An integrated biorefinery concept for conversion of sugar beet pulp into value-added chemicals and pharmaceutical intermediates

Abstract

Over 8 million tonnes of sugar beet are grown annually in the UK. Sugar beet pulp (SBP) is the main by-product of sugar beet processing which is currently dried and sold as a low value animal feed. SBP is a rich source of carbohydrates, mainly in the form of cellulose and pectin, including d-glucose (Glu), l-arabinose (Ara) and d-galacturonic acid (GalAc). This work describes the technical feasibility of an integrated biorefinery concept for the fractionation of SBP and conversion of these monosaccharides into value-added products. SBP fractionation is initially carried out by steam explosion under mild conditions to yield soluble pectin and insoluble cellulose fractions. The cellulose is readily hydrolysed by cellulases to release Glu that can then be fermented by a commercial yeast strain to produce bioethanol at a high yield. The pectin fraction can be either fully hydrolysed, using physico-chemical methods, or selectively hydrolysed, using cloned arabinases and galacturonases, to yield Ara-rich and GalAc-rich streams. These monomers can be separated using either Centrifugal Partition Chromatography (CPC) or ultrafiltration into streams suitable for subsequent enzymatic upgrading. Building on our previous experience with transketolase (TK) and transaminase (TAm) enzymes, the conversion of Ara and GalAc into higher value products was explored. In particular the conversion of Ara into l-gluco-heptulose (GluHep), that has potential therapeutic applications in hypoglycaemia and cancer, using a mutant TK is described. Preliminary studies with TAm also suggest GluHep can be selectively aminated to the corresponding chiral aminopolyol. The current work is addressing the upgrading of the remaining SBP monomer, GalAc, and the modelling of the biorefinery concept to enable economic and Life Cycle Analysis (LCA).

The Use of Acidic Hydrolysates after Furfural Production from Sugar Waste Biomass as a Fermentation Medium in the Biotechnological Production of Hydrogen

“…[8][9][10][11] or as substrates in chemical syntheses, e.g., for the production of fuels (bioethanol, methane, hydrogen), solvents, polymers, etc. [4,[12][13][14].…”

Potential of sugar beet vinasse as a feedstock for biocatalyst production within an integrated biorefinery context

“…Current work in our laboratory is investigating the utilisation of sugar beet pulp (SBP) as a renewable feedstock within the context of the AB Sugar Wissington biorefinery. Methods for the selective release of pectin from SBP have been established and for separation of the main monosaccharide components: l ‐arabinose and d ‐galacturonic acid . These have numerous industrial applications for production of biopolymers and hyperbranched polyesters and plasticisers .…”

Sustainable Galactarate‐Based Polymers: Multi‐Enzymatic Production of Pectin‐Derived Polyesters

“…Càrdenas‐Fernàndez et al reported the application of centrifugal partition chromatography (CPC) for simultaneous separation of all the pectin derived monosaccharides. CPC appears to be a promising separation technique for biorefinery applications, allowing a one‐step recovery of the two main monosaccharides present in SBP, i.e., Ara and GalA, with high yields and adequate purity from crude hydrolysate …”