Successive Application of Physicochemical and Enzymatic Treatments of Office Paper Waste for the Production of Bioethanol with Possible Using of Carbon Dioxide as an Indicator for the Determination of the Bioethanol Concentration

Abstract

The projected depletion of fossil fuels is a big challenge for the scientists and researchers to find out new alternative sources of energy. Using of environmental wastes as raw materials for energy productions is a new trend that most countries are directed to. Office paper wastes are sources of pure cellulosic wastes that could be intensively used as precursors for bioethanol production. Current study is concerning by liberating glucose units from office paper waste to be used as fermentable sugars for bioethanol production. Both of physical/chemical and enzymatic hydrolysis were applied in individual and successive processes to maximize the amount of produced sugars. The obtained results showed that both of autoclaving and acidic hydrolysis were efficient than microwaving and buffer hydrolysis. Both of 10% H2SO4 and 10% HCl were effectively able to release 5 and 4.9 mg/ml of glucose units from paper waste under autoclaving, respectively. However, the successive acidic and enzymatic hydrolysis elevated the glucose concentration to 7 mg/ml after 48 h of incubation. Both of SEM and FTIR were used to characterize the paper waste before and after hydrolysis. Both techniques proved the degradation of cellulosic fibers of the tested paper matrix in addition to the formation of new hydroxyl group that indicates the enzymatic break down of the bond that link the glucose units together. Saccharomyces cerevisiae strain showed an ability to ferment the liberated glucose units into 0.12% bioethanol. The released carbon dioxide gas was estimated using GC analysis and the obtained concentration was quite equal to the measured bioethanol concentration. These data prove the possibility of using CO2 concentration as an in-direct assay that reflects the exact concentration of formed bioethanol without the need of regular sampling of the ferment that may result in accidental microbial contamination.