Significance of yeasts and moulds occurring in maize dough fermentation for 'kenkey' production

Cereal-based fermented foods as microbiota-directed products for improved child nutrition and health in sub-Saharan Africa

Several strategies, programs and policies have long been developed and implemented to alleviate child malnutrition in sub-Saharan African countries. However, stunting and wasting still persist at an alarming rate, suggesting that alternative strategies are needed to induce faster progress toward the 2030 SDGs targets of reducing malnutrition. Gut microbiota-directed intervention is now being recognized as an unconventional powerful approach to mitigate malnutrition and improve overall child health. In an African setting, manufactured probiotic and synbiotic foods or supplements may not be successful owing to the non-affordability and high attachment of African populations to their food tradition. This review analyses the potential of indigenous fermented cereal-based products including porridges, doughs, beverages, bread- and yoghurt-like products, to be used as microbiota-directed foods for over 6 months children. The discussion includes relevant strategies to effectively enhance the beneficial effects of these products on gut microbiota composition for improved child health and nutrition in sub-Saharan Africa. Characterization of probiotic features and general safety of food processing in sub-Saharan Africa as well as randomized clinical studies are still lacking to fully ascertain the health effects and suitability of these fermented foods in preventing and treating child malnutrition and diarrhea.

Aflatoxins in maize flour produced in Mozambique and its risk assessment

This study investigated the occurrence of aflatoxins (B1, B2, G1, and G2) in maize flour produced in Mozambique and to assess the associated carcinogenic risk. At different opportunities, 30 samples of maize flour were collected in five flour processing factories. These were determined by high-performance liquid chromatography (HPLC) with fluorescence detection. AFB1 concentrations ranged from 0.25 to 0.33 μg kg-1. The levels of total aflatoxins ranged from 0.55 to 1.05 μg kg-1, with a mean of 0.89 μg kg-1, for which maximum limits (MLs) are 10 and 4 μg kg-1 for Mozambique and the European Union, respectively. The calculated Margin of Exposure (MOE) for men and women was 243 and 231, respectively, so several folds below the risk cut-off level, indicating that consumption of such maize flour poses a potential risk of hepatocarcinoma related to aflatoxin exposure due to high intake of this food, a staple diet in most African countries.

Peppermint essential oil and its nano-emulsion: Potential against aflatoxigenic fungus Aspergillus flavus in food and feed

A facultative parasite called Aspergillus flavus contaminates several important food crops before and after harvest. In addition, the pathogen that causes aspergillosis infections in humans and animals is opportunistic. Aflatoxin, a secondary metabolite produced by Aspergillus flavus, is also carcinogenic and mutagenic, endangering human and animal health and affecting global food security. Peppermint essential oils and plant-derived natural products have recently shown promise in combating A. flavus infestations and aflatoxin contamination. This review discusses the antifungal and anti-aflatoxigenic properties of peppermint essential oils. It then discusses how peppermint essential oils affect the growth of A. flavus and the biosynthesis of aflatoxins. Several cause physical, chemical, or biochemical changes to the cell wall, cell membrane, mitochondria, and associated metabolic enzymes and genes. Finally, the prospects for using peppermint essential oils and natural plant-derived chemicals to develop novel antifungal agents and protect foods are highlighted. In addition to reducing the risk of aspergillosis infection, this review highlights the significant potential of plant-derived natural products and peppermint essential oils to protect food and feed from aflatoxin contamination and A. flavus infestation.

Toxicogenic fungal profile, Ochratoxin A exposure and cancer risk characterization through maize (Zea mays) consumed by different age populations in the Volta region of Ghana

Maize (Zea mays) is an important staple food crop for the majority of Ghanaians. Maize is mostly contaminated by fungal species and particularly mycotoxins. This work aimed to identify and quantify the incidence of fungal infection and exposure to Ochratoxin A (OTA) as well as the health risk characterization in different age populations due to maize consumption in the Volta region. Maize samples were plated on Dichloran Rose Bengal Chloramphenicol (DRBC) agar, and Oxytetracycline Glucose Yeast Extract (OGYE) agar. All media were prepared in accordance with the manufacturers' instructions. The plates were incubated at 28 ± 2 °C for 5-7 days. High-Performance Liquid Chromatography connected to a fluorescence detector (HPLC-FLD) was used to analyze the ochratoxin A (OTA) levels in maize. Cancer risk assessments were also conducted using models prescribed by the Joint FAO/WHO Expert Committee on Additives (JECFA). The maize samples collected from the Volta region contained fungal population between the range of 3.08-4.58 log10 CFU/g. Eight (8) genera were recorded belonging to Aspergillus, Trichoderma, Penicillium, Fusarium, Saccharomyces, Mucor, Rhodotorula and Rhizopus. The species diversity includes A. flavus, A. niger, T. harzianum, P. verrucosum, F. oxysporum, Yeast, F. verticillioides, Rhodotorulla sp, A. fumigatus, R. stolonifer, M. racemosus species. Additionally, the ochratoxins level contained in the samples were very noteworthy and ranged from 1.22 to 28.17 μg/kg. Cancer risk assessments of OTA produced outcomes also ranged between 2.15 and 524.54 ng/kg bw/day, 0.03-8.31, 0.0323, and 0.07-16.94 for cases/100,000 person/yr for Estimated Daily Intake (EDI), Margin of Exposure (MOE), Average Potency, and Cancer Risks respectively for all age categories investigated. There was very high mycoflora load on the maize sampled from the Volta region, likewise the range of mycotoxins present in the maize grains, suggesting the potential to pose some adverse health effects with the populace of the Volta region.

Assessing Producers’ Knowledge in Good Manufacturing Practices during the Production of a Traditionally Fermented Food (Ga Kenkey) in the Ho Municipality, Ghana

Good manufacturing practice (GMP) is the primary sanitary and processing requirement necessary to ensure the production of safe foods. It ensures that the production facilities and processes have the necessary conditions to prevent potential hazards from contaminating foods. However, little is known about its application in the production of a traditionally fermented and well-patronized food like the Ga kenkey. This study was therefore designed to evaluate the knowledge and practices of Ga kenkey producers in GMPs. A self-administered questionnaire was prepared and used to recruit 42 Ga kenkey producers using convenient sampling techniques. Out of the 42 producers, 83.3% were females, between 18 and 33 years (61.9%) and single (42.9%), and have been in the business for about 0 to 5 years (69.1%). A significant number of producers had neither GMP, food safety nor HACCP training. The producers have inadequate knowledge of GMPs since majority of them do not use gloves and consider wearing them unnecessary. Even though the producers agreed that GMPs improve product qualities, the establishment of reputation, and customer satisfaction and identify problems within the production process, they however did not pay attention to any form of hazards during the production process. Therefore, since education, training, and experience had a significant ( $P\le 0.05$ ) positive influence on the producers’ knowledge and practices, sufficient training in GMPs coupled with regular supervision should be provided to the producers for the hygienic and safe production of this commonly patronized food.

