Proteolytic activities in togwa, a Tanzanian fermented food

Characterisation of the protein quality and composition of water kefir-fermented casein

This study aimed to assess the technique of natural fermentation by applying water kefir to the casein protein. The diverse microorganisms and their enzymes found naturally in the water kefir can influence casein's characteristics. The fermented casein's protein quality (digestibility and secondary protein structure) and composition (total soluble solids and nutritive and non-nutritive substances) were investigated. Our findings revealed that the fermented casein's protein digestibility and total phenolic content increased from 82.46 to 88.60 % and 7.6 to 8.0 mg gallic acid equivalent/100 g, respectively. In addition, their surface charge and hydrophobicity changed from -30.06 to -34.93 mV and 286.9 to 213.7, respectively. Furthermore, the fermented casein's secondary protein components, α-helix (decreased from 13.66 to 8.21 %) and random coil (increased from 16.88 to 19.61 %), were also altered during the fermentation. Based on these findings, the water kefir fermentation approach could be an effective, practical, non-thermal approach for improving casein's protein quality and composition.

Highlighting the Impact of Lactic-Acid-Bacteria-Derived Flavours or Aromas on Sensory Perception of African Fermented Cereals

Sensory characteristics and flavour profiles of lactic-acid-fermented foods are influenced by lactic acid bacteria (LAB) metabolic activities. The flavour compounds released/produced are directly linked to the sensory characteristics of fermented cereals. African fermented cereals constitute a staple, frequently consumed food group and provide high energy and essential nutrients to many communities on the continent. The flavour and aroma characteristics of fermented cereal products could be correlated with the metabolic pathways of fermenting microorganisms. This report looks at the comprehensive link between LAB-produced flavour metabolites and sensory attributes of African fermented cereals by reviewing previous studies. The evaluation of such data may point to future prospects in the application of flavour compounds derived from African fermented cereals in various food systems and contribute toward the improvement of flavour attributes in existing African fermented cereal products.

Enhanced protein degradation by black soldier fly larvae (Hermetia illucens L.) and its gut microbes

Black soldier fly larvae (BSFL) can convert a variety of organic wastes into biomass, and its gut microbiota are involved in this process. However, the role of gut microbes in the nutrient metabolism of BSFL is unclear. In this study, germ-free BSFL (GF) and gnotobiotic BSFL (GB) were evaluated in a high-protein artificial diet model. We used 16S rDNA sequencing, ITS1 sequencing, and network analysis to study gut microbiota in BSFL that degrade proteins. The protein reduction rate of the GB BSFL group was significantly higher (increased by 73.44%) than that of the GF BSFL group. The activity of gut proteinases, such as trypsin and peptidase, in the GB group was significantly higher than the GF group. The abundances of different gut microbes, including Pseudomonas spp., Orbus spp. and Campylobacter spp., were strongly correlated with amino acid metabolic pathways. Dysgonomonas spp. were strongly correlated with protein digestion and absorption. Issatchenkia spp. had a strong correlation with pepsin activity. Campylobacter spp., Pediococcus spp. and Lactobacillus spp. were strongly correlated with trypsin activity. Lactobacillus spp. and Bacillus spp. were strongly correlated with peptidase activity. Gut microbes such as Issatchenkia spp. may promote the gut proteolytic enzyme activity of BSFL and improve the degradation rate of proteins. BSFL protein digestion and absorption involves gut microbiota that have a variety of functions. In BSFL the core gut microbiota help complete protein degradation. These results demonstrate that core gut microbes in BSFL are important in protein degradation.

