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

Waste to Wealth: Dynamics and metabolic profiles of the conversion of jackfruit flake into value-added products by different fermentation methods

Thus far, little is known about whether jackfruit flake, a byproduct of jackfruit, can be used as a fermentation substrate to obtain value-added products through microbial fermentation. Here, jackfruit flake puree was fermented by three different ways: spontaneous fermentation (JF), inoculated with LAB (JFL), inoculated co-fermentation with LAB and yeast (JFC). In contrast to JF, the total polyphenol and flavonoid content and syndrome-associated enzyme inhibition are significantly increased in JFC at the end of fermentation. Electronic tongue analysis revealed that the JFC was significantly lower in astringency and higher in bitterness. 41 volatile compounds were identified during fermentation by HS-SPME-GC-MS, and JFC was richer in honey, rose, and fruity flavors. A total of 290 compounds were screened for discriminative pre- and post-fermentation differential metabolites by non-target metabolomics analysis. These results provide a potential reference for the conversion of jackfruit waste into functional products using fermentation.

Physicochemical and microbial community dynamics of Kocho fermented from different enset varieties in South West Ethiopia

Enset (Ensete ventricosum (Welw.) Cheesman) is an indigenous multipurpose plant in Ethiopia. More than 20 % of people in Ethiopia rely on enset for their subsistence livelihood. Its fermentation produces a starchy food named Kocho, which is yet poorly studied. In this study, physicochemical and microbial community dynamics of Kocho fermented from different enset varieties (Maziya, Genna, and Arkiya) were collected at Dawro Zone (Southern Ethiopia). Samples were collected at various fermentation times (days 1-60) for physicochemical and microbial (culture-dependent and culture-independent) characterization. Results showed that increasing fermentation time has a significantly strong positive (R2 = 0.768, p = 0.004) correlation between titrable acidity, and a significantly strong negative association with pH (R2 = -0.715, p = 0.009), moisture (R2 = -0.982, p < 0.05), ash (R2 = -0.932, p < 0.05), fat (R2 = -0.861, p < 0.05), fiber (R2 = -0.981, p < 0.05) and carbohydrate (R2 = -0.994, p < 0.001) contents. An increasing or decreasing trend of physicochemical parameters observed during enset fermentation is significantly associated with microbial community dynamics. Shifts of microbial community observed during culture-dependent analysis were also confirmed by metagenomic results. During fermentation, Firmicutes (39-68 %) > Proteobacteria (7-53 %) > Cyanobacteria (7-24 %) were dominant phyla in the three enset varieties. Gamma (traditional starter culture) is dominated by Lactobacillus plantrum and Lactobacillus manihotivorans most probably the two species that play a significant role in initiating enset fermentation.

The Weissella and Periweissella genera: up-to-date taxonomy, ecology, safety, biotechnological, and probiotic potential

Bacteria belonging to the genera Weissella and Periweissella are lactic acid bacteria, which emerged in the last decades for their probiotic and biotechnological potential. In 2015, an article reviewing the scientific literature till that date on the taxonomy, ecology, and biotechnological potential of the Weissella genus was published. Since then, the number of studies on this genus has increased enormously, several novel species have been discovered, the taxonomy of the genus underwent changes and new insights into the safety, and biotechnological and probiotic potential of weissellas and periweissellas could be gained. Here, we provide an updated overview (from 2015 until today) of the taxonomy, ecology, safety, biotechnological, and probiotic potential of these lactic acid bacteria.

