Ultrasonically-Assisted Dissolution of Sugarcane Bagasse during Dilute Acid Pretreatment: Experiments and Kinetic Modeling

Abstract

Ultrasonic irradiation is known to enhance various physicochemical processes. In this work, the effect of ultrasound on the dissolution of sugarcane bagasse was studied, with the specific aims of quantifying the effect at low solids loading and mild reaction conditions, and determining whether the enhancement of dissolution by ultrasound is independent of temperature. The effects of agitation speed, reaction time, and sonication were examined on the dissolution of the biomass substrate at varying reaction temperatures during the pretreatment process. Sugarcane bagasse was mixed with a 0.3 M solution of sulfuric acid in a reaction vessel to undergo pretreatment. A kinetic model was applied to the mass dissolution of the biomass, as sonicated runs showed higher mass losses at each reaction time, compared to the non-sonicated runs. The ultrasonic enhancement in mass dissolution was seen to increase for an increase in the reaction time. It was observed that the induction period for the dissolution was eliminated by the application of ultrasound. Ultrasound was found to be more effective than temperature at enhancing mass dissolution at low solids loadings, and the effect of ultrasound was also found to be dependent on the temperature employed.

A Novel Kinetic Modeling of Enzymatic Hydrolysis of Sugarcane Bagasse Pretreated by Hydrothermal and Organosolv Processes

“…For efficient conversion to obtain biofuels, cellulose polymers must be decomposed into small molecules, allowing microbial assimilation. Therefore, the outer layer of lignin needs to be broken down [9]. Sugarcane bagasse is an important byproduct with a high cellulose content [10,11].…”

“…The model did not distinguish EG from CBH. Due to the low amount of β-glucosidase, the model considered the enzyme only from Aspergillus niger;(5) The xylanase from the reaction medium was present in the cellulase used in the experimental assays; (6) The hemicelluloses of HB and OB were composed solely of xylan;(7) The conversion of cellobiose into glucose represented by r 2 occurred in solution and followed the Michaelis-Menten kinetics;(8) The conversion of xylan into xylose represented by r 4 occurred in a single reaction, absent intermediate compounds such as xylobiose;(9) The proportion of lignin exposed to the enzyme of the total lignin present in the pretreated bagasse was equal to 1, demonstrating that cellulose did not block the adsorption of enzymes on lignin[24]; (10) β-glucosidase did not adsorb to cellulose and lignin;(11) The lignin of the pretreated biomass was not degraded during enzymatic hydrolysis. Equations (2)-(8) describe the mass balance for the enzymatic hydrolysis model of HB and OB.…”