Factors in the protein enrichment of cassava by solid state fermentation

The enrichment of cassava protein content using solid substrate fermentation was studied on both laboratory and on-farm scales using Aspergillus niger as a starter. The effects of cassava particle size and of various nitrogen source ratios and mixing methods were investigated. Ammonium sulphate and urea as sources at respective levels of addition (g N kg⁻¹ substrate) of 10:10, 20:10 and 20:20 were used in combination with cassava alone and cassava mixed with rice bran and soya bean each having mixing levels of 50, 100 and 150 g kg⁻¹. The mixture was fermented for 84 h at 35°C and 90–95% RH on the laboratory scale and 29–31°C and 95–99% RH at the on-farm scale. The results indicated that cube sizes ranging from 0.3 to 0.5 cm³ gave good mycelial growth. Pure cassava alone at the 10:10 nitrogen addition level produced the highest protein yield of about 145 g kg⁻¹. The on-farm technique yielded higher protein enrichment compared with laboratory experiments. Cassava alone yielded 230 g kg⁻¹ protein while cassava with rice bran and cassava with soya bean each produced 210 g kg⁻¹ protein.