Biochemical and Microbiological Changes Associated with Fermentation of Durum Wheat for Lemzeïet Processing, a Traditional Algerian Fermented Food

In Algeria, “Lemzeïet” is prepared by the natural fermentation of wheat. This study aimed to follow the evolution of microbiological and biochemical properties of Lemzeïet with and without vinegar addition for 3, 6, 9 and 12 months. Lactic acid bacteria (LAB) were identified and the microbial count, as well as pH, acidity, protein, fat, ash and starch contents were determined. Results showed that Lemzeïet samples represented a safe product after the gradual absence of fungi. It also contained a significant load of LAB that were cocci or rods, white or yellow, grouped in chain, pair and tetrad. LAB isolates were mannitol positive, grew between 10 and 45 °C, showed resistance at 63.5 °C and the majority were homo-fermentative. Results showed a significant decrease in pH during fermentation regardless of the vinegar addition. Protein content increased up to 14.90% and 15.50% at the end of fermentation. The fat and starch contents decreased after 12 months of fermentation, regardless of the vinegar addition. Ash content remained high (1.41% and 1.45%) after six months of fermentation with and without vinegar, respectively. The microbiological and the biochemical characteristics of Lemzeïet make it a very interesting raw material in the manufacturing of healthy foods.

Effects of Fermentation on the Quality, Structure, and Nonnutritive Contents of Lentil (Lens culinaris) Proteins

Protein digestibility, secondary protein structure components, sugars, and phenolic compounds were analysed to investigate the effect of fermentation on the quality, structure, digestibility, and nonnutritive contents of lentil (Lens culinaris) proteins (LPs). Fermentation was carried out using water kefir seed. The initial pH of the unfermented LPs (6.8) decreased to pH 3.4 at the end of the fermentation on day 5. Protein digestibility increased from 76.4 to 84.1% over the 5 days of fermentation. Total phenolic content increased from 443.4 to 792.6 mg of GAE/100 g after 2 days of fermentation, with the sums of the detected phenolic compounds from HPLC analysis reaching almost 500 mg/100 g. The predominant phenolic compounds detected in fermented LPs include chlorogenic and epicatechin, while traces of rutin, ferulic acid, and sinapic acid were observed. Fermentation played a major role in the changes of the components in the secondary protein structure, especially the percentage of $\alpha$ -helices and random coils. In addition, the reduction in $\alpha$ -helix: $\beta$ -sheet ratio with the increase in protein digestibility was related to the prolongation of the fermentation time. The model used in this research could be a robust tool for improving protein quality, protein degradation, and nonnutritive nutrients using water kefir seed fermentation.

Cell-envelope proteinases from lactic acid bacteria: Biochemical features and biotechnological applications

Proteins displayed on the cell surface of lactic acid bacteria (LAB) perform diverse and important biochemical roles. Among these, the cell-envelope proteinases (CEPs) are one of the most widely studied and most exploited for biotechnological applications. CEPs are important players in the proteolytic system of LAB, because they are required by LAB to degrade proteins in the growth media into peptides and/or amino acids required for the nitrogen nutrition of LAB. The most important area of application of CEPs is therefore in protein hydrolysis, especially in dairy products. Also, the physical location of CEPs (i.e., being cell-envelope anchored) allows for relatively easy downstream processing (e.g., extraction) of CEPs. This review describes the biochemical features and organization of CEPs and how this fits them for the purpose of protein hydrolysis. It begins with a focus on the genetic organization and expression of CEPs. The catalytic behavior and cleavage specificities of CEPs from various LAB are also discussed. Following this, the extraction and purification of most CEPs reported to date is described. The industrial applications of CEPs in food technology, health promotion, as well as in the growing area of water purification are discussed. Techniques for improving the production and catalytic efficiency of CEPs are also given an important place in this review.

Nitrogen Fixation in Pozol, a Traditional Fermented Beverage

Traditional fermentations have been widely studied from the microbiological point of view, but little is known from the functional perspective. In this work, nitrogen fixation by free-living nitrogen-fixing bacteria was conclusively demonstrated in pozol, a traditional Mayan beverage prepared with nixtamalized and fermented maize dough. Three aspects of nitrogen fixation were investigated to ensure that fixation actually happens in the dough: (i) the detection of acetylene reduction activity directly in the substrate, (ii) the presence of potential diazotrophs, and (iii) an in situ increase in acetylene reduction by inoculation with one of the microorganisms isolated from the dough. Three genera were identified by sequencing the 16S rRNA and nifH genes as Kosakonia, Klebsiella, and Enterobacter, and their ability to fix nitrogen was confirmed.IMPORTANCE Nitrogen-fixing bacteria are found in different niches, as symbionts in plants, in the intestinal microbiome of several insects, and as free-living microorganisms. Their use in agriculture for plant growth promotion via biological nitrogen fixation has been extensively reported. This work demonstrates the ecological and functional importance that these bacteria can have in food fermentations, reevaluating the presence of these genera as an element that enriches the nutritional value of the dough.

