Fermentation of soybean meal improves isoflavone metabolism after soy biscuit consumption by adults

Bioconversion of lignans in flaxseed cake by fermented tofu microbiota and isolation of Enterococcus faecium strain ZB26 responsible for converting secoisolariciresinol diglucoside to enterodiol

Human intestinal microbiota plays a crucial role in converting secoisolariciresinol diglucoside, a lignan found in flaxseed, to enterodiol, which has a range of health benefits: antioxidative, antitumor, and estrogenic/anti-estrogenic effects. Given the high secoisolariciresinol diglucoside content in flaxseed cake, this study investigated the potential of co-fermenting flaxseed cake with fermented soybean product to isolate bacterial strains that effectively convert secoisolariciresinol diglucoside to enterodiol in a controlled environment (in vitro). The co-fermentation process with stinky tofu microbiota significantly altered the lignan, generating 12 intermediate lignan metabolites as identified by targeted metabolomics. One particular promising strain, ZB26, demonstrated an impressive ability to convert secoisolariciresinol diglucoside. It achieved a conversion rate of 87.42 ± 0.33%, with secoisolariciresinol and enterodiol generation rates of 94.22 ± 0.51% and 2.91 ± 0.03%, respectively. Further optimization revealed, under specific conditions (0.5 mM secoisolariciresinol diglucoside, pH 8, 30 °C for 3 days), ZB26 could convert an even higher percentage (97.75 ± 0.05%) of the secoisolariciresinol diglucoside to generate secoisolariciresinol (103.02 ± 0.16%) and enterodiol (3.18 ± 0.31%). These findings suggest that the identified strains ZB26 have promising potential for developing functional foods and ingredients enriched with lignans.

Factors driving the inter-individual variability in the metabolism and bioavailability of (poly)phenolic metabolites: A systematic review of human studies

This systematic review provides an overview of the available evidence on the inter-individual variability (IIV) in the absorption, distribution, metabolism, and excretion (ADME) of phenolic metabolites and its determinants. Human studies were included investigating the metabolism and bioavailability of (poly)phenols and reporting IIV. One hundred fifty-three studies met the inclusion criteria. Inter-individual differences were mainly related to gut microbiota composition and activity but also to genetic polymorphisms, age, sex, ethnicity, BMI, (patho)physiological status, and physical activity, depending on the (poly)phenol sub-class considered. Most of the IIV has been poorly characterised. Two major types of IIV were observed. One resulted in metabolite gradients that can be further classified into high and low excretors, as seen for all flavonoids, phenolic acids, prenylflavonoids, alkylresorcinols, and hydroxytyrosol. The other type of IIV is based on clusters of individuals defined by qualitative differences (producers vs. non-producers), as for ellagitannins (urolithins), isoflavones (equol and O-DMA), resveratrol (lunularin), and preliminarily for avenanthramides (dihydro-avenanthramides), or by quali-quantitative metabotypes characterized by different proportions of specific metabolites, as for flavan-3-ols, flavanones, and even isoflavones. Future works are needed to shed light on current open issues limiting our understanding of this phenomenon that likely conditions the health effects of dietary (poly)phenols.

Structural Characterization and Properties of Modified Soybean Meal Protein via Solid-State Fermentation by Bacillus subtilis

Soybean meal (SBM) is a high-quality vegetable protein, whose application is greatly limited due to its high molecular weight and anti-nutritional properties. The aim of this study was to modify the protein of soybean meal via solid-state fermentation of Bacillus subtilis. The fermentation conditions were optimized as, finally, the best process parameters were obtained, namely fermentation temperature of 37 °C, inoculum amount of 12%, time of 47 h, and material-liquid ratio of 1:0.58, which improved the content of acid-soluble protein. To explore the utilization of modified SBM as a food ingredient, the protein structure and properties were investigated. Compared to SBM, the protein secondary structure of fermented soybean meal (FSBM) from the optimal process decreased by 8.3% for α-helix content, increased by 3.08% for β-sheet, increased by 2.71% for β-turn, and increased by 2.51% for random coil. SDS-PAGE patterns showed that its 25-250 KDa bands appeared to be significantly attenuated, with multiple newborn peptide bands smaller than 25 KDa. The analysis of particle size and zeta potential showed that fermentation reduced the average particle size and increased the absolute value of zeta potential. It was visualized by SEM and CLSM maps that the macromolecular proteins in FSBM were broken down into fragmented pieces with a folded and porous surface structure. Fermentation increased the solubility, decreased the hydrophobicity, increased the free sulfhydryl content, decreased the antigenicity, improved the protein properties of SBM, and promoted further processing and production of FSBM as a food ingredient.