The metabolism and biotransformation of AFB1: Key enzymes and pathways

Aflatoxins B₁ (AFB₁) is a hepatoxic compound produced by Aspergillus flavus and Aspergillus parasiticus, seriously threatening food safety and the health of humans and animals. Understanding the metabolism of AFB₁ is important for developing detoxification and intervention strategies. In this review, we summarize the AFB₁ metabolic fates in humans and animals and the key enzymes that metabolize AFB₁, including cytochrome P450s (CYP450s) for AFB₁ bioactivation, glutathione-S-transferases (GSTs) and aflatoxin-aldehyde reductases (AFARs) in detoxification. Furthermore, AFB₁ metabolism in microbes is also summarized. Microorganisms specifically and efficiently transform AFB₁ into less or non-toxic products in an environmental-friendly approach which could be the most desirable detoxification strategy in the future. This review provides a wholistic insight into the metabolism and biotransformation of AFB₁ in various organisms, which also benefits the development of protective strategies in humans and animals.

Microbial Quality and Growth Dynamics in Shameta: A Traditional Ethiopian Cereal-Based Fermented Porridge

Shameta is a traditional, Ethiopian, cereal-based fermented porridge exclusively prepared for lactating mothers. The aim of this study was to determine the microbial quality of Shameta samples collected from households of lactating mothers and to determine microbial dynamics and physicochemical changes during laboratory fermentation of Shameta. Isolation and characterization of the dominant microbes and analysis of the physicochemical properties of samples were done following standard microbiological methods and analytical techniques. Results of this study showed that the highest mean count of lactic acid bacteria (8.33 log cfu/g) was recorded in a sample from laboratory-fermented barley-based Shameta, and the lowest (5.88 log cfu/g) in Shameta made from a mixture of barley and maize (BMS). In both barley-based and maize-based laboratory-prepared Shameta, the microflora were dominated by LAB, followed by yeasts. The dominant LAB were the genus Lactobacillus (74.85%), followed by Enterococcus (15.79%). It could be concluded that Shameta collected from households of lactating mothers are fairly safe for consumption, as the stringent physicochemical conditions of the final product could inhibit the growth of pathogens. However, as Shameta is a traditional fermented porridge fed to lactating mothers, we call for a further improvement to the fermentation process by using defined starter cultures.

Toxigenic mycoflora, aflatoxin and fumonisin contamination of poultry feeds in Ghana

The study was undertaken to identify the major mycotoxigenic fungi, aflatoxin and fumonisin levels in prepared poultry feeds in Ghana. Three hundred and fifty (350) prepared feed samples were randomly collected from 133 commercial poultry farms, 76 feed processors and eight (8) feed vendors in three major poultry producing regions of Ghana over two seasons. Fungi were isolated using the serial dilution method on potato dextrose agar and identified using standard methods of identification. Total aflatoxin and fumonisin levels were quantified using AgraStrip® Total Aflatoxin and Fumonisin Quantitative test Watex® from RomerLab, USA. Eight (8) different fungi were isolated from the feed samples with isolation frequency as follows: Aspergillus flavus (47%), A. niger (24%), A. fumigatus (17%), A. oryzae (3%), A. tamarii (2%), Penicillium sp. (3%), Colletotrichum sp. (4%) and Rhizopus sp. (0.1%). Feed samples collected during the rainy season recorded higher mean colony counts (3.39 ± 0.29) than that of the dry season (1.10 ± 0.18). Total aflatoxin and fumonisin levels ranged from 0 to 118 ppb with a mean of 57.25 ± 2.55 ppb, and 0.28-15 ppm with a mean of 1.54 ± 0.12 ppm, respectively. The study revealed co-occurrence of aflatoxin and fumonisin in all the feed samples. Significant correlations (r = 0.298, r = 0.694) (p < 0.05) were observed among the aflatoxin and fumonisin levels and the fungi isolated. Seventy-four percent (74%) of all the feed samples exceeded the 15 ppb Ghana Standards Authority threshold, the EU regulatory limit of 20 ppb and the FAO/WHO recommended maximum permissible limit of 30 ppb for poultry feeds. Although fumonisin levels were less than the EU guidance values of 20 ppm for poultry feeds, 20% of the samples were higher than the FAO/WHO maximum tolerable daily intake limit of 2 ppm. Proper handling of prepared feeds and ingredients could prevent or minimize toxigenic fungi contamination and lower the likelihood of mycotoxin development in poultry feeds.

The fate of mycotoxins during secondary food processing of maize for human consumption

Mycotoxins are naturally occurring fungal metabolites that are associated with health hazards and are widespread in cereals including maize. The most common mycotoxins in maize that occur at relatively high levels are fumonisins (FBs), zearalenone, and aflatoxins; furthermore, other mycotoxins such as deoxynivalenol and ochratoxin A are frequently present in maize. For these toxins, maximum levels are laid down in the European Union (EU) for maize raw materials and maize-based foods. The current review article gives a comprehensive overview on the different mycotoxins (including mycotoxins not regulated by EU law) and their fate during secondary processing of maize, based on the data published in the scientific literature. Furthermore, potential compliance with the EU maximum levels is discussed where appropriate. In general, secondary processing can impact mycotoxins in various ways. Besides changes in mycotoxin levels due to fractionation, dilution, and/or concentration, mycotoxins can be affected in their chemical structure (causing degradation or modification) or be released from or bound to matrix components. In the current review, a special focus is set on the effect on mycotoxins caused by different heat treatments, namely, baking, roasting, frying, (pressure) cooking, and extrusion cooking. Production processes involving multiple heat treatments are exemplified with the cornflakes production. For that, potential compliance with FB maximum levels was assessed. Moreover, effects of fermentation of maize matrices and production of maize germ oil are covered by this review.

Changes Occurring in Spontaneous Maize Fermentation: An Overview

Maize and its derived fermented products, as with other cereals, are fundamental for human nutrition in many countries of the world. Mixed cultures, principally constituted by lactic acid bacteria (LAB) and yeasts, are responsible for maize fermentation, thus increasing its nutritional value and extending the products’ shelf-life. Other microorganisms involved, such as molds, acetic acid bacteria, and Bacillus spp. can contribute to the final product characteristics. This review gives an overview of the impact of the activities of this complex microbiota on maize product development and attributes. In particular, starting from amylolytic activity, which is able to increase sugar availability and influence the microbial succession and production of exopolysaccharides, vitamins, and antimicrobial compounds, which improve the nutritional value. Further activities are also considered with positive effects on the safety profile, such as phytates detoxification and mycotoxins reduction.

