Sustainable bioenergy from microalgae: A systems perspective

全球能源需求和为满足这一需求而燃烧化石燃料的环境后果已证明是不可持续的。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的选择。但是，这需要发展经济上可行的可持续进程。利用微藻中的光合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于可持续能源生产是有吸引力的。然而，迄今为止，开发利用这一概念来改变能源经济的有效工艺被证明是难以捉摸的。我们认为，通过系统方法更好地了解微藻代谢将对这种情况产生影响，并能够开发可持续的生物能源生产过程，包括使用合成生物学和代谢工程的方法。任何此类工艺的成功开发都需要对与田间栽培相关的生物体进行表征，而不仅仅是实验室菌株。我们的目标是结合联合收割机英国和印度的设施和专业知识，在藻类学，生物修复，“组学”表征和生物化学工程进行系统级调查选定的微藻分离物有可能积累生物燃料前体和发展可持续的过程中，从微藻在印度和英国的生物能源发电。我们将在选定的分离株中进行系统级调查，以确定微藻中生物燃料前体（特别是碳水化合物，三酰甘油（TAG）和碳氢化合物）合成中涉及的关键代谢步骤。这将导致条件的优化，以最大限度地提高产品产量，并确定基因的菌株操作的目标。我们还将研究工程方法，以提高产品回收率，并研究典型的生物炼制案例，以开发可持续的生物能源生产工艺。 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，其中收集了500多个分离株，来自热带印度南部沿海地区丰富的生物多样性热点和来自北极的嗜冷菌株。其中一些分离株已被评估用于生物柴油生产，并将用于该项目。在马杜赖可获得具有碳氢化合物和TAG积累特征的淡水微藻，并事先获得DBT支持。在英国，SAMS在微藻的表征和维护方面拥有丰富的经验，与英国相关工艺的开发相关。我们将联合收割机这一专业知识与藻类系统生物学专业知识在谢菲尔德和剑桥，以研究如何参与积累的存储化合物，生物燃料前体的途径，以及如何建立其与生物体的生长关系（图1）。一种新的专利微泡技术纳入气升式循环生物反应器在谢菲尔德（WBJZ）开发的过程中的改进和产品回收也将进行调查。 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，最大限度地提高产品产量的优化条件，以及用于开发可持续产生燃料前体的生物过程的选定或新型菌株，这些燃料前体对印度和英国的能源经济产生影响。我们还提议在两国举办联合讲习班和互访，以便在工业界积极参与的情况下，在合作伙伴之间转让知识和专长。

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.