An integrated biorefinery concept for conversion of sugar beet pulp into value-added chemicals and pharmaceutical intermediates
An integrated biorefinery concept for conversion of sugar beet pulp into value-added chemicals and pharmaceutical intermediates
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DOI：
10.1039/c7fd00094d
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发表时间：
2017-09-01
影响因子：
3.4
通讯作者：
Lye, Gary J.
中科院分区：
文献类型：
--
作者：
Cardenas-Fernandez, Max;Bawn, Maria;Lye, Gary J.
英国每年种植超过800万吨甜菜。甜菜浆（SBP）是甜菜加工的主要副产品，目前被干燥并作为低价值的动物饲料出售。SBP是碳水化合物的丰富来源，主要以纤维素和果胶的形式存在，包括D-葡萄糖（Glu）、L-阿拉伯糖（Ara）和D-半乳糖醛酸（GalAc）。这项工作描述了一个综合的生物精炼概念的SBP分馏和转化这些单糖到增值产品的技术可行性。SBP分级首先通过在温和条件下蒸汽爆破进行，以产生可溶性果胶和不溶性纤维素级分。纤维素容易被纤维素酶水解以释放Glu，然后可以通过商业酵母菌株发酵以高产率生产生物乙醇。果胶级分可以使用物理化学方法完全水解，或者使用克隆的阿拉伯糖酶和半乳糖醛酸酶选择性水解，以产生富含Ara和富含GalAc的流。这些单体可以使用离心分配色谱法（CPC）或超滤分离成适合于后续酶促升级的流。基于我们以前使用转酮醇酶（TK）和转氨酶（TAm）酶的经验，探索了Ara和GalAc转化为更高价值的产物。特别地，描述了使用突变体TK将Ara转化为L-葡庚酮糖（GluHep），其在低血糖和癌症中具有潜在的治疗应用。TAm的初步研究也表明GluHep可以选择性胺化为相应的手性氨基多元醇。目前的工作是解决剩余SBP单体GalAc的升级，以及生物精炼概念的建模，以实现经济和生命周期分析（LCA）。
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).