Effect of cryopreservation and microencapsulation of lactic acid bacterium Enterococcus faecium MC13 for long-term storage

Selection of a galactose-positive mutant strain of Streptococcus thermophilus and its optimized production as a high-vitality starter culture

Streptococcus thermophilus is a common starter in yogurt production and plays an important role in the dairy industry. In this study, a galactose-positive (Gal+) mutant strain, IMAU20246Y, was produced using the chemical mutagen N-methyl-N'-nitro-N-nitrosoguanidine (NTG) from wild-type S. thermophilus IMAU20246, which is known to have good fermentation characteristics. The sugar content of milk fermented by either the mutant or the wild type was determined using HPLC; metabolism of lactose and galactose was significantly increased in the mutant strain. In addition, we used response surface methodology to optimize components of the basic M17 medium for survival ratio of the mutant strain. Under these optimal conditions, the viable counts of mutant S. thermophilus IMAU20246Y reached 4.15 × 108 cfu/mL and, following freeze-drying in the medium, retained cell viability of up to 67.42%. These results are conducive to production of a high-vitality starter culture and development of "low sugar, high sweetness" dairy products.

Potential Application of Yeast Cell Wall Biopolymers as Probiotic Encapsulants

Biopolymers of yeast cell walls, such as β-glucan, mannoprotein, and chitin, may serve as viable encapsulants for probiotics. Due to its thermal stability, β-glucan is a suitable cryoprotectant for probiotic microorganisms during freeze-drying. Mannoprotein has been shown to increase the adhesion of probiotic microorganisms to intestinal epithelial cells. Typically, chitin is utilized in the form of its derivatives, particularly chitosan, which is derived via deacetylation. Brewery waste has shown potential as a source of β-glucan that can be optimally extracted through thermolysis and sonication to yield up to 14% β-glucan, which can then be processed with protease and spray drying to achieve utmost purity. While laminarinase and sodium deodecyle sulfate were used to isolate and extract mannoproteins and glucanase was used to purify them, hexadecyltrimethylammonium bromide precipitation was used to improve the amount of purified mannoproteins to 7.25 percent. The maximum chitin yield of 2.4% was attained by continuing the acid-alkali reaction procedure, which was then followed by dialysis and lyophilization. Separation and purification of yeast cell wall biopolymers via diethylaminoethyl (DEAE) anion exchange chromatography can be used to increase the purity of β-glucan, whose purity in turn can also be increased using concanavalin-A chromatography based on the glucan/mannan ratio. In the meantime, mannoproteins can be purified via affinity chromatography that can be combined with zymolase treatment. Then, dialysis can be continued to obtain chitin with high purity. β-glucans, mannoproteins, and chitosan-derived yeast cell walls have been shown to promote the survival of probiotic microorganisms in the digestive tract. In addition, the prebiotic activity of β-glucans and mannoproteins can combine with microorganisms to form synbiotics.

Preparation and Evaluation of a Dosage Form for Individualized Administration of Lyophilized Probiotics

Probiotics have been used in human and veterinary medicine to increase resistance to pathogens and provide protection against external impacts for many years. Pathogens are often transmitted to humans through animal product consumption. Therefore, it is assumed that probiotics protecting animals may also protect the humans who consume them. Many tested strains of probiotic bacteria can be used for individualized therapy. The recently isolated Lactobacillus plantarum R2 Biocenol™ has proven to be preferential in aquaculture, and potential benefits in humans are expected. A simple oral dosage form should be developed to test this hypothesis by a suitable preparation method, i.e., lyophilization, allowing the bacteria to survive longer. Lyophilizates were formed from silicates (Neusilin® NS2N; US2), cellulose derivates (Avicel® PH-101), and saccharides (inulin; saccharose; modified starch® 1500). They were evaluated for their physicochemical properties (pH leachate, moisture content, water absorption, wetting time, DSC tests, densities, and flow properties); their bacterial viability was determined in conditions including relevant studies over 6 months at 4 °C and scanned under an electron microscope. Lyophilizate composed of Neusilin® NS2N and saccharose appeared to be the most advantageous in terms of viability without any significant decrease. Its physicochemical properties are also suitable for capsule encapsulation, subsequent clinical evaluation, and individualized therapy.

