Fermentation optimization and kinetic model for high cell density culture of a probiotic microorganism: Lactobacillus rhamnosus LS-8

Fermented sheep milk supplemented with Lactobacillus rhamnosus NM-94: Enhancing fermented milk quality and enriching microbial community in mice

Currently, many research efforts and product developments focus on goat milk, while studies on the development and probiotic function of sheep milk remain limited. In this study, the effects of Lactobacillus rhamnosus NM-94 on the physicochemical properties, viable count, texture, microrheology, flavor, and quality detection and intestinal flora of fermented milk were analyzed by adding or not adding L. rhamnosus NM-94 to 2 starter cultures. The results showed that the addition of L. rhamnosus NM-94 to sheep milk significantly reduced fermentation time by 2 h (12 h vs. 14 h). At 21 d of storage, the count of viable bacteria in fermented sheep milk supplemented with L. rhamnosus NM-94 (0.61 ± 0.06 × 109 cfu/mL) was surprisingly higher than that of the control milk (0.35 ± 0.03 × 109 cfu/mL). During the microrheological analysis of the fermentation stage, the elastic index, macroscopic viscosity index, and solid-liquid balance values of fermented sheep milk supplemented with L. rhamnosus NM-94 were greater than those of the control milk, indicating that the fermented sheep milk supplemented with L. rhamnosus NM-94 had a more stable gel structure and viscosity. In mice, fermented sheep milk supplemented with L. rhamnosus NM-94 has a variety of beneficial intestinal microorganisms and potential probiotic functions. This study provides new ideas for improving the function of sheep milk and expanding the sheep milk industry.

Statistical optimisation and analysis of biomass and exopolysaccharide production by Lacticaseibacillus rhamnosus LRH30

Exopolysaccharides (EPS) produced by lactic acid bacteria with immunomodulatory potential are promising natural food additives. This study employs small-scale, 250 mL bioreactors combined with a central composite design to optimise two important bioprocess parameters, namely temperature and airflow, to achieve high yields of biomass and EPS from Lacticaseibacillus rhamnosus LRH30 (L. rhamnosus LRH30). A quadratic model was determined to be the best fit for the production of both products. The optimum critical process parameters for maximised biomass were identified to be 37.01 °C with an airflow of 0.12 vvm, while optimum criteria was 20.1 °C with an airflow of 0.18 vvm for maximum EPS production. Under these optimized conditions, small-scale batch experiments yielded a biomass concentration of 10.1 g/L and an EPS yield of 520.2 mg/L. In comparison, scale-up experiments in 2L reactors resulted in a biomass concentration of 8.54 g/L (a reduction of 18%) and an EPS yield of 654.6 mg/L (an increase of 26%). The produced EPS was purified and characterised through Fourier transform infrared spectroscopy and showed characteristic peaks associated with polysaccharides. The immunomodulatory potential of the L. rhamnosus LRH30 cells and EPS was evaluated through cytokine and chemokine secretion in a J774A.1 murine macrophage, resulting in a predominantly anti-inflammatory effect of L. rhamnosus LRH30 and EPS.

Impact of pre-exposure stress on the growth and viability of Lactobacillus acidophilus in regular, buriti pulp and orange byproduct fermented milk products

The loss of probiotics viability in yogurts and fermented milk is a significant challenge in producing yogurt and fermented milk. Thus, pre-exposure of probiotics to stress conditions can be a viable alternative to increase the probiotic viability. Moreover, the use of fruit pulp and agro-industrial residues in these products has demonstrated promising results in promoting growth and improving the viability of probiotics. Thus, this study aimed to evaluate the effects of pre-exposure to acid, oxidative and osmotic stress on the growth and viability of Lactobacillus acidophilus in yogurts and naturally fermented milk containing buriti (Mauritia flexuosa Mart.) pulp or orange byproduct. L. acidophilus was individually pre-exposed to acid, oxidative, and osmotic stress and used in the production of yogurts and fermented milk to determine both the acidification profile and growth of the cultures. Furthermore, during cold storage, the post-acidification profiles and viability of microbial cultures added to the yogurts and fermented milk were monitored. Results showed that pre-exposure to stress conditions influenced the growth parameters as the growth rate (μ) and lag phase (λ) of L. acidophilus and the starter cultures of S. thermophilus and L. delbrueckii subsp. bulgaricus. Moreover, an increase in the viability of L. acidophilus - pre-exposed to acid stress - was observed on the 21st day of storage of natural yogurts containing orange byproduct compared with non-stressful conditions. This study reports new data on the growth of probiotic cultures pre-exposed to stress conditions in products added of pulps and agro-industrial residues, which have not yet been shown in the literature.

