Improved hydrolysis yields and silica recovery by design of experiments applied to acid-alkali pretreatment in rice husks

Author(s)

Moreira, Bruna R. ^[1] ; Breitkreitz, Marcia C. ^[1] ; Simister, Rachael ^[2] ; McQueen-Mason, Simon J. ^[2] ; Gomez, Leonardo D. ^[2] ; Rezende, Camila A. ^[1]

Affiliation

^[1] Univ Campinas UNICAMP, Inst Chem, POB 6154, BR-13083970 Campinas, SP - Brazil

^[2] Univ York, Ctr Novel Agr Prod CNAP, York YO10 5DD, N Yorkshire - England

• Document type: Journal article
• Source: INDUSTRIAL CROPS AND PRODUCTS; v. 170, OCT 15 2021.
• Web of Science Citations: 0

Abstract

In this work, a two-step pretreatment using acid and alkali was optimized for rice rusks (Oryza sativa) using a 2(5-1) fractional factorial design (FFD), followed by a central composite design (CCD) to further optimization of enzymatic saccharification. The effect of five variables was simultaneously evaluated: H2SO4 concentration (from 0-5.4 % w/w); NaOH concentration (0-6 % w/w); temperature (85-125 degrees C); time (20-100 min) and solid to liquid ratio (S/L = 5-12.5 % w/w). The best pretreatment conditions were: 1.8 % w/w of H2SO4 in the first step and 6 % w/w of NaOH at 85 degrees C for 100 min at a S/L = 12.5 % (w/w) in the alkaline step, which resulted in 58.7 mg of glucose/g substrate, an 8-fold increase compared to the sample in natura (7 mg/g). In rice husks, in contrast to the results commonly found in literature, NaOH extracts mainly silica instead of lignin, while H2SO4 has an important role in lignin removal. High purity silica (97 %) was isolated at high yields (70 %) from the alkaline liquor by a simple and scalable process, which could contribute to making ethanol production from this biomass economically viable. (AU)

• FAPESP's process: 18/23769-1 - Preparation and applications of nanostructures from plant biomass
• Grantee: Camila Alves de Rezende
• Support Opportunities: Regular Research Grants
• FAPESP's process: 16/13602-7 - Study on strategies to allow the integral use of lignocellulosic biomass
• Grantee: Camila Alves de Rezende
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Regular Program Grants