Unlocking the microbial potential of traditional african fermented milk products: a systematic review with quantitative descriptive synthesis of LAB diversity, safety and indigenous starter development perspectives

Traditional fermented milk products (TFMs) represent a cornerstone of food culture, nutrition and food security across Africa. This systematic review synthesizes microbiological, technological and functional data compiled from an initial corpus of 458 articles retrieved from PubMed and ScienceDirect, covering the period from 1990 to 2020, of which 73 were retained following a two-stage screening process. Articles were excluded on the basis of non-pertinent title or abstract (n = 66), data redundancy, or exclusive focus on physicochemical composition or manufacturing systems (n = 319). Three quantitative descriptive pooled analyses were conducted on the compiled data. Pooled analysis of microbiological contamination revealed that 50% of reviewed products exceeded the total plate count safety threshold of 7.0 Log10 CFU/mL, while coliform and fungal contamination exceeded international reference limits in 100% of quantified products, with mean loads of 4.63 ± 1.56 and 5.40 ± 1.59 Log10 CFU/mL respectively. Staphylococcus aureus was detected in 42.1% of all reviewed products. Diversity analysis of lactic acid bacteria (LAB) identified 41 species across seven genera from 126 species-level citations, with a Shannon diversity index of H' = 3.299 and a Pielou evenness index of J' = 0.888, indicating high bibliographic species richness across the reviewed literature. A sensitivity analysis excluding singleton species confirmed the robustness of these estimates (H' = 2.782, J' = 0.945). The family Lactobacillaceae dominated across all products (61.1%), with Lactiplantibacillus plantarum , Limosilactobacillus fermentum and Lacticaseibacillus rhamnosus as the most frequently identified species across the reviewed literature. Several indigenous strains demonstrated probiotic attributes including gastrointestinal tolerance, antimicrobial activity and bacteriocin production, with documented health benefits against diarrheal diseases, malnutrition and gastrointestinal disorders. This review further proposes a structured framework for the valorization of African indigenous LAB as region-specific starters and probiotics, addressing selection criteria, industrial development strategies and key scientific bottlenecks including antibiotic resistance, process standardization and regulatory harmonization. Harnessing this microbial biodiversity represents an innovative and sustainable lever for improving food safety and dairy industry development across the African continent. Systematic Review Registration https://osf.io/kc2gu .