Probiotic fermentation environment control under intelligent data monitoring

Probiotic fermentation studies are vital in many areas, particularly when it comes to feeding applications. This work examines probiotic fermentation in oil tea crops. The assessment of tea saponin-degrading bacteria and optimization of fermentation conditions using fermented oil tea cake under natural conditions, screening out six strains with strong ability to degrade tea saponin; selection of the best tea saponin degradation strain L.2 and recognition of its morphological features and ITS sequence to obtain L.2 strain is Aspergillus Niger. Oil tea is rich in tea saponin. Aspergillus Niger degraded tea saponins in oil teacakes at a rate of 93.96 % under the ideal conditions of 31.3 oC, 103.5 h, and 4.57 mL of initial acid addition. This has been accomplished via solid-state fermentation of L.2 using single factor studies and surface response optimization experiments. Moreover, Aspergillus Niger degraded tea saponins in oil tea cakes at a rate of 93.96% at the ideal circumstances of 31.3 C, 103.5 h, and 4.57 mL of initial acid addition.

Steps toward a digital twin for functional food production with increased health benefits

Lactobacillus rhamnosus (L. rhamnosus) is a commensal bacterium with health-promoting properties and with a wide range of applications within the food industry. To improve and optimize the control of L. rhamnosus biomass production in batch and fed-batch bioprocesses, this study proposes the application of artificial neural network (ANN) modelling to improve process control and monitoring, with potential future implementation as a basis for a digital twin. Three ANNs were developed using historical data from ten bioprocesses. These ANNs were designed to predict the biomass in batch bioprocesses with different media compositions, predict biomass in fed-batch bioprocesses, and predict the growth rate in fed-batch bioprocesses. The immunomodulatory effect of the L. rhamnosus samples was examined and found to elicit an anti-inflammatory response as evidenced by the inhibition of IL-6 and TNF-α secretion. Overall, the findings of this study reinforce the potential of ANN modelling for bioprocess optimization aimed at improved control for maximising the volumetric productivity of L. rhamnosus as an immunomodulatory agent with applications in the functional food industry.

The optimization of sequential fermentation in the dealcoholized apple juice for reducing lipids

Yeast and lactic acid bacteria are widely used in fermented foods and the nutrients and metabolites produced by fermentation have cholesterol degrading effects. This study utilized Xinjiang Aksu apples as the material to optimize the sequential fermentation process of different strains and construct a fermentation kinetic model to develop a functional fermentation product with low-sugar, probiotics-rich and lipid-lowering properties. The sequential fermentation of dealcoholized apple juice with Saccharomyces cerevisiae and Lactobacillus plantarum was optimized by response surface design, based on which a sequential fermentation kinetic model was constructed. The changes of short-chain fatty acids, cholesterol elimination rate and hydrophobic properties during the fermentation process were studied. The results showed that the kinetic model established under the optimal conditions could effectively predict the dynamic changes of the basic indexes during the fermentation process. After fermentation, the viable number of L. plantarum was 4.96 × 108 CFU/mL, short-chain fatty acids increased, the cholesterol elimination rate reached 45.06%, and the hydrophobicity was 51.37%, which had favorable lipid-lowering properties and hydrophobic effect. This research will provide a theoretical basis and technical support for the monitoring of microbial dynamics and functionalization development of sequentially fermented apple juice with different strains.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05741-z.

