High-density cultivation of Lactobacillus and Bifidobacterium using an automatic feedback feeding method

Key factors for the survival of Lactiplantibacillus plantarum IDCC 3501 in manufacturing and storage

Functional microbiome development has steadily increased; with this, the viability of microbial strains must be maintained not only after the manufacturing process but also at the time of consumption. Survival is threatened by various unavoidable factors during freeze-drying and shelf storage. Here, the aim was to optimize the manufacturing process of the functional strain Lactiplantibacillus plantarum IDCC 3501 after freeze-drying and storage. Explosive growth was achieved using a medium composition with two nitrogen sources and a mineral, and growth was drastically improved by neutralizing the medium pH during the culture of L. plantarum IDCC 3501. Culture optimization involved a smaller cell size, leading to less intracellular free water. Moreover, when maltodextrin (MD) powder was directly added to the harvested cells, some intracellular free water was extracted from the bacterial cells, resulting in a dramatic increase in the viability of L. plantarum IDCC 3501 after freeze-drying and subsequent storage. Furthermore, MD enhanced survival in a dose-dependent manner. Bacterial survival was correlated with lysozyme tolerance; therefore, the positive result might have been caused by the osmotic dehydration of intracellular free water, which would potentially damage the bacterial cells via ice crystallization and/or a phase transition during freeze-drying. These critical factors of L. plantarum IDCC 3501 processing provide perspectives on survival issues for manufacturing microbiome strains. KEY POINTS: • Culture conditions for probiotic bacteria were optimized for high growth yield. • Osmotic dehydration improved bacterial survival after manufacturing and shelf storage. • Reduction in intracellular free water content is crucial for intact survival.

Analysis of the effects of specific growth rate of Lactococcus lactis MG1363 on aerobic metabolism and its application to high-density culture

Lactic acid bacteria (LAB) are known to produce a large amount of lactate when cultured under non-aerated conditions, which inhibits their growth at high concentrations. Our previous studies have shown that LAB can be cultured without lactate production under aerated conditions at a low specific growth rate. In this study, we investigated the effects of specific growth rate on cell yield and the specific production rates of metabolites in aerated fed-batch cultures of Lactococcus lactis MG1363. The results showed that lactate and acetoin production could be suppressed at specific growth rates below 0.2 h^-1, whereas acetate production was the highest at a specific growth rate of 0.2 h^-1. When LAB was cultured at a specific growth rate of 0.25 h^-1 with the addition of 5 mg/L heme to assist ATP production by respiration, lactate and acetate production was suppressed, and cell concentration reached 19 g-dry-cell/L (5.6 × 10ˆ10 cfu/mL) with a high cell yield of 0.42 ± 0.02 g-dry-cell/g-glucose.

Characterization, High-Density Fermentation, and the Production of a Directed Vat Set Starter of Lactobacilli Used in the Food Industry: A Review

Lactobacilli have been widely concerned for decades. Bacteria of the genus Lactobacillus have been commonly employed in fermented food to improve the appearance, smell, and taste of food or prolong its shelf-life. They comprise 261 species (by March 2020) that are highly diverse at the phenotypic, ecological, and genotypic levels. Some Lactobacilli strains have been documented to be essential probiotics, which are defined as a group of living microorganisms that are beneficial to the health of the host when ingested in sufficiency. However, the characterization, high-density fermentation, and the production of a directed vat set (DVS) starter of Lactobacilli strains used in the food industry have not been systematically reported. This paper mainly focuses on reviewing Lactobacilli as functional starter cultures in the food industry, including different molecular techniques for identification at the species and strain levels, methods for evaluating Lactobacilli properties, enhancing their performance and improving the cell density of Lactobacilli, and the production techniques of DVS starter of Lactobacilli strains. Moreover, this review further discussed the existing problems and future development prospects of Lactobacilli in the food industry. The viability and stability of Lactobacilli in the food industry and gastrointestinal environment are critical challenges at the industrial scale. The new production equipment and technology of DVS starter of Lactobacilli strains will have the potential for large-scale application, for example, developing low-temperature spray drying, freezing granulation drying, and spray freeze-drying.

Bifidobacterium spp. as functional foods: A review of current status, challenges, and strategies

Members of Bifidobacterium are among the first microbes to colonize the human intestine naturally, their abundance and diversity in the colon are closely related to host health. Recently, the gut microbiota has been gradually proven to be crucial mediators of various metabolic processes between the external environment and the host. Therefore, the health-promoting benefits of Bifidobacterium spp. and their applications in food have gradually been widely concerned. The main purpose of this review is to comprehensively introduce general features, colonization methods, and safety of Bifidobacterium spp. in the human gut, highlighting its health benefits and industrial applications. On this basis, the existing limitations and scope for future research are also discussed. Bifidobacteria have beneficial effects on the host's digestive system, immune system, and nervous system. However, the first prerequisite for functioning is to have enough live bacteria before consumption and successfully colonize the colon after ingestion. At present, strain breeding, optimization (e.g., selecting acid and bile resistant strains, adaptive evolution, high cell density culture), and external protection technology (e.g., microencapsulation and protectants) are the main strategies to address these challenges in food application.

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.

Microbial physiological engineering increases the efficiency of microbial cell factories

Microbial cell factories provide vital platforms for the production of chemicals. Advanced biotechnological toolboxes have been developed to enhance their efficiency. However, these tools have limitations in improving physiological functions, and therefore boosting the efficiency (e.g. titer, rate, and yield) of microbial cell factories remains a challenge. In this review, we propose a strategy of microbial physiological engineering (MPE) to improve the efficiency of microbial cell factories. This strategy integrates tools from synthetic and systems biology to characterize and regulate physiological functions during chemical synthesis. MPE strategies mainly focus on the efficiency of substrate utilization, growth performance, stress tolerance, and the product export capacity of cell factories. In short, this review provides a new framework for resolving the bottlenecks that currently exist in low-efficiency cell factories.

Modification of media using food-grade components for the fermentation of Bifidobacterium and Lactobacillus strains in large-scale bioreactors

Probiotic bacteria continue to receive increasing attention in the food and feed industries. However, the production of Bifidobacterium and Lactobacillus at an industrial scale is challenging because of specific nutrient requirements and conditions, which are complicated and costly. We developed low-cost culture media by modifying the carbon and nitrogen sources for Bifidobacterium animalis subsp. lactis KMP-H9-01 and Lactobacillus reuteri KMP-P4-S03 from available food grade components. Sucrose (15 g/l) was selected as a suitable carbon source for both strains because it was the most economic and facilitated bacterial growth that was equal to that of glucose. The Bifidobacterium strain required beef extract as a nitrogen source to multiply. The fermentation of both strains using the modified media formula in 5-L and 50-L bioreactors showed that the highest cell counts of L. reuteri and B. animalis subsp. lactis were 9 and 9.8 log CFU/ml after 12-15 h, respectively. The concentration (g/l) ratio between lactate and acetate obtained from B. animalis subsp. lactis was 7:7.4 at 12 h and 11.4:10.6 at 40 h; the ratio was similar at both time points (6.9: 1.1) for L. reuteri. Thus, this economically modified food-grade medium for the large-scale fermentation of two probiotic bacteria was efficient.