Metataxonomic analysis of bacterial communities and mycotoxin reduction during processing of three millet varieties into ogi, a fermented cereal beverage.

Ogi is a fermented cereal beverage, made primarily from maize (Zea mays) and rarely from millets. Unlike maize-based ogi, little is known about the bacterial community and mycotoxin profile during the production of millet-based ogi. Therefore, the bacterial community dynamics and mycotoxin reduction during ogi processing from three millet varieties were investigated using next-generation sequencing of the 16S rRNA gene and liquid chromatography-tandem mass spectrometry, respectively. A total of 1163 amplicon sequence variants (ASVs) were obtained, with ASV diversity across time intervals influenced by processing stage and millet variety. ASV distribution among samples suggested that the souring stage was more influenced by millet variety than the steeping stage, and that souring may be crucial for the quality attributes of the ogi. Furthermore, bacterial community structure during steeping and souring was significantly differentiated (PERMANOVA, P < 0.05) between varieties, with close associations observed for closely-related millet varieties. Taxonomically, Firmicutes, followed by Actinobacteria, Bacteroidetes, Cyanobacteria and Proteobacteria phyla were relatively abundant (>1%). Lactic acid bacteria, such as Burkholderia-Caballeronia-Paraburkholderia, Lactobacillus, Lactococcus and Pediococcus, dominated most fermentation stages, suggesting their roles as key fermentative and functional bacteria in relation to mycotoxin reduction. About 52-100%, 58-100% and 100% reductions in mycotoxin (aflatoxins, beauvericin, citrinin, moniliformin, sterigmatocystin and zearalenone) concentrations were recorded after processing of white fonio, brown fonio and finger millet, respectively, into ogi. This study provides new knowledge of the dominant bacterial genera vital for the improvement of millet-based ogi through starter culture development and as well, elucidates the role of processing in reducing mycotoxins in millet ogi.

Traditionally Processed Beverages in Africa: A Review of the Mycotoxin Occurrence Patterns and Exposure Assessment.

African traditional beverages are widely consumed food-grade liquids processed from single or mixed grains (mostly cereals) by simple food processing techniques, of which fermentation tops the list. These beverages are very diverse in composition and nutritional value and are specific to different cultures and countries. The grains from which home-processed traditional beverages are made across Africa are often heavily contaminated with multiple mycotoxins due to poor agricultural, handling, and storage practices that characterize the region. In the literature, there are many reports on the spectrum and quantities of mycotoxins in crops utilized in traditional beverage processing, however, few studies have analyzed mycotoxins in the beverages themselves. The available reports on mycotoxins in African traditional beverages are mainly centered on the finished products with little information on the process chain (raw material to final product), fate of the different mycotoxins during processing, and exposure estimates for consumers. Regulations targeting these local beverages are not in place despite the heavy occurrence of mycotoxins in their raw materials and the high consumption levels of the products in many homes. This paper therefore comprehensively discusses for the 1st time the available data on the wide variety of African traditional beverages, the mycotoxins that contaminate the beverages and their raw materials, exposure estimates, and possible consequent effects. Mycotoxin control options and future directions for mycotoxin research in beverage production are also highlighted.

High-Throughput Sequence Analyses of Bacterial Communities and Multi-Mycotoxin Profiling During Processing of Different Formulations of Kunu, a Traditional Fermented Beverage.

Kunu is a traditional fermented single or mixed cereals-based beverage popularly consumed in many parts of West Africa. Presently, the bacterial community and mycotoxin contamination profiles during processing of various kunu formulations have never been comprehensively studied. This study, therefore, investigated the bacterial community and multi-mycotoxin dynamics during the processing of three kunu formulations using high-throughput sequence analysis of partial 16S rRNA gene (hypervariable V3-V4 region) and liquid chromatography tandem mass spectrometry (LC-MS/MS), respectively. A total of 2,303 operational taxonomic units (OTUs) were obtained across six processing stages in all three kunu formulations. Principal coordinate analysis biplots of the Bray-Curtis dissimilarity between bacterial communities revealed the combined influences of formulations and processing steps. Taxonomically, OTUs spanned 13 phyla and 486 genera. Firmicutes (phylum) dominated (relative abundance) most of the processing stages, while Proteobacteria dominated the rest of the stages. Lactobacillus (genus taxa level) dominated most processing stages and the final product (kunu) of two formulations, whereas Clostridium sensu stricto (cluster 1) dominated kunu of one formulation, constituting a novel observation. We further identified Acetobacter, Propionibacterium, Gluconacetobacter, and Gluconobacter previously not associated with kunu processing. Shared phylotypes between all communities were dominated by lactic acid bacteria including species of Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, and Weissella. Other shared phylotypes included notable acetic acid bacteria and potential human enteric pathogens. Ten mycotoxins [3-Nitropropionic acid, aflatoxicol, aflatoxin B1 (AFB1), AFB2, AFM1, alternariol (AOH), alternariolmethylether (AME), beauvericin (BEAU), citrinin, and moniliformin] were quantified at varying concentrations in ingredients for kunu processing. Except for AOH, AME, and BEAU that were retained at minimal levels of < 2 µg/kg in the final product, most mycotoxins in the ingredients were not detectable after processing. In particular, mycotoxin levels were substantially reduced by fermentation, although simple dilution and sieving also contributed to mycotoxin reduction. This study reinforces the perception of kunu as a rich source of bacteria with beneficial attributes to consumer health, and provides in-depth understanding of the microbiology of kunu processing, as well as information on mycotoxin contamination and reduction during this process. These findings may aid the development of starter culture technology for safe and quality kunu production.