Microbial and Physicochemical Dynamics of Kocho, Fermented Food from Enset

Over 20 million Ethiopians depend on enset (Ensete ventricosum) as a staple or costaple food. "Kocho," "Bulla," and "Amicho" are the three main food types obtained from enset. This review aimed to summarize the physicochemical and microbial dynamics of kocho. It is the most common food obtained from the scraped pseudostem and decorticated corm of enset after a long period of fermentation. The quality of kocho depends on the maturity of the enset plant, the enset processing method, the fermentation period, and the dynamics of microorganisms during the fermentation process. Microorganisms play a significant role in kocho fermentation to enhance its nutritional quality, improve sensory properties, and reduce spoilage and disease-causing agents. The populations of microbes available in kocho fermentation include lactic acid bacteria (LAB), Enterobacteriaceae, acetic acid bacteria (AAB), yeasts and molds, and Clostridium spp., which have both positive and negative impacts on kocho quality. There is a visible variation in microbial dynamics during kocho fermentation caused by the fermentation period. As the fermentation day increases, species of LAB also increase, whereas counts of Enterobacteriaceae decrease. This is due to a decrease in pH, which leads to an increase in titratable acidity. Moisture content also slightly decreases as fermentation progresses. Dynamics in the microbial population and physicochemical parameters ensure the development of desirable qualities in kocho and enhance the acceptability of the final product. Organic acids (such as lactic acid, acetic acid, and propionic acid), bacteriocins, phenolic compounds, flavonoids, and tannins are bioactive compounds produced by microorganisms during Kocho fermentation. Further research is needed on the molecular identification of microorganisms during Kocho fermentation.

Purdue improved crop storage bag for kocho fermentation; Ethiopian traditional fermented food from Enset (Ensete ventricosum)

Enset (Ensete ventricosm) is a multipurpose crop serving millions of Ethiopians as an alternative food source. However, the traditional kocho preparation is labor-intensive and results in poor quality. This study evaluated Purdue improved crop storage (PICS) bag as an alternative to an underground pit for kocho fermentation. The experiment was arranged in a factorial design with two fermentation systems (underground pit and PICS bag) and three fermentation times (30, 45 & 60 days) with 5 replications. Physico-chemical, proximate composition, microbial, and sensory evaluations of kocho were conducted following standard procedures. The results have revealed that protein and moisture contents were increased with fermentation time while crude fiber, carbohydrate, and total energy were decreased regardless of fermentation systems. The microbial results have demonstrated a reduction with extended fermentation but no significant difference between PICS and the underground pit. The sensory results have shown that PICS bag-fermented kocho has better overall sensory acceptability regardless of fermentation time. Generally, PICS bag-fermented kocho for 60 days has shown overall better kocho quality. The finding revealed that PICS bags could be used as an alternative to the traditional underground pit for better kocho quality. Further validation of the PICS bag as a fermentation container with various enset varieties and seasons with extended fermentation time is needed.

Microbial, physicochemical and proximate analysis of Tej collected from Amhara regional state of Ethiopia

Tej is an Ethiopian traditional alcoholic beverage with significant social and economic importance. Due to the spontaneous fermentation process of Tej, several issues such as safety, quality, and physicochemical properties of the final products is rquired to be assessed. Thus, this study was aimed to assess the microbial quality, physicochemical, and proximate properties of Tej associated with different maturity time. The microbial, physicochemical and proximate analyses were carried out by standard protocol. Lactic acid bacteria (6.30 log CFU/mL) and yeast (6.22 log CFU/mL) were the dominat microorganisms of all Tej samples at different maturity time, with significant differences (p = 0.001) in mean microbial count among samples. The mean pH, titratable acidity and ethanol content of Tej samples were 3.51, 0.79 and 11.04% (v/v), respectively. There were significant differences (p = 0.001) among the mean pH and titratable acidity values. The mean proximate compositions (%) of Tej samples were as follows: moisture (91.88), ash (0.65), protein (1.38), fat (0.47) and carbohydrate (3.91). Statistically significant differences (p = 0.001) were observed in proximate compositions of Tej samples from different maturity time. Generally, Tej maturity time has a great impact on the improvement of nutrient composition and the increment of the acidic contents which in turn suppress the growth of unwanted microorganisms. Further evaluation of the biological, and chemical safety and development of yeast-LAB starter culture are strongly recommended to improve Tej fermentation in Ethiopia.

