Effect of Alkaline and Hydrothermal Pretreatments in Sugars and Ethanol Production from Rice Husk Waste

José Ayala-Armijos, Byron Lapo (), Carolina Beltrán, Joaquín Sigüenza, Braulio Madrid, Estefanía Chérrez, Verónica Bravo and Diana Sanmartín
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José Ayala-Armijos: Grupo de Investigación BIOeng, Facultad de Ciencias Químicas y de la Salud, Universidad Técnica de Machala, Machala 070222, Ecuador
Byron Lapo: Grupo de Investigación BIOeng, Facultad de Ciencias Químicas y de la Salud, Universidad Técnica de Machala, Machala 070222, Ecuador
Carolina Beltrán: Grupo de Investigación BIOeng, Facultad de Ciencias Químicas y de la Salud, Universidad Técnica de Machala, Machala 070222, Ecuador
Joaquín Sigüenza: Grupo de Investigación BIOeng, Facultad de Ciencias Químicas y de la Salud, Universidad Técnica de Machala, Machala 070222, Ecuador
Braulio Madrid: Grupo de Investigación BIOeng, Facultad de Ciencias Químicas y de la Salud, Universidad Técnica de Machala, Machala 070222, Ecuador
Estefanía Chérrez: Grupo de Investigación BIOeng, Facultad de Ciencias Químicas y de la Salud, Universidad Técnica de Machala, Machala 070222, Ecuador
Verónica Bravo: Grupo de Investigación BIOeng, Facultad de Ciencias Químicas y de la Salud, Universidad Técnica de Machala, Machala 070222, Ecuador
Diana Sanmartín: Grupo de Investigación BIOeng, Facultad de Ciencias Químicas y de la Salud, Universidad Técnica de Machala, Machala 070222, Ecuador

Resources, 2024, vol. 13, issue 9, 1-15

Abstract: This study investigates the effectiveness of hydrothermal and alkaline pretreatment methods in enhancing the concentration of fermentable sugars derived from rice husk waste. After the pretreatments, enzymatic hydrolysis and fermentation processes were executed to evaluate the ethanol production from each pretreatment. Rice husk powder measuring ≤250 µm was used. For the alkaline pretreatment, sodium hydroxide (NaOH) was used at concentrations ranging from 0.5, 1 to 1.5% w/v. The efficacy of the hydrothermal pretreatment method was evaluated after 15, 30 and 45 min at 120 °C. The enzymatic hydrolysis process was performed over 144 h at 50 °C, pH 4.8 with an enzyme loading of 30 FPU (filter paper units). Fermentation was carried out at 37 °C using a strain of Saccharomyces cerevisiae Hansen 1883 (NCYC 366). Results indicated that the optimal conditions for alkaline pretreatment were observed at a 1.5% NaOH, while the best hydrothermal procedure was achieved at 120 °C and 45 min. The impact of these pretreatments was assessed based on the efficiency of enzymatic hydrolysis. The alkaline pretreatment resulted in 81.70% conversion of cellulose to glucose and 96.30% conversion of hemicellulose to xylose. In contrast, the hydrothermal pretreatment achieved 93% cellulose-to-glucose conversion and 83.35% hemicellulose-to-xylose conversion. The ethanol production registered ranged from 13 to 13.23 g·L−1, corresponding to a conversion factor of 0.43 for ethanol from fermentable sugars.

Keywords: enzymatic hydrolysis; cellulase; fermentable sugars; hydrothermal; alcoholic fermentation; Saccharomyces cerevisiae (search for similar items in EconPapers)
JEL-codes: Q1 Q2 Q3 Q4 Q5 (search for similar items in EconPapers)
Date: 2024
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