Improvement in the probiotic efficacy of Bacillus subtilis E20-stimulates growth and health status of white shrimp, Litopenaeus vannamei via encapsulation in alginate and coated with chitosan

The aim of this study was to increase the efficacy of probiotic Bacillus subtilis E20 by encapsulating the probiotic in alginate and coating it with chitosan. The protective effect was evaluated by firstly ensuring the viability of encapsulated probiotics in simulated gastrointestinal fluid (SGF) and simulated intestinal fluid (SIF) conditions and then at different storage temperatures. In addition, the encapsulated probiotic was incorporated into the diet to improve the growth performance and health status of white shrimp, Litopenaeus vannamei. B. subtilis E20 has the ability to survive in SGF when encapsulated in 1.5-2% alginate and coated with 0.4% chitosan. Furthermore, viability increased significantly in SIF compared to the probiotic encapsulated in 1% alginate and coated with 0.4% chitosan and the non-encapsulated probiotic. Longer storage time and adverse conditions affected probiotics' survival, which was improved by the encapsulation with significantly higher viability than the non-encapsulated probiotic at different temperatures and storage duration. Encapsulation of B. subtilis E20 and dietary administration at 10⁷ CFU kg^-1 decreased shrimp mortality after a Vibrio infection, thereby improving shrimp's disease resistance, while the non-encapsulated probiotic required 10⁹ CFU kg^-1 to achieve better resistance. Although the best results of growth performance, immune response, and disease resistance against Vibrio alginolyticus were found in the shrimp fed with the diets supplemented with encapsulated probiotic at >10⁸ CFU kg^-1, shrimp's growth performance and health status improved after being fed 10⁷ CFU kg^-1 encapsulated probiotic for 56 days. Together, the results of this study prove that encapsulation could improve the viability of probiotic in different gastrointestinal conditions and adverse storage temperatures. Overall, lower concentrations of encapsulated probiotic B. subtilis E20 (10⁷ CFU kg^-1) was able to increase the growth performance and health status of shrimp.

Novel Developments on Stimuli-Responsive Probiotic Encapsulates: From Smart Hydrogels to Nanostructured Platforms

Biomaterials engineering and biotechnology have advanced significantly towards probiotic encapsulation with encouraging results in assuring sufficient bioactivity. However, some major challenges remain to be addressed, and these include maintaining stability in different compartments of the gastrointestinal tract (GIT), favoring adhesion only at the site of action, and increasing residence times. An alternative to addressing such challenges is to manufacture encapsulates with stimuli-responsive polymers, such that controlled release is achievable by incorporating moieties that respond to chemical and physical stimuli present along the GIT. This review highlights, therefore, such emerging delivery matrices going from a comprehensive description of addressable stimuli in each GIT compartment to novel synthesis and functionalization techniques to currently employed materials used for probiotic’s encapsulation and achieving multi-modal delivery and multi-stimuli responses. Next, we explored the routes for encapsulates design to enhance their performance in terms of degradation kinetics, adsorption, and mucus and gut microbiome interactions. Finally, we present the clinical perspectives of implementing novel probiotics and the challenges to assure scalability and cost-effectiveness, prerequisites for an eventual niche market penetration.

Emerging Technologies and Coating Materials for Improved Probiotication in Food Products: a Review

From the past few decades, consumers' demand for probiotic-based functional and healthy food products is rising exponentially. Encapsulation is an emerging field to protect probiotics from unfavorable conditions and to deliver probiotics at the target place while maintaining the controlled release in the colon. Probiotics have been encapsulated for decades using different encapsulation methods to maintain their viability during processing, storage, and digestion and to give health benefits. This review focuses on novel microencapsulation techniques of probiotic bacteria including vacuum drying, microwave drying, spray freeze drying, fluidized bed drying, impinging aerosol technology, hybridization system, ultrasonication with their recent advancement, and characteristics of the commonly used polymers have been briefly discussed. Other than novel techniques, characterization of microcapsules along with their mechanism of release and stability have shown great interest recently in developing novel functional food products with synergetic effects, especially in COVID-19 outbreak. A thorough discussion of novel processing technologies and applications in food products with the incorporation of recent research works is the novelty and highlight of this review paper.

Role of c-di-GMP in improving stress resistance of alginate-chitosan microencapsulated Bacillus subtilis cells in simulated digestive fluids

OBJECTIVES

Probiotics (Bacillus subtilis 04178) were entrapped in alginate-chitosan microcapsules by high-voltage electrostatic process. The encapsulation pattern was established as entrapped low density cells with culture (ELDCwc). The performance of ELDCwc cells was investigated against stress environments of simulated digestive fluids.

RESULTS

After incubation in simulated gastric (pH 2.5) and intestinal fluids (4% bile salt) for 2 h, the survival rate of ELDCwc cells (18.19% and 27.54%) was significantly higher than that of the free cells (0.0000009% and 0.0005%). The reason why B. subtilis embedded in microcapsules can resist the stress environments was that the mass production of extracellular proteins and polysaccharides prompted B. subtilis to form cell aggregates. The production of extracellular proteins and polysaccharides were regulated by the concentration of c-di-GMP and the expression of ydaJKLMN operon, abbA, sinI, slrA, slrB, abrR and sinR.