The Metabolite Profiling and Microbial Community Dynamics during Pineapple By-Product Fermentation Using Co-Inoculation of Lactic Acid Bacteria and Yeast

Value-added utilization of pineapple waste is very import for the food industry and environmental protection. In this study, whey protein (2.6%, w/w) was added to pineapple waste in order to make up for the protein deficiency of the raw material and give the final products better flavor characteristics. Autochthonous Lactococcus lactis LA5 and Hanseniaspora opuntiae SA2 were used for the co-inoculation of pineapple by-products; during fermentation, the metabolite profiling and microbial community dynamics were investigated. Results showed that the contents of organic acids, total FAAs, total phenolic compounds and flavonoids significantly increased with fermentation, and 152 kinds of peptides were identified in the final products. Relevant analyses demonstrated that dominant strains including Lactococcus lactis, Hanseniaspora and Saccharomyces not only significantly promoted the accumulation of organic acids, total phenols and other active substances, but also inhibited the growth of pathogenic bacteria and further influenced the fermentation process of pineapple waste.

Composition of homegarden plants and cultural use in an indigenous community in Northwest Ethiopia

BACKGROUND

Homegardens in Northern Ethiopia received little investigation into the diversity of plants and no study and recording in the Gozamin District. This study was used to fill the gap in how cultural use and cultural importance conserve species diversity in homegardens in the different agroclimatic zones in northwestern Ethiopia.

METHODS

The study district and 12 kebeles were chosen using multistage and stratified random selection procedures based on traditional agroclimatic zones in the Gozamin District, Northwest Ethiopia, respectively. The number of plots chosen in each homegarden was determined by the homegarden's size, which ranges from 0.015 to 0.5 ha. These data were gathered by putting plots with a distance gradient from home (size: 10 × 10 m each). A semi-structured interview and complete plant inventory were conducted to document the informant's knowledge of plant species. Sørensen's similarity indices and Shannon-Wiener diversity indices were used to compare the similarity of sites and three agroclimatic zones, respectively. Direct matrix ranking, cultural importance (CI), the relative frequency of citation, and cultural value were used in quantitative analysis to compare the most common multipurpose plants.

RESULTS

A total of 238 culturally important plant species from 81 families were identified. The Kruskal-Wallis test showed that there was a significant difference among the three agroclimatic zones species diversity (H = 103.4, Hc = 111.2, p < 0.05). Of the total plant species recorded, 59% were reported to be utilized for environmental uses, 35% were food crops, and 35% were medicinal plant species. The same was true for the three agroclimatic zones; food and medicinal uses were the first and second most important use categories, respectively. The similarity index for 64% of the sites investigated was less than 0.5. Cordia africana (FC = 125) was the most culturally significant species with a value of 2.23 on the CI index.

CONCLUSION

Homegardens are multifunctional systems. The presence of different agroclimatic zones, cultural uses, cultural importance, and cultural value of the species are central to conserving plant species in the area. As the size of the garden increases, so does the diversity of species and uses. Our findings suggest that conservation strategies should take into account the links between plant composition and cultural importance.

The Neglected Traditional Enset (Ensete ventricosum) Crop Landraces for the Sustainable Livelihood of the Local People in Southern Ethiopia

Enset (Ensete ventricosum, Musaceae) is a neglected traditional multipurpose crop plant critical for Ethiopian food security. It has drawn a lot of attention in the last few years. This study was undertaken on the morphological diversity among the enset landraces and their cultural use for the livelihood of the people in Southern Ethiopia. The study was administered in four purposively selected kebeles of the Mareka District. A total of 145 individuals were interviewed using semistructured interviews, and field observation has also occurred. The descriptors for enset developed by the International Board for Plant Genetic Resources were used to measure the morphological features. This study found twenty-two enset landraces. Landraces were categorized into five groups based on their morphological trait variability. The highest mean was in cluster five, while the lowest was in cluster three. The highest landrace diversity was found in Ocha (n = 2.28) and the lowest in Guta (n = 2.17). This study confirmed that the study area has a diverse range of ecosystems. However, a reduction in production and the loss of some landraces were observed. As a result, the protection and preservation of enset landraces must be a priority for all responsible entities.