Occurrence and Importance of Yeasts in Indigenous Fermented Food and Beverages Produced in Sub-Saharan Africa

Indigenous fermented food and beverages represent a valuable cultural heritage in sub-Saharan Africa, having one of the richest selections of fermented food products in the world. In many of these indigenous spontaneously fermented food and beverages, yeasts are of significant importance. Several factors including raw materials, processing methods, hygienic conditions as well as the interactions between yeasts and other commensal microorganisms have been shown to influence yeast species diversity and successions. Both at species and strain levels, successions take place due to the continuous change in intrinsic and extrinsic growth factors. The selection pressure from the microbial stress factors leads to niche adaptation and both yeast species and strains with traits deviating from those generally acknowledged in current taxonomic keys, have been isolated from indigenous sub-Saharan African fermented food products. Yeasts are important for flavor development, impact shelf life, and nutritional value and do, in some cases, even provide host-beneficial effects. In order to sustain and upgrade these traditional fermented products, it is quite important to obtain detailed knowledge on the microorganisms involved in the fermentations, their growth requirements and interactions. While other publications have reported on the occurrence of prokaryotes in spontaneously fermented sub-Saharan food and beverages, the present review focuses on yeasts considering their current taxonomic position, relative occurrence and successions, interactions with other commensal microorganisms as well as beneficial effects and importance in human diet. Additionally, the risk of opportunistic yeasts is discussed.

Effects of intrinsic microbial stress factors on viability and physiological condition of yeasts isolated from spontaneously fermented cereal doughs

Fermented cereal doughs constitute a predominant part of West African diets. The environment of fermented doughs can be hostile for microbial survival due to high levels of microbial metabolites such as weak carboxylic organic acids and ethanol. In order to get a better understanding of the intrinsic factors affecting the microbial successions of yeasts during dough fermentation, survival and physiological responses of the yeasts associated with West African fermented cereal doughs were investigated at exposure to relevant concentrations of microbial inhibitory compounds. Three strains each of the predominant species, i.e. Saccharomyces cerevisiae, Kluyveromyces marxianus, Pichia kudriavzevii as well as the opportunistic pathogen Candida glabrata were studied. The strains were exposed to individual stress factors of cereal doughs, i.e. (i) pH 3.4, (ii) 3% (v/v) ethanol (EtOH_pH3.4), (iii) 285 mM lactic acid (LA_pH3.4) and (iv) 150 mM acetic acid (AA_pH3.4) as well as to combinations of these stress factors, i.e. (v) (LA + AA)_pH 3.4 and (vi) (LA + AA+EtOH)_pH 3.4. Growth and single cell viability were studied by flow cytometry using combined SYTO 13 and propidium iodide (PI) staining. Intracellular pH (pH_i), plasma membrane integrity and micro-colony development of stressed cells were studied by fluorescence microscopy using PI and carboxyfluorescein diacetate succinimidyl ester (CFDA-se). Viability of the yeast strains was not affected by pH 3.4 and 3% (v/v) ethanol (EtOH_pH3.4). 285 mM lactic acid (LA_pH3.4) reduced the specific growth rate (μ_max) from 0.27-0.41 h^-1 to 0.11-0.26 h^-1 and the viability from 100% to 2.6-41.7% at 72 h of exposure in most yeast strains, except for two strains of C. glabrata. 150 mM acetic acid (AA_pH3.4) as well as the combinations (LA + AA)_pH 3.4 and (LA + AA+EtOH)_pH 3.4 reduced μ_max to 0.0 h^-1 and induced significant cell death for all the yeast strains. Exposed to (LA + AA+EtOH)_pH 3.4, the most resistant yeast strains belonged to S. cerevisiae followed by P. kudriavzevii, whereas C. glabrata and K. marxianus were more sensitive. Strain variations were observed within all four species. When transferred to non-stress conditions, i.e. MYGP, pH 5.6, after exposure to (LA + AA+EtOH)_pH 3.4 for 6 h, 45% of the single cells of the most resistant S. cerevisiae strain kept their plasma membrane integrity, recovered their pH_i to near physiological range (pH_i = 6.1-7.4) and resumed proliferation after 3-24 h of lag phase. The results obtained are valuable in order to change processing conditions of the dough to favor the survival of preferable yeast species, i.e. S. cerevisiae and K. marxianus and inhibit opportunistic pathogen yeast species as C. glabrata.

Effects of Chitosan and Natamycin on Vacuum-Packaged Phyllo: A Pastry Product

The effects of vacuum packaging, chitosan (1.5%, w/v), and natamycin (10 mg/L, w/v) on phyllo pastry quality were studied by monitoring microbiological, chemical, and sensory changes. Five lots were prepared with or without vacuum packaging, chitosan, and natamycin: A, air packaged (control); V, vacuum packaged; VC, vacuum packaged with chitosan; VN, vacuum packaged with natamycin; and VCN, vacuum packaged with both chitosan and natamycin. Based on the sensory acceptability data, a shelf life of 6 (A), 12 (V), 14 (VN), 16 (VC), and 17 (VCN) days was obtained at 4°C. VCN treatment resulted in a shelf life extension of 11 days compared with the shelf life of the control. Microbiological data revealed that the combination of chitosan and natamycin resulted in significant reductions of microbial species (mesophilic total viable counts, yeasts and molds, psychrotrophic bacteria, lactic acid bacteria, Enterobacteriaceae, and enterococci) of 1 to 3 log CFU/g on the final day (day 18) of storage. Results suggest that the combination of chitosan and natamycin, which is an effective antifungal agent, can delay the spoilage of phyllo pastry while maintaining acceptable sensorial characteristics and the original freshness and appearance of the product.

