Top Ten Hot Topics in Probiotics Research (Part Two)

5 Probiotics and the Gut-Brain Axis

There is a close bidirectional communication between the gut and the brain, with communication pathways including neural, hormonal, and immune mediators. Gastrointestinal microbiota influence normal gut homeostasis and function by participating in the communication between the gut and the brain, maintaining appropriate behavior in the body.

Microbial metabolism has the ability to produce and regulate various compounds, and increasing evidence suggests that microbial communities and their metabolic products play a key role in bidirectional gut-brain communication. Some metabolic products of microbes are structurally similar to endogenous neurochemicals produced by the host's nervous system, thus the gastrointestinal microbiota can be regarded as a virtual endocrine organ of the body. This bidirectional communication system through which microbes interact with the brain is known as the microbiota-gut-brain axis. As a bidirectional communication neuroendocrine system of the body, microbial metabolic products can influence brain function and the body's stress response through this system. Similarly, neural communication signals from the brain can affect gastrointestinal motility, sensation, and secretion, thereby influencing microbial homeostasis. Changes in microbial homeostasis may be related to the onset of certain diseases, especially neurodegenerative diseases, and utilizing the interaction mechanisms of the microbiota-gut-brain axis can play an important role in the treatment of some diseases.

6 Probiotics and Diet

With the discovery of various health benefits, dietary fiber has received increasing attention. It can promote intestinal peristalsis, accelerate material transport, facilitate bowel movements, and promote the growth of beneficial gut bacteria, thus having prebiotic effects.

The intake of dietary fiber helps the growth of beneficial bacteria in the gut. Dietary fiber mainly consists of storage substances and secretions within plant cells, primarily gel-like substances such as pectin, carrageenan, arabinogalactan, xanthan gum, and galactomannan, glucan, alginate, CMC, etc. These substances are mostly indigestible in the stomach and enter the intestine, where they can be partially or completely fermented and degraded into polysaccharides, oligosaccharides, and gel-like substances, which can act as promoting factors for beneficial bacteria.

7 Probiotics and Prebiotics/Postbiotics

Probiotics refer to 'live' microorganisms that, when given in adequate amounts, confer health benefits to the host, while postbiotics or paraprobiotics refer to inactivated probiotic cells and their related metabolic byproducts, which also have the ability to provide health benefits to the host, including metabolic products (enzymes such as GPX, SOD, NADP peroxidase, proteins/peptides, extracellular polysaccharides (EPS), organic acids, lipids such as short-chain fatty acids) and the components of the microbial cells (peptidoglycan, wall teichoic acid, lipoteichoic acid, cell wall polysaccharides, cell surface-associated proteins, protein fibers). Compared to live probiotics, postbiotics have clear chemical structures, safe dosage parameters, longer shelf life, and good absorption, metabolism, distribution, and excretion capabilities.

8 Next-Generation Probiotics and Probiotic Mechanisms

Novel probiotics developed based on specific gut symbionts (also known as next-generation probiotics) are a research hotspot. The main characteristics of next-generation probiotics are: ① derived from the host's inherent gut symbionts, with a long co-evolutionary history with the host, adapted to the host's gut environment; ② their abundance in the host's gut microbiota can vary greatly, and they have rich material exchanges with other microbial communities, playing an important role in balancing the host's gut microbiota; ③ they produce specific metabolic products that have significant effects on the host's physiological functions.

In addition to traditional probiotics such as Lactobacillus and Bifidobacterium, which have a long history of consumption, Akkermansia muciniphila, Faecalibacterium prausnitzii, and Eubacterium hallii are currently well-studied human symbiotic strains that have the potential to enhance gut mucosal barrier and improve metabolic diseases, making them candidate strains for next-generation probiotics.

Currently, clinical evidence for the functions and safety of next-generation probiotics is still insufficient; furthermore, in-depth research is needed on the probiotic functions and mechanisms of strains, environmental tolerance, growth characteristics, and industrial application technologies, as well as regulatory framework development to promote the application of next-generation probiotics.

9 Probiotics and Food Safety

In vitro safety evaluation of probiotics. Researchers both domestically and internationally have proposed various safety evaluation indicators and methods for different characteristics of probiotic strains, such as hemolytic activity, bile salt hydrolase activity, virulence factor detection, antibiotic resistance, production of toxic metabolic products, degradation ability of gastrointestinal mucosal proteins, platelet aggregation, etc. The following will focus on the evaluation of hemolytic activity, virulence factor detection, antibiotic resistance, and production of toxic metabolic products.

In vitro efficacy evaluation of probiotics. Efficacy evaluation indicators include acid resistance, bile salt resistance, resistance to artificial gastrointestinal fluid, gastrointestinal mucosal adhesion, antibacterial activity, antiviral activity, cell surface activity (hydrophobicity, self-aggregation, and co-aggregation), immune regulation, anti-cancer and anti-mutagenic effects, production of extracellular polysaccharides, and biofilm formation. Referring to the FAO/WHO guidelines for the evaluation of food probiotics established in 2002, it is suggested that when evaluating the efficacy of a potential probiotic strain, emphasis should be placed on its acid resistance, bile salt resistance, resistance to artificial gastrointestinal fluid, gastrointestinal mucosal adhesion, and antibacterial activity.

10 Probiotics and Emerging Technologies

With the continuous development of basic disciplines such as microbiomics, molecular biology, bioinformatics, and modern biotechnology, more efficient, reliable, and cost-effective emerging technologies are being introduced into probiotic research. Technologies such as whole-genome sequencing, single-cell sequencing, metagenomics, transcriptomics, proteomics, and metabolomics can deeply reveal the genetic information, evolutionary relationships, physiological characteristics, metabolic networks, functional mechanisms, and industrial application potential of strains from different levels of DNA-RNA-protein-metabolites. Technologies such as cultivation omics and synthetic biology also provide methodological support for screening and developing next-generation probiotics with specific functions.

In terms of industrial application, more emerging technologies are being applied to the encapsulation, drying, delivery, and detection of probiotics, such as using new wall materials to achieve layer-by-layer encapsulation of strains and targeted intestinal delivery, and using flow cytometry for rapid real-time detection of live bacteria. In the future, more cutting-edge technologies related to biology and medical pharmaceuticals will inevitably be applied to the probiotic industry, further enhancing the technological competitiveness of the industry.

References:

[1] Research progress on microbial nutrient metabolism and the microbiome-gut-brain axis interaction

[2] Domestic and foreign research present situation and the development trend of dietary fiber

[3] New trends in the development and application of postbiotics

[4] Evolving trends in next-generation probiotics: a 5W1H perspective

[5] Next-generation probiotics: the spectrum from probiotic to live biotherapeutics

[6] Working group report on drafting guidelines for the evaluation of probiotics in food

Note: This article is for informational purposes only and is not intended as medical guidance.