First characterization of bioactive components in soybean tempe that protect human and animal intestinal cells against enterotoxigenic Escherichia coli (ETEC) infection

Dextran and levan exopolysaccharides from tempeh-associated lactic acid bacteria with bioactivity against enterotoxigenic Escherichia coli (ETEC)

Soybean tempeh contains bioactive carbohydrate that can reduce the severity of diarrhea by inhibiting enterotoxigenic Escherichia coli (ETEC) adhesion to mammalian epithelial cells. Lactic acid bacteria (LAB) are known to be present abundantly in soybean tempeh. Some LAB species can produce exopolysaccharides (EPS) with anti-adhesion bioactivity against ETEC but there has been no report of anti-adhesion bioactive EPS from tempeh-associated LAB. We isolated EPS-producing LAB from tempeh-related sources, identified them, unambiguously elucidated their EPS structure and assessed the bioactivity of their EPS against ETEC. Pediococcus pentosaceus TL, Leuconostoc mesenteroides WA and L. mesenteroides WN produced both dextran (α-1,6 linked glucan; >1000 kDa) and levan (β-2,6 linked fructan; 650-760 kDa) in varying amounts and Leuconostoc citreum TR produced gel-forming α-1,6-mixed linkage dextran (829 kDa). All four isolates produced EPS that could adhere to ETEC cells and inhibit auto-aggregation of ETEC. EPS-PpTL, EPS-LmWA and EPS-LmWN were more bioactive towards pig-associated ETEC K88 while EPS-LcTR was more bioactive against human-associated ETEC H10407. Our finding is the first to report on the bioactivity of dextran against ETEC. Tempeh is a promising source of LAB isolates that can produce bioactive EPS against ETEC adhesion and aggregation.

Metabolite Changes in Indonesian Tempe Production from Raw Soybeans to Over-Fermented Tempe

Tempe is fermented soybean from Java, Indonesia, that can serve as a functional food due to its high nutritional content and positive impact on health. Although the tempe fermentation process is known to affect its nutrient content, changes in the metabolite profile during tempe production have not been comprehensively examined. Thus, this research applied a metabolomics approach to investigate the metabolite profile in each step of tempe production, from soybean soaking to over-fermentation. Fourteen samples of raw soybeans, i.e., soaked soybeans (24 h), steamed soybeans, fungal fermented soybeans, and over-fermented soybeans (up to 72 h), were collected. Untargeted metabolomics by gas chromatography/mass spectrometry (GC-MS) was used to determine soybean transformations from various fermentation times and identify disparity-related metabolites. The results showed that soybeans samples clustered together on the basis of the different fermentation steps. The results also showed that sugar, sugar alcohol, organic acids, and amino acids, as well as fermentation time, contributed to the soybean metabolite profile transformations. During the fermentation of tempe, sugars and sugar alcohols accumulated at the beginning of the process before gradually decreasing as fermentation progressed. Specifically, at the beginning of the fermentation, gentiobiose, galactinol, and glucarate were accumulated, and several metabolites such as glutamine, 4-hydroxyphenylacetic acid, and homocysteine increased along with the progression of fermentation. In addition, notable isoflavones daidzein and genistein increased from 24 h of fermentation until 72 h. This is the first report that provides a complete description of the metabolic profile of the tempe production from soybean soaking to over-fermentation. Through this study, the dynamic changes at each step of tempe production were revealed. This information can be beneficial to the tempe industry for the improvement of product quality based on metabolite profiling.

Comparative nutritional and antimicrobial analysis of Himalayan black and yellow soybean and their okara

BACKGROUND

Soybean is believed to have good nutraceutical potential which is important for human health. Yellow soybean (YS) is generally used for the production of soymilk and other products, while black soybean (BS) is less explored. During the production of soymilk, residue, called okara is generated which is reported to have a good amount of nutrient content. Studies are generally performed with YS while BS is less explored. The present work is a comparison of the nutraceutical potential of BS and YS and their okara, mainly in terms of proximate, minerals, antinutrients, and isoflavone content and bioactivity of all types of samples in terms of antioxidant and antimicrobial activity.

RESULTS

Compared to raw soybean, protein content decreased significantly in both types of okara. Phytochemicals like ascorbic acid, catechin, quercetin, and gallic acid were significantly (P < 0.05) high in BS residue in comparison to respective raw soybean. Among isoflavones, daidzin and genistin were found significantly varying among all the samples, and glycitin and glycitein were not present in YS.

CONCLUSION

The nutraceutical potential and antimicrobial activity were comparative for both the raw beans and their okara, while the phytochemical contents and antioxidant activity were higher in the case of BS and its okara. © 2022 Society of Chemical Industry.

