Preservation of viability and anti-Listeria activity of lactic acid bacteria, Lactococcus lactis and Lactobacillus paracasei, entrapped in gelling matrices of alginate or alginate/caseinate

Improving the survival of Lactobacillus plantarum FZU3013 by phase separated caseinate/alginate gel beads

The phase separation behavior of mixed solution of caseinate (Cas) and alginate (Alg) was investigated. Lactobacillus plantarum FZU3013 was encapsulated using 4 % Cas/1 % Alg gel beads with a phase-separated structure. The bacteria were predominantly distributed in the Alg-rich continuous phase. The use of 4 % Cas/1 % Alg beads resulted in higher encapsulation efficiency for L. plantarum FZU3013 compared to 1 % Alg beads. After 5 weeks of storage at 4 °C, the viable count in 4 % Cas/1 % Alg beads was 8.3 log CFU/g, which was 1.1 log CFU/g higher than that of the 1 % Alg beads. When 1 % Alg beads of the smallest size were subjected to in vitro digestion, no viable bacteria could be detected at the end of the digestion, whereas the 4 % Cas/1 % Alg beads of the smallest size had a viable count of 3.9 log CFU/g. When the size of the 4 % Cas/1 % Alg beads was increased to 1000 μm, the viable count was 7.0 log CFU/g after digestion. The results of infrared spectroscopy and zeta potential indicated that hydrogen bonding and electrostatic interactions between caseinate and alginate reinforced the structure of the gel beads and improved the protection for L. plantarum FZU 3013.

Dual Role of Probiotic Lactic Acid Bacteria Cultures for Fermentation and Control Pathogenic Bacteria in Fruit-Enriched Fermented Milk

The food industry has been developing new products with health benefits, extended shelf life, and without chemical preservation. Bacteriocin-producing lactic acid bacteria (LAB) strains have been evaluated for food fermentation to prevent contamination and increase shelf life. In this study, potentially probiotic LAB strains, Lactiplantibacillus (Lb.) plantarum ST8Sh, Lacticaseibacillus (Lb.) casei SJRP38, and commercial starter Streptococcus (St.) thermophilus ST080, were evaluated for their production of antimicrobial compounds, lactic acid and enzyme production, carbohydrate assimilation, and susceptibility to antibiotics. The characterization of antimicrobial compounds, the proteolytic activity, and its inhibitory property against Listeria (List.) monocytogenes and Staphylococcus (Staph.) spp. was evaluated in buriti and passion fruit-supplemented fermented milk formulations (FMF) produced with LAB strains. Lb. plantarum ST8Sh was found to inhibit List. monocytogenes through bacteriocin production and produced both L(+) and D(-) lactic acid isomers, while Lb. casei SJRP38 mainly produced L(+) lactic acid. The carbohydrate assimilation profiles were compatible with those usually found in LAB. The potentially probiotic strains were susceptible to streptomycin and tobramycin, while Lb. plantarum ST8Sh was also susceptible to ciprofloxacin. All FMF produced high amounts of L(+) lactic acid and the viability of total lactobacilli remained higher than 8.5 log CFU/mL during monitored storage period. Staph. aureus ATCC 43300 in fermented milk with passion fruit pulp (FMFP) and fermented milk with buriti pulp (FMB), and Staph. epidermidis KACC 13234 in all formulations were completely inhibited after 14 days of storage. The combination of Lb. plantarum ST8Sh and Lb. casei SJRP38 and fruit pulps can provide increased safety and shelf-life for fermented products, and natural food preservation meets the trends of the food market.

