Probiotic and Starter Culture Properties of Lactic Acid Bacteria Isolated from Selected Ethiopian Fermented Foods and Beverages
| dc.contributor.advisor | Engidawor,Ephrem(Prof.) | |
| dc.contributor.advisor | Lebeer,Sarah(Prof.) | |
| dc.contributor.author | Adall,Seyoum Gizachew(Phd) | |
| dc.date.accessioned | 2025-08-13T08:13:03Z | |
| dc.date.available | 2025-08-13T08:13:03Z | |
| dc.date.issued | 2023-10 | |
| dc.description.abstract | Lactic acid bacteria (LAB) are a group of bacteria that form the majority of probiotics and are typically found in fermented products. Probiotics are currently accepted as reasonable alternative remedies in the control of infectious diseases and immuno-allergic disorders. Sub-Saharan African knowledge on cereal fermentations is largely unexplored and undocumented. Use of LAB as starter cultures is one of the key strategies to make most of these spontaneous African cereal fermentations of sufficient quality. The criteria for the selection of probiotic/probiotic starter strains include the functional characterization and safety assessments. This work aimed to isolate and assess in vitro probiotic and starter culture capacity of LAB strains from yoghurt, cheese, cottage cheese, Naaqe and Cheka. LAB were isolated by plating on MRS agar. Spot overlay, radial diffusion, and microdilution methods were used to assess antimicrobial activity against pathogens commonly causing foodborne diseases in Ethiopia. Species identification was done by 16S rRNA gene sequencing. Immunostimulatory activity was tested by measuring nuclear factor kappa B (NF-κB) and interferon regulatory factor (IRF) pathway activation in THP- 1 cell lines. In situ evaluation of starter culture performance of selected isolates from cereal beverages was conducted in a mock fermentation of Naaqe and Cheka. Genomes of three dairy isolates selected based on their potential probiotic properties were analyzed for the secondary metabolites biosynthetic gene clusters, resistome, virulome, and carbohydrate- active enzymes. 27 isolates from the dairy and 14 isolates from the cereal beverage samples were selected and identified to the species level. Limosilactobacillus fermentum was found to be the predominant species. Five strains from cottage cheese (L. plantarum 54B, 54C and 55A; L. pentosus 55B, and P. pentosaceus 95E) showed inhibitory activity against indicator pathogens tested. Six cereal beverages origin LAB strains also inhibited eight of the nine gastrointestinal indicator key pathogens tested. Strain-specific NF-κB and IRF iv activation was documented for dairy origin strains L. plantarum 54B, L. plantarum 55A and P. pentosaceus 95E. Three of the cereal beverages origin LAB isolates (L. fermentum 73B, 82C and 84C) significantly exhibited strain-specific NF-κB induction. During in situ primary fermentations, L. fermentum 73B, P. pentosaceus 74D, L. fermentum 44B, Weissella confusa 44D, L. fermentum 82C and Weissella cibaria 83E and their combinations demonstrated higher pH-lowering properties and colony-forming unit counts compared to the control spontaneous fermentation. The same pattern was also observed in the secondary mock fermentation by the Naaqe LAB isolates. Based on the whole genome sequence (WGS) analysis, Lactiplantibacillus plantarum 54B and 54C also showed to be closely related but different strains. The analysis also revealed that the three strains do not harbor resistome and virulome and have five classes of carbohydrate-active enzymes with several important functions. Cyclic lactone autoinducer, terpene, Type III polyketide synthases (T3PKS), ribosomally synthesized and post-translationally modified peptides (RiPP)-like gene clusters and complete riboflavin operon have been identified in the L. plantarum 55A genome. Overall, five isolates of dairy origin and six isolates of cereal beverages origin showed promising results in all assays and are novel probiotic and probiotic starter candidates of interest, respectively. | |
| dc.identifier.uri | https://etd.aau.edu.et/handle/123456789/6730 | |
| dc.language.iso | en_US | |
| dc.publisher | Addis Ababa University | |
| dc.subject | Cheka | |
| dc.subject | Comparative genome analysis | |
| dc.subject | Cottage cheese | |
| dc.subject | Ethiopia | |
| dc.subject | Lactic acid bacteria | |
| dc.subject | Lactiplantibacillus plantarum | |
| dc.subject | Naaqe | |
| dc.subject | Probiotics | |
| dc.subject | Probiotic starters | |
| dc.subject | Safety | |
| dc.subject | Traditional cereal beverages | |
| dc.title | Probiotic and Starter Culture Properties of Lactic Acid Bacteria Isolated from Selected Ethiopian Fermented Foods and Beverages | |
| dc.type | Thesis |