Biofuel Research Journal

Biofuel Research Journal

Maximising high solid loading enzymatic saccharification yield from acid-catalysed hydrothermally-pretreated brewers spent grain

Document Type : Research Paper

Authors
Stuart Wilkinson 1
Katherine A. Smart 2
Sue James 2
David J. Cook 1
1 Brewing Science Section, Division of Food Sciences, The University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire LE12 5RD, U.K.
2 SABMiller Plc, SABMiller House, Church Street West, Woking, Surrey, GU21 6HS, U.K.
10.18331/BRJ2016.3.2.7
Abstract
Enzyme saccharification of pretreated brewers spent grains (BSG) was investigated, aiming at maximising glucose production. Factors investigated were; variation of the solids loadings at different cellulolytic enzyme doses, reaction time, higher energy mixing methods, supplementation of the cellulolytic enzymes with additional enzymes (and cofactors) and use of fed-batch methods. Improved slurry agitation through aerated high-torque mixing offered small but significant enhancements in glucose yields (to 53 ± 2.9 g/L and 45% of theoretical yield) compared to only 41 ± 4.0 g/L and 39% of theoretical yield for standard shaking methods (at 15% w/v solids loading). Supplementation of the cellulolytic enzymes with additional enzymes (acetyl xylan esterases, ferulic acid esterases and α-L- arabinofuranosidases) also boosted achieved glucose yields to 58 – 69 ± 0.8 - 6.2 g/L which equated to 52 - 58% of theoretical yield. Fed-batch methods also enhanced glucose yields (to 58 ± 2.2 g/L and 35% of theoretical yield at 25% w/v solids loading) compared to non-fed-batch methods. From these investigations a novel enzymatic saccharification method was developed (using enhanced mixing, a fed-batch approach and additional carbohydrate degrading enzymes) which further increased glucose yields to 78 ± 4.1 g/L and 43% of theoretical yield when operating at high solids loading (25% w/v).

Graphical Abstract

Maximising high solid loading enzymatic saccharification yield from acid-catalysed hydrothermally-pretreated brewers spent grain

Highlights

  • Cellulolytic enzyme saccharification of pre-treated brewers spent grains was investigated at high solids loading.

  • Aerated high-torque mixing offered enhanced glucose yields to 53 g/L.

  • Fed-batch protocols enhanced glucose yields to 59 g/L.

  • Supplementary carbohydrate degrading enzymes boosted achieved glucose yields to 64 g/L.

  • A novel consolidated saccharification protocol further increased glucose yields to 78 g/L at 25% w/v solids loading. 

Keywords
Brewers Spent Grains
Bioethanol
Enzymatic saccharification
High solids loading
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Biofuel Research Journal
Volume 3, Issue 2 - Serial Number 2
Spring 2016
Pages 417-429