Chitosan-Sodium Caseinate Composite Edible Film Incorporated with Probiotic Limosilactobacillus fermentum: Physical Properties, Viability, and Antibacterial Properties

Single-use synthetic plastics that are used as food packaging is one of the major contributors to environmental pollution. Hence, this study aimed to develop a biodegradable edible film incorporated with Limosilactobacillus fermentum. Investigation of the physical and mechanical properties of chitosan (CS), sodium caseinate (NaCas), and chitosan/sodium caseinate (CS/NaCas) composite films allowed us to determine that CS/NaCas composite films displayed higher opacity (7.40 A/mm), lower water solubility (27.6%), and higher Young's modulus (0.27 MPa) compared with pure CS and NaCas films. Therefore, Lb. fermentum bacteria were only incorporated in CS/NaCas composite films. Comparison of the physical and mechanical properties of CS/NaCas composite films incorporated with bacteria with those of control CS/NaCas composite films allowed us to observe that they were not affected by the addition of probiotics, except for the flexibility of films, which was improved. The Lb. fermentum incorporated composite films had a 0.11 mm thickness, 17.9% moisture content, 30.8% water solubility, 8.69 A/mm opacity, 25 MPa tensile strength, and 88.80% elongation at break. The viability of Lb. fermentum after drying the films and the antibacterial properties of films against Escherichia coli O157:H7 and Staphylococcus aureus ATCC 29213 were also evaluated after the addition of Lb. fermentum in the composite films. Dried Lb. fermentum composite films with 6.65 log₁₀ CFU/g showed an inhibitory effect against E. coli and S. aureus (0.67 mm and 0.80 mm inhibition zone diameters, respectively). This shows that the Lb.-fermentum-incorporated CS/NaCas composite film is a potential bioactive packaging material for perishable food product preservation.

Microencapsulating Alginate-Based Polymers for Probiotics Delivery Systems and Their Application

Probiotics exhibit many health benefits and a great potential for broad applications in pharmaceutical fields, such as prevention and treatment of gastrointestinal tract diseases (irritable bowel syndrome), prevention and therapy of allergies, certain anticancer effects, and immunomodulation. However, their applications are limited by the low viability and metabolic activity of the probiotics during processing, storage, and delivery in the digestive tract. To overcome the mentioned limitations, probiotic delivery systems have attracted much attention. This review focuses on alginate as a preferred polymer and presents recent advances in alginate-based polymers for probiotic delivery systems. We highlight several alginate-based delivery systems containing various types of probiotics and the physical and chemical modifications with chitosan, cellulose, starch, protein, fish gel, and many other materials to enhance their performance, of which the viability and protective mechanisms are discussed. Withal, various challenges in alginate-based polymers for probiotics delivery systems are traced out, and future directions, specifically on the use of nanomaterials as well as prebiotics, are delineated to further facilitate subsequent researchers in selecting more favorable materials and technology for probiotic delivery.

Dissecting of the AI-2/LuxS Mediated Growth Characteristics and Bacteriostatic Ability of Lactiplantibacillus plantarum SS-128 by Integration of Transcriptomics and Metabolomics

Lactiplantibacillus plantarum could regulate certain physiological functions through the AI-2/LuxS-mediated quorum sensing (QS) system. To explore the regulation mechanism on the growth characteristics and bacteriostatic ability of L. plantarum SS-128, a luxS mutant was constructed by a two-step homologous recombination. Compared with ΔluxS/SS-128, the metabolites of SS-128 had stronger bacteriostatic ability. The combined analysis of transcriptomics and metabolomics data showed that SS-128 exhibited higher pyruvate metabolic efficiency and energy input, followed by higher LDH level and metabolite overflow compared to ΔluxS/SS-128, resulting in stronger bacteriostatic ability. The absence of luxS induces a regulatory pathway that burdens the cysteine cycle by quantitatively drawing off central metabolic intermediaries. To accommodate this mutations, ΔluxS/SS-128 exhibited lower metabolite overflow and abnormal proliferation. These results demonstrate that the growth characteristic and metabolism of L. plantarum SS-128 are mediated by the AI-2/LuxS QS system, which is a positive regulator involved in food safety. It would be helpful to investigate more bio-preservation control potential of L. plantarum, especially when applied in food industrial biotechnology.