In vitro digestion models for the design of safe and nutritious foods

Responsible development of future foods requires in depth understanding of food digestion in the human body based on robust research models, ranging from in vitro models to randomized controlled human trials. This chapter overviews fundamental aspects of food digestion, namely bioaccessibility and bioavailability, and models mirroring gastric, intestinal, and colonic conditions. Second, the chapter demonstrates the potential of in vitro digestion models to help screen adverse effects of food additives, such as Titanium dioxide or carrageenan, or underpin the determinants of macro- and micronutrient digestion in different strata of the population, for example digestion of emulsions. Such efforts support rationalized design of functional foods, such as infant formulae, cheese, cereals and biscuits which are validated in vivo or in randomized controlled trials.

Biscuits Prepared with Enzymatically-Processed Soybean Meal Are Rich in Isoflavone Aglycones, Sensorially Well-Accepted and Stable during Storage for Six Months

Soybean meal (SBM) is a co-product of the soybean oil industry that is rich in bioactive compounds, such as isoflavones. We aimed to study the effects of processing SBM by fermentation (Saccharomyces cerevisiae) (FSBM) and enzymatic hydrolysis (CelluMax C, a commercial cellulase) (ESBM) on its chemical composition, with emphasis on isoflavones. Fermentation increased protein content by 9%, ash content by 7%, dietary fiber by 11% and minerals by up to 38%, except for iron, which decreased by 26%. Fermentation completely removed oligosaccharides from SBM, while enzymatic processing decreased oligosaccharides by 45% in SBM. Both processes converted glycosylated isoflavones into the corresponding aglycones, the content of which increased by up to 7.7-fold. Biscuits containing SBM, FSBM and ESBM could be labeled as dietary sources of dietary fibers, potassium, phosphorous, calcium and zinc, as well as high in proteins, copper, iron, manganese and magnesium. While FSBM biscuits had lower sensory scores compared to SBM biscuits, ESBM biscuits had equivalent scores. During storage for 180 days at room temperature, the isoflavone profile of all biscuits remained stable. Moreover, storage did not impair microbiological and sensory qualities of any biscuits. Altogether, ESBM biscuits show great marketing potential.

Nutritional Metabolomics and the Classification of Dietary Biomarker Candidates: A Critical Review

Recent advances in metabolomics allow for more objective assessment of contemporary food exposures, which have been proposed as an alternative or complement to self-reporting of food intake. However, the quality of evidence supporting the utility of dietary biomarkers as valid measures of habitual intake of foods or complex dietary patterns in diverse populations has not been systematically evaluated. We reviewed nutritional metabolomics studies reporting metabolites associated with specific foods or food groups; evaluated the interstudy repeatability of dietary biomarker candidates; and reported study design, metabolomic approach, analytical technique(s), and type of biofluid analyzed. A comprehensive literature search of 5 databases (PubMed, EMBASE, Web of Science, BIOSIS, and CINAHL) was conducted from inception through December 2020. This review included 244 studies, 169 (69%) of which were interventional studies (9 of these were replicated in free-living participants) and 151 (62%) of which measured the metabolomic profile of serum and/or plasma. Food-based metabolites identified in ≥1 study and/or biofluid were associated with 11 food-specific categories or dietary patterns: 1) fruits; 2) vegetables; 3) high-fiber foods (grain-rich); 4) meats; 5) seafood; 6) pulses, legumes, and nuts; 7) alcohol; 8) caffeinated beverages, teas, and cocoas; 9) dairy and soya; 10) sweet and sugary foods; and 11) complex dietary patterns and other foods. We conclude that 69 metabolites represent good candidate biomarkers of food intake. Quantitative measurement of these metabolites will advance our understanding of the relation between diet and chronic disease risk and support evidence-based dietary guidelines for global health.

Biocompatible natural deep eutectic solvent-based extraction and cellulolytic enzyme-mediated transformation of Pueraria mirifica isoflavones: a sustainable approach for increasing health-bioactive constituents

The presence of specific gut microflora limits the biotransformation of Pueraria mirifica isoflavone (PMI) glycosides into absorbable aglycones, thus limiting their health benefits. Cellulolytic enzyme-assisted extraction (CAE) potentially solves this issue; however, solvent extraction requires recovery of the hydrophobic products. Here, we established the simultaneous transformation and extraction of PMIs using cellulolytic enzymes and natural deep eutectic solvents (NADESs). The NADES compositions were optimized to allow the use of NADESs as CAE media, and the extraction parameters were optimized using response surface methodology (RSM). The optimal conditions were 14.7% (v/v) choline chloride:propylene glycol (1:2 mol ratio, ChCl:PG) at 56.1 °C for the cellulolytic enzyme (262 mU/mL) reaction in which daidzin and genistin were extracted and wholly transformed to their aglycones daidzein and genistein. The extraction of PMIs using ChCl:PG is more efficient than that using conventional solvents; additionally, biocompatible ChCl:PG enhances cellulolytic enzyme activity, catalyzing the transformation of PMIs into compounds with higher estrogenicity and absorbability.

