Effects of Microbial Fermentation on Cyanide Contents and Proximate Composition of Cassava Tubers

Yellow and white varieties of cassava (Manihot esculenta) tubers were fermented for the reduction of cyanide content and nutritional improvement. The samples were steeped separately in rain water and allowed to ferment spontaneously for 4 days. The fermenting steep water was inoculated by Spread Plate method on Nutrient, De Man Rogosa Sharpe and McConkey Agar for bacterial isolation and on Sabouraud Dextrose Agar for isolation of fungi in triplicates and incubated. The isolates include: Staphylococcus aureus, Escherichia coli, Bacillus spp, Lactobacillus spp, Enterobacter spp, Aspergillus spp, Candida spp, and Saccharomyces spp. Fermentation caused a reduction in the cyanide content from 9.24±0.01 to 2.93±0.02 mg/100g and 9.85±0.03 to 3.15±0.04 mg/100g in the yellow and white cassava varieties respectively. The pH decreased in value while the titratable acidity increased in value for both cassava varieties. Proximate analyses showed significant increase in protein, crude fibre and moisture values in both cassava varieties but a decrease in ash and carbohydrate contents. Fermentation significantly reduced the cyanide contents (p ≤ 0.05) and improved nutritional status of the fermented cassava tubers. The fermented food was found pathogen-free thus safe for consumption.