Continuous Production of Mixed Lactic Starters Containing Probiotics Using Immobilized Cell Technology

Improvements in makkhan (traditional Indian cultured butter) production: a review

Since Vedic times, traditional Indian cultured butter or makkhan has been one of the most demanding and extensively used food items in the village households of Indian subcontinent. Its processing and overall quality suffers due to the use of conventional practices, which has probably discouraged the production of product in organized sectors. No scientific intervention has taken place to improve the product quality and process since the inception of makkhan making. As an initiative towards the improvement, the present study is focused to prepare a detail scientific background on chemistry, quality attributes, utilization, preparation methods, and storage of product for identifying challenges and scopes of overall improvement in production status. To validate the opportunities identified for the improvements in production various approaches especially mechanized approaches are suggested in this review.

Application of Polysaccharide-Based Hydrogels as Probiotic Delivery Systems

Polysaccharide hydrogels have been increasingly utilized in various fields. In this review, we focus on polysaccharide-based hydrogels used as probiotic delivery systems. Probiotics are microorganisms with a positive influence on our health that live in the intestines. Unfortunately, probiotic bacteria are sensitive to certain conditions, such as the acidity of the gastric juice. Polysaccharide hydrogels can provide a physical barrier between encapsulated probiotic cells and the harmful environment enhancing the cells survival rate. Additionally, hydrogels improve survivability of probiotic bacteria not only under gastrointestinal track conditions but also during storage at various temperatures or heat treatment. The hydrogels described in this review are based on selected polysaccharides: alginate, κ-carrageenan, xanthan, pectin and chitosan. Some hydrogels are obtained from the mixture of two polysaccharides or polysaccharide and non-polysaccharide compounds. The article discusses the efficiency of probiotic delivery systems made of single polysaccharide, as well as of systems comprising more than one component.

Potential probiotic characterization and effect of encapsulation of probiotic yeast strains on survival in simulated gastrointestinal tract condition

The present study is focused on probiotic characterization of four yeasts viz. Pichia barkeri VIT-SJSN01, Yarrowia lipolytica VIT-ASN04, Wickerhamomyces anomalus VIT-ASN01 and Saccharomyces cerevisiae VIT-ASN03 isolated from food samples based on their auto-aggregation, co-aggregation ability and haemolytic activity. All the yeast strains showed good self-adhering and co-adhering potentiality with a value index of greater than 85%. None of the strains exhibited haemolysis which confirmed their non-pathogenic nature. Yeast strains were encapsulated in sodium alginate, sodium alginate coated with chitosan and sodium alginate-gelatinized with starch. Size and morphology of the beads and capsules were determined using SEM analysis. Encapsulation output and viability under storage condition was investigated. It was found that probiotic yeasts encapsulated in sodium alginate beads, chitosan coated beads and microcapsules showed better survival to simulated gastrointestinal conditions compared to free cells.

Multi-Fixed-Bed Bioreactor System Applied for Bioprocess Development of Immobilized Lactic Acid Bacteria

The multi-fixed-bed bioreactor“Multiferm”provides a downscaled system for the development of fixed-bed processes with immobilized microorganisms or cells. It consists of twelve single fixed-bed units that can be operated independently. Different bacterial strains, carriers used for immobilization, media or flow rates can be studied in one compact experimental set-up. Experiments can be run in parallel to allow for determination of experimental errors. In these studies several continuous cultivations were carried out withLactobacillus delbrueckiissp.bulgaricususing different dilution rates and culture durations as proof-of-concept for theMultiferm. Parameters relevant for process design such as reproducibility of simultaneously performed cultures, optimal dilution rate and long-term performance were determined by means of volume specific lactate and biomass productivity. First indications on a reduced growth rate of the cells due to immobilization were found.

Influence of the addition of Lactobacillus acidophilus La-05, Bifidobacterium animalis subsp. lactis Bb-12 and inulin on the technological, physicochemical, microbiological and sensory features of creamy goat cheese

We evaluated the effects of addition of probiotic cultures and inulin on the quality of creamy goat cheese.

Probiotics in fish and shellfish culture: immunomodulatory and ecophysiological responses

Aquaculture is emerging as one of the most viable and promising enterprises for keeping pace with the surging need for animal protein, providing nutritional and food security to humans, particularly those residing in regions where livestock is relatively scarce. With every step toward intensification of aquaculture practices, there is an increase in the stress level in the animal as well as the environment. Hence, disease outbreak is being increasingly recognized as one of the most important constraints to aquaculture production in many countries, including India. Conventionally, the disease control in aquaculture has relied on the use of chemical compounds and antibiotics. The development of non-antibiotic and environmentally friendly agents is one of the key factors for health management in aquaculture. Consequently, with the emerging need for environmentally friendly aquaculture, the use of alternatives to antibiotic growth promoters in fish nutrition is now widely accepted. In recent years, probiotics have taken center stage and are being used as an unconventional approach that has numerous beneficial effects in fish and shellfish culture: improved activity of gastrointestinal microbiota and enhanced immune status, disease resistance, survival, feed utilization and growth performance. As natural products, probiotics have much potential to increase the efficiency and sustainability of aquaculture production. Therefore, comprehensive research to fully characterize the intestinal microbiota of prominent fish species, mechanisms of action of probiotics and their effects on the intestinal ecosystem, immunity, fish health and performance is reasonable. This review highlights the classifications and applications of probiotics in aquaculture. The review also summarizes the advancement and research highlights of the probiotic status and mode of action, which are of great significance from an ecofriendly, sustainable, intensive aquaculture point of view.

