Green production of bio-ethanol from cellulosic fiber waste and its separation using polyacrylonitrile-co-poly methyl acrylate membrane

Abstract

The world is currently suffering substantially from the over-use of fossil fuels and worsening global climate change. The recycling and conversion of various types of biomass wastes for production of bio-ethanol have recently received increasing interest around the world to overcome the upcoming fuel shortage. In this work, the cellulosic fibers from textile industry wastes were used as biomass resource for liberation of glucose units. The cellulosic fibers were treated by some acids or alkali reagents followed by application of ultrasonic waves or autoclaving or microwave radiation as green technologies for improving hydrolysis rate. The cellulase enzyme from Trichoderma reesei was later applied to increase the concentration of glucose yield to reach 1133.33 mg/dl. Glucose units were then fermented by yeast isolate that was identified by amplification and sequencing of 18S rRNA as Pichia kluyveri (accession number MF184994). The parameters of pH, temperature, inoculum size, and aerobic/anaerobic conditions were optimized revealing that cultivation of 10% of the yeast isolate at pH 5 and 25 °C under anaerobic conditions are the ideal parameters for higher bio-ethanol production rates (33.9%). The produced bio-ethanol compared with standard 25% ethanol was separated by using amicon cell ultra-filtration that contains poly acrylonitrile co methyl acrylate membrane at different nitrogen pressures. The membrane was characterized by SEM, FTIR, Raman spectroscopy, TGA, IEC, and tensile strength measurement. The hydrophilicity/hydrophobicity of the prepared membrane was investigated using contact angle and water/ethanol uptake. Finally, the prepared polymeric membrane integrated amicon cell succeeded to increase the prepared ethanol concentration from 194.25 to 478.74 mg/ml which approximately elevated from 25 to 61.6%. On the other hand, the bio-ethanol concentration was increased from 256.41 to 540.82 mg/ml which approximately elevated from 33.9 to 69.6%. The obtaining bioethanol concentration is considered cost efficient, where the combined fermentation and separation processes succeeded to convert one ton of cellulosic fiber wastes into 105 l of bioethanol with approximate estimation cost of 103.9$ per liter through lab scale study.