Assessment of alkaline peroxide-assisted wet air oxidation pretreatment for rice straw and its effect on enzymatic hydrolysis

• Published in: Cellulose (London) Vol. 24; no. 11; pp. 4885 - 4898
• Main Authors: Morone, Amruta, Chakrabarti, Tapan, Pandey, R. A.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.11.2017; Springer Nature B.V
• Subjects: Bioconversion; Biomass; Bioorganic Chemistry; Carbohydrates; Cellulose; Ceramics; Chemistry; Chemistry and Materials Science; Composites; Design of experiments; Furfural; Glass; Glucose; Hydrogen peroxide; Hydroxymethylfurfural; Lignin; Lignocellulose; Mathematical models; Multiple objective analysis; Natural Materials; Optimization; Organic Chemistry; Original Paper; Oxidation; Physical Chemistry; Polymer Sciences; Pretreatment; Recovery; Saccharification; Soaking; Solubilization; Straw; Sugar; Sustainable Development; Saccharification; Delignification; Hydrogen peroxide; Alkaline wet air oxidation pretreatment; Rice straw
• ISSN: 0969-0239; 1572-882X
• DOI: 10.1007/s10570-017-1451-2

Biomass recalcitrance is considered to be one of the impediments in bioconversion of lignocellulosic biomass (LCB) to sugars. Rice straw, a potential lignocellulosic waste, owing to the surplus availability, renewability and high carbohydrate content was used as a model LCB in the present study. The alkaline hydrogen peroxide-assisted wet air oxidation (APWAO) was evaluated as plausible pretreatment for rice straw based on the 2 3 —factorial experimental design with a goal to reduce biomass recalcitrance by enhancing the cellulose recovery, hemicellulose solubilization, lignin removal and concomitantly generating limited degradation products. APWAO resulted in an overall cellulose recovery ranging from 80.54 to 93.02%, hemicellulose solubilization of 36.44–82.08% and lignin removal of 65.95–81.11% (all on w/w basis) respectively and absence of potent inhibitors viz. furfural and 5-hydroxymethylfurfural. The statistically significant pretreatment factors that affected each of these responses were assessed and optimum pretreatment conditions were determined to be biomass soaking in 0.5% H 2 O 2 for 14 h succeeded by wet air oxidation (WAO) at 190 °C, 6 bar, 20 min by multi-objective numerical optimization. Further, the morphological and structural changes occurring as a result of pretreatment were scrutinized using SEM and FT-IR. APWAO further ensued in enhanced cellulose accessibility during enzymatic saccharification indicated by the glucose yield ranging from 113.97 to 200.34 g/kg untreated rice straw. Thus, the combined pretreatment (APWAO) i.e. pre-soaking in alkaline H 2 O 2 followed by WAO was shown to enhance glucose yields owing to significant delignification.