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.
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•Selective fermentation is a viable route for producing fructose and ethanol.•Highly concentrated fructose solutions were produced from date syrups.•Scaling the fermentors by 100 folds has minimal effect on fermentation performance.•External mass transfer resistance affects fermentation performance.