Development of microencapsulation delivery system for long-term preservation of probiotics as biotherapeutics agent

The administration of probiotic bacteria for health benefit has rapidly expanded in recent years, with a global market worth $32.6 billion predicted by 2014. The oral administration of most of the probiotics results in the lack of ability to survive in a high proportion of the harsh conditions of acidity and bile concentration commonly encountered in the gastrointestinal tract of humans. Providing probiotic living cells with a physical barrier against adverse environmental conditions is therefore an approach currently receiving considerable interest. Probiotic encapsulation technology has the potential to protect microorganisms and to deliver them into the gut. However, there are still many challenges to overcome with respect to the microencapsulation process and the conditions prevailing in the gut. This review focuses mainly on the methodological approach of probiotic encapsulation including biomaterials selection and choice of appropriate technology in detailed manner.

Microbe-microbe interactions in mixed culture food fermentations

Most known natural and industrial food fermentation processes are driven by either simple or complex communities of microorganisms. Obviously, these fermenting microbes will not only interact with the fermentable substrate but also with each other. These microbe-microbe interactions are complex but thought to be crucial for obtaining the desired product characteristics. Microbial interactions are mediated through a variety of molecular and physiological mechanisms. Examples of interaction mechanisms which have an impact on the outcome of food fermentation processes will be discussed. Finally, the technological and scientific challenges associated with the production and propagation of complex mixed starter cultures are briefly addressed. Research on the composition and functionality of complex microbial consortia is gaining momentum and will open new avenues for controlling and improving food fermentation processes, and developing new applications for mixed cultures.

Probiotic encapsulation technology: from microencapsulation to release into the gut

Probiotic encapsulation technology (PET) has the potential to protect microorgansisms and to deliver them into the gut. Because of the promising preclinical and clinical results, probiotics have been incorporated into a range of products. However, there are still many challenges to overcome with respect to the microencapsulation process and the conditions prevailing in the gut. This paper reviews the methodological approach of probiotics encapsulation including biomaterials selection, choice of appropriate technology, in vitro release studies of encapsulated probiotics, and highlights the challenges to be overcome in this area.

Modern approaches in probiotics research to control foodborne pathogens

Foodborne illness is a serious public health concern. There are over 200 known microbial, chemical, and physical agents that are known to cause foodborne illness. Efforts are made for improved detection, control and prevention of foodborne pathogen in food, and pathogen associated diseases in the host. Several commonly used approaches to control foodborne pathogens include antibiotics, natural antimicrobials, bacteriophages, bacteriocins, ionizing radiations, and heat. In addition, probiotics offer a potential intervention strategy for the prevention and control of foodborne infections. This review focuses on the use of probiotics and bioengineered probiotics to control foodborne pathogens, their antimicrobial actions, and their delivery strategies. Although probiotics have been demonstrated to be effective in antagonizing foodborne pathogens, challenges exist in the characterization and elucidation of underlying molecular mechanisms of action and in the development of potential delivery strategies that could maintain the viability and functionality of the probiotic in the target organ.

Development of silk fibroin-based beads for immobilized cell fermentations

Silk fibroin was evaluated as a new matrix for immobilized cell fermentation. Silk fibroin was extracted from Bombyx mori cocoon, purified, concentrated in polyethylene glycol solution and diluted to 3 wt% with distilled water. This fibroin solution was used to encapsulate sensitive cells of the probiotic strain, Bifidobacterium longum ATCC 15707. Polymer droplets produced with an encapsulator were collected in liquid nitrogen and lyophilized. A low overall survival of 0.2% was measured after lyophilization. Lyophilized beads were hardened for 24 h under vacuum with an atmosphere of 89% relative humidity. The inoculated beads were colonized in two successive batch fermentations. Structure of silk fibroin beads and colonization of cells were examined with scanning electron microscopy. Colonized beads were tested in continuous fermentations for cell production. A biomass productivity of 1.7 x 10(9) CFU ml(-1) h(-1) was achieved, which was limited by loss of bead structure. This instability might be due to bead degradation by proteolytic activity of cells and/or limited mechanical stability during continuous fermentation in the stirred tank reactor.

