Assessment of Integrated Microalgal-Bacterial Ecosystems for Bioenergy Production - Optimization-based Methodology

许多微生物生态系统作为其正常活动的一部分，具有为社会提供服务和改善环境质量的潜力。有些可以降解有机物或追踪污染水、空气或土壤的污染物。另一些可以将废物转化为有价值的可再生资源，包括生物能源、生物材料和高价值产品。这种通用能力为在综合生物过程中结合几个微生物生态系统提供了可能性，在综合生物过程中，可以同时生产各种类型的生物能源或生物材料，并处理多种污染源。该项目的重点是将微藻光生物反应器与厌氧消化器相结合的综合生物过程。虽然微藻目前被认为是最有前途的生物燃料原料之一，因为它们富含碳的脂质具有很高的生产率，但上述与厌氧消化的结合提供了一种有效的方法来回收存在于废藻生物质中的营养物质-在脂质提取之后。总的来说，综合微藻-细菌生态系统将能够以生物燃料和沼气的形式生产生物能源，同时处理烟道气和废水。然而，与传统的生物精炼厂不同的是，在传统的生物精炼厂中，通过加工可利用的生物质原料获得生物基产品和能源的光谱，在集成的微藻/细菌系统中培养原料成为该过程的一个组成部分。因此，光生物反应器不能再与藻类下游处理分开设计和运行。还必须特别注意微生物对环境和操作变化的适应以及各种微生物之间的强相互作用。这种复杂性使得仅仅基于工程直觉来设计和操作这些过程极具挑战性。本项目的主要目的是通过应用基于数学模型的过程分析、设计和操作的系统方法来研究集成的微藻-细菌过程。我们的目标是双重的：(i)对可持续生物能源生产和二氧化碳捕获的综合微藻-细菌系统进行评估；（二）确定可靠的设计和运行策略。一个重要的挑战是过程可变性和建模不确定性的存在，这对当前不确定性下的优化技术提出了挑战。因此，本提案的另一个主要目标是开发分析和优化集成微藻-细菌系统所需的关键方法和工具。虽然英国和世界各地正在开展许多实验研究和示范项目，以确定最合适的藻类菌株，并将藻类生物燃料生产扩展到主要的工业过程，但该项目将是第一个应用系统的、基于模型的优化方法的项目，该方法充分考虑了操作问题以及它们与设计决策的相互作用。预计操作方面的考虑将为关键设计决策带来第一要素的响应，例如需要在单独的生物反应器中操作藻类生长和脂质生产，以及是否在厌氧消化步骤之前提取脂质。识别操作瓶颈的能力也将为菌株改进提供有价值的见解和指导，例如通过基因工程。最后，有人认为，只有与大宗化学品、食品和饲料原料的生产相结合，才能实现用于生物燃料的微藻经济可持续生产。虽然从微藻中联合生产多种化合物仍然是一个挑战，但通过该项目开发的方法将为实现这种生物精制的最佳方式带来关键见解。

Many microbial ecosystems, as part of their normal activity, have the potential to provide services to society and improve environmental quality. Some can degrade organic or trace contaminants that pollute water, air or soil. Others can transform waste materials into valuable renewable resources, including bioenergy, biomaterials and high-value products. This generic capability opens the possibility for combining several microbial ecosystems in integrated bioprocesses, where various types of bioenergy or biomaterials are produced and multiple sources of pollution are treated, all at the same time.The focus in this project is on integrated bioprocesses that couple a microalgae photobioreactor with an anaerobic digester. While microalgae are currently considered one of the most promising feedstocks for biofuels due to their high productivity of carbon-rich lipids, the said combination with anaerobic digestion provides an efficient means of recycling the nutrients present in the waste algal biomass--after lipid extraction. On the whole, integrated microalgal-bacterial ecosystems will be capable of producing bioenergy in the form of biofuel and biogas, while treating both flue gas and wastewater. However, unlike in traditional biorefineries where a spectrum of bio-based products and energy are obtained by processing an available biomass feedstock, growing the feedstock becomes an integral part of the process in an integrated microalgal/bacterial system. Therefore, a photobioreactor can no longer be designed and operated separately from the algal downstream processing. Special attention must also be paid to the microbial adaptation to environmental and operational changes as well as the strong interactions between the various kinds of microorganisms. This intricacy makes it extremely challenging to design and operate these processes solely based on engineering intuition.It is a principal aim of this project to investigate integrated microalgal-bacterial processes by applying systematic methods of process analysis, design and operation, that are based on mathematical models. Our objective is twofold: (i) make an assessment of integrated microalgal-bacterial systems for sustainable bioenergy production and CO2 capture; and (ii) determine reliable design and operation strategies. An important challenge is the presence of process variability and modeling uncertainty, which challenges the current state-of-the-art of optimization under uncertainty. It is therefore another principal aim of this proposal to develop the crucial methods and tools needed for the analysis and optimization of integrated microalgal-bacterial systems.While many experimental research and demonstration programs are being carried out in the UK and worldwide to identify the most suitable algae strains and expand algal biofuel production to a major industrial process, this project will be the first of its kind to apply a systematic, model-based optimization methodology, that takes full account of operational issues as well as their interplay with design decisions. It is expected that operational considerations will bring a first element of response regarding critical design decisions, such as the need to operate algae growth and lipid production in separate bioreactors, and whether or not to extract the lipids before the anaerobic digestion step. The ability to identify operational bottlenecks will also provide valuable insight and guidance for strain improvement, e.g. via genetic engineering. Finally, it has been argued that economically sustainable production of microalgae for biofuels may only be achieved if combined with production of bulk chemicals, food, and feed ingredients. While the coproduction of multiple compounds from microalgae remains a challenge, the methodology developed through this project will bring on key insight on the best way to achieve such biorefining.