In Vitro Evaluation of Dietary Fiber Anti-Infectious Properties against Food-Borne Enterotoxigenic Escherichia coli

Dietary fibers have well-known beneficial effects on human health, but their anti-infectious properties against human enteric pathogens have been poorly investigated. Enterotoxigenic Escherichia coli (ETEC) is the main agent of travelers’ diarrhea, against which targeted preventive strategies are currently lacking. ETEC pathogenesis relies on multiple virulence factors allowing interactions with the intestinal mucosal layer and toxins triggering the onset of diarrheal symptoms. Here, we used complementary in vitro assays to study the antagonistic properties of eight fiber-containing products from cereals, legumes or microbes against the prototypical human ETEC strain H10407. Inhibitory effects of these products on the pathogen were tested through growth, toxin production and mucus/cell adhesion inhibition assays. None of the tested compounds inhibited ETEC strain H10407 growth, while lentil extract was able to decrease heat labile toxin (LT) concentration in culture media. Lentil extract and specific yeast cell walls also interfered with ETEC strain H10407 adhesion to mucin beads and human intestinal cells. These results constitute a first step in the use of dietary fibers as a nutritional strategy to prevent ETEC infection. Further work will be dedicated to the study of fiber/ETEC interactions within a complex gut microbial background.

Tripartite relationship between gut microbiota, intestinal mucus and dietary fibers: towards preventive strategies against enteric infections

The human gut is inhabited by a large variety of microorganims involved in many physiological processes and collectively referred as to gut microbiota. Disrupted microbiome has been associated with negative health outcomes and especially could promote the onset of enteric infections. To sustain their growth and persistence within the human digestive tract, gut microbes and enteric pathogens rely on two main polysaccharide compartments, namely dietary fibers and mucus carbohydrates. Several evidences suggest that the three-way relationship between gut microbiota, dietary fibers and mucus layer could unravel the capacity of enteric pathogens to colonise the human digestive tract and ultimately lead to infection. The review starts by shedding light on similarities and differences between dietary fibers and mucus carbohydrates structures and functions. Next, we provide an overview of the interactions of these two components with the third partner, namely, the gut microbiota, under health and disease situations. The review will then provide insights into the relevance of using dietary fibers interventions to prevent enteric infections with a focus on gut microbial imbalance and impaired-mucus integrity. Facing the numerous challenges in studying microbiota-pathogen-dietary fiber-mucus interactions, we lastly describe the characteristics and potentialities of currently available in vitro models of the human gut.

Tempeh: A semicentennial review on its health benefits, fermentation, safety, processing, sustainability, and affordability

Tempeh is a fermented food made of mainly soybeans and is a nutritious, affordable, and sustainable functional source of protein. Globally, tempeh is a widely accepted fermented product. Although there is a growing body of literature on tempeh, most research has focused on unfermented soybeans, thus the impact of tempeh fermentation on biological properties of soybeans has been largely left scattered. The objective of this review is to summarize the literature of tempeh fermentation over the past 60 years. A search of articles on tempeh published from 1960 to 2020 was performed using the Cochrane Library, Web of Science, EBSCOhost FSTA database, and Google Scholar. References from identified articles were reviewed for additional sources. In total, 321 papers were selected for this review, of which 64 papers were related to the health benefits of tempeh. This review concluded that sufficient evidence exists in the literature supporting tempeh fermentation as a low-cost, health-promoting, and sustainable food processing technology to produce protein-rich foods using various beans, legumes, and grains. This comprehensive review suggests further studies are needed on tempeh fermentation and its impact on human health; research and standardization of nonsoy tempeh; assessment of food safety-improving modification in tempeh production system; and initiatives supporting the sourcing of local ingredients in tempeh production.

Linoleic acid, α-linolenic acid, and monolinolenins as antibacterial substances in the heat-processed soybean fermented with Rhizopus oligosporus

Antibacterial activities against Staphylococcus aureus and Bacillus subtilis were found in an ethanol fraction of tempe, an Indonesian fermented soybean produced using Rhizopus oligosporus. The ethanol fraction contained free fatty acids, monoglycerides, and fatty acid ethyl esters. Among these substances, linoleic acid and α-linolenic acid exhibited antibacterial activities against S. aureus and B. subtilis, whereas 1-monolinolenin and 2-monolinolenin exhibited antibacterial activity against B. subtilis. The other free fatty acids, 1-monoolein, monolinoleins, ethyl linoleate, and ethyl linolenate did not exhibit bactericidal activities. These results revealed that R. oligosporus produced the long-chain polyunsaturated fatty acids and monolinolenins as antibacterial substances against the Gram-positive bacteria during the fungal growth and fermentation of heat-processed soybean.