Microbiological assessment of maize ogi cofermented with pigeon pea

Maize was cofermented with pigeon pea for ogi production and evaluated for microbiological qualities. White maize and pigeon pea were mixed at ratios of 90:10, 80:20, 70:30, 60:40, and 50:50, respectively, with 100:0 serving as the control. Mixtures were cofermented for 96 h at 27 ± 2°C, and microbiological and sensory qualities analyzed were carried out using analysis of variance. Values were significant at p ≤ .05. Results showed that there was a gradual decrease in the pH and increase in total titratable acidity (TTA), respectively, during fermentation in all the samples. At the end of fermentation, pH ranged from 3.47 to 4.27 and TTA ranged from 0.47% to 0.54%, respectively. Total heterotrophic count (THPC) ranged from 5.76 to 5.90 log cfu/g; lactic acid bacteria (LAB) from 6.15 to 5.98 log cfu/g; and yeasts from 5.51 to 5.79 log cfu/g. Microorganisms isolated were lactic acid bacteria (Lactobacillus buchneri, L. casei, L. pentosus, Pediococcus pentosaceus), yeasts (Saccharomyces cerevisiae, Candida kefyr, C. krusei, C. tropicalis), molds (Aspergillus niger, A. flavus, Penicillium oxalicum, Mucor racemosus and Rhizopus stolonifer) and other aerobic bacteria (Klebsiella oxytoca, Enterobacter amnigenus, Staphylococcus xylosus, Bacillus subtilis, B. firmus, Corynebacterium kutscheri, C. striatum, and C. afermentans). In conclusion, the total heterotrophic plate count (THPC) in fortified maize: pigeon pea products was very high. This could constitute health hazards to infants as weaning foods. However, the microbial loads could be reduced through heat treatment as ogi is usually boiled or treated with boiled water before consumption and it can therefore be concluded that the fortified maize: pigeon pea products could be used as weaning foods.

Occurrence of lactic acid bacteria and yeasts at species and strain level during spontaneous fermentation of mawè, a cereal dough produced in West Africa

Mawè is a West African spontaneous fermented cereal-based dough. Different types of mawè exist varying in type of cereal and/or production condition, with fermentations lasting 24-48 h. With the aim of obtaining a comprehensive understanding of the microbial ecology of mawè processing, a microbiological characterisation was performed for four mawè types, produced at eight sites in Benin. At the onset of the fermentations lactic acid bacteria (LAB) and yeast counts were on average 7.5 ± 1.03 and 4.8 ± 0.79 Log₁₀ cfu/g, which increased to 9.2 ± 0.38 and 7.4 ± 0.42 Log₁₀ cfu/g, respectively, at the end of the fermentations. LAB (n = 321) and yeasts (n = 298), isolated during the fermentations, were identified. The predominant LAB and yeast species were Lactobacillus fermentum and Pichia kudriavzevii, respectively, followed by Kluyveromyces marxianus, all present throughout the mawè fermentations. Further, microbial successions took place with Weissella confusa occurring mostly at the onset, while Pediococcus acidilactici and Saccharomyces cerevisiae were mainly associated with the end of the fermentations. Species diversity was influenced both by type of cereal and production condition. The dominating strain clusters of L. fermentum and P. kudriavzevii were ubiquitous and strain diversities were influenced by type of cereal and production site.

Enhancement of attributes of cereals by germination and fermentation: a review

The nutritional quality of cereals and the sensorial properties of their products are sometimes inferior as compared to other sources of food which is due to the lower protein content and starch availability, the presence of determined antinutrients (phytic acid, tannins, and polyphenols) and the coarse nature of the grains. To ameliorate the nutritional qualities of cereals, they are processed in a number of ways. This review summarizes the enhancement in the nutritional value as well as the functional characteristics of cereals due to germination and fermentation treatment. The protein concentration increases and the amino acid profile is balanced by germination and fermentation. The antinutritional factors are reduced increasing the mineral availability from the cereals. Germination enhances the quality of nutrients and bioactive compounds of cereals thereby increasing the content in proteins, amino acids, sugars, and vitamins. The functional properties of cereals is enhanced due to generation of biofunctional substances, increase in protein solubility, in vitro protein digestibility and lowering of glycemic index.

Phytase-producing capacity of yeasts isolated from traditional African fermented food products and PHYPk gene expression of Pichia kudriavzevii strains

Phytate is known as a strong chelate of minerals causing their reduced uptake by the human intestine. Ninety-three yeast isolates from traditional African fermented food products, belonging to nine species (Pichia kudriavzevii, Saccharomyces cerevisiae, Clavispora lusitaniae, Kluyveromyces marxianus, Millerozyma farinosa, Candida glabrata, Wickerhamomyces anomalus, Hanseniaspora guilliermondii and Debaryomyces nepalensis) were screened for phytase production on solid and liquid media. 95% were able to grow in the presence of phytate as sole phosphate source, P. kudriavzevii being the best growing species. A phytase coding gene of P. kudriavzevii (PHYPk) was identified and its expression was studied during growth by RT-qPCR. The expression level of PHYPk was significantly higher in phytate-medium, compared to phosphate-medium. In phytate-medium expression was seen in the lag phase. Significant differences in gene expression were detected among the strains as well as between the media. A correlation was found between the PHYPk expression and phytase extracellular activity.

Experiences with the use of a starter culture in the fermentation of maize for 'kenkey' production in Ghana

Controlled fermentation of maize was carried out using six strains of Lactobacillus fermentum and one strain of yeast, Saccharomyces cerevisiae, isolated from traditionally fermented maize dough as starter cultures for inoculum enrichement. The fermentations were monitored by pH, acidity, microbiological analysis and taste panel evaluation of two products, kenkey and koko, prepared from the fermented doughs. The strains of L. fermentum used as starter culture dominated the microflora during fermentation and in most inoculated doughs the required pH was attained by 24 h instead of 48 h of dough fermentation. Higher contents of lactic acid bacteria and yeasts were observed in inoculated doughs at the initial stages of fermentation but the spontaneously fermented doughs attained similar lactic acid bacteria and yeasts counts by 24 h of dough fermentation. The organoleptic quality of kenkey and koko prepared from doughs fermented with starter culture for 48 h was not significantly different from the traditional products. Kenkey prepared from doughs fermented for 24 h with starter culture were found to be unacceptable by the taste panel although similarly produced koko was acceptable.

Yeast dynamics during spontaneous fermentation of mawè and tchoukoutou, two traditional products from Benin

Mawè and tchoukoutou are two traditional fermented foods largely consumed in Benin, West Africa. Their preparations remain as a house art and they are the result of spontaneous fermentation processes. In this study, dynamics of the yeast populations occurring during spontaneous fermentations of mawè and tchoukoutou were investigated using both culture-dependent and -independent approaches. For each product, two productions were followed. Samples were taken at different fermentation times and yeasts were isolated, resulting in the collection of 177 isolates. They were identified by the PCR-DGGE technique followed by the sequencing of the D1/D2 domain of the 26S rRNA gene. The predominant yeast species identified were typed by rep-PCR. Candida krusei was the predominant yeast species in mawè fermentation followed by Candida glabrata and Kluyveromyces marxianus. Other yeast species were detected in lower numbers. The yeast successions that took place during mawè fermentation lead to a final population comprising Saccharomyces cerevisiae, C. krusei and K. marxianus. The yeast populations dominating the fermentation of tchoukoutou were found to consist of S. cerevisiae, almost exclusively. Other yeast species were detected in the early stages of fermentation. For the predominant species a succession of biotypes was demonstrated by rep-PCR for the fermentation of both products. The direct analysis at DNA and RNA levels in the case of mawè did not reveal any other species except those already identified by culture-based analysis. On the other hand, for tchoukoutou, four species were identified that were not detected by the culture-based approach. The spontaneous fermentation of mawè and tchoukoutou in the end were dominated by a few autochthonous species.

