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Comparison between solid-state and powder-state alkali pretreatment on saccharification and fermentation for bioethanol production from rice straw

Shabina Yeasmin, Chul-Hwan Kim, Shah Md. Asraful Islam, Ji-Young Lee
Preparative biochemistry & biotechnology 2016 v.46 no.3 pp. 229-237
Fourier transform infrared spectroscopy, absorbance, alkali treatment, atomic force microscopy, biomass, ethanol, ethanol fermentation, ethanol production, glucose, hydrolysis, lignin, rice straw, saccharification, scanning electron microscopy, sodium hydroxide
The efficacy of different concentrations of NaOH (0.25%, 0.50%, 0.75%, and 1.00%) for the pretreatment of rice straw in solid and powder state in enzymatic saccharification and fermentation for the production of bioethanol was evaluated. A greater amount of biomass was recovered through solid-state pretreatment (3.74 g) from 5 g of rice straw. The highest increase in the volume of rice straw powder as a result of swelling was observed with 1.00% NaOH pretreatment (48.07%), which was statistically identical to 0.75% NaOH pretreatment (32.31%). The surface of rice straw was disrupted by the 0.75% NaOH and 1.00% NaOH pretreated samples as observed using field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). In Fourier-transform infrared (FT-IR) spectra, absorbance of hydroxyl groups at 1,050 cm ⁻¹ due to the OH group of lignin was gradually decreased with the increase of NaOH concentration. The greatest amounts of glucose and ethanol were obtained in 1.00% NaOH solid-state pretreated and powder-state hydrolyzed samples (0.804 g g ⁻¹ and 0.379 g g ⁻¹, respectively), which was statistically similar to the use of 0.75% NaOH (0.763 g g ⁻¹ and 0.358 g g ⁻¹, respectively). Thus, solid-state pretreatment with 0.75% NaOH and powder-state hydrolysis appear to be suitable for fermentation and bioethanol production from rice straw.