Microbial community shifts association with physicochemical parameters: Visualizing enset bacterial wilt from different states of enset health

Bacterial wilt of enset caused by Xanthomonas campestris is a devastating disease in Ethiopia, where enset is domesticated and served as a staple food for about 20 million people in the country. While enset is infected by bacteria, it shows different wilting stages. However, the microbial community shifts at the different stages of enset infection and associated physicochemical parameter changes remain poorly understood. This study was aimed to visualize the proportion of enset wilt bacterium from other microbial community and its association with physicochemical parameter at different states of enset health. Soil and enset (zero, first, second and third stages) samples were collected from three districts in Gamo Highlands for physicochemical and biological (culture dependent and16S rRNA gene sequence) analysis. The results of culture dependent analysis which has been complemented by 16S rRNA gene sequence confirmed that increasing trends were observed for Xanthomonadaceae, Pseudomonadaceae, Lactobacillaceae and Flavobacteriaceae, while Bacillaceae and Enterobacteriaceae showed progressive decrease from zero to the third stage. Particularly, the 16S rRNA data showed that Xanthomonadaceae increased significantly from zero to different (2.5 × 10² times at the onset of disease and 1.0-2.0 × 10⁴ times at the second and third) stages of enset infection. Most physicochemical results showed that a decreasing trends from zero to third stage, while few parameters are showing an increasing trend. Moisture content (R² ≥ 0.951, P ≤ 0.049) of the soil and plant samples positively influenced Xanthomonas abundance, while this bacterium showed a strongly negative significant correlation with pH (R² ≥ -0.962, P ≤ 0.038), temperature (R² ≥ -0.958, P ≤ 0.042), OM (R² ≥ -0.952, P ≤ 0.048), and TN (R² ≥ -0.951, P ≤ 0.049). A strongly negative significant correlation (R² ≥ -0.948, P ≤ 0.050) was also observed between Xanthomonas and nutrients (K, Mg, Ca, and Cu). Overall, this study implies that different environmental factors found a key driving force of Xanthomonas proportional increment from low abundance at zero stage to higher abundance at the last stage of enset infection suggesting that considering these factors help to design an effective enset disease management strategy, for which further studies will be needed.

Influence of fermentation time on proximate composition and microbial loads of Enset, (Ensete ventricosum), sampled from two different agroecological districts

In southern Ethiopian households, kocho is one of the staple foods which can be kept longer and fermented naturally using locally prepared pits, but evidence about the influences of fermentation of kocho at a different time and agroecology on proximate compositions and microbial loads are limited. Fermented kocho samples at different fermentation times were collected from highland and midland districts of Sidama region of Ethiopia. The standard procedure of AOAC (2005) method was followed. Four microbiological load analyses were conducted. Factorial analysis using JMP 13 was conducted. Across the fermentation time, total carbohydrate, ash, crude protein, and crude fat ranged 36%-40%, 1.9%-3.2%, 3%-4.3%, and 0.1%-0.3%, respectively. The highest total ash content was observed in week one of fermentation both in midland and highland samples. However, in midland, the increment of fermentation time showed a reduction of total ash percentage. Crude protein and fat were observed similar both in midland and highland (p > .05). The titrable acidity of Kocho varied from 0.16% to 0.22%. It was shown that it increased in the first three months of fermentation. It was also found to be increased as the fermentation time is increasing. Aerobic mesophilic, lactic acid bacteria, yeast, and mold were highly observed in Kocho as compared to Enterobacteriaceae. The loads varied across the fermentation time. Enterobacteriaceae and yeast and mold count of Kocho decreased with increased fermentation time. In conclusion, agroecology did not affect crude protein percentage as the fermentation time is increased. However, it was shown that fermentation increases protein and fat percentages. The increment of the acidic contents may also suppress the microbial growth for better food safety of kocho products.

