Ultrasound irradiation in the production of ethanol from biomass

Abstract

a b s t r a c tEthanol produced from renewable biomass, such as lignocellulosic feedstock, is one of the alternative energy resources that can be environmentally friendly. However, physical and chemical barriers caused by the close association of the main components of lignocellulosic biomass, as well as starch, hinder the hydrolysis of cellulose and hemicellulose in lignocellulose as well as amylase and amylopectin in starch to fermentable sugars. One of the main goals of pretreatment for enzymatic hydrolysis is to increase the enzyme accessibility for improving digestibility of cellulose and starch. Ultrasound irradiation applied to cellulosic materials and starch-based feedstock was found to enhance the efficiency of hydrolysis and subsequently increase the sugar yield. Prior research conducted on applying ultrasonic technology for cellulose and starch pretreatment has considered a variety of effects on physical and chemical characteristics, hydrolysis efficiency and ethanol yield. This paper reviews the application of ultrasound irradiation to cellulose and starch prior to and during hydrolysis in terms of sugar and ethanol yields. It also addresses characteristics such as accessibility, crystallinity, degree of polymerization, morphological structure, swelling power, particle size and viscosity as influenced by ultrasonic treatment.

Structure, Morphology, Thermostability and Irradiation-Mediated Degradation Fractions of Hemicellulose Treated with γ-Irradiation

“…As located primarily in the secondary cell walls, hemicellulose together with cellulose and lignin builds up the plants with a combination of mechanical support and transport property. To improve the conversion of hemicellulose into higher value chemicals and biofuels, myriads of pretreatment options have been intensively established to degrade hemicellulosic materials, including mechanical milling [8], steam explosion [9], acid or alkali [10], exposure to supercritical fluids [11], ionic liquids [12], thermochemical treatment in water [13], microwave [14], ultrasound [15] and irradiation pretreatment [16,17].…”

Chemocatalytic hydrolysis of cellulose into glucose over solid acid catalysts

“…The effects of ultrasound are the consequence of the cavitation phenomenon involving the formation, growth and collapse of microbubbles in the liquid phase [221]. By imploding, these microbubbles can create the locally high pressure (up to 1000 bar) and temperature (up to 5000 • C), leading to high-energy radical mechanisms and interesting physicochemical functions [222], hence, ultrasound-assisted pretreatment of cellulose has attracted much attention in recent years [223][224][225][226][227][228][229][230]. In 2007 and 2009, Mikkola et al [231] and Sun et al [232] reported that an ultrasonic pretreatment could improve the solubility of cellulose in [AMIM]Cl and [EMIM]OAc, respectively, which was ascribed to that ultrasonic pretreatment could destroy the hydrogen bonds of cellulose and then facilitat the penetration and diffusion of ionic liquids into the structure of cellulose [233].…”

Construction of mathematical model of dissolution process of solids under action of ultrasound

“…Solubility of oil in the solvent is increased using ultrasound. Ultrasound treatment of cellulose and starch is analyzed in [15]. It violates their structure to improve fermentation hydrolysis.…”