Abstract

Sorghum is a promising crop for the animal feed and fuel ethanol production. Presence of cyanide in its biomass, particularly in the tips of young leaves, carries some risk of toxicity to livestock and microbes, especially when at an immature stage of growth, its application may be restricted. The study was carried out at Indian Agricultural Research Institute, New Delhi with nine forage sorghum cultivars to determine cyanide content and its detoxification and fermentation. The cyanide content in sorghum biomass varied with the development stages and plant height. It ranged from 5.41 to 6.65 mg/100g at heading (50 to 82 cm height) and gradually decreased at flowering stage (82 to 175 cm height) from 2.75 to 3.46 mg/100 g. The minimum cyanide content was observed at milking (1.68 to 2.66 mg/100g) and dough stage (1.49 to 2.75 mg/100g) when the height was 175 to 220 cm.Saccharomyces cerevisiae strain, NCIM, 3186 was used to carry out fermentation of sorghum juice and found capable of detoxification and reduction of the cyanide content up to 84.6% improving the ethanol yield and fermentation efficiency by 91.8%. Thus, the utilization of sorghum cultivars at milking and dough stage could be considered safe to be for feed and fuel ethanol production.

Key words: Cyanide, detoxification, sorghum, Saccharomyces cerevisiae, ethanol yield.