Optimization of the fermentation time and bacteria cell concentration in the starter culture for cyanide acid removal from wild cassava (Manihot glaziovii)

Cassava is one of the most widespread starchy tuberous roots in Indonesia, being one of the typical plants used in the starch market. However, due to the high cyanide content (338.41 ppm), these roots become a poison if they are unsuitably processed. Therefore, a detoxification process is needed to reduce the cyanide level to the safe level for human consumption (10 ppm). This study was focused on (i) the investigation of the detoxification potential of fermentation with Lactobacillus plantarum (L. plantarum) on the cyanide level of wild cassava tubers (Manihot glaziovii) and (ii) the optimization of the fermentation time and bacteria cell number in the starter culture. The fermentation was performed for different periods of time (12, 24 and 36 h) and various initial bacteria cell number (7x10¹⁰, 7x10¹¹, 1.05x10¹², and 3.5x10¹² L. plantarum cells). The results showed a significant decrease of the cyanide level, 97 % of cyanide degradation being noticed after 36 h of fermentation for an initial bacterial cell number of 3.5x10¹² cells. Hence, the strong point of the study consists of a noteworthy reduction of the cyanide content in wild cassava in short periods, whereas the protein content was increased (from 1.5% to 3.5%) in Modified Cassava Flour (MOCAF).