<b>Microbial Fermentation of African Oil Bean Seeds (</b><b><i>Pentaclethra macrophylla</i></b><b>): A Systematic Review and Meta-analysis of Microbial, Nutritional, Physicochemical, and Functional Changes</b>

African oil bean seed (Pentaclethra macrophylla) is an underutilized indigenous legume that is known to have considerable nutritional and functional potential. When fermented into Ugba, a traditional Nigerian condiment, it results in improved nutritional and sensory characteristics. The systematic review aimed at synthesize available evidence on microbial fermentation of African oil bean seeds in Nigeria, with a focus on fermentation processes, microbial succession, nutritional changes, physicochemical transformations, functional properties, and product quality. The study entailed a systematic literature search conducted in PubMed, ScienceDirect, Google Scholar, African Journals Online (AJOL), Connected Papers, and ResearchGate for studies published between 2015 and 2025. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The reviewed studies were those conducted in Nigeria and investigated microbial fermentation of African oil bean seeds or Ugba. Data extracted included fermentation methods, duration, temperature, packaging materials, starter cultures, dominant microorganisms, nutritional composition, physicochemical characteristics, and functional or sensory outcomes. Where sufficient quantitative data were available, nutritional outcomes were considered for meta-analysis. Results: A total of 48,175 records were identified from the initial search, out of which 1,524 duplicates were removed. Following title and abstract screening, 45,046 records were further excluded, while 1,605 reports were sought for retrieval. A total of 25 full-text articles were assessed for eligibility, with 12 excluded while 13 studies were included in the qualitative synthesis. The findings from the studies showed that African oil bean fermentation is predominantly conducted through spontaneous or controlled solid-state fermentation. However, product characteristics are reported to be highly influenced by fermentation duration, temperature, packaging material, and starter culture. Among the isolated organisms during fermentation, Bacillus species, particularly B. subtilis, were observed to be predominant, and lactic acid bacteria such as Lactobacillus plantarum, were also reported. Furthermore, fermentation was reported to increase protein availability and reduce carbohydrate and selected antinutritional components. Comparatively, controlled fermentation using selected starter cultures demonstrated greater consistency in nutritional improvement, microbial quality, and sensory characteristics than spontaneous fermentation. Microbial fermentation represents an effective biotechnological approach for improving the nutritional quality, microbiological characteristics, physicochemical properties, and functional value of African oil bean seeds. However, substantial differences in fermentation conditions and limited industrial-scale validation show the need for standardized fermentation protocols, optimized starter cultures, and improved food safety controls.