This work investigated the effect of single starter cultures on the anti-nutrient, mineral contents and viscosity of fermenting 'ogwo', a fermented gruel from sorghum-Irish potato mixture. The organisms used were Lactobacillus acidophilus, L. fermentum, L. plantarum, Geotrichum candidum and Saccharomyces cerevisiae. There were significant reductions (P < 0.05) in the anti-nutrient contents of the samples fermented with starter cultures than the sample fermented naturally. The highest reductions were observed in phytic acid, saponin and flavonoid contents of L. plantarum fermented sample and in oxalate and tannin contents of sample fermented with S. cerevisiae and L. acidophilus respectively. Sodium, Calcium, Phosphorus, Copper and Manganese contents of 'ogwo' produced with starter cultures increased while fluctuations were observed in their Potassium, Magnesium and Zinc contents. The viscosities of the starter culture fermented samples reduced more than the naturally fermented sample with the highest and lowest reductions in L. fermentum and L. plantarum respectively. The results of this work showed that Lactobacillus and yeasts were good candidates for reducing the anti-nutrient contents and the viscosities as well as improving the mineral contents of the gruel.