Modified soybean meal polysaccharide with high adhesion capacity to Salmonella

Carbohydrates are known to act as analog receptors for bacteria and therefore are promising alternatives for the control and prevention of bacterial infections. The present study evaluated the chemical structure of modified soybean meal polysaccharides and their capacity to adhere enterobacteria (Salmonella Typhimurium) and to interfere with the bacteria adhesion to the known analogue receptors, using in vitro assays. For this, soybean meal suspensions were subjected to a thermochemical extraction process and structural analyses showed that the fraction with higher adhesion and adhesion-inhibition potential, SAP, was constituted by two types of polysaccharides: a partially depolymerized pectin, of high molar mass, composed of xylogalacturonan and rhamnogalacturonan regions (SAP1, 545.5 kDa), and a (1 → 4)-linked-β-D-galactan of low molar mass (SAP2, 8.7 kDa). The results showed a high affinity of Salmonella for galactans, while high molar mass pectins showed no adhesion capacity. The chemical compositions of the fractions suggested that galactose could be responsible for the recognition process in the adhesion process. Other factors, such as structure and degree of polymerization of the polymers, may also be influencing the adhesion process. Modified soybean meal polysaccharides appear to be a promising alternative agent to antibiotics for the control and prevention of foodborne diseases.

Antimicrobial potential of cauliflower, broccoli, and okara byproducts against foodborne bacteria

The antimicrobial potential of cauliflower, broccoli, and okara byproducts was assessed against Gram-positive and Gram-negative bacteria. Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, Bacillus cereus, and Listeria monocytogenes serovar 4b growth behavior was assessed under exposure to 5% vegetable byproducts added to the reference medium, buffered peptone water (0.1% [wt/vol]), at 37°C. Although the byproducts were not effective against L. monocytogenes, they were bactericidal against Salmonella Typhimurium, E. coli O157:H7, and B. cereus. The most promising results were achieved with the cauliflower-Salmonella Typhimurium combination, because the bacterial population was reduced by 3.11 log10 cycles after 10 h of incubation at 37°C as a result of 5% cauliflower addition. Further studies were carried out for this combination, at different cauliflower concentrations (0, 0.5, 1, 5, 10, and 15%) and at temperatures in the range of 5-37°C. The greatest inactivation level (6.11 log10 cycles) was achieved at refrigeration temperature (5°C) using 15% cauliflower addition. Both temperature and cauliflower concentration significantly (p≤0.05) influenced the Salmonella Typhimurium inactivation level. The kinetic parameters were adjusted to mathematical models. The modified Gompertz mathematical model provided an accurate fit (root-mean-square error (RMSE) [0.00009-0.21] and adjusted-R(2) [0.81-0.99]) to experimental Salmonella Typhimurium survival curves describing inactivation kinetics of the pathogen to the antimicrobial effect of cauliflower byproduct.

Antibacterial and antidiarrheal activities of plant products against enterotoxinogenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) produces two types of enterotoxins: heat-labile (LT) and heat-stable (STa and STb). These molecules are involved in the induction of secretory diarrhea in animals including humans. This condition is currently treated using a fluid replacement therapy and antibiotics. This treatment is often not available to people in developing countries, and several die from the condition provoke by ETEC. Over the years, plants and plant extracts have been use as traditional medicine to treat various gastrointestinal ailments including diarrhea. Many of these plant products have been claimed to be active against diarrhea, however few have been extensively studied. The main objective of this review was to gather the scattered information on the antidiarrheal activities reported for various plant products on ETEC. This includes two major effects: (1) The inhibitory effect on bacterial growth or viability and (2) The interference with ETEC enterotoxins activity upon the intestinal epithelium. We will focus on plant products and extracts for which we have major indications of their biological activity against ETEC and their enterotoxins. Because Vibrio cholerae toxin (CT) is structurally, antigenically and mechanistically related to LT, it will also be discussed in this review.

Antibiofilm polysaccharides

Bacterial extracellular polysaccharides have been shown to mediate many of the cell-to-cell and cell-to-surface interactions that are required for the formation, cohesion and stabilization of bacterial biofilms. However, recent studies have identified several bacterial polysaccharides that inhibit biofilm formation by a wide spectrum of bacteria and fungi both in vitro and in vivo. This review discusses the composition, modes of action and potential biological roles of antibiofilm polysaccharides recently identified in bacteria and eukarya. Some of these molecules may have technological applications as antibiofilm agents in industry and medicine.