Fermentation of enset ( Ensete ventricosum ) in the Gamo highlands of Ethiopia: Physicochemical and microbial community dynamics

Abstract

Enset (Ensete ventricosum) provides staple food for 15 million people in Ethiopia after fermentation into kocho. The fermentation process has hardly been investigated and is prone to optimization. The aim of this study was to investigate the physicochemical and microbial dynamics of fermentation practices in the Gamo highlands. These practices show local variation, but two steps were omnipresent: scraping of the pseudostem and fermenting it in a pit or a bamboo basket. Enset plants were fragmented and fermented for two months in order to investigate the physicochemical (temperature, moisture content, pH and titratable acidity) and microbial dynamics (total viable aerobic counts, counts of Enterobacteriaceae, lactic acid bacteria, yeasts and moulds and Clostridium spores counts, and Illumina Miseq sequencing). Samples were taken on days 1, 7, 15, 17, 31 and 60. The pH decreased, whereas the titratable acidity increased during fermentation. Of all counts those of lactic acid bacteria and Clostridium spores increased during fermentation. Leuconostoc mesenteroides initiated the fermentation. Later on, Prevotella paludivivens, Lactobacillus sp. and Bifidobacterium minimum dominated. These three species are potential candidates for the development of a starter culture.

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

“…has frequently been found already at the beginning of kocho fermentation (Andeta et al 2018; Gashe 1987a). Nevertheless, in the culture- independent identification by Andeta et al (2018), its frequency varied between 10 and 30%. It is possible that the sensitivity of our assay was not high enough to detect this species in the initial fermentation stages.…”

“…Infection of humans mainly occurs upon contact with infected animals (Maughan and Van der Auwera 2011). Moreover, the presence of anaerobic spore forming bacteria ( Clostridia ) in kocho has also been demonstrated (Andeta et al 2018; Gashe 1987a). In our study, we did not have the technical opportunity to test for Clostridia , but one can assume that they were present in the tested food material.…”

“…This implies that the role of yeasts in kocho fermentation is still unclear. It has been hypothesised that yeasts may hydrolyse the starch to provide simple sugars for subsequent lactic acid fermentation (Andeta et al 2018; Karssa et al 2014). However, none of our identified yeasts is able to utilise starch, even maltose, the major disaccharide from starch degradation, is only assimilated by C. jadinii , which was isolated from the long- term fermented kocho (Table 1).…”

“…Yeasts were in many cases only identified to the genus level and frequently invalid taxonomic terms were used, making it impossible to draw any conclusion about the role of yeast species in kocho fermentation (Gashe 1987a, b; Gizaw et al 2016; Tsegay et al 2016). Very recently, Andeta et al (2018), used 16S ribosomal RNA (rRNA) gene sequencing to identify bacteria from enset samples within the range of one to 60 days of fermentation period. Yeasts and moulds were quantified by cultivation on selective media but not identified.…”

Effect of fermentation system on the physicochemical and microbial community dynamics during enset (Ensete ventricosum ) fermentation

“…; Andeta et al . ). Fermentation of kocho takes several months and it is traditionally carried out in an underground pit or in a bamboo basket, also known as ‘erosa’ (Gashe ; Andeta et al .…”