Development of a real-time RT-PCR method for enumeration of viable Bifidobacterium longum cells in different morphologies

Viability of probiotic bacteria is traditionally assessed by plate counting which has several limitations, including underestimation of cells in aggregates or chains morphology. We describe a quantitative PCR (qPCR)-based method for an accurate enumeration of viable cells of Bifidobacterium longum NCC2705 exhibiting different morphologies by measuring the mRNA levels of cysB and purB, two constitutively expressed housekeeping genes. Three primer-sets targeting short fragments of 57-bp of cysS and purB and one 400-bp fragment of purB were used. Cell quantification of serially diluted samples showed a good correlation coefficient of R(2) 0.984 +/- 0.003 between plate counts and qRT-PCR for all tested primer sets. Loss of viable cells exposed to a lethal heat stress (56 degrees C, 10, 20 and 30 min) was estimated by qRT-PCR and plate counts. No significant difference was observed using qRT-PCR targeting the 400-bp fragment of purB compared to plate counts indicating that this fragment is a suitable marker of cell viability. In contrast, the use of the 57-bp fragments led to a significant overestimation of viable cell counts (18 +/- 3 and 7 +/- 2 fold for cysB and purB, respectively). Decay of the mRNA fragments was studied by treatment of growing cells with rifampicin prior qRT-PCR. The 400-bp fragment of purB was faster degraded than the 57-bp fragments of cysB and purB. The 400-bp fragment of purB was further used to enumerate viable cells in aggregate state. Cell counts were more than 2 log(10) higher using the qRT-PCR method compared to plate counts. Growing interest in probiotic characteristics of aggregating bacteria cells make this technique a valuable tool to accurately quantify viable probiotic bacteria exhibiting heterogeneous morphology.

Freezing resistance improvement of Lactobacillus reuteri by using cell immobilization

Lactobacillus reuteri shows certain beneficial effects to human health and is recognized as a probiotic. However, its application in frozen foods is still not popular because of its low survival during freezing and frozen storage. Cell immobilization technique could effectively exert protection effects to microbial cells in order to enhance their endurance to unfavorable environmental conditions as well as to improve their viability and cell concentration. Ca-alginate and kappa-carrageenan were used to immobilize L. reuteri in this research, and the immobilized cells were exposed to different freezing temperatures, i.e. -20 degrees C, -40 degrees C, -60 degrees C, -80 degrees C, and stored at -40 degrees C and -80 degrees C for 12 weeks. The objectives were to study the protection effects of cell immobilization against the adverse conditions of freezing and frozen storage, and the effects of freezing temperatures to the immobilized cells. Cell immobilization was used to raise the survival of L. reuteri during freezing and frozen storage in order to develop frozen foods with the probiotic effects of L. reuteri. Results indicated that immobilized L. reuteri possessed better survival in both freezing and frozen storage. The survival of immobilized L. reuteri was higher than that of free cells, and the effects of lower freezing temperature were better than higher freezing temperature. The immobilization effects of Ca-alginate were found to be superior to kappa-carrageenan. Cell immobilized L. reuteri exhibits potential to be used in frozen foods.

Fermentation technologies for the production of probiotics with high viability and functionality

There is growing scientific evidence supported by mechanistic and clinical studies that probiotics can provide health benefits. As probiotics are highly sensitive to many environmental factors, and because the propagation of many strains of intestinal origin is not straightforward, most commercial strains are selected on the basis of their technological properties - ruling out some strains with promising health properties. To date, probiotic production has almost exclusively been carried out using conventional batch fermentation and suspended cultures, in some cases combined with the use of sublethal stresses to enhance cell viability, the addition of protectants or microencapsulation to provide cell protection. However, other less conventional fermentation technologies, such as continuous culture and immobilized cell systems, could have potential for enhancing the performance of these fastidious organisms. These technologies might be employed to develop strains with improved physiology and functionality in the gut and to enlarge the range of commercially available probiotics, as well as expanding product applications.

Increased stress tolerance of Bifidobacterium longum and Lactococcus lactis produced during continuous mixed-strain immobilized-cell fermentation

AIMS

The effect of immobilization and long-term continuous culture was studied on probiotic and technological characteristics of lactic acid and probiotic bacteria.

METHODS AND RESULTS

A continuous culture in a two-stage system was carried out for 17 days at different temperatures ranging from 32 to 37 degrees C, with a first reactor containing Bifidobacterium longum ATCC 15707 and Lactococcus lactis subsp. lactis biovar. diacetylactis MD immobilized separately in gel beads, and a second reactor operated with free cells released from the first reactor. The tolerance of free cells from both strains produced in the effluent medium of both reactors to hydrogen peroxide, simulated gastric and intestinal juices, antibiotics and nisin, and freeze-drying markedly increased with culture time and was generally higher after 6 days than that of stationary-phase cells produced during free-cell batch fermentations. The reversibility of the acquired tolerance of B. longum, but not L. diacetylactis, to antibiotics was shown during successive free-cell batch cultures.

CONCLUSIONS

Free cells produced from continuous immobilized-cell culture exhibited altered physiology and increased tolerance to various chemical and physico-chemical stresses.

SIGNIFICANCE AND IMPACT OF THE STUDY

Continuous culture with immobilized cells could be used to produce probiotic and lactic acid bacteria with enhanced technological and probiotic characteristics.