CONCLUSIONS

c-di-GMP is important for the production of extracellular polymer substance to enhance probiotic viability in stress environments.

Solid inoculants as a practice for bioaugmentation to enhance bioremediation of hydrocarbon contaminated areas

Vacuum freeze-drying is a scientifically advanced method to prepare solid inoculants from oil degrading bacterium. The introduction of oil-degrading microbes or bioaugmentation can be an efficient way to bioremediate oil spills in marine areas, where oil-degrading bacteria are deficient. The purpose of this study is to evaluate the potential use of solid inoculants of LZ-2 bacteria to enhance the degradation rate of crude oil. In this study, response surface methodology (RSM) was incorporated into the experimental design to optimize a response, which is influenced by different protectants. Our results showed that five factors have interactive and synergistic protective effects on the growth of LZ-2. Optimal growth of freeze-dried LZ-2 (63.8%) was observed with a 10.5% solution of skim milk supplemented with 14.3% sucrose, 14.4% of trehalose, 4.9% of glycerin and 14.7% of β-cyclodextrin. The culture grew in medium containing crude oil (3 g L^-1) at 37 °C at 150 rpm for 30 d, GC and GC-MS analysis showed biodegradation of 44.2 and 21.6% for total saturate and aromatic hydrocarbons respectively. These results indicated that the solid inoculants of LZ-2 bacteria had the potential to be used for ex-situ bioremediation of hydrocarbon pollutants associated with crude oil.

Cryopreservation and fast recovery of enriched syngas-converting microbial communities

Over the last decades, the use of mixed microbial communities has attracted increasing scientific attention due to their potential biotechnological applications in several emerging technological platforms such as the carboxylate, bioplastic, syngas and bio-electrochemical synthesis platforms. However, this increasing interest has not been accompanied by a parallel development of suitable cryopreservation techniques for microbial communities. While cryopreservation methods for the long-term storage of axenic cultures are well established, their effectiveness in preserving the microbial diversity and functionality of microbial communities has rarely been studied. In this study, the effect of the addition of different cryopreservation agents on the long-term storage of microbial communities at -80 °C was studied using a stable enrichment culture converting syngas into acetate and ethanol. The cryopreservation agents considered in the study were glycerol, dimethylsulfoxide, polyvinylpyrrolidone, Tween 80 and yeast extract, as well as with no addition of cryopreservation agent. Their effectiveness was evaluated based on the microbial activity recovery and the maintenance of the microbial diversity and community structure upon revival of the microbial community. The results showed that the commonly used glycerol and no addition of cryopreservation agent were the least recommendable methods for the long-term frozen storage of microbial communities, while Tween 80 and polyvinylpyrrolidone were overall the most effective. Among the cryoprotectants studied, polyvinylpyrrolidone and especially Tween 80 were the only ones assuring reproducible results in terms of microbial activity recovery and microbial community structure preservation.

Encapsulation of Lactobacillus plantarum ATCC 8014 and Pediococcus acidilactici ATCC 8042 in a freeze-dried alginate-gum arabic system and its in vitro testing under gastrointestinal conditions

The aim of this study was to investigate the viability of Pediococcus acidilactici ATCC 8042 and Lactobacillus plantarum ATCC 8014 in a freeze-dried capsules system prepared with sodium alginate and gum arabic using the extrusion technique. The capsules made with alginate 2% (w/v)/gum arabic 2% (w/v) showed higher hardness (7.12 ± 0.71 N), with highly cohesive (0.81 ± 0.02) and elastic (0.99 ± 0.00) features on the Texture Profile Analysis (TPA), as well as higher sphericity with 1.75 ± 0.12 mm y 1.73 ± 0.13 mm diameter axes and regularity in their surface by Scanning Electron Microscopy (SEM). The use of skimmed milk at 10% as a cryoprotector in the freeze-drying process allowed the obtention of high viability percentages (88% a 96%) for both strains. Best results of viability for P. acidilactici encapsulated was with the use of alginate 2% (w/v)/gum arabic 2% (w/v) (92%±2.65), and L. plantarum with the use of alginate 2% (w/v) (84.71%±10.33) during the gastrointestinal environment challenge.

