Optimizing yields of bioproducts in mixotrophic cultures of micro algae

浮游植物是单细胞的海洋和淡水植物，可以作为有价值的天然产品的来源进行培养。这些包括脂质（必需营养素，如ω-6脂肪酸，但也有甘油三酯，生物柴油的前体），可用于原料的蛋白质，抗氧化剂（类胡萝卜素和类黄酮）和潜在的药物。大量培养浮游植物也被用作处理营养物含量高的废水沃茨的一种手段，以补救流域和沿海沃茨的富营养化。沿海富营养化是造成缺氧和全球有害藻华发生率增加的原因。两者都是环境和经济代价高昂的。*许多产生高价值化合物的浮游植物可以以混合营养方式生长，这是一种混合营养模式，其中细胞既是自养（光合作用）又是异养（利用不稳定的有机化合物）。混合营养可以大大提高生长速率和细胞产量，但了解甚少。因此，筛选最佳条件是通过试验和错误进行的。该项目将开发一个概念框架，用于预测混合营养生长和细胞组成作为光强度，温度和营养物质可用性的函数，通过扩展广泛使用的模型，动态平衡模型。这将定义用于扩展模型的物种的最佳生长，最大化三种高价值化合物的产量。它还将提供一种手段，集中优化条件的菌株生产其他有价值的化合物在未来。混合营养培养的细菌污染或多或少是不可避免的，细菌可以胜过浮游植物竞争有机基质，并可能导致大量死亡。因此，在不抑制浮游植物生长的情况下抑制细菌生长对于经济上可行的培养是必要的。该项目将测试使用一种经过验证的技术-紫外线-C辐射，作为一种差别压力源，可以抑制细菌生长而不影响浮游植物。最后，许多有价值的产品在压力条件下被上调。当培养物达到收获的最佳条件时，评估是否成功培养。生物光学技术是理想的，因为它们对细胞组成和功能的变化敏感，是非破坏性的，并且可以真实的时间使用。该项目将开发和地面实况生物光学签名，以评估生产高价值化合物的细胞收获的准备情况。提高产量和更有效地筛选菌株将促进下一代浮游植物的培养，作为目标天然产品的细胞工厂和受污染废水的补救手段。这将转化为一种新的水产养殖形式，并使加拿大和全世界的沿海和内陆沃茨更加清洁。

Phytoplankton are single-celled marine and freshwater plants that can be cultivated as sources of valuable natural products. These include lipids (essential nutrients like omega-6 fatty acids but also triacylgylerides, the precursors of biodiesel), proteins that can be used in feedstocks, antioxidants (carotenoids and flavonoids), and potential pharmaceuticals. Mass culture of phytoplankton has also been tested as a means of treating wastewaters that are high in nutrients to remediate eutrophication in watersheds and coastal waters. Coastal eutrophication is responsible for hypoxia and an increased incidence of harmful algal blooms worldwide. Both are environmentally and economically costly.***Many phytoplankton that produce high-value compounds can be grown mixotrophically, a mixed nutritional mode in which the cells are both autotrophic (photosynthetic) and heterotrophic (utilizing labile organic compounds). Mixotrophy can greatly increase growth rates are cell yields but is poorly understood. Consequently, screening for optimal conditions proceeds by trial and error.*** This project will develop a conceptual framework for predicting mixotrophic growth and cell composition as a function of light intensity, temperature, and nutrient availability by extending a widely-used model, the Dynamic Balance model. This would define growth optima for the species used to extend the model, maximizing yield of three high-value compounds. It would also provide a means to focus optimization of conditions for strains producing other valuable compounds in the future.*** Bacterial contamination of mixotrophic culture is more-or-less inevitable and the bacteria can out-compete the phytoplankton for the organic substrates and can cause mass mortality. Suppression of bacterial growth without inhibiting growth of the phytoplankton is therefore essential for economically-feasible cultivation. This project will test use of a proven technology, ultraviolet-C radiation, as a differential stressor that could inhibit bacterial growth without affecting the phytoplankton.*** Last, many valuable products are up-regulated under conditions of stress. Successful cultivation assessing when the culture has reached the optimum condition for harvesting. Bio-optical techniques are ideal for this as they are sensitive to changes in cell composition and function, are non-destructive, and can be used in real time. This project will develop and ground-truth bio-optical signatures that would assess readiness for harvest of cells producing high-value compounds.*** The enhanced production and more efficient screening of strains will facilitate next-generation cultivation of phytoplankton as cell factories for targeted natural products and as means of remediating contaminated wastewaters. This would translate to a novel form of aquaculture and to clearer coastal and inland waters in Canada and worldwide.