Alternative culture medium design for biomass production of autochthonous meat starter Latilactobacillus sakei sp. sakei ACU-2

The autochthonous strain Latilactobacillus sakei sp. sakei ACU-2 was selected as a meat starter culture for dry sausage production. Transferring this strain from laboratory scale to industry requires an increase in biomass production, while lowering process costs. In this study, a combination of techniques was applied in order to optimize the culture medium composition to enhance biomass production of L. sakei ACU-2. One variable at a time experiments, Plackett-Burman design, and mixture design were performed to fulfill the strain nutritional requirements. Eventually, the optimized formulation contained 19.46 g/L yeast extract; 8.28 g/L whey protein concentrate; 2.26 g/L soy peptone; 30 g/L cerelose; 1 g/L Tween 80; 5 g/L sodium acetate; 0.2 g/L magnesium sulfate and 0.05 g/L manganese sulfate. When L. sakei ACU-2 was cultivated in a bioreactor using the alternative medium, an enhancement of 75.5% of biomass production was achieved, in comparison to its growth in the commercial de Man, Rogosa, and Sharpe medium. Furthermore, a reduction of 62-86% of the cost was also attained. These results support a promising large-scale application of the designed medium for high biomass yields of the starter culture at minor costs.

Influence of anaerobic biotransformation process of agro-industrial waste with Lactobacillus acidophilus on the rheological parameters: case of study of pig manure

This study evaluated the rheological behavior of the pig waste biotransformation process to produce lactic acid (LA) and biomass with Lactobacillus acidophilus in a stirred reactor. In addition, cell growth, carbohydrate consumption, and LA production were measured at three different agitation speeds, 100, 150, and 200 rpm at 37 °C, with a reaction time of 52 h. During the development of the process, the kinetic and rheological parameters were obtained using the logistic, Gompertz, generalized Gompertz, Ostwald de Waele, and Herschel-Bulkley mathematical models, respectively. The substrate used was pig manure, to which molasses was added at 12% v/v to increase the concentration of carbohydrates. The results suggest that mass exchange is favorable at low agitation speeds. Nevertheless, the presence of molasses rich in carbohydrates as a carbon source modifies the characteristics of the fluid, dilatant (n > 1) at the beginning of the process to end up as pseudoplastic (n < 1) due to the addition of exopolysaccharides and the modification of the physical structure of the substrate. This effect was confirmed by the Herschel-Bulkley model, which presented a better fit to the data obtained, in addition to finding a direct relationship between viscosity and pH that can be used as variables for the control of bioconversion processes of pig manure into biomass rich in Lactobacillus acidophilus.

Probiotics media: significance, challenges, and future perspective - a mini review

The health benefits associated with probiotics have increased their application in pharmaceutical formulations and functional food development. High production of probiotic biomass requires a cost-effective production method and nutrient media optimization. The biomass production of probiotics can be enhanced by optimizing growth parameters such as substrate, pH, incubation time, etc. For economical industrial production of probiotic biomass, it is required to design a new medium with low cost. Wastes from the food industries are promising components for the development of the low-cost medium. Industrial wastes such as cheese whey and corn steep liquor are excellent examples of reliable sources of nitrogen for the biomass production of probiotic bacteria. The increased yield of biomass reduced the cost of production. This review focuses on the importance of probiotic media for biomass production and its challenges.

Graphical Abstract

Influence of nitrogen sources on the tolerance of Lacticaseibacillus rhamnosus to heat stress and oxidative stress

It has been found that 32 genes related to nitrogen source metabolism in Lacticaseibacillus rhamnosus are downregulated under both heat stress and oxidative stress. In this study, the influence of different nitrogen sources within the growth medium on the tolerance of L. rhamnosus to heat stress and oxidative stress was investigated. Tryptone-free MRS was found to enhance the tolerance of L. rhamnosus hsryfm 1301 to heat stress and oxidative stress during the whole growth period, and this result was universal for all L. rhamnosus species analyzed. The strongest strengthening effect occurred when the OD₆₀₀ value reached 2.0, at which the survival rates under heat stress and oxidative stress increased 130-fold and 40-fold, respectively. After supplementing phenylalanine, isoleucine, glutamate, valine, histidine, or tryptophan into the tryptone-free MRS, the tolerance of L. rhamnosus to heat stress and oxidative stress exhibited a sharp drop. The spray drying survival rate of L. rhamnosus hsryfm 1301 cultured in the tryptone-free MRS rose to 75% (from 30%), and the spray dried powder also performed better in the experimentally simulated gastrointestinal digestion. These results showed that decreasing the intake of amino acids is an important mechanism for L. rhamnosus to tolerate heat stress and oxidative stress. When L. rhamnosus is cultured for spray drying, the concentration of the nitrogen source's components should be an important consideration.

