of lactic and acetic acid bacteria and yeasts exhibited higher tolerance to acidic pH and simulated gastrointestinal conditions when the cells were protected with skim milk and piglet feed, compared with washed cells. The results indicated the feasibility of producing a probiotic product at a low cost with a potential application in animal feed.

Biotechnology of freeze-dried sour clotted milk with pumpkin and topinambour

The research aimed to substantiate rational parameters of the vacuum freeze-dried sour clotted milk biotechnology. It was revealed that the use of novel starters containing cultures that can synthesize exopolysaccharides provided a symbiotic relationship of fermented milk system particles and prevented its disintegration in freeze dry products rehydration. This was confirmed by microscopic analysis of histological preparations prepared from rehydrated samples of freeze-dried sour clotted milk. It was shown that the addition of topinambour powder resulted in production of freeze-dried sour clotted milk with organoleptic parameters not meeting established requirements. Adding freeze-dried pumpkin powder to the sour clotted milk formulation contributes to increased survival of lactic acid bacteria cells during vacuum freeze drying by an order of magnitude in average. It has been shown that the combined use of novel starter cultures and prebiotics results in production of freeze-dried sour clotted milk with required quality parameters.

Co-Microencapsulated Black Rice Anthocyanins and Lactic Acid Bacteria: Evidence on Powders Profile and In Vitro Digestion.

Two multi-functional powders, in terms of anthocyanins from black rice (Oryza sativa L.) and lactic acid bacteria (Lactobacillus paracasei, L. casei 431®) were obtained through co-microencapsulation into a biopolymer matrix composed of milk proteins and inulin. Two extracts were obtained using black rice flour as a raw material and hot water and ethanol as solvents. Both powders (called P1 for aqueous extract and P2 for ethanolic extract) proved to be rich sources of valuable bioactives, with microencapsulation efficiency up to 80%, both for anthocyanins and lactic acid bacteria. A higher content of anthocyanins was found in P1, of 102.91 ± 1.83 mg cyanindin-3-O-glucoside (C3G)/g dry weight (DW) when compared with only 27.60 ± 17.36 mg C3G/g DW in P2. The morphological analysis revealed the presence of large, thin, and fragile structures, with different sizes. A different pattern of gastric digestion was observed, with a highly protective effect of the matrix in P1 and a maximum decrease in anthocyanins of approximatively 44% in P2. In intestinal juice, the anthocyanins decreased significantly in P2, reaching a maximum of 97% at the end of digestion; whereas in P1, more than 45% from the initial anthocyanins content remained in the microparticles. Overall, the short-term storage stability test revealed a release of bioactive from P2 and a decrease in P1. The viable cells of lactic acid bacteria after 21 days of storage reached 7 log colony forming units (CFU)/g DW.

Functionalisation of rice bran assisted by ultrasonication and fermentation for the production of rice bran–lingonberry pulp‐based probiotic nutraceutical

SummaryA probiotic nutraceutical based on functionalised rice bran (RB) supplemented with lingonberry (Vaccinium vitis‐idaea L.) pulp (LP) at various levels (10–50 g/100 g d.w.) was developed. Prior to immobilisation of lactic acid bacteria (LAB) cells, RB‐LP matrix was structured by ultrasound (US) (850 kHz; power 160 W) for 20 min at 40 °C. Xanthan gum and sodium alginate were used for the stabilisation of RB‐LP matrix. Survival and fermentative activity of the immobilised LAB cells was studied by monitoring pH, cell number, antimicrobial activity, lactic acid and acetic acid production. US treatment increased by 17.5% soluble dietary fibre (SDS) contents in RB but reduced on average by 49.9% hyperoside, quercetin, quercitrin and coumaric acid contents in LP material. RB substrate supplemented with LP (20–50 g/100 g d.w.) resulted in higher antimicrobial activity against Escherichia coli, Salmonella typhimurium and Staphylococcus aureus for Lactobacillus brevis, and against Bacillus cereus and Staphylococcus aureus for Pediococcus acidilactici. RB‐LP matrix stabilised with alginate–xanthan and alginate maintained 8.09–8.67 log CFU g−1 live cells of immobilised L. brevis after 7 weeks of storage at 4 °C. In the case of protection under simulated in vitro digestion conditions, RB‐LP gels with sodium alginate demonstrated the highest cell survival with 4.25 CFU g−1 viable cells remaining in the product and 5.23 log CFU g−1 live cells in the digestion medium.

In English

A promising direction for long-term storage of cells at relatively high temperatures may be their encapsulation with nanoscale biologically inert materials capable of creating a shell around microdroplets of a cell suspension, which, on the one hand, provides the possibility of gas exchange between the suspension and the external environment, and on the other hand, inhibits the processes of cell life, so transferring them to a state close to suspended animation. The method of low-temperature 1H NMR spectroscopy was used to study the process of hydration of lactobacilli, the effect of a weakly polar organic medium on it and the encapsulation of cells with silica. The aim of this work was to study the hydration of cell suspensions and the viability of lactic acid bacteria cells encapsulated with silica and the penetration possibility of such an active substance as trifluoroacetic acid into them. As a result of the studies carried out, it has been shown that the spectral parameters of water in concentrated cell suspensions of lactic acid bacteria strongly depend on the concentration of the suspension, which is probably associated with the possibility of the formation of a stable cell gel, which can be encapsulated by silica particles without its destruction in both air and a chloroform medium with addition of trifluoroacetic acid. The radial distribution curves of non-freezing water clusters have two maxima corresponding to R = 2 and 20–100 nm. The contribution to the distribution of the second maximum increases with increasing water concentration.

Damage-free light-induced assembly of intestinal bacteria with a bubble-mimetic substrate

Rapid evaluation of functions in densely assembled bacteria is a crucial issue in the efficient study of symbiotic mechanisms. If the interaction between many living microbes can be controlled and accelerated via remote assembly, a cultivation process requiring a few days can be ommitted, thus leading to a reduction in the time needed to analyze the bacterial functions. Here, we show the rapid, damage-free, and extremely dense light-induced assembly of microbes over a submillimeter area with the “bubble-mimetic substrate (BMS)”. In particular, we successfully assembled 104–105 cells of lactic acid bacteria (Lactobacillus casei), achieving a survival rate higher than 95% within a few minutes without cultivation process. This type of light-induced assembly on substrates like BMS, with the maintenance of the inherent functions of various biological samples, can pave the way for the development of innovative methods for rapid and highly efficient analysis of functions in a variety of microbes.