A systematic review to identify biomarkers of intake for fermented food products

Background

Fermented foods are ubiquitous in human diets and often lauded for their sensory, nutritious, and health-promoting qualities. However, precise associations between the intake of fermented foods and health have not been well-established. This is in part due to the limitations of current dietary assessment tools that rely on subjective reporting, making them prone to memory-related errors and reporting bias. The identification of food intake biomarkers (FIBs) bypasses this challenge by providing an objective measure of intake. Despite numerous studies reporting on FIBs for various types of fermented foods and drinks, unique biomarkers associated with the fermentation process (“fermentation-dependent” biomarkers) have not been well documented. We therefore conducted a comprehensive, systematic review of the literature to identify biomarkers of fermented foods commonly consumed in diets across the world.

Results

After title, abstract, and full-text screening, extraction of data from 301 articles resulted in an extensive list of compounds that were detected in human biofluids following the consumption of various fermented foods, with the majority of articles focusing on coffee (69), wine (69 articles), cocoa (62), beer (34), and bread (29). The identified compounds from all included papers were consolidated and sorted into FIBs proposed for a specific food, for a food group, or for the fermentation process. Alongside food-specific markers (e.g., trigonelline for coffee), and food-group markers (e.g., pentadecanoic acid for dairy intake), several fermentation-dependent markers were revealed. These comprised compounds related to the fermentation process of a particular food, such as mannitol (wine), 2-ethylmalate (beer), methionine (sourdough bread, cheese), theabrownins (tea), and gallic acid (tea, wine), while others were indicative of more general fermentation processes (e.g., ethanol from alcoholic fermentation, 3-phenyllactic acid from lactic fermentation).

Conclusions

Fermented foods comprise a heterogeneous group of foods. While many of the candidate FIBs identified were found to be non-specific, greater specificity may be observed when considering a combination of compounds identified for individual fermented foods, food groups, and from fermentation processes. Future studies that focus on how fermentation impacts the composition and nutritional quality of food substrates could help to identify novel biomarkers of fermented food intake.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12263-021-00686-4.

Neither soyfoods nor isoflavones warrant classification as endocrine disruptors: a technical review of the observational and clinical data

Soybeans are a rich source of isoflavones, which are classified as phytoestrogens. Despite numerous proposed benefits, isoflavones are often classified as endocrine disruptors, based primarily on animal studies. However, there are ample human data regarding the health effects of isoflavones. We conducted a technical review, systematically searching Medline, EMBASE, and the Cochrane Library (from inception through January 2021). We included clinical studies, observational studies, and systematic reviews and meta-analyses (SRMA) that examined the relationship between soy and/or isoflavone intake and endocrine-related endpoints. 417 reports (229 observational studies, 157 clinical studies and 32 SRMAs) met our eligibility criteria. The available evidence indicates that isoflavone intake does not adversely affect thyroid function. Adverse effects are also not seen on breast or endometrial tissue or estrogen levels in women, or testosterone or estrogen levels, or sperm or semen parameters in men. Although menstrual cycle length may be slightly increased, ovulation is not prevented. Limited insight could be gained about possible impacts of in utero isoflavone exposure, but the existing data are reassuring. Adverse effects of isoflavone intake were not identified in children, but limited research has been conducted. After extensive review, the evidence does not support classifying isoflavones as endocrine disruptors.

Isoflavone-enriched soybean leaves attenuate ovariectomy-induced osteoporosis in rats by anti-inflammatory activity

BACKGROUND

With an increasing aging population, postmenopausal osteoporosis has become a global public health problem. Previous evidence has shown that postmenopausal osteoporosis is a skeletal disease mainly caused by estrogen deficiency, generally accompanied by inflammation, and dietary isoflavones may ameliorate postmenopausal osteoporosis by anti-inflammatory activity. We have generated isoflavone-enriched soybean leaves (IESLs), but their anti-inflammatory activity and effect on attenuating osteoporosis are still obscure. Here, we determined the isoflavone profiles of IESLs and evaluated their anti-inflammatory activity in lipopolysaccharide-stimulated RAW 264.7 cells and anti-osteoporotic effects on ovariectomy-induced osteoporosis in rats.

