Isolation and characterization of some dominant yeast strains for ethanol production from coffee (<i>Coffea arabica</i> L.) wastes

Abstract

The current study was initiated to isolate and characterize yeasts from wet Arabica coffee processing wastes for bioethanol production. Yeast isolates were collected from wet Arabica coffee processing effluent 1, effluent 2, effluent 3, pulp 1 and pulp 2. They were screened and characterized for ethanol production following their carbohydrate fermentation using standard methods. The selected ethanol producing isolates from pulp (ACP12) and effluent (ACE12) showed significantly high counts of 2.16 ± 1.00 x 10⁸ and 1.21 ± 1.00 x 10⁸ CFU/ml, respectively at 20% glucose concentration. The isolate ACP12 showed even higher population number (9.7 ± 1.00 x 10⁷ CFU/ml) than the standard culture (Saccharomyces cerevisiae) with colony count of 8.7 ± 1.00 x 10⁷ CFU/ml at 30°C and at pH 5. Based on morphological, physiological and biochemical characteristics, the two isolates (ACE12 and ACP12) were tentatively identified to the genus Saccharomyces. Isolate ACP12 showed the maximum ethanol production (6.2 g/l) from pulp 1 with sugar concentrationon (90%) compared to the standard isolate (5.49 g/l) and the other test yeasts. From this study, it can be concluded that isolate ACP12 has the potential for ethanol production from coffee pulps compared to the other test yeast isolates and needs further supplementary activities to qualify it for industrial application.

Keywords: Arabica coffee, Coffee wastewater, Ethanol production, Fermentation