What are the 4 major trends in the future of food fermenters?

With the development of modern food industry, the use of fermentation agent plays an important role in improving the quality and manufacturing efficiency of fermented food, which is the key to realize the standardization and scale of fermented food industrial production. An excellent fermenter should not only have the basic activity of a fermenter, but also have the diversified functions of improving the quality of food such as flavor and texture, as well as nutrition.
In this paper, we look forward to the future development trend of fermentation agent, in order to provide ideas and reference for related researchers’ scientific research and innovation, and help them deepen their scientific research innovation and practical application.
Biological characterization of fermenter strains with excellent production and probiotic properties
Food fermentation is the process of producing food or beverage through the growth of desired microorganisms and enzymatic conversion of food components, and the structural composition of the flora in the fermentation system, the metabolites produced, and other factors collectively determine the properties of the final product, such as texture, flavor, nutrition, and safety.
Therefore, the characterization of biological properties (such as physiological properties, metabolic properties, resistance, etc.) of the fermenter strains can be used to better screen the excellent strains for fermentation production, which can help optimize the fermentation process and the development of functional products.
(1) Physiological characterization: including the growth rate of the strain, suitable temperature, pH range, oxygen demand, etc. Understanding the physiological characteristics of the strain helps to determine its growth and metabolic capacity under different conditions.
(2) Metabolic characterization: study the metabolic pathways, metabolites, enzyme systems, etc. Through the analysis of metabolic pathways and metabolites, the main metabolic pathways of strains and their ability to utilize the substrate and the beneficial metabolites produced (e.g. organic acids, vitamins, etc.) can be determined.
(3) Analysis of stress-tolerant characteristics: the study of the strain’s ability to adapt to unfavorable environmental factors, such as high temperature, low temperature, acidity and alkalinity, salt concentration, etc., to understand the strain’s stress-tolerant characteristics will help to determine its stability in practical applications.
4) Evaluation of probiotic properties: If the strain is considered to have probiotic properties, such as the production of active metabolites beneficial to human health, the ability to regulate the intestinal flora.
The wide variety and number of food microorganisms and the large differences in physiological phenotypes among different strains/colonies pose a great challenge for screening strains with excellent properties. Although traditional screening methods can identify fermenter strains with excellent production and probiotic properties, they are often laborious and inefficient, and there is an urgent need to establish high-throughput targeted screening methods.
In recent years, research results from top journals such as Cell and its subpublications have shown that the physiological properties and beneficial effects of fermenter strains are closely related to their specific functional genes (clusters), which suggests that fermenter strains with excellent production and beneficial properties can be predicted and targeted from the perspective of genetic background.
Therefore, in-depth analysis of the genetic background, physiological phenotypes and functional characteristics of different potential fermenter strains, and clarification of the association mechanism between characterized genomes and microbial excellent production and fermentation characteristics can provide targets and directions for efficient screening of excellent fermenter strains.
For example, we can use UHPLC-QE-MS to analyze the differences in the ability of different strains to metabolize food matrix (e.g., sugars, proteins, fats, etc.) to produce flavor substances (e.g., aldehydes, ketones, esters, etc.) and nutrients (e.g., amino acids, nucleotides, short-chain peptides, etc.), and then analyze the potential genes (clusters), metabolic pathways, and functional characteristics of the genomes that are related to specific metabolite production in the strains by using the multi-omics coupling and bioinformatics. (clusters), metabolic pathways and regulatory mechanisms; further validation using CRISPR, homologous recombination and other gene editing technologies, and then targeting key genes (clusters) related to the production characteristics of the strain.
Through in vitro models, animal models and clinical trials to assess the differences in specific efficacy of different fermenter strains, and combining with comparative genomics methods to identify potential functional genes (clusters) affecting the efficacy of the probiotic, and then using gene knockout methods and sterile mouse models to validate and identify functional genes (clusters) affecting the efficacy of the strains, thus providing a molecular target for the efficient selection and breeding of strains with specific probiotic efficacy.
Functional analysis and molecular regulation of beneficial metabolites in fermenter strains
A large number of beneficial metabolites (e.g., γ-aminobutyric acid, vitamins, etc.) produced during food fermentation are beneficial to enhance the nutritional value of fermented foods. The beneficial effects of metabolites of different types or structures may show significant differences, and their production is strain-specific.
Therefore, analyzing the characteristic metabolites and their functions of fermenter strains, and exploring the regulatory mechanisms and molecular regulation laws of beneficial metabolites, bacteria and substrates can provide a theoretical basis for the mining of strains with high production of beneficial metabolites.
Based on the genomic big data of fermentation strains, bioinformatics software such as AntiSMASH and BiG-SLiCE were used to predict the biosynthetic gene clusters (BGCs) of beneficial metabolites and their bioactivities in combination with the MIBiG database.
Integrated techniques such as ion exchange and gel/affinity chromatography were used to isolate and purify the characteristic metabolites and structurally characterize them, and the quantitative-effect relationship of the beneficial metabolites of the fermenter strains exerting their efficacy was further elucidated by the in vitro intestinal simulation and animal experiments as an integrated functional evaluation model.
