High salt concentration affects the microbial diversity of cassava during fermentation, as revealed by 16S rRNA gene sequencing

Authors: ZHOU, WEI - Florida A & M University; ANANGA, ANTHONY - Florida A & M University; Ukuku, Dike; ARYEE, ALBERTA - Delaware State University

Submitted to: Fermentation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2023
Publication Date: 8/3/2023
Citation: Zhou, W., Ananga, A., Ukuku, D.O., Aryee, A. 2023. High salt concentration affects the microbial diversity of cassava during fermentation, as revealed by 16S rRNA gene sequencing. Fermentation. 9(8):727. https://doi.org/10.3390/fermentation9080727.
DOI: https://doi.org/10.3390/fermentation9080727

Interpretive Summary: The demand for consumption of cassava and avenues for its diversification as a food ingredient has grown worldwide. Information related to microbial populations of fermented cassava and the beneficial effect on health is limited. Cassava was fermented by adding 0-25% salt concentration during 8 weeks of fermentation at ambient temperature (25-30°C) to monitor bacterial diversity. Colonies were identified using the National Center for Biotechnology Information (NCBI) database and a proprietary pool of universal 16S rRNA primers (species-specific) were used to amplify microbial species in the samples. Addition of salt up to 20% led to an increase in the populations of Lactobacillus and Lactiplantibacillus among the natural microflora, and above 20% salt level, Weissella species showed highest resistance to salt concentration while Limosilactobacillus species dominated the natural microflora of fermented cassava.

Technical Abstract: Background: Cassava play an important role in the daily life and diet of the populations worldwide. Current trends are creating avenues for diversification and its use as a food ingredient. Information related to fermentation of cassava and the microbial population involved, and the beneficial effects on health is limited. Method: To investigate the bacterial diversity in fermented cassava, cassava was treated by six levels of salt concentration for 8 weeks at ambient temperature (25-30°C). A total of 30 bacterial isolates were selected for molecular characterization. A proprietary pool of universal 16S rRNA primers and species-specific primers were used to amplify a wide variety of species in clonal samples. Results: Our results showed that treatments with and without salt (0 - 25%) led to an increase in the populations of Lactobacillus and Lactiplantibacillus within the natural microflora. Treatment with 20% and 25% salt concentrations led to detection of Weissella, a new genus. Also, Lactobacillus, Weissella and Lactiplantibacillus populations account for 54, 40 and 6% of the bacterial populations detected at =20% salt concentration. A National Center for Biotechnology Information (NCBI) database was used to identify the strains and the sequences of all 30 colonies led to the identification of 17 strains. Also, the sequencing results classified the 30 isolates into four groups, of which ~76.67% were Limosilactobacillus. Our phylogenetic analysis showed that all 17 strains clearly fell into three clusters. The RNA type of all strains indicate 16S ribosomal RNA. Conclusion: Our results showed the resistance of Weissella to high salt concentration and Limosilactobacillus as the dominant colony in the bacterial population from fermented cassava.