Effects of different carbon sources on metabolic profiles of carbohydrates in Streptococcus thermophilus during fermentation

BACKGROUND

Streptococcus thermophilus is a major starter used in the dairy industry and it could improve the flavor of fermented products. It is necessary to improve biomass of S. thermophilus for its application and industrialization. The utilization of carbon sources directly affects the biomass of S. thermophilus. Therefore, the carbohydrate metabolism of S. thermophilus should be investigated.

RESULTS

In the present study, metabolic parameters and gene expression of S. thermophilus S-3 with different carbon sources were investigated. The physicochemical results showed that S. thermophilus S-3 had high lactose utilization. Transcriptome analysis found that approximately 104 genes were annotated onto 15 carbohydrate metabolic pathways, of which 15 unigenes were involved in the phosphotransferase system and 75 were involved in the ATP-binding cassette transporter system. In addition, 171 differentially expressed genes related to carbohydrate metabolism were identified. Expression of the galactose metabolism genes lacSZ and galKTEM increased significantly from the lag phase to the mid-exponential growth phase as a result of the global regulator protein, catabolite control protein A (CcpA). The high expression of galK in the mid- to late- phases indicated that the metabolite galactose is re-transported for intracellular utilization. CcpA regulation may also induce high expressions of glycolytic pathway regulated-genes related to lactose utilization, including ldh, fba, eno, pfkA, bglA, pgi, pgm and pyk, producing optimal glycolytic flux and S. thermophilus S-3 growth.

CONCLUSION

The present study provides new insights into the carbon metabolism regulation and provide theoretical support for high-density fermentation of S. thermophilus S-3. © 2022 Society of Chemical Industry.

Challenges in the production and use of probiotics as therapeuticals in cancer treatment or prevention

Probiotics were defined as microbial strains that confer health benefits to their consumers. The concept has evolved during the last twenty years, and today metabolites produced by the strains, known as postbiotics, and even dead cells, known as paraprobiotics are closely associated to them. The isolation of commensal strains from human microbiome has led to the development of next generation probiotics. This review aims to present an overview of the developments in the area of cancer prevention and treatment, intimately related to advances in the knowledge of the microbiome role in its genesis and therapy. Strain identification and characterization, production processes, delivery strategies and clinical evaluation are crucial to translate results into the market with solid scientific support. Examples of recent tools in isolation, strain typification, quality control and development of new probiotic strains are described. Probiotics market and regulation were originally developed in the food sector, but these new strategies will impact the pharmaceutical and health sectors, requiring new considerations in regulatory frameworks.

Design of experiments and design space approaches in the pharmaceutical bioprocess optimization

The optimization of pharmaceutical bioprocesses suffers from several challenges like complexity, upscaling costs, regulatory approval, leading to the risk of delivering substandard drugs to patients. Bioprocess is very complex and requires the evaluation of multiple components that need to be monitored and controlled in order to attain the desired state when the process ends. Statistical design of experiments (DoE) is a powerful tool for optimizing bioprocesses because it plays a critical role in the quality by design strategy as it is useful in exploring the experimental domain and providing statistics of interest that enable scientists to understand the impact of critical process parameters on the critical quality attributes. This review summarizes selected publications in which DoE methodology was used to optimize bioprocess. The main objective of the critical review was to clearly demonstrate potential benefits of using the DoE and design space methodologies in bioprocess optimization.

