A green process for simultaneous production of fructose and ethanol via selective fermentation

Abstract

Date (Phoenix dactylifera L.) fruits can provide a renewable source for the production of fructose and ethanol through selective fermentation processes. The effects of scale-up on ethanol yield and remaining fructose from date syrup in three 1 L, 7.5 L and 80 L fermentors were investigated. Fermentations were simultaneously conducted in the fermentors (working volume ratios of 1:10:100) using date syrups having an initial total sugars concentration of 142.5 g/L and Saccharomyces cerevisiae ATCC 36859 at 30 °C and 120 rpm. Experiments showed good and comparable results for the three fermentors. Glucose was completely consumed in the three fermentors. Fructose remained was 83.5%, 89.6% and 90.7% in the 1 L, 7.5 L and 80 L fermentors. The ethanol yields were 59.1%, 76.4% and 75.4%. The fructose fraction in the final syrup was >93% in the three fermentors. Statistically insignificant differences (p > 0.05) were obtained for the two larger fermentors. A kinetic model based on Monod equation was developed and successfully tested against the experimental data; also, the hydrodynamic was investigated using dimensionless correlations. A conceptual framework for the process was proposed. These results could provide a step forward towards commercialization of this clean process.