Probiotics in Food Systems: Significance and Emerging Strategies Towards Improved Viability and Delivery of Enhanced Beneficial Value

Preserving the efficacy of probiotic bacteria exhibits paramount challenges that need to be addressed during the development of functional food products. Several factors have been claimed to be responsible for reducing the viability of probiotics including matrix acidity, level of oxygen in products, presence of other lactic acid bacteria, and sensitivity to metabolites produced by other competing bacteria. Several approaches are undertaken to improve and sustain microbial cell viability, like strain selection, immobilization technologies, synbiotics development etc. Among them, cell immobilization in various carriers, including composite carrier matrix systems has recently attracted interest targeting to protect probiotics from different types of environmental stress (e.g., pH and heat treatments). Likewise, to successfully deliver the probiotics in the large intestine, cells must survive food processing and storage, and withstand the stress conditions encountered in the upper gastrointestinal tract. Hence, the appropriate selection of probiotics and their effective delivery remains a technological challenge with special focus on sustaining the viability of the probiotic culture in the formulated product. Development of synbiotic combinations exhibits another approach of functional food to stimulate the growth of probiotics. The aim of the current review is to summarize the strategies and the novel techniques adopted to enhance the viability of probiotics.

Chitosan Coating Applications in Probiotic Microencapsulation

Nowadays, probiotic bacteria are extensively used as health-related components in novel foods with the aim of added-value for the food industry. Ingested probiotic bacteria must resist gastrointestinal exposure, the food matrix, and storage conditions. The recommended methodology for bacteria protection is microencapsulation technology. A key aspect in the advancement of this technology is the encapsulation system. Chitosan compliments the real potential of coating microencapsulation for applications in the food industry due to its physicochemical properties: positive charges via its amino groups (which makes it the only commercially available water-soluble cationic polymer), short-term biodegradability, non-toxicity and biocompatibility with the human body, and antimicrobial and antifungal actions. Chitosan-coated microcapsules have been reported to have a major positive influence on the survival rates of different probiotic bacteria under in vitro gastrointestinal conditions and in the storage stability of different types of food products; therefore, its utilization opens promising routes in the food industry.

Hydrogel Cryopreservation System: An Effective Method for Cell Storage

At present, living cells are widely used in cell transplantation and tissue engineering. Many efforts have been made aiming towards the use of a large number of living cells with high activity and integrated functionality. Currently, cryopreservation has become well-established and is effective for the long-term storage of cells. However, it is still a major challenge to inhibit cell damage, such as from solution injury, ice injury, recrystallization and osmotic injury during the thawing process, and the cytotoxicity of cryoprotectants. Hence, this review focused on different novel gel cryopreservation systems. Natural polymer hydrogel cryopreservation, the synthetic polymer hydrogel cryopreservation system and the supramolecular hydrogel cryopreservation system were presented, respectively. Due to the unique three-dimensional network structure of the hydrogel, these hydrogel cryopreservation systems have the advantages of excellent biocompatibility for natural polymer hydrogel cryopreservation systems, designability for synthetic polymer hydrogel cryopreservation systems, and versatility for supramolecular hydrogel cryopreservation systems. To some extent, the different hydrogel cryopreservation methods can confine ice crystal growth and decrease the change rates of osmotic shock in cell encapsulation systems. It is notable that the cryopreservation of complex cells and tissues is demanded in future clinical research and therapy, and depends on the linkage of different methods.

Development of a Teat Bio-sealant and Evaluation of its Technological and Functional Properties

A teat bio-sealant was developed using Weissella cibaria, and the bio-sealant's technological and functional properties were assessed. The development included four experimental phases that were analyzed using independent experimental designs. Initially, sterilized or pasteurized Aloe vera gels were used, and the effect of heat treatment was investigated. In the second phase, the effects of time, storage temperature, and addition of cryopreservatives on the viability of the probiotic were observed. The third phase consisted of evaluating the synergistic effects of the cryopreservatives. The fourth phase involved selecting a material that would provide viscosity to the teat sealant. Technological and functional properties were measured in terms of viability of W. cibaria, and antimicrobial activity against Staphylococcus aureus and Streptococcus agalactiae was also analyzed. A mixture of milk powder and glycerol preserved this antimicrobial activity. Pullulan provided greater viscosity and maintained the technological and functional properties of the bio-sealant for 29 days. This teat bio-sealant can be used as an alternative for the prevention of bovine mastitis.

