Cassava Leaves as an Alternative Nitrogen Source for Ethanol Fermentation.

Cassava (Manihot esculenta Crantz) leaves contain high protein content (ca 20%). This study aimed to evaluate application of the leaves as a nitrogen source for Saccharomyces cerevisiae in ethanol fermentation by comparing it with general nitrogen sources in yeast malt (YM) media. Mild pretreatments: liquid hot water, alkaline, and dilute acid, were conducted to extract amino nitrogen from the leaves while minimizing degradation. The liquid fraction from the liquid hot water pretreatment (CLWP) showed the highest amino nitrogen content of 271 ± 25 mg of N/L. Most free amino acids in CLWP were glutamic acid (22 g/kg leaves) and aspartic acid (20 g/kg leaves). After 24 h of fermentation, the equal glucose and nitrogen concentration media with CLWP gave 5 times higher ethanol content (10% v/v) than the absence of CLWP conditions (2% v/v). Free amino acids in the leaves provided a greater benefit to yeasts in ethanol production than other traditional chemical sources. Cassava leaves had high potential to be used as a nitrogen source for ethanol fermentation. [ABSTRACT FROM AUTHOR]