In addition, by exploring the dynamic relationship between the bacteria, beneficial metabolites and substrates during the fermentation process of the fermenter strains at the genome and metabolite levels, the functional genes and metabolic pathways related to the synthesis and regulation of beneficial metabolites can be clarified.
By constructing a kinetic model of bacterial growth, product generation and substrate consumption, we can investigate the regulation laws of pH, nutrient substrate and coenzymes on the synthesis of metabolites by strains, so as to realize the targeted regulation of beneficial metabolites.
Taking the acquisition of high GABA-producing strains as an example, based on the genomic data, the gad manipulators related to GABA synthesis of the strains were identified by comparative genomics, including gadA and gadB, the key genes for GABA biosynthesis, as well as the gene responsible for the function of GABA transport in the cell membrane, gadC; it was determined that Lactobacillus shortus was the only strain of Lactobacillus that carries complete gad manipulators through the genomic analysis. manipulator. In vitro tests revealed that Lactobacillus casei NCL912 produced (205.8±8.0) g/L of GABA, whereas Lactobacillus plantarum KCTC3103, which does not possess the manipulator, produced only 0.67 g/L. The results of the in vitro assay showed that Lactobacillus casei NCL912 was the only strain of Lactobacillus plantarum with a complete gad manipulator.
In addition, the effect of different concentrations (0, 10, 20, 30, 40, 50, and 100 μmol/L) of pyridoxal phosphate (PLP) on GABA production by Lactobacillus shortum RK03 was investigated, and it was found that the highest GABA production was achieved at PLP concentrations of 10 μmol/L and 20 μmol/L in the culture medium.
Analysis of the material basis for the symbiosis and synergistic effect of complex fermenter strain groups
Symbiosis and synergism of complex fermenter strains can promote the growth of bacteria, optimize the production of metabolites, thus improving the overall fermentation efficiency and food quality, and also enhance the stability of the product by maintaining the stability of the microbial community.
The material basis of symbiosis and synergy of compound fermenter strains involves various biochemical and microbiological mechanisms, mainly including the following:
(1) Complementary metabolic pathways: different strains may have different metabolic pathways and enzyme systems, and these pathways complement each other in substrate conversion and metabolite production, thus increasing the overall metabolic capacity.
2) Mutual use of metabolites: the metabolites generated by the decomposition of substrates by certain strains may be the substrates required for the growth of other strains, and this symbiotic relationship promotes the complete utilization of substrates and reduces the accumulation of metabolites.
(3) Enzyme synergy: the enzymes secreted by different strains of bacteria may have complementary functions and work together in the degradation or transformation of substrates, thus accelerating the reaction rate.
(4) Symbiotic substance exchange: different strains of bacteria may exchange substances, such as nutrients, signaling molecules, etc., through the secretion of substances or inter-cellular connection structure, and this symbiotic exchange promotes the mutual coordination and growth regulation between strains.
(5) Environmental factor regulation: symbiotic relationship may make the strains’ adaptability to environmental factors enhanced, such as certain strains can produce antioxidant substances or surfactants to help other strains better adapt to environmental stress.
Compound fermenter strains group symbiosis and synergism mainly depend on positive interactions between microorganisms, such as cross-feeding, group sensing and so on.
1) Cross-feeding. Cross-feeding refers to the metabolic inter-feeding relationship in which strains of bacteria/strain utilize metabolites secreted by other strains of bacteria/strain (including carbon sources, nitrogen sources, amino acids, vitamins and other growth factors) to promote their own growth.
The synergistic symbiosis between Lactobacillus bulgaricus and Streptococcus thermophilus composite fermenter during milk fermentation is a typical cross-feeding pattern. Streptococcus thermophilus has a weak casein degradation ability of protease (prtS), and it cannot obtain enough amino acids for growth directly from the milk system, while Lactobacillus bulgaricus exhibits strong protein hydrolysis ability, which can provide Streptococcus thermophilus with the amino acids required for growth (such as histidine, methionine and proline), small molecule peptides, etc., whereas most of Lactobacillus bulgaricus lacks pyruvate-formate cleaving enzyme as well as enzymes related to folate synthesis, and therefore is unable to synthesize folate, formate and pyridine, etc., which are required for the growth of the strain.
Streptococcus thermophilus has high pyruvate-formate lyase activity as well as an intact folate synthesis pathway, which can provide Lactobacillus bulgaricus with these essential substances.
2) Group induction. Group sensing is a phenomenon of strain/strain group communication mediated by self-inducers. Certain microorganisms produce signaling molecules and release them into the environment, which, when their concentration reaches a certain threshold, will trigger cells to respond to the signaling molecules, which in turn specifically activate downstream gene expression. This mode of interaction influences the relationship between microbial communities.
Such signaling molecules vary in different strains, such as N-acyl-homoserine lactone (AHL) present in Gram-negative bacteria, self-inducing peptides (Streptococcus lactis peptide, phytolactobacillusin, etc.) and furoseboryl boronate in Gram-positive bacteria, and signaling molecules detected in yeast are mainly aromatic alcohols such as farnesol, tryptophanol, and tyrosol, among other substances.
