From Napier grass to bioethanol and beyond: sustainable urea and oxalic acid pretreatments with valorization of pretreatment filtrates for plant growth and pigment enhancement

Information from the abstract

In this study, Napier grass (NG) was pretreated with oxalic acid (OA) and urea under varying conditions to enhance enzymatic saccharification and subsequent ethanol yields. Unlike conventional acid and alkali pretreatments, urea offers a cost-effective option, while OA provides an effective organic acid-based approach. Optimization of pretreatment revealed that OA pretreatment at 120 °C for 120 min with a solid-to-liquid ratio of 1:6 produced the highest reducing sugar yield of 0.24 g/g. In comparison, urea pretreatment achieved a maximum of 0.40 g/g at 100 °C for 6 h with a solid-to-liquid ratio of 1:10. Structural changes in the pretreated biomass were confirmed by FTIR and XRD analyses, showing effective delignification and improved cellulose accessibility. Fermentation studies demonstrated that Pichia kudravzevii performed better than Saccharomyces cerevisiae under optimized conditions, with simultaneous saccharification and fermentation (SSF) yielding higher ethanol than separate hydrolysis and fermentation (SHF). Additionally, the urea-pretreatment filtrate was repurposed in seed germination assays and pigment analysis. While germination rates varied among species, wheatgrass was identified as the most suitable candidate for pigment analysis, showing up to a 2.7-fold increase in chlorophyll and a 1.5-fold increase in carotenoids compared to the control.

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Related topics: Biofuel production and bioconversion · Anaerobic Digestion and Biogas Production · Bioenergy crop production and management