This paper provides an overview of previous work on an integrated biorefinery concept for the conversion of Sugar Beet Pulp (SBP) into a range of value-added fuels and chemicals and current work re-evaluating the product portfolio. Over 8 million tonnes of sugar beet are grown annually in the UK and it is a major crop across northern Europe. 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; the major components of the pectin being D-glucose (25%, Glu), L-arabinose (21%, Ara), D-galacturonic acid (20%, GalAc) and D-galactose (6%, Gal). The challenge for integrated biorefinery design is to ensure complete utilization of the SBP substrate whilst maximizing the value of the product portfolio. In this work we demonstrate processes for SBP fractionation and recovery/purification of the released polysaccharides and/or monosaccharides for various applications. SBP fractionation was carried out by steam explosion yielding soluble pectin and insoluble cellulose fractions. In our initial studies, the cellulosic fraction was enzymatically hydrolysed to Glu and used for yeast-based bioethanol production at close to theoretical yield. The pectin fraction can then be either fully hydrolysed (using physico-chemical methods) or selectively hydrolysed (using novel arabinases and galacturonases), yielding Ara-rich and GalAc-rich streams. These processes can be achieved in a continuous manner using either Centrifugal Partition Chromatography (CPC) or a two-step enzyme-membrane reactor cascade. In our previous work, biosynthetic routes for the production of aminopolyols, for pharmaceutical applications, from Ara and GalAc were established based on the use of transketolase (TK) and omega-transaminase (TAm) enzymes. Current work seeks to use the released Ara as a low-calorie sweetener and to convert the released GalAc into biodegradable polymers. The use of intact cellulose nanofibres (CNFs) as cell scaffolds, or for the preparation of superhydrophobic films and coatings, is also being explored rather than their complete hydrolysis for biofuel production. The experimental results obtained are the basis for ongoing technoeconomic and life cycle analyses.

An integrated biorefinery concept for conversion of sugar beet pulp into value-added products: Re-evaluating the product portfolio

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