Conversion of starch from dry common beans ( Phaseolus vulgaris L.) to ethanol

Abstract

Dry common beans ( Phaseolus vulgaris L.) were evaluated for potential conversion of starch to ethanol. Eight varieties of beans with average starch content of 46% (db) were assayed in a laboratory-scaled process based upon the commercial corn dry grind fermentation process. Ethanol yield was 0.43–0.51 g ethanol/g glucose (0.19–0.23 g ethanol/g beans). The average ethanol yield for the eight bean types was 92% of maximum theoretical yield, demonstrating that starch from beans could be efficiently converted to ethanol. Ethanol concentration obtained from 20% (w/w) solids loading was 3.5–4.4% (w/v). The residual fermentation solids contained, on a dry basis, 37.1–43.6% crude protein, 10.8–15.1% acid detergent fiber and 19.1–31.3% neutral detergent fiber.