RESULTS

IESLs had a high content of total isoflavone. Hydrolysate of IESLs (HIESLs) was rich with the aglycones daidzein and genistein, and HIESLs can significantly inhibit lipopolysaccharide-induced inflammation by reducing messenger RNA expression of iNOS, COX-2, IL6, and IL1β. Moreover, ovariectomized rats receiving aqueous extracts of IESLs (HIESLs) orally maintained more bone mass than control rats did, which was attributed to inhibition of osteoclastogenesis by downregulating the messenger RNA expression of the bone-specific genes RANKL/OPG, OC, and cathepsin K, and the inflammation-related genes IL6, NFκB, and COX-2.

CONCLUSION

IESLs may attenuate postmenopausal osteoporosis by suppressing osteoclastogenesis with anti-inflammatory activity and be a potential source of functional food ingredients for the prevention of osteoporosis. © 2020 Society of Chemical Industry.

Production of Bovine Equol-Enriched Milk: A Review

Simple Summary

Milk and dairy products contain many substances beneficial to human health; moreover, the contents of some of these substances can be enhanced. This is also the case of isoflavones which are compounds of plant origin that can be ingested and metabolized by cattle and, subsequently, secreted into bovine milk. An especially healthful substance called equol is ranked among isoflavone metabolites, commonly produced in the digestive tract of cattle. Equol content in milk can be modified by using feedstuffs with different contents of isoflavones or by milk processing and storage.

Abstract

Milk and dairy products are important sources of nutrients in the human diet because they contain a number of essential substances and other biologically active components. Many of these substances can be modified, and thus offer opportunities to use milk and dairy products as functional food. Isoflavones are particularly important in human nutrition due to their diverse pharmacological and antioxidant properties. The clinical effectiveness of isoflavone-rich products is believed to be dependent on their ability to metabolize daidzein to equol, which may directly exert cancer preventive effects. However, only approximately 30–40% of humans are able to produce equol, while animals, in general, produce equol. Equol is the predominant product of bacterial metabolism of isoflavones and can be found in various amounts in some food of animal origin, especially in milk. Therefore, milk and dairy products can be considered to be sources of equol for humans who are not able to produce this metabolite. When the content of isoflavones in milk is to be modified, two groups of factors should be considered, i.e., dietary factors that include the source of isoflavones and the processing effects on feedstuffs and animal factors that include the intake of isoflavones, ruminal and postruminal changes, and the health and physiological status of animals. The approximate content of isoflavones in milk can be predicted using carry-over rates for different dietary sources or using a formula that describes the relationship between equol concentration in milk and formononetin intake. Processing and storage can affect the content and profile of isoflavones in milk and dairy products.

Transformation of Pueraria candollei var. mirifica phytoestrogens using immobilized and free β-glucosidase, a technique for enhancing estrogenic activity

Pueraria candollei var. mirifica (PM) has a significant beneficial effect on postmenopausal symptoms associated with estrogen deficiency. However, the estrogenic activity and intestinal absorption of isoflavonoid glycosides derived from PM, such as daidzin and genistin, are significantly lower than those of their aglycones. To enhance the estrogenic activity of the PM extract, we developed β-glucosidase and its immobilized form to increase the PM aglycone content (daidzein and genistein). The enzyme immobilization was done by alginate beads, and the resulting β-glucosidase alginate beads have a diameter of about 0.20 cm. Response surface methodology (RSM) was used to optimize certain parameters, such as the pH, temperature, and ethanol concentration. The optimal conditions of β-glucosidase for daidzein and genistein production were pH of 4.8–4.9, a temperature in the range 46.3–49.1 °C, and ethanol concentration of 10.0–11.0%. The ANOVA results indicated that the design experiment involving free and immobilized β-glucosidase was the best fit by quadratic models, which had adjusted R² values between 0.8625 and 0.9318. Immobilized β-glucosidase can be reused up to nine times and maintained efficacy of greater than 90%. Treatment of the PM extract with β-glucosidase increased the estrogenic activity of the PM extract by 8.71- to 23.2-fold compared to that of the untreated extract. Thus, β-glucosidase has a high potential for enhancing the estrogenic activity of PM constituents, and it can be applied on an industrial scale to increase the utility of these natural products.

Transformation of Pueraria candollei var. mirifica phytoestrogens by β-glucosidase increases estrogenic activity.