Structural Modification of Empty and Partially Filled Paddy Grain Through Hydrothermal Pre‐treatment as a Novel Substrate for Fermentable Glucose Production

Abstract In this study, two conditions of empty and partially filled paddy grain (EPFG) (unground and ground) are pre‐treated using a mild hydrothermal process at 120 °C at 30–120 min. The pre‐treatment condition which shows potential structural changes for sugar conversion (gelatinization of starch, reduction of hemicellulose to 11.8%, and increased in cellulose to 43.3%) involves combination of dry grinding and hydrothermal pre‐treatment at 60 min. In this condition, the starch and sugars released in the liquid fraction is high at 127 and 37.1 mg g −1 , respectively, which can easily be converted into glucose without the need of enzyme usage. The effectiveness of the pre‐treatment on EPFG structural changes is further confirmed through scanning electron microscopy (SEM) and X‐ray diffraction (XRD), showing disruption of structures leading to amorphous biomass. Glucose production of pre‐treated ground EPFG (G‐EPFG) shows higher value at 30.13 g L −1 for 10% solid loading than the untreated samples. Overall, the results suggest that EPFG produced as waste in paddy milling factories can be a potential feedstock for a biorefinery based on the findings and processes derived from this study.