Microbial Succession During Composting of Fruit and Vegetable Waste in Yola North and Yola South, Adamawa State, Nigeria

Abstract

The escalating generation of fruit and vegetable waste in Nigerian urban centers poses serious environmental and public health challenges, yet the microbial communities driving composting processes in tropical regions remain poorly characterized. This study established a baseline assessment of physicochemical properties and microbial assemblages in pre-composting soils collected from fruit and vegetable waste aggregation points in Yola North (n=8) and Yola South (n=7), Adamawa State, Nigeria. Standard microbiological spread plate techniques, biochemical characterization, and morphological identification were employed to enumerate and identify bacterial and fungal isolates. Results revealed that Yola South soils contained significantly higher moisture (23.8±4.2% vs. 19.2±3.5%, p=0.038) and organic matter (5.9±1.2% vs. 4.5±0.9%, p=0.024) than Yola North. However, total heterotrophic bacterial counts were unexpectedly higher in Yola North (53.4±8.9 × 10⁵ CFU/g) compared to Yola South (40.1±6.2 × 10⁵ CFU/g, p=0.005). From 121 bacterial isolates, eight genera were identified, with Bacillus spp. (27.8–30.6%) and Pseudomonas aeruginosa (16.7–20.4%) predominated. Among 257 fungal isolates, seven genera were recovered, dominated by Aspergillus flavus (19.3–20.3%), Trichoderma sp. (17.4– 19.3%), and Aspergillus niger (14.3–15.9%). Shannon–Wiener diversity indices showed no significant differences between locations for bacteria (H'=2.28–2.35) or fungi (H'=2.48–2.52), indicating conserved community structures. Pearson correlation analysis revealed strong positive associations between microbial densities and both moisture (r=0.52–0.59) and organic matter (r=0.61–0.65), alongside a robust inter-kingdom correlation (r=0.72). The counterintuitive lower bacterial density in Yola South, despite higher organic matter, suggests unmeasured suppressive factors such as trace heavy metals or oxygen-limited microsites. These findings provide a critical baseline for optimizing composting strategies, leveraging native Trichoderma populations for lignocellulose degradation, while managing Aspergillus flavus to prevent aflatoxin contamination. Future research should employ metagenomic sequencing and heavy metal profiling to identify factors limiting bacterial activity in organic-rich tropical soils.