Ethanol production from acid-pretreated and detoxified rice straw as sole renewable resource

Germec M., TURHAN İ.

BIOMASS CONVERSION AND BIOREFINERY, vol.8, no.3, pp.607-619, 2018 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 8 Issue: 3
  • Publication Date: 2018
  • Doi Number: 10.1007/s13399-018-0310-1
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.607-619
  • Keywords: Rice straw, Pretreatment, Response surface methodology, Detoxification, Chemical composition, Ethanol fermentation, DILUTE SULFURIC-ACID, SACCHAROMYCES-CEREVISIAE, PICHIA-STIPITIS, NITRIC-ACID, FERMENTATION, OPTIMIZATION, HYDROLYSATE, EXTRACT, BAGASSE
  • Akdeniz University Affiliated: Yes


Renewable resources are the most abundant available and inexpensive materials on the earth. This study was undertaken not only to optimize acid pretreatment conditions of rice straw but also to produce ethanol from the detoxified rice straw hydrolysate (RSH) by the yeasts Saccharomyces cerevisiae and Scheffersomyces stipitis. Box-Behnken response surface design was used to determine optimum temperature (105-135 A degrees C), dilute sulfuric acid ratio (1-5%, w/v), and solid-to-liquid ratio (1:19-1:15, w/v). Results indicated that the optimum hydrolysis conditions of rice straw were 126.5 A degrees C, 1:15 solid-to-liquid ratio (w/v) and 5% acid ratio (w/v). Reducing sugar concentration (RSC) was 21.50 g/L (0.323 g sugar/g biomass) under optimal conditions. After detoxification process with activated charcoal, the percentage removal of acetic acid, hydroxymethyl furfural, 2-furaldehyde, and phenolics was 2.01, 78.58, 100, and 94.67%, respectively. The catalytic efficiency of sulfuric acid was achieved to be 3.40 and 5.33 g/g in non-detoxified and detoxified RSHs, respectively. The ethanol yields and maximum production rates for S. cerevisiae and S. stipitis (ATCC 58784 and ATCC 58785) were calculated as 47.20% of theoretical ethanol yield and 0.37 g/L/h, 42.95% of theoretical ethanol yield and 0.09 g/L/h, and 48.81% of theoretical ethanol yield and 0.07 g/L/h, respectively. Consequently, rice straw can be a good substrate source for production of value-added products such as ethanol by fermentation. Besides, in the case of further improvement of fermentation media in terms of inhibitors, especially of acetic acid, better fermentation results would be obtained.