Perin Giorgio, Gambaro Francesca, Morosinotto Tomas
Department of Biology, University of Padova, Padua, Italy.
Front Plant Sci. 2022 Apr 4;13:846496. doi: 10.3389/fpls.2022.846496. eCollection 2022.
Microalgae represent a sustainable source of biomass that can be exploited for pharmaceutical, nutraceutical, cosmetic applications, as well as for food, feed, chemicals, and energy. To make microalgae applications economically competitive and maximize their positive environmental impact, it is however necessary to optimize productivity when cultivated at a large scale. Independently from the final product, this objective requires the optimization of biomass productivity and thus of microalgae ability to exploit light for CO fixation. Light is a highly variable environmental parameter, continuously changing depending on seasons, time of the day, and weather conditions. In microalgae large scale cultures, cell self-shading causes inhomogeneity in light distribution and, because of mixing, cells move between different parts of the culture, experiencing abrupt changes in light exposure. Microalgae evolved multiple regulatory mechanisms to deal with dynamic light conditions that, however, are not adapted to respond to the complex mixture of natural and artificial fluctuations found in large-scale cultures, which can thus drive to oversaturation of the photosynthetic machinery, leading to consequent oxidative stress. In this work, the present knowledge on the regulation of photosynthesis and its implications for the maximization of microalgae biomass productivity are discussed. Fast mechanisms of regulations, such as Non-Photochemical-Quenching and cyclic electron flow, are seminal to respond to sudden fluctuations of light intensity. However, they are less effective especially in the 1-100 s time range, where light fluctuations were shown to have the strongest negative impact on biomass productivity. On the longer term, microalgae modulate the composition and activity of the photosynthetic apparatus to environmental conditions, an acclimation response activated also in cultures outdoors. While regulation of photosynthesis has been investigated mainly in controlled lab-scale conditions so far, these mechanisms are highly impactful also in cultures outdoors, suggesting that the integration of detailed knowledge from microalgae large-scale cultivation is essential to drive more effective efforts to optimize biomass productivity.
微藻是一种可持续的生物质来源，可用于制药、营养保健品、化妆品应用，以及食品、饲料、化学品和能源领域。然而，为了使微藻应用在经济上具有竞争力，并最大限度地发挥其对环境的积极影响，有必要在大规模培养时优化其生产力。无论最终产品如何，这一目标都需要优化生物质生产力，从而优化微藻利用光进行二氧化碳固定的能力。光是一个高度可变的环境参数，会随着季节、一天中的时间和天气条件不断变化。在微藻大规模培养中，细胞自身遮光会导致光分布不均匀，并且由于混合作用，细胞会在培养物的不同部位之间移动，从而经历光照的突然变化。微藻进化出了多种调节机制来应对动态光照条件，然而，这些机制并不适应大规模培养中自然和人为波动的复杂组合，这可能会导致光合机构过度饱和，进而引发氧化应激。在这项工作中，我们讨论了目前关于光合作用调节及其对最大化微藻生物质生产力影响的知识。快速调节机制，如非光化学猝灭和循环电子流，对于应对光强的突然波动至关重要。然而，它们的效果较差，尤其是在1 - 100秒的时间范围内，研究表明在此期间光波动对生物质生产力的负面影响最大。从长期来看，微藻会根据环境条件调节光合装置的组成和活性，这种适应反应在室外培养中也会被激活。虽然到目前为止，光合作用的调节主要是在受控的实验室规模条件下进行研究的，但这些机制在室外培养中也具有很大影响，这表明整合来自微藻大规模培养的详细知识对于推动更有效的生物质生产力优化努力至关重要。
