Bacterial community dynamics in spontaneously fermented Ghanaian cereals, legumes, root, tuber and plantain flours.

Abstract

Background: Spontaneous fermentation is among the oldest food preservation methods, with evidence of enhancing the nutritional and sensorial qualities of products and the synthesis of health-promoting compounds. However, the bacterial communities responsible for these transformative changes remain poorly understood, notably across diverse indigenous Ghanaian substrates, including grains and starchy roots, tubers, and plantains.

Method: The study aimed to examine bacterial community diversity in the spontaneous fermentations of selected Ghanaian raw materials for complementary food, namely maize, millet, sorghum, sweetpotato, cassava, soybean and plantain. Fermentation lasted 48 h, with samples collected at 6-h intervals. The pH and total titratable acidity (TTA) were determined using standard protocols over the fermentation period. DNA was extracted directly from the fermented food samples using ZymoBIOMICS™ kits, and full-length 16 S rDNA sequencing was performed on the Pacific Biosciences Sequel IIe long-read sequencing platform. Data processing involved DADA2 and taxonomic classification against the SILVA database v138.1, with analysis conducted using R version 4.4.3.

Results: Fermented cereals exhibited increasing bacterial diversity over time, dominated by Weissella confusa, Enterococcus hirae, and Pediococcus acidilactici. Soybean fermentation showed distinct microbial communities with fluctuating diversity. Starch-rich roots, tubers, and plantain supported the growth of Leuconostoc mesenteroides, Weissella confusa, Gluconobacter frateurii, Fructobacillus fructosus, and Pediococcus pentosaceus. Enterococcus faecium favored acidic conditions, while Weissella confusa and Leuconostoc mesenteroides adapted to the fluctuating pH conditions in specific crop substrates.

Conclusion: The fermented flours showed increased bacterial diversity over time, dominated by lactic acid bacteria (LAB) and acetic acid bacteria. The fermentation patterns among the plant-based substrates differed in terms of bacterial behavior and their response to pH and TTA over time. Understanding the bacterial community dynamics not only enhances our knowledge of bacterial ecosystems but also offers a foundation for refining the safety, consistency, and nutritional quality of fermented foods.