Potential of probiotics from fermented cereal-based beverages in improving health of poor people in Africa

Milk and milk products; particularly yoghurts have almost exclusively been used as media for probiotic delivery to human being for a very long time. Despite health benefits such products have to humans; that include supply of nutrients, prevention and cure of certain communicable and non-communicable diseases; the presence of allergens, increased lactose intolerance, hypercholesterolemia effects, the need for vegetarian probiotic products, cultural food taboos against milk, and religious beliefs have led to limitations on the use of milk and its products as probiotic vehicles in many places including Africa. Such limitations have led to more researches worldwide on alternative delivery media for probiotics in order to meet the food preferences and demands of people affected by milk and milk products. An integrative approach has been used to find common ideas and concepts from different studies. Different food matrices have been tested for their ability to carry probiotics and cereals and cereal products have been found as among suitable substrates for the purpose. Some investigations have revealed that traditional African fermented cereal-based beverages are potential probiotic carriers because of the probiotic Lactobacillus spp. and yeasts which are involved in the fermentation of such products. This offers an opportunity for the African cereal beverages to be used to provide probiotic health benefits to the majority of African populations. Thus, this review provides information on probiotics including sources, types, health benefits, vehicles for their delivery and specifically also on challenges and future prospects for cereal-based probiotics development and consumption in Africa.

Harnessing Microbes for Sustainable Development: Food Fermentation as a Tool for Improving the Nutritional Quality of Alternative Protein Sources

In order to support the multiple levels of sustainable development, the nutritional quality of plant-based protein sources needs to be improved by food technological means. Microbial fermentation is an ancient food technology, utilizing dynamic populations of microorganisms and possessing a high potential to modify chemical composition and cell structures of plants and thus to remove undesirable compounds and to increase bioavailability of nutrients. In addition, fermentation can be used to improve food safety. In this review, the effects of fermentation on the protein digestibility and micronutrient availability in plant-derived raw materials are surveyed. The main focus is on the most important legume, cereal, and pseudocereal species (Cicer arietinum, Phaseolus vulgaris, Vicia faba, Lupinus angustifolius, Pisum sativum, Glycine max; Avena sativa, Secale cereale, Triticum aestivum, Triticum durum, Sorghum bicolor; and Chenopodium quinoa, respectively) of the agrifood sector. Furthermore, the current knowledge regarding the in vivo health effects of fermented foods is examined, and the critical points of fermentation technology from the health and food safety point of view are discussed.

