Impact of Traditional Fermentation on Microbiome and Nutritional Profile of Sorghum-Based Grits

Thesis Abstract

Traditional fermentation is a widespread food-processing practice that shapes the microbiological and nutritional landscape of staple foods in many communities, yet its impact on sorghum-based grit nutritional quality and gut-relevant microbiome remains underexplored. This study addresses the gap by examining how traditional fermentation of sorghum influences the microbial community structure, functional potential, and associated nutritional profiles of the resulting grits, with implications for food security and dietary health in sorghum-dependent regions. The aim is to quantify shifts in microbial diversity and composition during fermentation, determine changes in macro- and micronutrient content, and evaluate the relationship between microbiome dynamics and nutrient availability. Specific objectives are to (1) characterize the baseline microbiota of raw sorghum and the fermentation substrates used in traditional processing; (2) monitor temporal changes in microbial diversity, abundance of lactic acid bacteria and fermentative consortia, and predicted functional pathways during 0, 24, 48, and 72 hours of fermentation using 16S rRNA gene sequencing and shotgun metagenomics; (3) assess the nutritional profile of sorghum grits at each fermentation stage, including proximate composition, mineral content (Fe, Zn, Ca), phytic acid, polyphenols, with anti-nutritional factor reduction; (4) evaluate in vitro digestibility and estimated glycemic index of grits across fermentation stages; (5) model associations between microbial community metrics and nutritional outcomes using multivariate regression and redundancy analysis; and (6) compare locally produced grits with commercially milled counterparts to determine practical implications for nutrient bioavailability. A mixed-methods design will be employed in a field laboratory setting. The population comprises traditional sorghum producers and their processing facilities in two agro-ecological zones, with a purposive sample of 60 fermentation batches drawn across three villages. Data collection will include (i) structured observations and producer interviews to document fermentation practices and environmental variables, (ii) biological sampling at four fermentation time points (0, 24, 48, 72 hours) for microbiome analysis, (iii) chemical analyses of grits using standard AOAC methods for proximate composition, atomic absorption spectroscopy for minerals, high-performance liquid chromatography for phytic acid and phenolics, and (iv) in vitro digestion assays simulating human gastrointestinal conditions to estimate digestibility and glycemic response. Microbiome characterization will utilize 16S rRNA gene sequencing with Illumina MiSeq and metagenomic sequencing on a subset (n=12 batches) to infer functional potential. Nutritional analyses will quantify protein, fat, carbohydrate, moisture, ash, minerals, phytic acid, tannins, and total phenolics. Data analysis will involve descriptive statistics, alpha and beta diversity metrics (Shannon, Simpson, Bray-Curtis), differential abundance testing (DESeq2), and functional profiling (PICRUSt2 and HUMAnN3). Regression models will examine relationships between microbial indices and nutritional outcomes, while path analysis will explore mediation by fermentation metabolite profiles. Theoretical framing will draw on the Community Assembly Theory and the Nutritional Ecology framework to interpret microbial succession and nutrient bioavailability dynamics. Expected findings include a progressive enrichment of lactic acid bacteria and fermentative consortia with concurrent reductions in phytic acid and tannins, leading to improved mineral bioavailability and in vitro digestibility. Metagenomic data are anticipated to reveal enrichment of carbohydrate-active enzymes and short-chain fatty acid production pathways that correlate with increased digestibility and altered glycemic potential. It is anticipated that fermentation duration will be a critical predictor of nutrient enhancement, with diminishing returns beyond 48 hours in certain contexts due to acidification or texture constraints. The study will contribute to knowledge by linking traditional fermentation microbiomes to quantifiable nutritional improvements in sorghum-based products, offering evidence for optimizing community-based processing practices to maximize nutrient density and digestibility. Policy-relevant recommendations will include guidelines for best-practice fermentation durations, standardization of processing steps without eroding cultural authenticity, and potential biofortification strategies through controlled starter cultures. The study will also identify context-specific constraints related to sanitation, batch-to-batch variability, and sensory acceptance that influence adoption. In conclusion, the research is expected to demonstrate that traditional fermentation substantively modulates the sorghum microbiome to reduce anti-nutritional factors and enhance mineral availability and digestibility, thereby improving the nutritional quality of sorghum-based grits. Recommendations will emphasize scalable, culturally appropriate fermentation guidelines, integration with local nutrition programs, and avenues for further work on linking microbiome profiles to long-term health outcomes in sorghum-dependent populations.