Unlocking sugar beet pulp via novel hydrogen peroxide-tween 80 and polypropylene glycol pretreatments: Mechanistic insights and comparative techno-economic analysis

Sugar beet pulp (SBP) is an abundant polysaccharide-rich agro-industrial residue with distinctly low lignin and significant pectin content. Suitable pretreatment strategies tailored to SBP constituents are thus critical for its valorisation to diverse products. We developed two novel pretreatments, hydrogen peroxide-tween 80 (PS) and polypropylene glycol (PPG) and benchmarked them against dilute hydrochloric acid pretreatment (DAP). The process development includes response surface optimization, sequential pectinase-cellulase hydrolysis, and a techno-economic analysis (TEA). DAP achieved 75% theoretical arabinose yield (28.59 g/L) while solubilizing 80% of pectin, recovered via ethanol precipitation. A subsequent cellulase hydrolysis released 45.1 g/L glucose at 83% theoretical yield. PS removed 62-67% lignin through oxidative delignification with minimal sugar loss (less than 2 g/L), and PPG substantially improved enzyme accessibility through solvent-mediated surface disruption with negligible PPG loading. Sequential enzymatic hydrolysis produced 59.4 g/L and 55.3 g/L total sugars (ara + GalA dominant) from the pectinase stage, and 69.6 g/L and 81.7 g/L (glucose dominant) from the cellulase stage, for PS and PPG, respectively. TEA, using 100 MT SBP/day as plant capacity, showed that the production costs per kg of sugar mixtures were $0.41, $1.03, and $0.96 for DAP, PS, and PPG, respectively. However, DAP's apparent cost advantage is contingent on pectin co-product revenue. Without this credit, its production cost rises to $1.05/kg. This work validates PS and PPG as viable novel pretreatments and establishes a comparative framework linking process chemistry, enzymatic performance, and economics for pretreatment selection in SBP-based 2G biorefinery.