Investigation of effects of different cassava cultivars with respect to hydrogen cyanide content on their starch hydrolysis

Abstract

The effects of Hydrogen Cyanide (HCN) contents of different cultivars of cassava on the kinetic and extent of hydrolysis were studied. The results obtained showed that between 75 and 80% of HCN content had been lost during processing. Starches from cultivars with different HCN contents, Iditeru White-leaves 70.2 mg/kg, Iditeru Red-leaves 46.4 mg/kg and 920057 34.6 mg/kg, representing bitter, intermediate and sweet cultivars, respectively, were enzymatically hydrolyzed into reducing sugars. Conversion of starch to reducing sugars reached 246.2 g/L for Iditeru white-leaves, 267.9 g/L for Iditeru red-leaves and 262.2 g/L for 920057 with corresponding Dextrose Equivalent (DE) of 82.1, 89.3 and 87.4%, respectively. Statistical analysis showed that there was no significant difference (p > 0.05) in the amount of reducing sugars released in the cassava starch hydrolysates (CSH) and the % DE obtained. After 24 hr of cultivation of Saccharomyces cerevisiae on the CSH as the sole carbon source for the production of baker’s yeast on a bench scale bioreactor, the microorganism was able to utilize 80 and 81% of the sugars present in the CSH of Iditeru-white leaves and 920057 cultivars, respectively. Maximum baker’s yeast production of 8.8 and 9.1 g/L were obtained for Iditeru-white leaves and 920057 cultivars, respectively. Statistical analysis showed that there was no significant difference (p > 0.05) in the amount of reducing sugars consumed in the CSH as well as the baker’s yeast produced. Hence, HCN contents of different cultivars of cassava had no significant effect on both the rate and extent of hydrolysis. Also, the HCN contents did not affect the performance of the microorganism employed in this work.Keywords: Cassava, starch, cultivars, hydrogen cyanide, hydrolysis