Microbial Succession and Effect of Fermentation on the Proximate Composition of Sweet Potato Tubers, Leaves and Vines

Abstract

This study was aimed at determining the effect of fermentation on the proximate composition of sweet potato tubers, leaves and vines. The study involved the spontaneous fermentation of the substrates for five days (120h). Physico-chemical properties and microbial counts were determined during the fermentation period. Lactic acid bacteria and yeasts were isolated and characterized. Proximate composition of the substrates were determined at the end of the fermentation period. The results obtained show that the aerobic plate counts range from 6.80x105±1.00x105- 8.40x106±1.00x105CFU/g, lactic acid bacteria count range from 1.70x105±1.30x105- 1.60x107±6.00x106 CFU/g and fungal count range from 2.50x105±8.00x104- 7.75x106±5.50x105 CFU/g. The counts were significantly different in most cases (p≤0.05). The lactic acid bacteria and yeast isolated and identified from the study include Lactobacillus plantarum, L. buchneri, L. delbrueckii, L. brevis, L. lactis, L. fructovorans, L. colloides, L. pentosus, Leuconostoc mesenteroides, Weisella confusa, Candida krusei, C. utilis, C. ciferii, C. spherical, C. rugosa, C. zeylanoides, C. guilliermondii, C. lipolytica, C. tropicalis, C. boidinii, Saccharomyces cerevisiae, Rhodoturulaminuta, R. glutinis, Kodamaeaohmeri, Kloekerasp. The results of the proximate composition show that there was increase in both Nitrogen free extract and metabolisable energy and decrease in protein content and ash content after fermentation. Findings from this study imply that fermentation of these substrates is characterized by a wide variety of lactic acid bacteria and yeasts with positive effect on the proximate composition of the substrates.