Determination of yeast diversity in ogi, mawè, gowé and tchoukoutou by using culture-dependent and -independent methods

The maize based ogi and mawè and the sorghum based gowé and tchoukoutou are traditional, spontaneously fermented products widely consumed by the population of Benin (West Africa). Yeast occurrence in the products, as sold on local markets at different locations, was studied using a combination of culture-dependent and independent methods. Number of yeasts is varied from 3.75 log10 colony forming units (cfu)/g for ogi to 5.60 log10 cfu/g for tchoukoutou. Isolated yeasts (236) were identified based on different migration profiles on denaturing gradient gel electrophoresis (DGGE) and 26S rRNA gene sequencing. Candida krusei was the yeast most frequently isolated with strongest predominance in the maize based products. Other predominant yeast present at equal or lower incidence were Clavispora lusitaniae and Saccharomyces cerevisiae in ogi and mawè, Cl. lusitaniae, Candida tropicalis and Kluyveromyces marxianus in gowè and Cl. lusitaniae, S. cerevisiae and Candida rugosa in tchoukoutou. Grouping of C. krusei isolates (164) by rep-PCR analysis indicated that several biotypes were involved in fermentation of the four products. The DGGE analysis on the DNA directly extracted from the food matrices demonstrated the presence of Dekkera bruxellensis and Debaryomyces hansenii, not detected by the culture-based approach. This is the first study combining culture-dependent and independent methods to reveal predominant yeast species and biotypes in traditional foods from Benin.

The dominant microbial community associated with fermentation of Obushera (sorghum and millet beverages) determined by culture-dependent and culture-independent methods

Obushera includes four fermented cereal beverages from Uganda namely: Obutoko, Enturire, Ekitiribita and Obuteire, whose microbial diversity has not hitherto been fully investigated. Knowledge of the microbial diversity and dynamics in these products is crucial for understanding their safety and development of appropriate starter cultures for controlled industrial processing. Culture-dependent and culture-independent techniques including denaturating gradient gel electrophoresis (DGGE) and mixed DNA sequencing of polymerase chain reaction (PCR) amplified ribosomal RNA genes were used to study the bacteria and yeast diversity of Obushera. The pH dropped from 6.0-4.6 to 3.5-4.0 within 1-2 days for Obutoko, Enturire and Obuteire whereas that of Ekitiribita decreased to 4.4 after 4 days. Counts of lactic acid bacteria (LAB) increased from 5.0 to 11.0 log cfug(-1) and yeasts increased from 3.4 to 7.1 log cfug(-1) while coliform counts decreased from 2.0 to <1 log cfug(-1) during four days of fermentation. LAB and yeast isolates were identified by rRNA gene sequence analysis. LAB isolates included: Enterococcus spp., Lactobacillus (Lb.) plantarum, Lb. fermentum, Lb. delbrueckii, Lactococcus lactis, Leuconostoc lactis, Streptococcus (S.) infantarius subsp. infantarius, Pediococcus pentosaceus and Weisella (W.) confusa. DGGE indicated predominance of S. gallolyticus, S. infantarius subsp. infantarius, Lb. fermentum, Lb. delbrueckii, W. confusa, Lb. reuteri, Fructobacillus spp., L. lactis and L. lactis. Yeast isolates included Clavispora lusitaniae, Cyberlindnera fabianii, Issatchenkia orientalis and Saccharomyces cerevisiae. DGGE indicated predominance of S. cerevisiae in Obutoko, Enturire and Obuteire and also detected Pichia spp. and I. orientalis in Obutoko. Obushera produced in the laboratory was initially dominated by Enterobacteriaceae and later by Lactococcus spp. Enterobacteriaceae and Bacillus spp. were also detected in Ekitiribita. Development of starters for Obushera may require combinations of LAB and S. cerevisiae for Obutoko, Enturire and Obuteire and LAB for Ekitiribita.

Biodiversity and probiotic potential of yeasts isolated from Fura, a West African spontaneously fermented cereal

Fura is a spontaneously fermented pearl millet product consumed in West Africa. The yeast species involved in the fermentation were identified by pheno- and genotypic methods to be Candida krusei, Kluyveromyces marxianus, Candida tropicalis, Candida rugosa, Candida fabianii, Candida norvegensis and Trichosporon asahii. C. krusei and K. marxianus were found to be the dominant species. Survival in pH 2.5 or in the presence of bile salts (0.3% (w/v) oxgall) and growth at 37°C were independently determined as indicators of the survival potential of the isolates during passage through the human gastrointestinal tract. Selected yeast species isolates were assessed for their probiotic potential. All of the examined yeast isolates survived and grew at human gastrointestinal conditions in pH 2.5, 0.3% (w/v) oxgall at 37°C. The effect on the transepithelial electrical resistance (TEER) across polarized monolayers of intestinal epithelial cells of human (Caco-2) and porcine (IPEC-J2) origin, were determined. The Caco-2 cells and IPEC-J2 cells displayed clearly different relative TEER results. The strains of C. krusei, K. marxianus, C. rugosa and T. asahii were able to increase the relative TEER of Caco-2 monolayers after 48h. In comparison, the relative TEER of IPEC-J2 monolayers decreased when exposed to the same yeasts, even though T. asahii did not differ significantly from Saccharomyces cerevisiae var. boulardii which is used as a human probiotic. C. tropicalis resulted in the largest relative TEER decrease for both the human and the porcine cell model assays. Hyphal growth was observed for C. albicans and C. tropicalis after 48h of incubation with polarized Caco-2 monolayers, whereas this was not the case for the remaining yeast species. In the present study new yeast strains with potential probiotic properties have been isolated to be used potentially as starter cultures for fura production.

