Yeasts and bacteria associated with kocho, an Ethiopian fermented food produced from enset (Ensete ventricosum)

Genet Birmeta,Volkmar Passoth,Albina Bakeeva

doi:10.1007/s10482-018-1192-8

Genet Birmeta, Volkmar Passoth + Show 1 more

Open Access

https://doi.org/10.1007/s10482-018-1192-8

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Abstract

Enset (Ensete ventricosum) is the basis of the staple food consumed by about 20% of the Ethiopian population. Kocho is one of the food products generated from enset by spontaneous fermentation of decorticated and pulverized pseudostem and corm sections. We isolated culturable microbes associated with kocho from different stages of fermentation. Twelve yeast species, six lactic acid bacteria (LABs) species and eleven species of aerobic bacteria were identified by sequencing ITS/D1D2 regions of 26S rDNA of yeasts and 16S rDNA of bacteria, respectively. More yeast species were identified in fresh (fermented for 2–5 days) kocho, compared to long-term (7–12 months) fermented kocho, while we observed an opposite trend for LABs. In fresh kocho, the most frequently isolated yeast species were Pichia exigua, Galactomyces geotrichum, and Pichia fermentans. From mid-term (3–4 months) kocho most frequently Candida cabralensis, G. geotrichum, and Candida ethanolica were isolated. In the long-term fermentations, the most frequently isolated yeast was Saturnispora silva. Lactobacillus plantarum was the most frequently isolated LAB in both fresh and mid-term kocho. In long-term fermented kocho, Acetobacter pasteurianus and L. plantarum were most frequently isolated. L. plantarum was consistently isolated from all the three stages of fermentation. Aerobic bacteria in fresh kocho were mostly gram-negative, with Raoultella planticola and Pantoea agglomerans being the most frequently isolated species. In long-term fermented kocho, mainly gram-positive, spore-forming bacteria of the genus Bacillus were found, among them also species of the Bacillus cereus group, Bacillus anthracis and Bacillus thurigiensis.

Highlights

Enset or false banana (Ensete ventricosum (Welw.) Chessman) is a staple food crop used by about 20% of Ethiopian population
Little is known about the microbial flora associated with enset, the processes involved in production of the traditional fermented starchy foods are not well understood
Sampling Fresh samples were obtained from five farms of South-West Ethiopia (N: 7°44038.14800, E: 35°28034.38840, height 2271 m above sea level; N: 8°5011.9400, E: 37°59020.0400 height 2392 m above sea level; N: 8°54015.91200, E: 42°7036.94800, height 1600 m above sea level; N: 9°1059.30400, E: 38°4500.28800, height 2449 m above sea level; N: 10°2305.2800, E: 39°803.87600, height 2285 m above sea level): newly prepared kocho (2–5 days old, freshly decorticated and pulverised), medium time and long-time fermented samples from farmers homestead plots, wrapped with layers of leaf sheets and buried in underground pits

Summary

Introduction

Enset or false banana (Ensete ventricosum (Welw.) Chessman) is a staple food crop used by about 20% of Ethiopian population. In long-term fermented kocho, Acetobacter pasteurianus and L. plantarum were most frequently isolated. It was our intention to isolate yeasts and bacteria from short (2–5 days)-, middle (3–4 months) - and long-period (7 months to 1 year) fermented enset materials and to identify these microbes by molecular methods, namely: 16S rDNA and D1D2 region of the 26S rDNA and/or ITS region to reliably identify bacteria and yeasts, respectively, to species level.

Results

Conclusion