Evaluation of consolidated bioprocessing as a strategy for production of fuels and chemicals from lignocellulose

综合生物加工作为木质纤维素生产燃料和化学品策略的评估

基本信息

批准号：
BB/I00534X/2
负责人：
David Jonathan Leak
金额：
$ 41.17万
依托单位：
University of Bath
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=BB%2FI00534X%2F2
关键词：
Evaluation consolidated bioprocessing strategy production

项目摘要

There are a number of reasons why it is imperative to look at alternatives to fossil fuels as sources of energy and chemicals. Of immediate concern is the major contribution that the burning of fossil fuels is making to greenhouse gas accumulation. While power stations might address this through carbon capture, this is not feasible for distributed systems such as transport and chemicals. Therefore, there is a strong drive to find renewable sources of liquid fuels and chemicals. Currently, this is being addressed using glucose obtained from maize or wheat starch, which is having a negative impact on the price of starch for food. We urgently need to find ways to use the more abundant carbohydrates found in woody material and grasses (lignocellulose), either purpose grown or as wastes. However, this is currently uneconomic due mainly to the cost of releasing the useful carbohydrate from woods and grasses (pre-treatment). This project will address the economics of pre-treatment by exploring the benefits of an approach called 'Consolidated Bioprocessing' (CBP). Current methods rely on acids or alkalis to break down either the lignin and/or some of the long chains (polymers) of carbohydrates found in woody material, followed by treatment with enzyme cocktails, generally referred to as cellulases, but typically containing a complex mixture of enzyme activities, to produce monomeric carbohydrates. These cellulases are typically bought from one of the two major enzyme producers and add a significant cost and greenhouse gas contribution to the process. The concept of CBP envisages that the micro-organism that produces the desired end-product also produces some/all of the enzymes necessary to break down the carbohydrate polymers, so reducing these additional costs. In order to be able to investigate the benefits and disadvantages of CBP within the timescale of the programme we intend to work with a group of bacteria known as Geobacillus spp which grow best in the 50-70oC temperature range and already have the ability to use some of the intermediates produced from polymer degradation. In this way we should only have to engineer in a limited array of novel activities, and we already have the genetic tools and organisms containing the relevant additional enzymatic activities that we require. The project will focus on using miscanthus, a high-yielding grass under consideration in the USA and Europe as a purpose-grown lignocellulosic feedstock. This will be pre-treated by two established methods that leave the polymeric carbohydrates largely intact but disrupt the lignin. Having constructed suitable bacterial strains for CBP the intention is to generate information that allows us to judge the practically and economics of the process when operated at a large scale. This will be done largely by generating models, based on information gathered from small scale operations, and applying appropriate scaling-up criteria. Factors such as the consequence of including significant amounts of solids in the fermentation process and the 'cost' to the organism of producing extra enzymes will be examined. Because CBP is still largely a concept, there are a number of areas of process development which may impact overall practicality and economics which will need to be addressed during the project. By doing this we intend to produce the first genuine assessment of the practicalities of CBP and guidelines on areas that may need further improvement.

出于多种原因，必须寻找化石燃料的替代品作为能源和化学品的来源。当前令人担忧的是化石燃料的燃烧对温室气体积累造成的主要影响。虽然发电站可以通过碳捕获来解决这个问题，但这对于运输和化学品等分布式系统来说是不可行的。因此，人们迫切需要寻找液体燃料和化学品的可再生来源。目前，正在使用从玉米或小麦淀粉中获得的葡萄糖来解决这个问题，这对食品淀粉的价格产生了负面影响。我们迫切需要找到方法来利用木质材料和草（木质纤维素）中发现的更丰富的碳水化合物，无论是专门种植的还是作为废物的。然而，目前这是不经济的，主要是因为从木材和草中释放有用的碳水化合物（预处理）的成本。该项目将通过探索“综合生物处理”（CBP）方法的优势来解决预处理的经济问题。目前的方法依靠酸或碱来分解木质素和/或木质材料中发现的碳水化合物的一些长链（聚合物），然后用酶混合物（通常称为纤维素酶，但通常含有复杂的混合物）进行处理酶活性，产生单体碳水化合物。这些纤维素酶通常是从两个主要酶生产商之一购买的，并且给该过程增加了显着的成本和温室气体排放。 CBP 的概念设想，产生所需最终产品的微生物也会产生分解碳水化合物聚合物所需的部分/全部酶，从而减少这些额外成本。为了能够在计划的时间范围内研究 CBP 的优点和缺点，我们打算与一组称为土芽孢杆菌属的细菌合作，这些细菌在 50-70oC 的温度范围内生长最好，并且已经能够使用一些聚合物降解产生的中间体。通过这种方式，我们只需设计有限的一系列新活性，并且我们已经拥有包含我们所需的相关附加酶活性的遗传工具和生物体。该项目将重点使用芒草，这是一种在美国和欧洲考虑用作专门种植的木质纤维素原料的高产草。这将通过两种既定方法进行预处理，使聚合碳水化合物基本保持完整，但会破坏木质素。为 CBP 构建合适的细菌菌株，目的是生成信息，使我们能够判断大规模操作时该工艺的实用性和经济性。这主要是通过根据小规模运营收集的信息生成模型并应用适当的扩大标准来完成。将检查发酵过程中包含大量固体的后果以及生物体生产额外酶的“成本”等因素。由于 CBP 在很大程度上仍然是一个概念，因此有许多工艺开发领域可能会影响项目期间需要解决的整体实用性和经济性。通过这样做，我们打算对 CBP 的实用性进行首次真正的评估，并针对可能需要进一步改进的领域制定指南。