One Health, Fermented Foods, and Gut Microbiota

Changes in present-day society such as diets with more sugar, salt, and saturated fat, bad habits and unhealthy lifestyles contribute to the likelihood of the involvement of the microbiota in inflammatory diseases, which contribute to global epidemics of obesity, depression, and mental health concerns. The microbiota is presently one of the hottest areas of scientific and medical research, and exerts a marked influence on the host during homeostasis and disease. Fermented foods and beverages are generally defined as products made by microbial organisms and enzymatic conversions of major and minor food components. Further to the commonly-recognized effects of nutrition on the digestive health (e.g., dysbiosis) and well-being, there is now strong evidence for the impact of fermented foods and beverages (e.g., yoghurt, pickles, bread, kefir, beers, wines, mead), produced or preserved by the action of microorganisms, on general health, namely their significance on the gut microbiota balance and brain functionality. Fermented products require microorganisms, i.e., Saccharomyces yeasts and lactic acid bacteria, yielding alcohol and lactic acid. Ingestion of vibrant probiotics, especially those contained in fermented foods, is found to cause significant positive improvements in balancing intestinal permeability and barrier function. Our guts control and deal with every aspect of our health. How we digest our food and even the food sensitivities we have is linked with our mood, behavior, energy, weight, food cravings, hormone balance, immunity, and overall wellness. We highlight some impacts in this domain and debate calls for the convergence of interdisciplinary research fields from the United Nations’ initiative. Worldwide human and animal medicine are practiced separately; veterinary science and animal health are generally neither considered nor inserted within national or international Health discussions. The absence of a clear definition and subsequent vision for the future of One Health may act as a barrier to transdisciplinary collaboration. The point of this mini review is to highlight the role of fermented foods and beverages on gut microbiota and debate if the need for confluence of transdisciplinary fields of One Health is feasible and achievable, since they are managed by separate sectors with limited communication.

Pichia kudriavzevii as a representative yeast of North Patagonian winemaking terroir

Terroir concept includes specific soil, topography, climate, landscape characteristics and biodiversity features. In reference to the last aspect, recent studies investigating the microbial biogeography (lately called 'microbial terroir') have revealed that different wine-growing regions maintain different microbial communities. The aim of the present work was to identify potential autochthonous fermentative yeasts isolated from native plants in North Patagonia, Schinus johnstonii, Ephedra ochreata and Lycium chilense, that could be associated to the specific vitivinicultural terroir of this region. Different Pichia kudriavzevii isolates were recovered from these plants and physiologically and genetically compared to regional wine isolates and foreign reference strains of the same species. All isolates were subjected to molecular characterization including mtDNA-RFLP, RAPD-PCR and sequence analysis. Both wine and native P. kudriavzevii isolates from Patagonia showed similar features, different from those showed by foreign strains, suggesting that this species could be part of a specific regional terroir from North Patagonia.

Lactic acid bacteria as a cell factory for the delivery of functional biomolecules and ingredients in cereal-based beverages: a review

In this review, we aim to describe the mechanisms by which LAB can fulfil the novel role of efficient cell factory for the production of functional biomolecules and food ingredients to enhance the quality of cereal-based beverages. LAB fermentation is a safe, economical, and traditional method of food preservation foremost, as well as having the additional benefits of flavor, texture, and nutrition amelioration. Additionally, LAB fermentation in known to render cereal-based foods and beverages safe, in a chemical-free, consumer-friendly manner, from an antinutrient and toxigenic perspective. Huge market opportunities and potential exist for food manufacturers who can provide the ideal functional beverage fulfilling consumer needs. Newly developed fermented cereal-based beverages must address markets globally including, high-nutrition markets (developing countries), lifestyle choice consumers (vegetarian, vegan, low-fat, low-salt, low-calorie), food-related non-communicable disease sufferers (cardiovascular disease, diabetes), and green label consumers (Western countries). To fulfil these recommendations, a suitable LAB starter culture and cereal-based raw materials must be developed. These strains would be suitable for the biopreservation of cereal beverages and, ideally, would be highly antifungal, anti-mycotoxigenic, mycotoxin-binding and proteolytic (neutralize toxic peptides and release flavor-contributing amino acids) with an ability to ferment cereals, whilst synthesizing oligosaccharides, thus presenting a major opportunity for the development of safe cereal-based prebiotic functional beverages to compete with and replace the existing dairy versions.

Protein Degradation in Wheat Sourdough Fermentation with Lactobacillus plantarum M616

Hydrolysis of wheat proteins during sourdough fermentation was determined in the present study. Sourdoughs were characterized with respect to cell counts, pH, TTA, and proteolytic activity as well as the quantity of total proteins and water-soluble proteins. Moreover, composition analysis of total proteins and water-soluble proteins using SDS-PAGE was carried out. Sourdough fermentation using Lactobacillus plantarum showed a decrease in pH and increase in TTA during fermentation. Fermentation resulted in hydrolysis and solubilization of wheat proteins. It demonstrated that protein hydrolysis in sourdough was mainly caused by pH-dependent activation of cereal enzymes according to change in proteolytic activity.