Enhancing ectoine production by recombinant Escherichia coli through step-wise fermentation optimization strategy based on kinetic analysis

In this study, the recombinant ectoine-producing Escherichia coli ET01 was constructed by introducing the ectABC operon from Halomonas venusta ZH. To further improve ectoine production, the regulation of the fermentation process was systematically investigated. First, the effects of the initial glucose concentrations and glucose feeding mode on ectoine production were analyzed. Using a combination of pH-feedback feeding and glucose-controlled feeding, the ectoine titer reached 25.5 g/L, representing an 8.8-fold increase over standard batch culture. Then, the effects of dissolved oxygen (DO) levels (50, 40, 30, or 20%) on ectoine production were studied, and a DO control strategy was developed based on the fermentation kinetics. When the final optimized two-stage fermentation strategy was used, the ectoine titer reached 47.8 g/L, which was the highest level of ectoine produced by E. coli fermentation. The fermentation regulation strategy developed in this study might be useful for scaling up the commercial production of ectoine.

Effect of culture medium optimization on the secondary metabolites activity of Lysobacter antibioticus 13-6

Fermentation products of Lysobacter antibioticus 13-6 have antagonistic activity against devastating phytopathogenic bacerium Xanthomonas oryzae pv. oryzicola. The production of Lysobacter antibioticus 13-6 secondary metabolites was increased by optimizing the fermentation medium; using a single-factor screening test, Plackett-Burman Design, and Box-Behnken Design. The medium's final formulation for active secondary metabolites high-yield included peptone 5 g/L, glucose 4.73 g/L, MgSO₄·7H₂O 2.33 g/L, and K₂HPO₄ 2.21 g/L. We compared phenazine-1-carboxylic acid (PCA) contents of L. antibioticus 13-6 in the initial and optimized mediums through HPLC. It was found PCA contents of the optimized medium are two folds more than in the initial medium. We also detected the relative expression of five phenazine genes of L. antibioticus 13-6 via RT-qPCR, and it was found that genes: phzB, C, S, and NO1 have more significant expression compared with the initial medium, while gene phzD has found just significant. Further, we revealed that the optimal fermentation conditions for secondary metabolites were: fermentation time 60 hours, shaking speed 160 rpm, inoculum size 3%, and the initial pH = 7.0. In the end, it was determined that the antimicrobial activity and quality of L. antibioticus 13-6 secondary metabolites were increased by about 41.75% and 2-times, respectively, after the optimization of the fermentation medium.

Bacillus cereus liquid fertilizer was produced from Agaricus bisporus industrial wastewater

During the Agaricus bisporus canning processes, a large number of water-soluble elements were dissolved into the processing hot water. This study was conducted to use the industrial wastewater of A. bisporus to prepare agricultural microbial fertilizer. In the work, the influence of 6 different liquid fermentation factors on the total biomass of living Bacillus cereus was evaluated with the one-factor-at-a-time method and the Plackett-Burman design. The total biomass of living B. cereus was most influenced by fermentation temperature, shaking speed, and inoculation volume, which were identified as the most critical independent variables for the B. cereus biomass. The approximate ranges of optimal fermentation conditions for the three key factors were identified by the path of steepest ascent. The center point of these factors were 24 ℃ of temperature, 250 rpm of shaking speed and 12 % inoculum amount, respectively. The Box-Behnken design was applied to derive a statistical model for optimizing the three fermentation factors for B. cereus biomass. After further optimizations based on statistical predictions, the optimum fermentation parameters for B. cereus cultured in the A. bisporus industrial wastewater were fermentation temperature of 24.8 °C, shaking speed of 234 rpm, inoculum dose of 12.2 % (v:v, %), industrial wastewater concentration of 4%, initial pH values of 6.5, loading liquid of 60 mL/250 mL, and culture time of 24 h. Culturing with the optimal fermentation conditions resulted in the biomass of B. cereus of 1.35 ± 0.02 × 10⁹ Obj/mL (N = 3), which was consistent with the predicted values (1.32 × 10⁹ Obj/mL) predicted by the corresponding regression models (p < 0.05), and more, was also far higher than that of the standard of agricultural bacterial fertilizers in People's Republic of China. Further, the results of field trial indicated that the of B. cereus liquid fertilizer can remarkably enhance the yield of Brassica chinensis L. It is practicable to make use of the industrial wastewater of A. bisporus to prepare the microbial fertilizer.

