Capture and mitigation of small point source CO2 emissions using regional bioprospected microalgae

大规模生产光合作用的绿色微藻是20年前提出的，通过其脂质的酯交换反应作为第三代生物燃料（生物柴油）的一个令人兴奋的前景。然而，大规模生产生物柴油尚未真正实现经济效益，部分原因是需要提供足够的二氧化碳来提高生产率。为了解决这个问题，微藻提供了减少工业废气中温室气体二氧化碳的机会，将其作为主要的碳源——然而，许多工业废气中酸性成分的存在会降低微藻生长介质的pH值，从而抑制微藻的生产力。加拿大有31,000多个淡水湖，是世界上最大的未开发的光合微藻资源来源。此外，自19世纪以来，进行了广泛的矿山勘探，特别是在北部地区，由于历史上缺乏矿山关闭计划，许多矿山留下了重要的遗产，例如酸性矿山排水（AMD）影响了水体。这些目前不提供使用后的价值，实际上经常被视为一种负担。加拿大有超过7500个废弃矿场，估计环境责任达100亿美元。由于AMD而进化的压力水生环境导致高金属浓度和低pH值。这些条件可能导致生态系统破坏和微藻选择性，但也会导致微藻表达所需的特性（由于暴露于废气而对低pH值产生抗性）和更高水平的有价值的保护性次级代谢物。这些代谢物包括适合酯交换成用于生物柴油的脂肪酸甲酯（FAMEs）的脂类（脂肪酸），以及其他理想的化合物，如多不饱和脂肪酸（如欧米茄3）、类胡萝卜素和聚酮。我们还发现微藻提取物具有非常显著的抗菌活性和抗癌活性。因此，对低pH值的抵抗力以及脂质和其他增值代谢物的共同生产可能显著有助于微藻大规模生产的经济性。这项研究的最终目标是通过研究如何绘制一条路线来建设性地利用非生产性场地、受影响的水体和温室气体排放，从而帮助设计出社会效益。为此，它将首次对加拿大北部压力环境中的本地微藻物种进行生物勘探和表征，并分离出那些表现出高度有价值的特征和特征的物种。此外，它将研究如何减轻区域废气源中的二氧化碳，以提高选定的生物前景微藻的生产，并随后最大化所需代谢物的表达。从长远来看，这种综合方法将从其他非生产性资源中提供新的经济机会，特别是对于加拿大北部的小型和偏远社区。

Mass-production of photosynthetic green microalgae was put forward two decades ago as an exciting prospect for third-generation biofuels (biodiesel) through transesterification of their lipids. However, mass production of biodiesel has yet to be truly economic, in part due to supplying sufficient CO2 to boost productivity. To address this, microalgae offer the opportunity to mitigate the greenhouse gas CO2 in industrial off-gasses by using it as their primary carbon source - however, the presence of acid component to many industrial off-gasses can inhibit microalgal productivity by reducing the pH of medium they grow in. There over 31,000 freshwater lakes in Canada representing the World's largest untapped source of photosynthetic microalgae resources. Further, since the 19th century there has been extensive mine exploration, particularly across the north, and a historic lack of mine closure plans has meant that many left significant legacies, such as acid mine drainage (AMD) impacted water bodies. These currently offer no after-use value and indeed are often regarded a liability. There are more than 7500 abandoned mine sites across Canada representing an estiamated $10 billion in environmental liability. Stressed aquatic environments that have evolved due to AMD result in high metal concentrations and low pH. These conditions can lead to ecosystem disruption and microalgae selectivity, but also to expression of a desired microalgal characteristic (resistance to low pH resulting from exposure from off-gas) and greater levels of valuable protective secondary metabolites. These metabolites include lipids (fatty acids) suitable for transesterification into fatty acid methyl esters (FAMEs) for biodiesel, but also other desirable compounds such as polyunsaturated fatty acids (such as omega 3s), carotenoids and polyketides. We have also found microalgal extracts that exhibit very notable antibacterial activity and anticancer activities. Resistance to low pH and co-production of lipids and other value-adding metabolites could, therefore, significantly aid the economics of mass production of microalgae. The ultimate goal of this research is to help devise societal benefits by working out how to map a route to constructively utilize both non-productive sites, impacted water bodies, and greenhouse gas emissions. To do this, it will for the first-time bioprospect and characterize indigenous microalgal species from stressed environments in northern Canada, and isolate those that exhibit highly valuable traits and characteristics. Further, it will study how the CO2 in regional off-gas sources can be mitigated to enhance production of selected bioprospected microalgae, and subsequently maximize expression of desirable metabolites. For the long-term, this combined approach will offer the possibility of new economic opportunities from otherwise non-productive resources, especially for small and remote communities across northern Canada.