Silage making of maize stover and banana pseudostem under South Ethiopian conditions: evolution of pH, dry matter and microbiological profile

The study was conducted to evaluate the microbial dynamics during silage of maize stover and banana pseudostem in the environmental conditions of southern Ethiopia. To meet this objective, microsilos containing either maize stover or banana pseudostem, both with and without molasses, were prepared. Subsequently, samples were analysed on day 0, 7, 14, 30, 60 and 90 of the fermentation process. As a result, on day 7, all treatments except banana pseudostem without molasses showed a significant reduction in pH. It was also this silage type that supported the growth of Enterobacteriaceae longer than three other silage types, i.e. until 30 days. The yeasts and moulds and the Clostridum endospore counts also showed a reducing trend in early fermentation and afterwards remained constant until day 90. Illumina MiSeq sequencing revealed that Leuconostoc, Buttiauxella species and Enterobacteriaceae were the most abundant bacteria in the initial phases of the fermentation. Later on, Buttiauxella, Lactobacillus, Weissella and Bifidobacterium species were found to be dominant. In conclusion, silage of the two crop by-products is possible under South Ethiopian conditions. For banana pseudostem, the addition of molasses is crucial for a fast fermentation, in contrast to maize. Upscaling needs to be investigated for the two by-products.

Micronutrient composition and microbial community analysis across diverse landraces of the Ethiopian orphan crop enset

Enset (Ensete ventricosum) is a major starch staple and food security crop for 20 million people. Despite substantial diversity in morphology, genetics, agronomy and utilization across its range, nutritional characteristics have only been reported in relatively few landraces. Here, we survey nutritional composition in 22 landraces from three enset growing regions. We present mineral characterization of enset corm tissue, free amino acid characterization of raw and processed (fermented) tissues and genomic analysis of the microbial community associated with fermentation. We show that compared to regionally important tubers and cereals, enset is high in calcium, iron, potassium and zinc and low in sodium. We report changes in free amino acid composition due to processing, and establish that the bacteria genera Acetobacter, Lactobacillus and Bifidobacterium, predominate during fermentation. Nutritional and microbial variation presents opportunities to select for improved composition, quality and safety with potentially significant impacts in food security and public health.

Diversity and distribution of yeasts in indigenous fermented foods and beverages of Ethiopia

BACKGROUND

As one of the origin centers of domesticated plants in the world, Ethiopia is rich in diversified fermented foods and beverages, in which yeasts are usually among the essential functional microorganisms. This study aims to investigate yeast species diversity and distribution in indigenous fermented products in Ethiopia using conventional isolation and molecular identification methods.

RESULT

Yeast cell counts in 221 samples of various Ethiopian traditional fermented products, including fermented staple foods, alcoholic beverages, dairy products, and condiments, were compared using the typical dilution plating method. A total of 475 yeast isolates were recovered from these samples and 41 yeast species belonging to 25 genera were identified from yeast isolates using the sequence analysis of the D1/D2 domain of the large subunit of rRNA gene. Candida humilis, Wickerhamomyces anomalus, Meyerozyma guilliermondii, Pichia kudriavzevii, and Saccharomyces cerevisiae were the most dominant species that were widely distributed among the majority of the fermented products analyzed in the current study.

CONCLUSION

Significant variations were encountered both in yeast cell counts, diversity, and distribution of yeast species among different types of fermented products and even among different samples of the same types of fermented products. It calls for a more extensive and systematic microbiological study of Ethiopian indigenous fermented foods, beverages and other related products that can be helpful for standardization and large-scale production of these foods in Ethiopia. © 2020 Society of Chemical Industry.

A review on nutritional profile of the food from enset

Purpose

This paper is a systemic review on enset plant’s role in Ethiopian people’s life as the source of food. This paper aims to summarize the traditional processing and preparation methods of enset-based foods and their nutritional composition.