Identification of lactic acid bacteria isolated during traditional fura processing in Ghana

Fura is a millet-based spontaneously fermented dumpling produced and consumed in parts of West Africa, particularly Nigeria, Burkina Faso and Ghana. From eight traditional fura production sites in northern Ghana, 862 lactic acid bacteria were isolated and identified to species level using a combination of genotypic and phenotypic methods including (GTG)(5)-based PCR fingerprinting and 16S rRNA gene sequencing, multiplex PCR by means of recA gene sequence comparison, conventional morphological characteristics and carbohydrate fermentation profiling. During millet dough fermentation, pH decreased from 5.6-6.4 to 4.1-3.7 and total lactic acid bacteria (LAB) counts increased from 4.4-5.3 to 7.9-9.2 log(10) (cfu/g). The initial stages of the fermentation were characterized by co-dominance of homo- and heterofermentative species of Pediococcus acidilactici, Weisella confusa, Lactobacillus fermentum, Lactobacillus reuteri, Lactobacillus salivarius, and Lactobacillus paraplantarum whereas L. fermentum was dominating at the end of the fermentation. L. fermentum was predominant in all fermentations (p < 0.05) and a high uniformity was observed among production sites regarding the dominance of L. fermentum. L. fermentum and W. confusa were isolated in all production sites and almost at all fermentation stages indicating that they are indigenous to traditional fura processing. The other LAB bacteria species which comprised a minor proportion of the total LAB occurred occasionally and in an irregular pattern among the production sites.

Microbiological and physicochemical characterisation of caxiri, an alcoholic beverage produced by the indigenous Juruna people of Brazil

Caxiri is a traditional fermented alcoholic beverage produced from cassava and sweet potatoes by the indigenous Juruna or Yudjá people in Brazil. Our results showed that caxiri fermentation is invariably associated with the following: (i) an increase in the total microbial population, with yeast being the largest group detected; (ii) a decrease in reducing sugars, malic, tartaric, succinic, oxalic and propionic acid; and (iii) a final product characterised by a high content of ethanol and a high concentration of lactic acid. The microbial community dynamics were investigated by culture-based and culture-independent approaches. Fermentation was assisted by a complex microbial community that changed in structure and composition during the fermentative process. The bacterial population ranged from 3.05 to 5.33 log/mL, and the yeast population varied from 3.27 log CFU/mL to 7.34 log CFU/mL, showing that yeasts dominated the fermentation process after 48 h. A total of 343 colonies of bacteria and 205 colonies of yeasts were isolated and initially grouped by Amplified Ribosomal DNA Restriction Analysis (ARDRA) and by biochemical features. Phylogenetic analysis of the 16S rRNA gene sequences of representative isolates showed that the bacteria were mainly represented by endospore-forming low-G+C content Gram-positive bacilli (Bacillus spp.; 61.5% of the isolates), with Bacillus pumilus, Bacillus spp. (Bacillus cereus group), and Bacillus subtilis being the main species identified. The species Sphingomonas sp. and Pediococcus acidilactici were also found. The dominant yeast identified was Saccharomyces cerevisiae. Rhodotorula mucilaginosa, Pichia membranifaciens, Pichia guilliermondii and Cryptococcus luteolus were also found. According to the Polymerase Chain Reaction and Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis, the microbial communities present during fermentation were probably from the raw materials, ambient or present on the utensils used during beverage preparation. The results indicated the necessity to combine both culture-dependent and culture-independent methods for a better description of the microbial communities in indigenous starch fermentations. Also, pH values decreased from 4.76 to 3.15 during fermentation. The ethanol concentration was 83.9 g/L and lactic acid reached 27.89 g/L by the end of the fermentation process.

Indigenous perception and characterization of Yanyanku and Ikpiru: two functional additives for the fermentation of African locust bean

Indigenous perception, processing methods, and physicochemical and microbiological characteristics of Yanyanku and Ikpiru, two additives used to produce fermented African locust bean condiments, Sonru and Iru, were evaluated. According to producers, these additives accelerate the fermentation and soften the texture of the condiments. Yanyanku is produced by spontaneous fermentation with either Hibiscus sabdariffa or Gossypium hirsutum or Adansonia digitata seeds, whereas only Hibiscus sabdariffa seeds are used for Ikpiru. Both additives, with pH values ranging between 6.2 and 10 and Bacillus spores varying between 5.5 and 8.9 Log(10) (CFU/g), could be considered as softening additives or enrichment inocula to produce condiments.

Theobroma cacao L., "The food of the Gods": quality determinants of commercial cocoa beans, with particular reference to the impact of fermentation

The quality of commercial cocoa beans, the principal raw material for chocolate production, relies on the combination of factors that include the type of planting material, the agricultural practices, and the post-harvest processing. Among these, the fermentation of the cocoa beans is still the most relevant since it is the process whereby the precursors of the cocoa flavor arise. The formation of these precursors depends on the activity of different microbial groups on the beans pulp. A comparison of fermentations in different countries showed that a well-defined microbial succession does not always take place and that the role of Bacillus spp. in this process remains unclear. Considering the overriding importance of the fermentation to achieve high quality commercial cocoa beans, we discuss the need of addressing the impact of the farming system, the ripeness state of the pods, and the role of microbial interactions on the fermentation in future research. In addition, the problem of high acidification cocoa beans, aspects dealing with the volatile fraction of the flavor, and the cocoa butter properties, all were identified as critical aspects that need further investigation. The standardization of the microbiological methods and the application of metagenomic approaches would magnify the knowledge in this domain.

Impact of ecological factors on the stability of microbial associations in sourdough fermentation

The limits for the stability of the microbial association 1 (Lactobacillus sanfranciscensis and Candida humilis) and association 2 (Lactobacillus reuteri, Lactobacillus johnsonii and Issatchenkia orientalis) during sourdough fermentation were evaluated by investigating the effects of the ecological factors substrate, refreshment time, temperature, amount of backslopping and competing species in different combinations on their growth. Sourdoughs were fermented in 28 batches under different conditions using the associations and possible competing strains as starters. The dominating microbiota was characterized by bacteriological culture, rRNA gene sequence analysis and RAPD-PCR. Association 1 was found to be competitive in doughs with rye and wheat flour at temperatures between 20 and 30 °C, refreshment times of 12 and 24 h, amounts of backslopping dough from 5 to 20% and against all competing lactic acid bacteria and yeasts. The processing parameters for the competitiveness of the association 2 were temperatures of 35-40 °C, refreshment times of 12-24 h and the substrates rye bran, wheat and rye flour, but not in every case. Issatchenkia orientalis could only grow when enough oxygen was available. Its cell counts fell rapidly under the limit of detection when using high amounts of doughs (small ratio of surface to volume) and refreshment times of 12 h. In conclusion, the results demonstrated that the two associations were remarkably stable under most of the investigated process conditions.