These signaling molecules mediated group sensing plays an important role in fermentor interactions by promoting cellular autolysis, increasing strain environmental stress tolerance, etc. e.g. AI-2 was shown to enhance interaction with Lactobacillus bulgaricus by increasing acid tolerance and metabolic rate of Streptococcus thermophilus.
Since each strain has a unique metabolic potential with differences in the type, amount, and timing of metabolite production, the presence and strength of interactions between composite fermenter strains depends on the specific combination of strains.
Future research will use artificial intelligence technology to build a multi-strain co-fermentation metabolic symbiosis network, combined with transcriptomics, metabolomics and other means to analyze the regulation of gene expression, characteristic metabolites, signaling molecules and other material change rules in the process of co-fermentation of different species of strains, and to explore the material basis of group symbiosis and synergistic effect of composite food fermenters based on group sensing, cross-feeding and other interactions to provide a theoretical basis for the research and creation of excellent composite fermenters. Provide theoretical basis for the research and creation of excellent composite fermenters.
Quality Formation Mechanism and Directional Regulation of Specialty Fermented Foods
The quality formation process of specialty fermented foods is a process in which microorganisms metabolize proteins, lipids and carbohydrates in the food matrix to produce unique flavors and nutrients, and the diversity of microorganisms and their metabolites is the core factor affecting this process.
In order to realize the targeted regulation of the quality of specialty fermented foods, firstly, it is necessary to clarify the quality formation mechanism of specialty fermented foods under natural inoculation conditions, i.e., how the fermenting microorganisms form unique microbial communities and metabolize them precisely.
Secondly, as the original microbial community in fermented foods has the defects of high complexity, poor stability and functional redundancy, which easily cause the fluctuation of fermented product quality, constructing a composite fermenter through the selection and recombination of characteristic microbial strains for fermentation is essential to improve the targeted regulation of fermented food quality.
The quality formation mechanism and directional regulation of fermented food involves a number of factors, including raw material selection, fermentation strains, fermentation conditions, and production processes.
(1) Strain selection: the strain of fermented food is one of the key factors affecting the quality, and the selection of suitable fermentation strains can regulate the flavor, texture, and nutritional composition of the food through its metabolites, enzyme system and other characteristics; the type and proportion of strains will affect the metabolites and their interactions during the fermentation process, which in turn affects the quality of the final product.
(2) Fermentation conditions: controlling fermentation conditions is the key to regulating the quality of fermented food, including temperature, humidity, pH, oxygen content and other factors will affect the growth and metabolic activity of strains, which in turn affects the product’s texture, taste, nutrient composition, and so on.
(3) Types of raw materials: different raw materials have different composition and characteristics, which will also have an important impact on the quality of fermented food, selecting high-quality raw materials, and according to the different requirements of the fermentation process for processing and treatment, can improve the product taste, color, aroma and so on.
(4) Auxiliary fermentation agent: some special fermented foods need to add auxiliary fermentation agent, such as yeast, lactobacillus, Aspergillus, etc., to promote the fermentation process and regulate the quality of the product; a reasonable choice of the type and proportion of the fermentation agent can enhance the product’s characteristics of flavor and nutrient composition.
(5) Fermentation process control: close control of the fermentation process is the key to ensure product quality, including fermentation time, fermentation temperature, stirring speed and other parameters of the regulation, will affect the degree of fermentation and final quality of the product.
(6) Dynamic regulation of microbial community: the dynamic change of microbial community of fermented food has an important impact on product quality, through the reasonable design of fermentation process, can control the composition of microbial community at different stages, so as to realize the directional regulation of product quality.
In realizing the targeted regulation of the quality of specialty fermented foods based on food fermentation agents, the first task is to deeply explore the structure of microbial communities and their functions, as well as the succession laws of these communities in specialty fermented foods under the framework of joint multi-omics analysis.
With the help of in-depth analysis of the interactions among enzyme, bacterial and substance systems, the association between the core functional microbiota and food quality will be revealed.
On this basis, the environmental factors (e.g., humidity, pH, oxygen and temperature, etc.) and biological factors (e.g., initial microbial abundance, latency and microbial interactions, etc.) affecting composite fermentation-mediated food fermentation were explored, and the optimal composition ratio of recombinant composite fermenter strains and optimal environmental factors were analyzed by simulated fermentation and mathematical modeling.
Wang et al. used 16SrRNA sequencing technology, non-target metabolomics technology combined with statistical methods such as correlation analysis to identify the core microbiota that produce specific flavor compounds during white wine fermentation, and reproduced the flavor compounds in white wine fermentation by the recombinant composite fermenter strains, which realized the targeted regulation of fermented food flavors. This achievement not only shows the potential of directional regulation of fermented food quality, but also brings new research ideas and technical paths to the field of food science.
Comprehensively analyzing the latest domestic and international studies, it is found that lactic acid bacteria fermenters are the core of the research in the field of food fermentation. Screening of fermenter strains with excellent production and probiotic properties and the development of multi-strain synergistic composite fermenters are the development trends in the food fermentation industry.