Development and storage studies of high density macrocapsules containing Lactobacillus spp. strains as nutritional supplement in young calves

The aim of this study was to evaluate different production methodologies of probiotic macrocapsules with high bacterial densities destined to lactating calves. Three types of capsules containing Lactobacillus casei DSPV318T and Lactobacillus plantarum DSPV354T were prepared from an overnight culture in whey medium: (1) mixing the culture with calcium alginate and then, reincubating the capsules in whey (RC); (2) concentrating the biomass by centrifugation and mixing the pellet with calcium alginate (CC) at different concentrations with respect to the initial culture (5X and 12.5X); (3) CC with cryoprotectants: whey permeate (Per) and glycerol (Gly). Chitosan coating was evaluated. Capsules were freeze-dried and viability was assessed before freezing, after freeze-drying and every two weeks for 84 days of storage at room temperature, 4°C and -20°C. CC showed higher cell densities than RC. Storage temperature affected viability: greater viability at lower temperature. Moreover, the effect of temperature was influenced by other factors, such as capsule coating, culture neutralization and cryoprotectants. Coating improved viability at room temperature; however no effect was observed at 4°C. Culture neutralization allowed greater survival during storage. Cryoprotectants improved viability during freezing, but they also generated a positive or negative effect depending on storage temperature. The best results were: at refrigeration Gly12.5X exhibited counts above 10⁹CFU/capsule until day 70 and Per12.5X until day 56 of storage and at -20°C Gly12.5X showed counts above 10⁹CFU/capsule until the end of the study (84 days). A 10⁹CFU capsule is the daily dose per calf which would facilitate the administration of this probiotic inoculum to field animals.

Microencapsulation of Lactobacillus Acidophilus by Xanthan-Chitosan and Its Stability in Yoghurt

Microencapsulations of Lactobacillus acidophilus in xanthan-chitosan (XC) and xanthan-chitosan-xanthan (XCX) polyelectrolyte complex (PEC) gels were prepared in this study. The process of encapsulation was optimized with the aid of response surface methodology (RSM). The optimum condition was chitosan of 0.68%, xanthan of 0.76%, xanthan-L. acidophilus mixture (XLM)/chitosan of 1:2.56 corresponding to a high viable count (1.31 ± 0.14) × 1010 CFU·g-1, and encapsulation yield 86 ± 0.99%, respectively. Additionally, the application of a new encapsulation system (XC and XCX) in yoghurt achieved great success in bacterial survival during the storage of 21 d at 4 °C and 25 °C, respectively. Specially, pH and acidity in yogurt were significantly influenced by the new encapsulation system in comparison to free suspension during 21 d storage. Our study provided a potential encapsulation system for probiotic application in dairy product which paving a new way for functional food development.

Microencapsulation of Lactobacillus plantarum DKL 109 using External Ionic Gelation Method

The aim of this study was to apply the external ionic gelation using an atomizing spray device comprised of a spray gun to improve the viability of Lactobacillus plantarum DKL 109 and for its commercial use. Three coating material formulas were used to microencapsulate L. plantarum DKL 109: 2% alginate (Al), 1% alginate/1% gellan gum (Al-GG), and 1.5% alginate/3% gum arabic (Al-GA). Particle size of microcapsules was ranged from 18.2 to 23.01 μm depending on the coating materials. Al-GA microcapsules showed the highest microencapsulation yield (98.11%) and resulted in a significant increase in survivability of probiotic in a high acid and bile environment. Encapsulation also improved the storage stability of cells. The viability of encapsulated cells remained constant after 1-mon storage at ambient temperature. The external ionic gelation method using an atomizing spray device and the Al-GA seems to be an efficient encapsulation technology for protecting probiotics in terms of scale-up potential and small microcapsule size.

Cross-linked polymer nanofibers for hyperthermophilic enzyme immobilization: approaches to improve enzyme performance

We report an enzyme immobilization method effective at elevated temperatures (up to 105 °C) and sufficiently robust for hyperthermophilic enzymes. Using a model hyperthermophilic enzyme, α-galactosidase from Thermotoga maritima, immobilization within chemically cross-linked poly(vinyl alcohol) (PVA) nanofibers to provide high specific surface area is achieved by (1) electrospinning a blend of a PVA and enzyme and (2) chemically cross-linking the polymer to entrap the enzyme within a water insoluble PVA fiber. The resulting enzyme-loaded nanofibers are water-insoluble at elevated temperatures, and enzyme leaching is not observed, indicating that the cross-linking effectively immobilizes the enzyme within the fibers. Upon immobilization, the enzyme retains its hyperthermophilic nature and shows improved thermal stability indicated by a 5.5-fold increase in apparent half-life at 90 °C, but with a significant decrease in apparent activity. The loss in apparent activity is attributed to enzyme deactivation and mass transfer limitations. Improvements in the apparent activity can be achieved by incorporating a cryoprotectant during immobilization to prevent enzyme deactivation. For example, immobilization in the presence of trehalose improved the apparent activity by 10-fold. Minimizing the mat thickness to reduce interfiber diffusion was a simple and effective method to further improve the performance of the immobilized enzyme.