Design/methodology/approach

Available scientific articles were collected and reviewed for enset plant evaluation, description, enset plant’s role in Ethiopian people’s food security, post harvesting and traditional processing of enset plants, microbiology of the fermented enset foods, different foods reported from enset, nutritional profile of the three food from enset base (kocho, bulla and amicho) and other non-food applications of enset plant.

Findings

Enset plant has a predominant role in people living in the southern part of Ethiopia. This plant is drought-tolerant and provides many non-food applications. Harvesting of the enset plant, preparing for fermentation and food preparations follow the traditional route by using the indigenous knowledge and practices. Limited studies have been reported on the microbiology of the enset fermentation, but various types of microbes have been reported. In case of nutritional composition, foods from enset are reported to contain high carbohydrate and minerals content, such as calcium, potassium and zinc, but limited protein content; they are also the best source of the essential amino acids such as lysine and leucine. Limited data are available on vitamins, anti-oxidant and fatty acids profiles of enset-based foods. The existing data indicate variations, and the reasons for variability are discussed in this paper.

Originality/value

Scientific reviews on enset food nutrition profile and related issues are scarce; this paper will compile information about enset plant-based foods for researchers for their future research.

Characterization of the microbiota and volatile components of kocho, a traditional fermented food of Ethiopia

Kocho is a traditional product in Ethiopia, prepared by fermenting parts of ‘false banana’ plants (Ensete ventricosum). Fermentation practices of kocho vary depending on the region of Ethiopia. In this study, 14 kocho samples originating from four different areas were investigated. They varied both in the fermentation technique and the duration of fermentation. Samples were analysed to determine the microbial community using culture-independent 16S amplicon high-throughput sequencing. In addition, bacterial strains were isolated and identified. Furthermore, the volatile profiles were characterized by HS-SPME treatment coupled with GC/MS. The results indicated that Lactobacillus and Acetobacter were the most dominant genera during kocho fermentation with Lactobacillus plantarum and Lactobacillus brevis being the prevalent species of Lactobacillus. The analysis of the volatile profiles demonstrated that acetic acid and butanoic acid prevailed in all samples. Our results showed that kocho samples prepared in different areas and using different processing methods varied both in the composition of the microbiota and in their volatile profiles.

Optimization of Enset Fermentation in the Production of Kocho Using Response Surface Methodology

Response surface methodology (RSM) was used for optimization of enset fermentation process. Two numerical (time and amount of starter culture) and one categorical variable (types of starter strain) was used for evaluation of sensory quality of kocho. The physicochemical properties, proximate composition and color of kocho product were also analyzed. It was found that the coefficient of determination (R2) of the response variables were greater than 80% described that high percentage of the variability was defined by the model. These findings revealed that fermentation time, amount of starter culture and types of starter strain affected the sensory attributes of kocho. The preferred sensory quality of kocho was produced using 2% L. plantarum as starter strain at 6 days of fermentation time.

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

AIMS

The present study was conducted to assess the effect of three different fermentation systems on fermentation of enset into kocho.

METHODS AND RESULTS

Nine enset plants were processed, mixed and fermented in either a pit, a bamboo basket or a sauerkraut jar. Samples were taken on days 1, 7, 15, 31, 60 and 90. Moisture content and pH generally decreased and titratable acidity increased during fermentation. Total viable aerobic counts were generally high for all samples and Enterobacteriaceae counts were reduced to below the detectable level after day 1 for the pits and jars and after day 7 for the baskets. Illumina MiSeq sequencing of 16S ribosomal RNA genes revealed that Leuconostoc and Lactococcus spp. were the most abundant lactic acid bacteria in the initial phases of the fermentation. Later on, Lactobacillus, Weissella and Bifidobacterium dominated.

CONCLUSIONS

The type of fermentation system used had an effect on the microbial dynamics and the effect increased towards the end of fermentation.

SIGNIFICANCE AND IMPACT OF THE STUDY

Millions of people in Ethiopia daily consume kocho prepared in either a pit or a basket. These systems show practical problems, but this study shows that fermentation is also possible in a sauerkraut jar.

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

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.