Integrating membrane processes into hydroponics systems to promote plant growth, recover added-value root exudates and recycle nutrients

水培法是一种受控制的无土农业系统，它使作物能够在不适合作物生产的土地上逆季生长。2015年，水培农业估计价值214亿美元，预计年增长率为7%。水培农场比传统农业有几个优势，包括单位面积的植物产量增加3到10倍，在管理良好的农场中，水的利用效率提高90%。许多园艺作物通常在商业垂直水培农场种植，因为这些系统提供高质量和产量。然而，水培植物向营养液中散发出大量的植物化学物质。在封闭的水培系统中，营养液的持续循环导致这些植物化学物质积累，导致自毒性。更换营养液是典型的做法，但成本高、劳动密集、效率低，并导致系统停机。相比之下，从植物废料中提取的植物化学物质正越来越多地找到一系列技术应用，在循环经济中提供额外的收入。植物从根部分泌出许多代谢物，如具有促进人体健康的抗氧化特性的多酚，以及在调节植物生长和发育以及植物与微生物相互作用中起作用的分子。因此，根分泌物是用作植物生物刺激素或植物保护产品的新活性的潜在来源。本项目旨在利用豌豆苗的水培栽培作为模型系统来解决自毒性问题并允许养分循环，同时利用有效的膜分离从根渗出物中回收有机分子并评估其特性。为了实现这一目标，将遵循两种平行的方法，以尽量减少植物毒性渗出物的负面影响。首先，我们将寻求优化生长环境（再循环流量，温度等），以了解水培培养条件如何影响植物毒素的产生。其次，我们将尝试在水培系统中建立一个半中试规模的膜过滤过程，以连续去除渗出物。由于根渗出物可能含有有价值的化合物（例如，在人类/动物营养中）或可以筛选新的活性（例如，作为植物生物刺激素或抗菌剂），这种综合过滤为开发分离的植物化学物质提供了额外的机会。该提案是多学科的，涉及各种互补背景的小组。特别是，该项目涉及化学/生物过程工程（营养成分和/或流速，以促进渗出液的生产和回收），膜科学（使用适当的膜），分析化学（使用适当的方法来表征渗出液的成分），和植物生理学（评估植物生长和体外和体内生物测定，以确定渗出液的新应用）。如果成功，这个创新项目将彻底改变水培栽培系统。我们的研究结果将为未来无土植物生长和化学生产农场使用合并系统的技术可行性提供证据。当进一步发展时，我们的想法将有助于建立下一代生物炼制原理，能够从植物根系中分离出有价值的化学物质，同时生产更多的作物生物量。总之，我们提出了一种高度创新，但相对简单，无化学物质和可扩展的工艺来刺激水培渗出液中化合物的生产和回收。这将最大限度地提高植物生长，并解决这种系统中存在的自毒性商业问题，同时为水培农业引入新的收入途径。

Hydroponics are controlled soilless agricultural systems that enable crops to be grown out of season on land otherwise poorly suited for crop production. In 2015, hydroponic farming was estimated to be worth $21.4 billion, with an expected annual growth of 7%. Hydroponic farms have several advantages over traditional farming, including 3 to 10 times more plant production per unit space, and up to 90% more efficient use of water in well-managed farms. Many horticultural crops are routinely grown in commercial vertical hydroponic farms because of the high quality and yields these systems provide. However, plants in hydroponic culture exude high amounts of phytochemicals into the nutrient solution. Continuous recycling of nutrient solutions in closed hydroponic systems causes these phytochemicals to accumulate, leading to autotoxicity. Replacing the nutrient solution is typical, but is costly, labour-intensive, inefficient and causes system downtime.In contrast, phytochemicals extracted from plant wastes are increasingly finding a range of technological applications, offering additional revenue within a circular economy. Plants exude many metabolites from their roots, such as polyphenols, which have antioxidant properties that promote human health, along with molecules that have roles in regulating plant growth and development, and in plant-microbe interactions. Root exudates are therefore a potential source of novel activities for use as plant biostimulants or plant protection products.This project seeks to use hydroponic cultivation of pea shoots as a model system to solve autotoxicity problems and allow nutrient recycling, whilst simultaneously exploiting efficient membrane separation to recover organic molecules from root exudates and evaluate their properties. To achieve this, two parallel approaches will be followed to minimise the negative effects of phytotoxic exudates. First, we will seek to optimise the growth environment (recirculation flow, temperature, etc.) to understand how hydroponic culture conditions influence the production of phytotoxins. Secondly, we will try to establish a semi-pilot scale membrane filtration process within a hydroponic system to continuously remove exudates. Since root exudates may contain valuable compounds (e.g. in human/animal nutrition) or can be screened for novel activities (e.g. as plant biostimulants or antimicrobial agents), such integrated filtration provides additional opportunities to exploit the fractionated phytochemicals. The proposal is multidisciplinary and involves groups of various complementary backgrounds. In particular, the project involves chemical/bio-process engineering (nutrient composition and/or flow rates to facilitate the production and recovery of exudates), membrane science (use of appropriate membranes), analytical chemistry (use appropriate methodologies to characterise the composition of the exudates), and plant physiology (assessing plant growth and in-vitro and in-vivo bioassays to identify novel applications of exudates). If successful, this innovative project could revolutionise hydroponic culture systems. Our results will provide evidence for the technological feasibility of using merged systems for future soilless plant growth and chemical-producing farms. When developed further, our ideas will contribute towards establishing next generation biorefinery principles, able to isolate valuable chemicals from the plant root system while producing more crop biomass. In summary, we propose a highly innovative, but relatively simple, chemical-free and scalable process to stimulate the production and recovery of compounds from hydroponic exudates. This will maximize plant growth and resolve an existing commercial problem of autotoxicity in such systems, whilst simultaneously introducing the potential for new revenue routes for hydroponic farming.