A novel staggered hybrid SSF approach for efficient conversion of cellulose/hemicellulosic fractions of corncob into ethanol

Volume 98, December 2016, Pages 16–22

Special Issue: New Horizons in Biofuels Production and Technologies

Edited By Ashok Pandey, Duu Jong Lee, Samir K. Khanal and Reeta Rani Singhania

Highlights

A novel staggered hybrid SSF approach for ethanol production.

Co-utilization of pentose and hexose streams.

Malbranchea cinnamomea is a source of catalytically active cellulases.

Efficient saccharification of acid pretreated corncob using in-house enzymes.

Abstract

The following study reports bioconversion of corncob into ethanol using hybrid approach for co-utilization of dilute acid hydrolysate (pentose rich stream) and hexose rich stream obtained by enzymatic saccharification employing commercial cellulase Cellic CTec2 as well as in-house cellulase preparations derived from Malbranchea cinnamomea, Scytalidium thermophilium and a recombinant Aspergillus strain. Acid hydrolysis (1% H2SO4) of corncob at 1:15 solid liquid ratio led to removal of 80.5% of hemicellulosic fraction. The solid glucan rich fraction (63.5% glucan, 8.3% pentosans and 27.9% lignin) was hydrolysed at 10% substrate loading rate with different enzymes for 72 h at 50 °C resulting in release of 732 and 535 (mg/g substrate) total sugars by Cellic CTec2 and M. cinnamomea derived enzymes, respectively. The fermentation of enzyme hydrolysate with co-culture of Saccharomyces cerevisiae and Pichia stipitis added in sequential manner resulted in 3.42 and 2.50% (v/v) ethanol in hydrolysate obtained from commercial Cellic CTec2 and M. cinnamomea, respectively. Employing a hybrid approach, where dilute acid hydrolysate stream was added to solid residue along with enzyme Cellic CTec2 during staggered simultaneous saccharification and fermentation at substrate loading rate of 15% resulted in 252 g ethanol/kg corncob.

Keywords

  • H2SO4 pretreatment;
  • Corncob residue;
  • Enzymatic hydrolysis;
  • Saccharification;
  • Cellic CTec2;
  • Malbranchea cinnamomea

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