Enzymatic approaches to renewable monomers and polymers from nature

解决塑料问题对英国来说非常重要。新的天然来源和可降解聚合物的新途径将是使我们的社会受益的关键途径之一。在诺丁汉，我们最近开始探索直接从自然界中提取新的单体和聚合物。在这个项目中，我们汇集了诺丁汉大学在生物催化和超临界流体方面的两套专业知识，在清洁合成有价值的新材料方面迈出了一步。Vernonia galamensis（铁皮草）是一种天然物质，这种植物广泛存在，原产于非洲东部，目前在加拿大和美国也有潜在的商业机会。羊油酸占籽油中脂肪酸的80%，它含有非常有用的环氧化物和烯烃功能。我们的项目旨在开发一系列新型聚合物、表面活性剂和从伏诺酸中提取的洗涤剂；应用于包装、个人护理、化妆品甚至轻质复合材料。像克罗达这样的公司将对这些特别感兴趣，因为它们能够使用自然可用的可再生材料，并降低其产品的碳足迹。脂肪酸链中保留的独特功能为开发新材料和应用提供了巨大的灵活性。此外，这种方法还可以作为新业务/供应链的基础，使撒哈拉以南非洲国家受益，并可以利用当前的全球挑战。诺丁汉大学的初步工作被证明是有希望的，新的单体（上面提到的不饱和二酸是我们现在正在试验的几种之一）和由这些单体制成的聚合物已经被开发出来。单体：超临界流体萃取已被证明是一种非常有效和温和的方法，用于在低温下从种子中提取甘油三酯油，同时保留重要的反应功能。然后我们用常规化学方法水解并释放出羊油酸，然后进一步用常规化学方法转化成各种新单体（二醇、二酸、二胺等）。然而，这两种过程所需要的路线在环境上是不可接受的，而且效率低下和浪费。现在，我们将利用诺丁汉在生物催化方面的新专长来克服这些障碍。将建立筛选程序，仔细评估广泛的酯酶，以找到最有效的途径，通过水解甘油三酯以高效和清洁的方式释放油酸。此外，将油酸转化为有用的功能化单体需要烯烃功能化或环氧化物的打开，这可以通过使用水解酶和/或环氧化物水解酶的酶促方法选择性地更好地实现。聚合物：缩聚聚合通常在熔体中进行，需要高温来克服粘度问题并去除水分。酶在这种条件下不能起作用，只能使用金属催化剂，而且在这种条件下，有用的烯烃或环氧树脂功能也失去了。我们已经证明，scCO2可以通过塑化单体和生长聚合物来显著降低反应粘度，因此可以在接近环境温度的情况下进行反应。scCO2还有助于去除水的副产品。这种低温处理提供了一个独特的机会，可以引入酶来控制聚合，并开发理想的功能化线性材料。通过合作，我们现在将筛选广泛的脂肪酶、水合酶和环氧化物水合酶来催化聚合，并创建一个新的聚合体系库。

Tackling the plastics problem is of huge importance to the UK. New routes to new naturally sourced and degradable polymers will be one of the key approaches that will benefit our society. At Nottingham we have recently begun to explore the development of new monomers and polymers directly from Nature. In this project we bring together two sets of Nottingham expertise in biocatalysis and supercritical fluids to make a step change in the clean synthesis of valuable new materials.Vernolic acid is a natural material from the seeds of Vernonia galamensis (ironweed), a plant widely available and native to eastern Africa that is also now being grown for potential commercial opportunities in both Canada and the USA. Vernolic acid makes up 80% of the fatty acids in the seed oil and is remarkable in that it contains very useful epoxide and olefinic functionalities. Our project is targeted at developing a range of novel polymers, surfactants and detergents from vernolic acid; with applications across packaging, personal care, cosmetics and even light-weight composites. These will be of particular interest to companies like Croda because of the ability to use a naturally available, renewable material and to lower the carbon footprint of their products. The unique functionalities retained in the fatty acid chain provide tremendous flexibility for developing new materials and applications. Moreover, this approach could also be the basis for a new business / supply chain that could benefit countries in sub-Saharan Africa and could tap into the current Global Challenges.Initial work at Nottingham has proved promising and new monomers (the unsaturated diacid above is one of several that we have now trialled) and polymers from these monomers have been developed.Monomers: Supercritical fluid extraction has proven to be a remarkably efficient and gentle methodology for extraction of the triglyceride oil from the seeds at low temperature whilst retaining the important reactive functionalities. We have then used conventional chemistries to hydrolyse and release the vernolic acid and then further conventional chemistries to convert into a wide range of new monomers (diols, diacids, diamines etc.). However, both of these processes have required routes that are not environmentally acceptable and are inefficient and wasteful. Now, we will exploit new Nottingham expertise in biocatalysis to overcome these hurdles. A screening program will be set up to carefully assess a wide range of esterases in order to find the most efficient route to releasing vernolic acid by hydrolysis from the triglyceride in an efficient and clean way. Additionally, conversion of the vernolic acid to useful functionalised monomers requires either functionalization of the olefin or opening of the epoxide and this could be much better achieved selectively via an enzymatic approach using hydratases and/or epoxide hydrolases.Polymers: Polycondensation polymerisation is typically carried out in the melt and requires high temperatures to overcome viscosity issues and to drive off water. Enzymes cannot operate under such conditions and only metal catalysts have been used, also under these conditions the useful olefin or epoxy functionalities are lost. We have shown that scCO2 can dramatically lower reaction viscosity by plasticising the monomer and growing polymer and hence allows reactions at near ambient temperature. The scCO2 also assists in removing the water by-product. This lower temperature processing provides a unique opportunity to introduce enzymes to allow controlled polymerisation and to develop desirable functionalised linear materials. Working together, we will now screen a wide range of lipases, hydratases and epoxide hydrolases to catalyse polymerisation and to create a library of new polymeric systems.