Sourdough in gluten-free bread-making: an ancient technology to solve a novel issue?

The increasing demand for high quality gluten-free (GF) bread, clean labels and natural products is raising the need for new approaches in GF bread-making. Sourdough is the foremost fermentation used for baking purposes and it has been proven to be ideal for improving the texture, palatability, aroma, shelf life and nutritional value of wheat and rye breads. These characteristic features derive from the complex metabolic activities of the sourdough-resident lactic acid bacteria and yeasts, e.g. acidification, production of exopolysaccharides, proteolytic- amylolytic- and phytase activity, and production of antimicrobial substances. These effects have been extensively studied and well described for traditional baking, whereas little is known about the role of sourdough in GF baking. Yet, the microbiological and qualitative characterisation of local GF fermented products indicate an overlap with the microbiota of wheat/rye fermentation and suggest that the positive metabolic activities of the sourdough microbiota are still retained during fermentation of GF crops. Thus, the use of sourdough in GF baking may be the new frontier for improving the quality, safety and acceptability of GF bread.

The microbiota of Lafun, an African traditional cassava food product

Lafun is a fermented cassava food product consumed in parts of West Africa. In the present work the microorganisms (aerobic bacteria (AB), lactic acid bacteria (LAB) and yeasts) associated with the fermentation of Lafun under traditional conditions have for the first time been studied using a combination of pheno- and genotypic methods. During Lafun fermentation the AB count ranged from 6-7 log(10) CFU/g at the beginning to 9 log(10) CFU/g at the end. Similarly, the number of LAB increased from 5 log(10) CFU/g to 9 log(10) CFU/g during the process while the yeast load increased from 3 log(10) CFU/g at the onset of the fermentation to 5-6 log(10) CFU/g at the end of the fermentation. A total of 168 isolates (31 AB, 88 LAB, and 49 yeasts) were isolated and identified by means of phenotypic tests, PCR-based methods and 16S rRNA gene sequencing. The aerobic bacteria were mostly identified as belonging to the Bacillus cereus group (71%). The B. cereus isolates lacked the genetic determinant specific for cereulide producers but harboured several genes encoding the heat-labile toxins hemolysin BL and nonhemolytic enterotoxin as detected by PCR. The other aerobic bacteria isolated were Gram negative and identified as Klebsiella pneumoniae and Pantoea agglomerans. The dominant LAB were identified as Lactobacillus fermentum (42% of LAB isolates) followed by Lactobacillus plantarum (30%) and Weissella confusa (18%). Seven isolates remained unidentified and constitute probably a novel LAB species. The predominant yeast species associated with Lafun fermentation were Saccharomyces cerevisiae (22% of yeast isolates), Pichia scutulata (20%), Kluyveromyces marxianus (18%), Hanseniaspora guilliermondii (12%), Pichia rhodanensis (8%) and Candida glabrata (8%) as well as Pichia kudriavzevii, Candida tropicalis and Trichosporon asahii at lower incidence (<5% each).

Adaptability of lactic acid bacteria and yeasts to sourdoughs prepared from cereals, pseudocereals and cassava and use of competitive strains as starters

The adaptability of lactic acid bacteria (LAB) and yeasts to sourdoughs prepared from cereals, pseudocereals and cassava was investigated using PCR-DGGE and bacteriological culture combined with rRNA gene sequence analysis. Sourdoughs were prepared either from flours of the cereals wheat, rye, oat, barley, rice, maize, and millet, or from the pseudocereals amaranth, quinoa, and buckwheat, or from cassava, using a starter consisting of various species of LAB and yeasts. Doughs were propagated until a stable microbiota was established. The dominant LAB and yeast species were Lactobacillus fermentum, Lactobacillus helveticus, Lactobacillus paralimentarius, Lactobacillus plantarum, Lactobacillus pontis, Lactobacillus spicheri, Issatchenkia orientalis and Saccharomyces cerevisiae. The proportion of the species within the microbiota varied. L. paralimentarius dominated in the pseudocereal sourdoughs, L. fermentum, L. plantarum and L. spicheri in the cassava sourdough, and L. fermentum, L. helveticus and L. pontis in the cereal sourdoughs. S. cerevisiae constituted the dominating yeast, except for quinoa sourdough, where I. orientalis also reached similar counts, and buckwheat and oat sourdoughs, where no yeasts could be detected. To assess the usefulness of competitive LAB and yeasts as starters, the fermentations were repeated using flours from rice, maize, millet and the pseudocereals, and by starting the dough fermentation with selected dominant strains. At the end of fermentation, most of starter strains belonged to the dominating microbiota. For the rice, millet and quinoa sourdoughs the species composition was similar to that of the prior fermentation, whereas in the other sourdoughs, the composition differed.

Risk assessment of aflatoxins in food in Africa

Aflatoxins are secondary metabolites of the fungi Aspergillus flavus and A. parasiticus, occur widely on many staple foods and cause a broad range of detrimental health effects in animals and humans. As a consequence, maximum tolerated levels (MTLs) have been legislated in many countries. However, in developing countries where food safety compliance can be low and significant levels of the food supply are locally consumed by the producers or purchased at local markets, more comprehensive strategies are required. In this regard, risk analysis with its components of risk assessment, risk management and risk communication, is an important tool in dealing with food safety issues. Risk assessment for aflatoxin B(1) in Africa has been performed using the carcinogenic potency, established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and applying it to typical food products and consumption across the continent, to illustrate the significant health implications caused by the intake of high levels of contaminated foods. Highlighted in this assessment is the fact that even low levels of contamination, which might of themselves fall within legislated limits, can have serious health implications due to high levels of consumption, i.e. meeting a MTL does not of itself guarantee food safety. Recent developments have highlighted the growth retardation and immune suppression caused by aflatoxin exposure in human populations in west Africa. Using the limited data available on both these health effects, a first step has been taken to incorporate them into a risk assessment paradigm quantifying the risk of immunosuppression, malnutrition and stunting in children exposed to aflatoxins and highlighting again how excessive consumption of foods meeting MTLs can carry significant health risks.

Lactic acid bacteria and yeasts associated with gowé production from sorghum in Bénin

AIMS

To identify the dominant micro-organisms involved in the production of gowé, a fermented beverage, and to select the most appropriate species for starter culture development.

