Sustainable bioenergy from microalgae: A systems perspective

事实证明，全球能源需求以及为满足这一需求而燃烧化石燃料的环境后果是不可持续的。生物能源有可能减轻碳排放问题，并为能源生产提供可再生选择。但是，这需要发展经济上可行的可持续进程。利用微藻的光自养代谢将太阳能和二氧化碳转化为有机燃料前体的概念对可持续能源生产具有吸引力。然而，迄今为止，利用这一概念来改变能源经济的有效流程的开发一直难以实现。我们相信，通过系统方法对微藻代谢的更深入了解将使这种情况有所不同，并使生物能源生产的可持续过程得以发展，包括使用合成生物学和代谢工程的方法。任何这类过程的成功开发都需要对与田间栽培相关的生物体进行特征描述，而不仅仅是实验室菌株。我们的目标是结合英国和印度在生理学、生物修复、“组学”特征和生物化学工程方面的设施和专业知识，对选定的微藻分离物进行系统级调查，这些微藻分离物有可能积累生物燃料前体，并在印度和英国开发可持续的微藻生物能源生产过程。我们将在选定的分离物中进行系统级调查，以确定微藻中生物燃料前体（特别是碳水化合物、三酰甘油（TAGs）和碳氢化合物）合成的关键代谢步骤。这将导致条件的优化，以最大限度地提高产品产量，并确定基因目标的菌株操作。我们还将研究提高产品回收率的工程方法，并调查典型的生物炼制案例，以开发可持续的生物能源生产过程。BDU的印度合作伙伴在DBT的支持下建立了一个海洋微藻储存库，收集了500多个分离株，来自热带南印度沿海地区丰富的生物多样性热点地区和来自北极的嗜冷菌株。其中一些分离物已被评估用于生产生物柴油，并将用于该项目。在马杜赖可以获得以碳氢化合物和TAG积累为特征的淡水微藻，这些微藻具有事先DBT支持。在英国，SAMS在与英国相关流程的发展相关的微藻的表征和维护方面拥有丰富的经验。我们将把这些专业知识与谢菲尔德大学和剑桥大学现有的藻类系统生物学专业知识结合起来，研究生物燃料前体储存化合物积累的途径，以及如何建立其与生物生长的关系（图1）。谢菲尔德大学（WBJZ）开发的气升式循环生物反应器中采用了一种新型专利微泡技术，该技术还将用于工艺改进和产品回收。拟议的工作将导致确定相关藻类生物转化中的关键代谢步骤，优化产品产量最大化的条件，并选择或新的菌株用于开发可持续生产燃料前体的生物过程，这将对印度和英国的能源经济产生影响。我们还建议在两国举行联合讲习班和互访，以便在工业界积极参与的情况下，在伙伴之间转移知识和专门技术。

Global energy demand and the environmental consequences of fossil fuel combustion to satisfy this demand is proving to be unsustainable. Bio-energy has the potential to mitigate carbon emission concerns and provide a renewable option for energy generation. But, this requires development of sustainable processes that are economically viable. The concept of using photoautotrophic metabolism in microalgae to convert solar energy and carbon dioxide to organic fuel precursors is attractive for sustainable energy generation. However, development of efficient processes that use the concept to make a difference to the energy economy has so far proved elusive. We believe that a greater understanding of microalgae metabolism derived through a systems approach will make a difference to this scenario and enable development of sustainable processes for bio-energy generation, including approaches that use synthetic biology and metabolic engineering. The successful development of any such process will require characterisation of organisms that are relevant to field cultivation rather than just laboratory strains. We aim to combine UK and Indian facilities and expertise in phycology, bioremediation, 'omic' characterisations and biochemical engineering to conduct a systems level investigation on selected microalgae isolates with potential to accumulate biofuel precursors and develop sustainable processes for bio-energy generation from microalgae in India and the UK. We will perform a systems level investigation in selected isolates to determine key metabolic steps involved in the synthesis of biofuel precursors (in particular, carbohydrates, triacylglycerols (TAGs) and hydrocarbons) in microalgae. This will lead to optimisation of conditions to maximize product yields, and the identification of gene targets for strain manipulations. We will also examine engineering approaches to enhance product recovery and investigate exemplar biorefinery cases to enable the development of sustainable processes for bio-energy generation. Indian partners at BDU have established a repository of marine microalgae with DBT support that has over 500 isolates in its collection, from the rich biodiversity hotspots of tropical southern Indian coastal areas and psychrophilic strains from the Arctic. Some of these isolates have been assessed for biodiesel generation and will be available for the project. Freshwater microalgae characterised for hydrocarbon and TAG accumulation with prior DBT support is available at Madurai. In the UK, SAMS have extensive experience at characterisation and maintenance of microalgae with relevance to the development of UK-related processes. We will combine this expertise with algae systems biology expertise available at Sheffield and Cambridge to investigate how pathways involved in accumulation of storage compounds that are biofuel precursors and how establish its relationship with growth of the organism (Figure 1). A novel patented microbubble technology incorporated in an airlift loop bioreactor developed at Sheffield (WBJZ) will also be investigated for process improvements and product recovery. The proposed work will result in the identification of key metabolic steps in relevant algal biotransformations, optimised conditions that maximise product yields and selected or novel strains for use in developing bioprocess for sustainable generation of fuel precursors that make a difference to the energy economy in India and the UK. We also propose to hold joint workshops in the two countries and exchange visits to enable transfer of knowledge and expertise between partners, with active industrial involvement.