Use of encapsulated lactic acid bacteria as bioprotective cultures in fresh Brazilian cheese

There is great interest for biopreservation of food products, and encapsulation may be a good strategy to extend the viability of protective cultures. In this study, Lactobacillus paraplantarum FT-259 and Lactococcus lactis QMF 11 were separately encapsulated in casein/pectin (C/P) microparticles, which were tested for antilisterial and anti-staphylococcal activity in fresh Minas cheese (FMC) stored at 8 °C. The encapsulation efficiency for both lactic acid bacteria (LAB) was 82.5%, with viability over 6.2 log CFU/g after storage of C/P microparticles for 90 days under refrigeration. Interestingly, free Lb. paraplantarum and free Lc. lactis grew significantly in refrigerated FMC, both in the presence and absence of pathogens, but only the first significatively grew when encapsulated. Encapsulation increased the antilisterial activity of Lb. paraplantarum in FMC. Moreover, Lc. lactis significantly inhibited listerial growth in FMC in both its free and encapsulated forms, whereas Staphylococcus aureus counts were only significantly reduced in the presence of free Lc. lactis. In conclusion, these results indicate that C/P microparticles are effective carriers of LAB in FMC, which can contribute for the assurance of the safety of this product.

Improving nisin production by encapsulated Lactococcus lactis with starch/carboxymethyl cellulose edible films

In this study, Lactococcus lactis was embedded in a film of corn starch (NS) and carboxymethyl cellulose (CMC) prepared using a casting method. At a CMC:NS ratio of 5:5, the composite film had the best comprehensive properties. Scanning electron microscopy images clearly showed that L. lactis was effectively embedded. The film with 1.5 % L. lactis showed the best performance and the lowest water vapor transmission rate (5.54 × 10^-11 g/m s Pa. In addition, the edible film retained a viable count of 5.64 log CFU/g of L. lactis when stored at 4 °C for 30 days. The composite film with 1.5 % L. lactis showed the highest release of nisin (3.35 mg/mL) and good antibacterial activity against Staphylococcus aureus (53.53 %) after 8 days. Therefore, this edible film is a viable alternative antimicrobial strategy for the active packaging of foods containing low moisture content.

Characterization and in vitro evaluation of a vaginal gel containing Lactobacillus crispatus for the prevention of gonorrhea

The increasing resistance of Neisseria gonorrhoeae to any current antibiotic treatment and the difficulties associated with the use of prevention means such as condom urge the need for alternative methods to prevent this sexually transmitted infection. In this work, a prevention strategy based on the use of a vaginal gel containing Lactobacilli was assessed in vitro. A Lactobacillus crispatus strain (ATCC 33197) was selected based on the published data on its ability to inhibit Neisseria gonorrhoeae. Its probiotic properties were first characterized. Then, a thermo-sensitive hydrogel containing 21.5% of poloxamer 407, 1% of sodium alginate and 9log₁₀ CFU of Lactobacillus crispatus per gel sample (5 g) was developed. The gelation temperature and the rheological characteristics of this formulation appeared suitable for a vaginal administration. Lactobacillus crispatus was viable in the gel for six months although a large amount of the bacteria was not culturable. The ability of Lactobacillus crispatus to inhibit Neisseria gonorrhoeae was still observed with the gel. Such system, thus, appeared promising for the prevention of gonorrhea.

Evaluation of Factors Affecting Antimicrobial Activity of Bacteriocin from Lactobacillus plantarum Microencapsulated in Alginate-Gelatin Capsules and Its Application on Pork Meat as a Bio-Preservative

Antimicrobial compounds from traditional fermented foods have shown activity against a wide range of pathogen and spoilage microorganisms for several years. In this study, a Lactic acid bacteria (LAB), isolated from Vietnamese traditional fermented yogurt (Lactobacillus plantarum SC01), was encapsulated in alginate-gelatin (ALG-GEL) and the effect of incubation temperature, medium pH and surfactants were assessed. The aims of this research were to evaluate antimicrobial activity of bacteriocin produced by L. plantarum SC01. Another aim the research was to study the quality of pork meat treated with its Bacteriocin in 2 h as a bio-preservative at different storage times (0 h, 12 h, 24 h and 48 h) in room temperature, compared to control (treated with salt 40.0%). The antimicrobial activity of L. plantarum SC01 was identified through the inhibition rate of five indicator organisms, including Escherichia coli, Salmonella sp., Staphylococcus aureus, Listeria monocytogenes, and Bacillus subtilis by co-culture method. The results showed that L. plantarum SC01 microencapsulated in ALG-GEL (2.5% alginate and 6.0% gelatin, w/v) and 3.0% bacteria supplied into modified MRS medium (MRSOPTSC01) produced highly active compound inhibited the growth of indicator organisms at a density of 10⁴⁻10⁸ CFU/mL. Antibacterial compounds were highly active in a treatment at 80 °C; not to be affected by pH; affected by surfactant as Ethylenediaminetetraacetic acid (EDTA), Sodium dodecyl sulfate (SDS), and Tween. Moreover, LAB obtained from this study show the potent Bacteriocin in its usage as a preservative in food.