METHODS AND RESULTS

Samples of sorghum gowé produced twice at three different production sites were taken at different fermentation times. DNA amplification by internal transcribed spacer-polymerase chain reaction of 288 lactic acid bacteria (LAB) isolates and 16S rRNA gene sequencing of selected strains revealed that the dominant LAB responsible for gowé fermentation were Lactobacillus fermentum, Weissella confusa, Lactobacillus mucosae, Pediococcus acidilactici, Pediococcus pentosaceus and Weissella kimchii. DNA from 200 strains of yeasts was amplified and the D1/D2 domain of the 26S rRNA gene was sequenced for selected isolates, revealing that the yeasts species were Kluyveromyces marxianus, Pichia anomala, Candida krusei and Candida tropicalis.

CONCLUSIONS

Gowé processing is characterized by a mixed fermentation dominated by Lact. fermentum, W. confusa and Ped. acidilactici for the LAB and by K. marxianus, P. anomala and C. krusei for the yeasts.

SIGNIFICANCE AND IMPACT OF THE STUDY

The diversity of the LAB and yeasts identified offers new opportunities for technology upgrading and products development in gowé production. The identified species can be used as possible starter for a controlled fermentation of gowé.

NovaSil clay intervention in Ghanaians at high risk for aflatoxicosis. I. Study design and clinical outcomes

A 3-month double-blind and placebo-controlled, phase IIa clinical trial was conducted in Ghana to investigate the safety, tolerance and aflatoxin-sorption efficacy of dietary NovaSil (NS). Volunteers (507 subjects) were clinically screened to evaluate their general health, pregnancy status and blood AFB(1)-albumin adduct levels. Of these subjects, 177 were randomly assigned to three groups: high-dose (HD), low-dose (LD) and placebo-control (PL) groups receiving 3.0, 1.5 and 0 g NS day(-1) in capsules. Trained study-monitors supervised NS capsule administration to participants and recorded side-effects daily. Physical examinations were performed monthly. Blood and urine samples were collected for laboratory analysis. Approximately 92% of the participants (162 of 177) completed the study and compliance rate was over 97%. Overall, 99.5% of person x time reported no side-effects throughout the study. Mild to moderate health events ( approximately 0.5% of person x time) were recorded in some participants. Symptoms included nausea, diarrhea, heartburn and dizziness. These side-effects were statistically similar among all three groups. No significant differences were shown in hematology, liver and kidney function or electrolytes in the three groups. These findings demonstrate that NS clay is apparently safe and practical for the protection of humans against aflatoxins in populations at high risk for aflatoxicosis.

Significance of yeasts in the fermentation of maize for ogi production

Saccharomyces cerevisiae, Candida krusei, C. tropicalis, Geotrichum candidum, G. fermentans and Rhodotorula graminis were isolated during the fermentation of maize for ogi production. All the isolates except Geotrichum fermentans and Rhodotorula graminis were able to degrade phytate. All the yeasts strains exhibited lipase and esterase activities. Only S. cerevisiae (2.60%) and C. krusei (7.41%) exhibited amylase activities. Candida sp. produced wider zone of inhibition than the other yeasts strains tested during lipase activity while S. cerevisiae strains produced significantly wider zone of clearing as compared to the other yeasts for esterase activities. The study of inter-relationships between Lactobacillus plantarum and yeasts (C. krusei and S. cerevisiae) showed that the growth of the yeast strains were enhanced during fermentation by the presence of the lactic acid bacteria, but the growth of the L. plantarum strain was significantly enhanced especially by the C. krusei.

Surface binding of aflatoxin B1 by Saccharomyces cerevisiae strains with potential decontaminating abilities in indigenous fermented foods

Saccharomyces cerevisiae constitutes one of the most important microorganisms involved in food fermentations throughout the world. Aflatoxin B(1) binding abilities of S. cerevisiae strains isolated from indigenous fermented foods from Ghana, West Africa were tested in vitro. Results show that aflatoxin binding was strain specific with 7 strains binding 10-20%, 8 strains binding 20-40% and 3 strains binding more than 40% of the added aflatoxin B(1) when grown and incubated under standard conditions. Binding by two of the strains was further characterized. Highest binding capacity was seen with cells collected at the exponential growth phase with the strains A18 and 26.1.11 binding 53.0 and 48.8% of the total toxin respectively and the binding reduced towards the stationary phase. Aflatoxin B(1) binding increased steadily when the cells were incubated with 1 to 20 microg/ml of aflatoxin B(1). Binding was not affected by the cells grown at temperatures ranging from 20 to 37 degrees C, but was significantly reduced at 15 degrees C. Binding seems to be a physical phenomenon with cells treated at 52, 55 and 60 degrees C for 5 and 10 min or 120 degrees C for 20 min binding significantly higher quantities (more than 2-fold in 120 degrees C treated cells) of aflatoxin B(1) than their viable counterpart. Similarly, when the cells were treated with 2 M HCl for 1 h, up to 2-fold increase in binding was observed. The results obtained show that some strains of S. cerevisiae, viable or non-viable, are effective aflatoxin binders and these properties should be considered in the selection of starter cultures for relevant indigenous fermented foods where high aflatoxin level is a potential health risk.

Determinants of the variability of aflatoxin-albumin adduct levels in Ghanaians

Hepatocellular carcinoma (HCC) is a multifactorial disease with various host and environmental factors involved in its etiology. Of these, aflatoxin exposure has been established as an important risk factor in the development of HCC; the presence of aflatoxin-albumin (AA) adducts in the blood serves as a valuable biomarker of human exposure. In this study, the relationship between a variety of different HCC host factors and the incidence of AA adduct levels was examined in a Ghanaian population at high risk for HCC. These factors included age, gender, hepatitis virus B (HVB) and hepatitis C virus (HCV) status, and genetic polymorphisms in both microsomal epoxide hydrolase (mEH) and glutathione S-transferases (GSTs). Blood samples were analyzed for AA adducts and HBV and HCV status. GSTM1 and GSTT1 deletion polymorphisms and mEH exon 3 and exon 4 single-nucleotide polymorphisms (SNPs) were determined from urine samples. In univariate analysis, age, HBV and HVC status, and GSTT1 and mEH exon 3 genotypes were not associated with AA adduct levels. However, mean adduct levels were significantly higher in both females and individuals typed heterozygous for mEH exon 4 (vs. wild types). Stratification analysis also showed that gender along with mEH exon 4 genotype and HBV status had a significant effect on adduct levels. Both females typed HBsAg+ and males with mEH exon 4 heterozygote genotypes showed significantly higher adduct levels as compared to the HBsAg- and wild types, respectively. Understanding the relationships between these host factors and the variability in aflatoxin-adduct levels may help in identifying susceptible populations in developing countries and for targeting specific public health interventions for the prevention of aflatoxicoses in populations with HCC and chronic liver diseases.