Simultaneous Production Of Fructose And Bioethanol Through Bioconversion Of Date Sugars

Abstract

Fructose, the sweetest natural sugar with sweetness index of 1.3 - 2.0 times that of sucrose with low calories and suitable to be taken by diabetes is an important monosaccharide in food industry. It is commercially marketed as 42, 55 and 95% concentration. Production of fructose and bio-ethanol from low quality low-cost dates and economical evaluation of the process were the main objectives of this study. The study covered a comprehensive literature review on different sources of sugars including dates and the method of extracting and separating date's sugars. A full detailed materials and methods used were included showing the equipment used in extraction, isomerization and fermentation. 10, 15 and 20% sugar concentrations of date extracts were subjected to fermentation using wild strain Saccharomyces Cerevisiae, yeast. High Performance Liquid Chromatograph, (HPLC) was used for detection and determination of sugars and ethanol. Other parameters were also measured, such as pH, Total Dissolved Solids (TDS) and conductivity. A flow sheet describing the whole process of production of fructose and ethanol from dates was established using SuperProTM Designer® software simulation package, where material balances and economic evaluation were evaluated. Results on extraction showed that for both types of dates, sugar extracted was found to be directly proportional with extraction time, temperature and date to water ratio and inversely proportional to the pH and the optimum conditions for extraction was found to at room temperature using water to date ratio of 4.5 for 60 minutes extraction time. ix Two kinetic expressions for isomerization of glucose to fructose were suggested. The first model is simple model with no complex formation, while the second model with a one-step complex formation. The agreement obtained with the second model was found to be better than that obtained with the first t model. Fermentation experiments on date extracts showed that, for different extract concentrations under investigation, the yeast consumes glucose at rates more than fructose leading to high fructose concentrations. Both types of dates extracts were found to undergo the same fermentation behaviour, but, for simultaneous production of 55% HFS and ethanol, fermentation of Jaw extract was found to be more suitable compared to Sifri extracts in terms of fermentation time. No significant difference was noticed when Jaw date extract was fermented at 30 or 35 °C for production of 55% HFS. Both temperatures showed that the 55% HFS can be obtained in a relatively short time within 12 to 18 hours, depending on concentration used, without the need for complex processes such as the currently used multistage chromatic process. The presence of organic nutrients in the date extracts was found to play a crucial role in fermentation process. Economic evaluation and sensitivity analysis based on fermentation process was performed using SuperPro Designer soft-ware to treat 20000 ton of dates to produce 9,572,812.69 kg HFS/year. Results showed a significant potential in using wild strain Sccharomyces serevisiae in fermentation of date extracts to obtain HFS that can be marketed with gross margin of 21.88%, x return on investment (ROI) 22.42%, internal rate of return (IRR) 17.73% and payback period of four years and six months. The study recommends moving to the next step of scaling up and conducting the fermentation experiments on pilot plat scale and studying the effect of increasing the fermenotr volume on other fermentation parameters, beside enhancing the yield and selectivity of fructose by using mutant yeast for fermenting Jaw extract rather than using wild strain yeast.