Revalorization of Sunflower Stalk Pitch As Feedstock for the Coproduction of Pectin and Glucose Using a Two-Step Dilute Acid Pretreatment Process

Abstract

Background: Sunflower stalk pith, residue from the processing of sunflower, is rich in pectin and cellulose, thereby acting as an economic raw material for the acquisition of these compounds. In order to increase the commercial value of sunflower processing industry, a two-step sequential dilute sulfuric acid treatment combined with subsequent enzymatic hydrolysis was conducted on spent sunflower stalk pith to obtain the value-added products, pectin and glucose. Results: In this study, pectin was firstly extracted with a mild condition to avoid pectin degradation, which conducted at 95℃ with a pH of 2.0 for 2 h, and approximately 0.12 g/g of pectin could be recovered. Then the remaining solids followed by extracted pectin were subjected to the reinforced treatment process with 0.75% H2SO4 at 150 oC for 30 min to further improving enzymatic hydrolysis efficiency. Moreover, a fed-batch enzymatic hydrolysis was successfully performed with a solid 16% content, the glucose titer reached 103.1 g/L with a yield of 83.6 %.Conclusion: Finally, approximately 140 g pectin and 260 g glucose were produced from 1 kg of raw sunflower stalk pith using the integrated biorefinery process. This work put forward a two-step dilute acid pretreatment combined with enzymatic hydrolysis method to produce pectin and glucose from sunflower spent waste.