Preparation and Characterization of Lactobacilli-Loaded Composite Films with Sustaining Antipathogenic Activity and Preservation Effect

Bioactive composite films were obtained by adding Lactobacillus paracasei into a hydroxypropyl cellulose (HPC)-konjac flour (KF) matrix through a casting method. The mechanical, optical, and barrier properties were tested to determine the influence of the addition of lactobacilli into complex films. For purpose of evaluating the surface morphology of the composite films, scanning electron microscopy and atomic force microscopy were carried out. Fourier transform infrared spectroscopy and X-ray diffraction analyses were conducted to evaluate intermolecular interactions and crystallinity, respectively. Moreover, the microbial viability of the lactobacilli and the antibacterial activities of the bioactive films against pathogenic organisms were measured. The results indicated that the mechanical properties, crystalline properties, oxygen permeability, and color characteristics were not notably altered; nevertheless, the gloss and water vapor barrier properties were relatively weakened by the incorporation of L. paracase. The HPC-KF-L. paracasei films were effective in inhibiting both gram-positive (Listeria monocytogenes, Staphylococcus aureus) and gram-negative (Escherichia coli, Salmonella typhimurium) pathogens, and the films can retain physical property and antibacterial activity within a storage period of 30 days. The composite films, acting as suitable carriers for L. paracasei and possessing noteworthy bacteriostatic activities, could be developed as bioactive packaging for preserving food.

PRACTICAL APPLICATION

For the sake of the high desires of consumers for food safety and quality, the development of innovative bioactive packaging has attracted wide attention. In this work, the prepared films containing lactic acid bacteria showed great physical property, antipathogenic activity, and fresh-keeping property preservation, and have great application potential in fresh food preservation.

Modelling the microbial dynamics and antimicrobial resistance development of Listeria in viscoelastic food model systems of various structural complexities

Minimal processing for microbial decontamination, such as the use of natural antimicrobials, is gaining interest in the food industry as these methods are generally milder than conventional processing, therefore better maintaining the nutritional content and sensory characteristics of food products. The aim of this study was to quantify the impact of (i) structural composition and complexity, (ii) growth location and morphology, and (iii) the natural antimicrobial nisin, on the microbial dynamics of Listeria innocua. More specifically, viscoelastic food model systems of various compositions and internal structure were developed and characterised, i.e. monophasic Xanthan gum-based and biphasic Xanthan gum/Whey protein-based viscoelastic systems. The microbial dynamics of L. innocua at 10 °C, 30 °C and 37 °C were monitored and compared for planktonic growth in liquid, or in/on (immersed or surface colony growth) the developed viscoelastic systems, with or without a sublethal concentration of nisin. Microscopy imaging was used to determine the bacterial colony size and spatial organisation in/on the viscoelastic systems. Selective growth of L. innocua on the protein phase of the developed biphasic system was observed for the first time. Additionally, significant differences were observed in the colony size and distribution in the monophasic Xanthan gum-based systems depending on (i) the type of growth (surface/immersed) and (ii) the Xanthan gum concentration. Furthermore, the system viscosity in monophasic Xanthan gum-based systems had a protective role against the effects of nisin for immersed growth, and a further inhibitory effect for surface growth at a suboptimal temperature (10 °C). These findings give a systematic quantitative insight on the impact of nisin as an environmental challenge on the growth and spatial organisation of L. innocua, in viscoelastic food model systems of various structural compositions/complexities. This study highlights the importance of accounting for system structural composition/complexity when designing minimal food processing methods with natural antimicrobials.