Growth Kinetics of Probiotic Lactobacillus Strains in the Alternative, Cost-Efficient Semi-Solid Fermentation Medium

The growing need for Lactobacillus bacteria usage in industry and the expending probiotic market led to a search for new cost-efficient fermentation media from which a high yield of these bacteria could be obtained. The following study aimed to elaborate cultivation medium, for Lactobacillus spp. growth, which main components would be wheat, maize, barley, and rye flours. The optimal temperature for Lactobacillus growth in new semi-solid fermentation (SSF) medium, water content, and pH of the medium were analyzed by the plate count method. It was established, that the highest bacteria counts were obtained from cultures conducted in the SSF medium with flours to water ratio of 1:1.5 with a natural pH of 6.0 at 37 °C. Subsequently, the growth kinetics of analyzed strains, in both MRS and the SSF media, were studied. The newly designed media contributed to the increased duration of selected Lactobacillus strains lag phase, which varied from 1.98 to 5.64; nevertheless, the maximum growth rate of the strains was two times higher in the SSF medium rather than in MRS, which also resulted in shorter generation time. The developed medium has the potential to become a new cost-efficient fermentation medium for Lactobacillus spp.

A review of nondairy kefir products: their characteristics and potential human health benefits

Functional foods are foods that, in addition to having nutrients, contain in their composition ingredients that act specifically on body functions associated with the control and reduction of the risk of developing some diseases. In this sense, kefir, a group of microorganisms in symbiosis, mainly yeasts and lactic acid bacteria, stands out. The trend of ingesting kefir has been focused on the development of products that serve specific consumers, such as those who are lactose-intolerant, vegans and vegetarians, and consumers in general who seek to combine the consumption of functional products with the improvement of their health and lifestyle. This overview provides an insight into kefir, presenting the technological process to produce a nondairy beverage and evidence of the benefits of its use to reduce the risk of disease. We also discuss regulatory aspects of products fermented using kefir. Until now, the use of kefir (isolated microorganism, kefiran, or fermented product) has demonstrated the potential to promote an increase in the number of bifidobacteria in the colon and an increase in the glycemic control while reducing the blood cholesterol and balancing the intestinal microbiota, which helps in reducing constipation and diarrhea, improving intestinal permeability, and stimulating and balancing the immune system. However, the literature still has gaps that need to be clarified, such as the consumption dose of kefir or its products to cause some health benefit.

Potential of natamycin to control growth of Zygosaccharomyces spp. in apple juice during storage

In this research, anti-yeast activity of natamycin in apple juice inoculated with both Zygosaccharomyces rouxii and Z. bailii during the storage at different temperatures was investigated. For this purpose, a response surface methodology approach was used to test and optimize effects of some processing variables; storage time (1, 21 and 41 days), storage temperature (4, 12 and 20 °C), sodium benzoate as a positive control (0, 0.05 and 0.1%) and natamycin concentration (0, 30 and 60 mg/L) on several physicochemical and bioactive properties of the apple juice samples. The results showed that the natamycin performed a remarkable anti-yeast effect on Z. bailii rather than on Z. rouxii. The brix levels of the samples decreased and so the turbidity values increased significantly due to the yeast activity during the storage. Bioactive properties were also significantly affected by the natamycin which was also revealed to increase the antioxidant capacity of apple juice during storage. Using multiple response optimization technique, it was calculated that minimum yeast count (YC) values would occur at storage time = 38.64 and 40.9 days, storage temperature = 19.81 and 14.4 °C, sodium benzoate level (fixed to 0%) and natamycin concentration = 40 and 51.9 mg/L for the samples inoculated with Z. bailii and Z. rouxii, respectively. It was concluded that the bioactive properties of apple juice could be preserved by addition of natamycin which is suggested to be a natural inhibitor during the storage.