Purification and characterization of a proteinase from the probiotic Lactobacillus rhamnosus OXY

A proteinase produced by the human gastrointestinal isolate Lactobacillus rhamnosus strain OXY was identified and characterized. The prtR2 gene coding for proteinase activity was detected in the examined strain. The PCR primers used were constructed on the basis of the sequence of the prtR2 proteinase gene from Lactobacillus rhamnosus GG. The enzyme was purified by fast protein liquid chromatography (FPLC) using CM-Sepharose Fast Flow and Sephacryl S-300 columns. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the enzyme had a relatively low molecular mass of 60 kD. Protease activity was observed at a pH range from 6.5 to 7.5 with optimum k(cat)/K(m) values at pH 7.0 and 40°C. Maximum proteolytic activity (59 U mL(-1)) was achieved after 48 hr of cultivation. The activity of the enzyme was inhibited only by irreversible inhibitors specific for serine proteinases (PMSF and 3,4-dichloro-isocumarine), suggesting that the enzyme was a serine proteinase. Proteinase activity was increased by Ca(2+) and Mg(2+), and inhibited by Cu(2+), Zn(2+), Cd(2+), and Fe(2+).

New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre?

Epidemiological studies have clearly shown that whole-grain cereals can protect against obesity, diabetes, CVD and cancers. The specific effects of food structure (increased satiety, reduced transit time and glycaemic response), fibre (improved faecal bulking and satiety, viscosity and SCFA production, and/or reduced glycaemic response) and Mg (better glycaemic homeostasis through increased insulin secretion), together with the antioxidant and anti-carcinogenic properties of numerous bioactive compounds, especially those in the bran and germ (minerals, trace elements, vitamins, carotenoids, polyphenols and alkylresorcinols), are today well-recognised mechanisms in this protection. Recent findings, the exhaustive listing of bioactive compounds found in whole-grain wheat, their content in whole-grain, bran and germ fractions and their estimated bioavailability, have led to new hypotheses. The involvement of polyphenols in cell signalling and gene regulation, and of sulfur compounds, lignin and phytic acid should be considered in antioxidant protection. Whole-grain wheat is also a rich source of methyl donors and lipotropes (methionine, betaine, choline, inositol and folates) that may be involved in cardiovascular and/or hepatic protection, lipid metabolism and DNA methylation. Potential protective effects of bound phenolic acids within the colon, of the B-complex vitamins on the nervous system and mental health, of oligosaccharides as prebiotics, of compounds associated with skeleton health, and of other compounds such as alpha-linolenic acid, policosanol, melatonin, phytosterols and para-aminobenzoic acid also deserve to be studied in more depth. Finally, benefits of nutrigenomics to study complex physiological effects of the 'whole-grain package', and the most promising ways for improving the nutritional quality of cereal products are discussed.

The effect of fermentation and storage on free amino acids of tarhana

A study on the evaluation of free amino acids (FAAs) in tarhana during fermentation and storage was performed. The FAAs in tarhana were determined by RP-HPLC with a fluorescence detector following extraction from the sample and derivatization with dansyl chloride. The amount of FAAs increased significantly (p<0.01) during fermentation and storage. The increase in the content of total free amino acids (TFAAs) and total free essential amino acids (TFEAAs) of fermented tarhana, which was used with yogurt bacteria and baker's yeast, was 57% and 93%, respectively. The amino acids primarily responsible for the increase were valine and tryptophan followed by methionine, alanine, isoleucine + leucine, phenylalanine, arginine, proline, and lysine. The TFAA content of tarhana at the end of fermentation was found to be 8% of total protein (16.8%). The ratio of TFEAAs/TFAAs was initially 0.46 and increased to 0.57 at the end of fermentation. The TFAA content of wet tarhanas was higher than that of the dry counterpart. It was found that the TFAA content of dry tarhana was 25% lower than the fresh wet tarhana (FWT), at the end of fermentation. It was concluded that the decrease in FAAs in dry tarhana was due to the Maillard reaction and partial degradation of FAAs during dehydration.

