Alkaline deacetylation as a strategy to improve sugars recovery and ethanol production from rice straw hemicellulose and cellulose

Rafael Cunha de Assis Castro, Bruno Guedes Fonseca, Hilton Túlio Lima dos Santos, Isabela Silveira Ferreira, Solange Ines Mussatto, Inês Conceicao Roberto

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Abstract

A mild alkaline pretreatment (deacetylation) prior to the dilute acid pretreatment was evaluated as a strategy to improve the sugars recovery and ethanol production from both hemicellulose and cellulose fractions of rice straw. This pretreatment was carried out using different conditions of temperature (50–70 °C) and NaOH loading (20–80 mg NaOH/g biomass), which were combined according to a 22 central composite design. In this step the removal of acetyl groups as well as the impact of this step on biomass composition were evaluated. In order to assess the impact of the deacetylation on hemicellulosic hydrolysate composition, the influence of the reaction time (30–90 min) and sulfuric acid concentration (0.5–1.5% w/v) was also studied, using the alkaline-pretreated solid (deacetylated) and rice straw in natura. The best sequential pretreatment conditions were scaled-up to 50-L reactor, being obtained a cellulose-rich pretreated solid (cellulignin) and a hemicellulosic hydrolysate, which was concentrated to 70 g/L xylose to be used as fermentation medium. A significant improvement on ethanol production from xylose by Scheffersomyces stipitis NRRL Y-7124 was observed when the biomass was submitted to deacetylation (about 4-fold). The enzymatic conversion of cellulose was also improved (from 73 to 89%) when the deacetylated cellulignin was used, resulting in an enhancement of the ethanol production (from 12.7 to 20.4 g/L) during the simultaneous saccharification and fermentation with Kluyveromyces marxianus NRRL Y-6860. In brief, biomass deacetylation prior to dilute acid pretreatment was an efficient strategy for rice straw processing, substantially improving the ethanol production from both pentose and hexose sugars.
Original languageEnglish
JournalIndustrial Crops and Products
Number of pages9
ISSN0926-6690
Publication statusE-pub ahead of print - 2016
Externally publishedYes

Keywords

  • Rice straw
  • Deacetylation
  • Dilute acid pretreatment
  • Hemicellulosic hydrolysate
  • SSF
  • Ethanol

Cite this

de Assis Castro, R. C., Guedes Fonseca, B., Lima dos Santos, H. T., Silveira Ferreira, I., Mussatto, S. I., & Conceicao Roberto, I. (2016). Alkaline deacetylation as a strategy to improve sugars recovery and ethanol production from rice straw hemicellulose and cellulose. Industrial Crops and Products.