Optimization of Dilute Sulfuric Acid Pretreatment to Maximize Combined Sugar Yield from Sugarcane Bagasse for Ethanol Production

Abstract

Increasing fermentable sugar yields per gram of biomass depends strongly on optimal selection of varieties and optimization of pretreatment conditions. In this study, dilute acid pretreatment of bagasse from six varieties of sugarcane was investigated in connection with enzymatic hydrolysis for maximum combined sugar yield (CSY). The CSY from the varieties were also compared with the results from industrial bagasse. The results revealed considerable differences in CSY between the varieties. Up to 22.7 % differences in CSY at the optimal conditions was observed. The combined sugar yield difference between the best performing variety and the industrial bagasse was 34.1 %. High ratio of carbohydrates to lignin and low ash content favored the release of sugar from the substrates. At mild pretreatment conditions, the differences in bioconversion efficiency between varieties were greater than at severe condition. This observation suggests that under less severe conditions the glucose recovery was largely determined by chemical composition of biomass. The results from this study support the possibility of increasing sugar yields or improving the conversion efficiency when pretreatment optimization is performed on varieties with improved properties.

Impact of cultivar selection and process optimization on ethanol yield from different varieties of sugarcane

“…This observation differs from the results found in previous studies when the pretreatment was conducted in a tubular reactor [12,16,29]. This could be due to the fact that the range of pretreatment conditions evaluated was close to the optimum for CSY.…”

“…The combination of cultivar selection and process optimization have the potential to enhance sugar conversion efficiency and increase ethanol output per feedstock and further reduce pretreatment severity and enzyme requirement, thereby reducing operating cost [13,14,29]. …”

“…The uncoded values were calculated according to Equation 1. The selection of the pretreatment conditions were based on previous studies [29]. The acid loading and solids loading were kept constant at 0.5% (w/w) and 10% (w/v), respectively.…”

Current challenges on the production and use of cellulolytic enzymes in the hydrolysis of lignocellulosic biomass

“…143 Estratégias para a redução do teor de lignina na própria planta precisam ser desenvolvidas, porém sem alterar o desenvolvimento da planta ou causar efeitos indesejáveis, sendo que a maior limitação para o processo de redução da lignina seria a falta de especificidade do tecido exibida em abordagens clássicas de modificação da lignina. 144 Alguns tipos de pré-tratamentos com ácido diluído, 145,146 por explosão a vapor, 147,148 organosolv, 149 hidrotérmico, 150,151 entre outros, promovem a relocalização e/ou a remoção de parte da lignina da parede celular, garantindo maiores valores de conversão. [152][153][154][155] Além disso, tais processos também podem atuar aumentando a exposição da lignina, além de modificar a sua estrutura.…”

Sugarcane Bagasse Pretreatment Methods for Ethanol Production

“…The natural structure of lignocellulosic material is extremely recalcitrant to enzymatic hydrolysis. Therefore, the pretreatment step is required for efficient enzymatic hydrolysis of cellulose by removal of lignin and hemicellulose, reduction of cellulose crystallinity and increase the porosity of the biomass [21]. Each pretreatment has a different effect on the cellulose, hemicellulose, and lignin fraction.…”