Evaluation of the fermentability of oat fractions obtained by debranning using lactic acid bacteria

AIMS

The overall kinetics of the fermentation of four oat fractions obtained by debranning using three potentially probiotic lactic acid bacteria were investigated. The main objective was to study the suitability of these fractions as fermentation media for the growth and the metabolic production of bacteria isolated from human intestine.

METHODS AND RESULTS

The cell growth, lactic acid production and substrate uptakes of the three lactobacilli was monitored for 30 h. An unstructured mathematical model was used to describe and fit the experimental data. In the medium from fraction B (1-3% pearlings or beta-glucan-rich fraction) all strains reached the highest cell populations, maximum growth rates and maximum lactic acid productions. This could be because of the high levels of total fibre and beta-glucan of this fraction. Limited growth and lactic acid formation was found in medium A (0-1% pearlings or bran-rich fraction).

CONCLUSIONS

Medium B (1-3% pearling fraction) is the most suitable for fermentation and produces considerably higher probiotic cell concentrations.

SIGNIFICANCE AND IMPACT OF THE STUDY

Debranning technology could be used to separate fractions from cereal grains for the production of functional formulations with higher probiotic levels than the ones that were obtained with the whole grain.

Proteolysis in model sourdough fermentations

Model wheat doughs started with six different lactic acid bacteria (LAB), with or without a commercial baker's yeast culture, were used to study proteolysis in sourdough fermentations. Cell counts, pH, and free amino acid concentration were measured. Sequential extraction of dough samples was performed to separate wheat proteins. The salt-soluble protein fraction (albumins and globulins) was analyzed by RP-HPLC and SDS-PAGE, whereas propanol-soluble (gliadins) and insoluble (glutenins) protein fractions were analyzed by SDS-PAGE only. Multivariate statistical methods were used for the analysis of results. The presence of yeasts and LAB affected RP-HPLC and SDS-PAGE patterns of the salt-soluble fraction in a complex way. The only changes in the gluten proteins that could be related to the presence of LAB were the appearance of new protein fragments (20 and 27 kDa) from gliadins and the degradation of high molecular weight glutenin subunits.

Biodiversity of Lactobacillus sanfranciscensis strains isolated from five sourdoughs

AIMS

Five different sourdoughs were investigated for the composition of lactic acid bacteria (LAB) and the biodiversity of Lactobacillus sanfranciscensis strains.

METHODS AND RESULTS

A total of 57 strains were isolated from five sourdoughs. Isolated strains were all identified by the 16S rDNA sequence and species-specific primers for L. sanfranciscensis. Results of identification showed that LAB strains were L. sanfranciscensis, Lactobacillus plantarum, Lactobacillus paralimentarius, Lactobacillus fermentum, Lactobacillus pontis, Lactobacillus casei, Weisella confusa and Pediococcus pentosaceus. A total of 21 strains were identified as L. sanfranciscensis and these isolates were detected in all five sourdoughs. Ribotyping was applied to investigate the relationship between intraspecies diversity of L. sanfranciscensis and sourdough. A total of 22 strains of L. sanfranciscensis including L. sanfranciscensis JCM 5668T were compared by ribotyping. The dendrogram of 21 ribotyping patterns showed four clusters, and L. sanfranciscensis JCM 5668T was independent of the others. The different biotypes of L. sanfranciscensis were present in two sourdoughs compared with other three sourdoughs.

CONCLUSIONS

The LAB compositions of five sourdoughs were different and the relationship between intraspecies diversity of L. sanfranciscensis strains and five sourdoughs was shown by ribotyping.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrated that ribotyping was useful for distinguishing L. sanfranciscensis strains. A further important result is that the intra-species diversity of L. sanfranciscensis strains seems to be related to the sourdough preparation.