Comparative Study of the Single and Double-Stage Thermochemical Pretreatment of Gracilaria sp. for Biogas Feedstock

delignification hydrolysis macroalgae pretreatment thermochemical double-stage

Authors

  • Elli Prastyo Department of Chemical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Jalan Grafika 2, Yogyakarta 55281, , Indonesia
  • Rochim Bakti Cahyono Department of Chemical Engineering, Faculty of Engineering, Universitas Gadjah Mada, Jalan Grafika 2, Yogyakarta 55281, , Indonesia
  • Lisendra Marbelia Bioprocess Engineering Research Group, Universitas Gadjah Mada, Jalan Grafika No. 2, Sleman, Yogyakarta 55281, Indonesia
  • Wiratni Budhijanto
    wiratni@ugm.ac.id
    Bioprocess Engineering Research Group, Universitas Gadjah Mada, Jalan Grafika No. 2, Sleman, Yogyakarta 55281, Indonesia
October 28, 2025
December 11, 2025

Downloads

The objective of this study was to evaluate the effects of single-stage thermochemical pretreatment using sodium hydroxide (NaOH) and a double-stage pretreatment combining NaOH and hydrochloric acid (HCl) on the production of reducing sugars and total phenolic compounds (TPC). The influence of pretreatment duration (30–120 minutes) and solvent concentration (NaOH: 0.2–1 N; HCl: 0.05–0.4 N) at 100 °C was systematically investigated. The results showed that the double-stage pretreatment led to a higher yield of reducing sugars while maintaining relatively low TPC levels. Analysis of variance (ANOVA) revealed that, in the single-stage pretreatment, NaOH concentration had a more pronounced effect than treatment duration. Conversely, in the double-stage pretreatment, duration had a greater influence than HCl concentration. Overall, the double-stage pretreatment, involving NaOH-induced delignification followed by acid-catalyzed hydrolysis, offers a promising strategy for the efficient conversion of macroalgae into reducing sugars while minimizing phenolic compound accumulation.