School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300, Nibong Tebal, Penang, Malaysia.
International Center for Biotechnology, Osaka University, 2-1 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Environ Res. 2023 Jul 1;228:115872. doi: 10.1016/j.envres.2023.115872. Epub 2023 Apr 11.
Mass microalgal-bacterial co-cultures have come to the fore of applied physiological research, in particularly for the optimization of high-value metabolite from microalgae. These co-cultures rely on the existence of a phycosphere which harbors unique cross-kingdom associations that are a prerequisite for the cooperative interactions. However, detailed mechanisms underpinning the beneficial bacterial effects onto microalgal growth and metabolic production are rather limited at the moment. Hence, the main purpose of this review is to shed light on how bacteria fuels microalgal metabolism or vice versa during mutualistic interactions, building upon the phycosphere which is a hotspot for chemical exchange. Nutrients exchange and signal transduction between two not only increase the algal productivity, but also facilitate in the degradation of bio-products and elevate the host defense ability. Main chemical mediators such as photosynthetic oxygen, N-acyl-homoserine lactone, siderophore and vitamin B12 were identified to elucidate beneficial cascading effects from the bacteria towards microalgal metabolites. In terms of applications, the enhancement of soluble microalgal metabolites is often associated with bacteria-mediated cell autolysis while bacterial bio-flocculants can aid in microalgal biomass harvesting. In addition, this review goes in depth into the discussion on enzyme-based communication via metabolic engineering such as gene modification, cellular metabolic pathway fine-tuning, over expression of target enzymes, and diversion of flux toward key metabolites. Furthermore, possible challenges and recommendations aimed at stimulating microalgal metabolite production are outlined. As more evidence emerges regarding the multifaceted role of beneficial bacteria, it will be crucial to incorporate these findings into the development of algal biotechnology.
大规模微藻-细菌共培养已成为应用生理学研究的热点，特别是在优化微藻的高价值代谢物方面。这些共培养依赖于存在一个藻球，其中蕴藏着独特的跨领域的相互关系，这是合作相互作用的前提。然而，目前对于有益细菌对微藻生长和代谢产物产生的有利影响的详细机制还相当有限。因此，本篇综述的主要目的是阐明在互利相互作用中，细菌如何为微藻代谢提供动力，或者反之亦然，这是基于藻球这个化学交换的热点。两者之间的营养物质交换和信号转导不仅增加了藻类的生产力，而且有助于生物产物的降解，并提高宿主的防御能力。主要的化学介质，如光合作用产生的氧气、N-酰基高丝氨酸内酯、铁载体和维生素 B12，被确定为从细菌到微藻代谢物的有益级联效应的阐明。就应用而言，可溶性微藻代谢物的增强通常与细菌介导的细胞自溶有关，而细菌生物絮凝剂可以帮助微藻生物质收获。此外，本文还深入探讨了通过代谢工程（如基因修饰、细胞代谢途径微调、目标酶的过表达和关键代谢物通量的转移）进行基于酶的交流的讨论。此外，还概述了针对刺激微藻代谢产物生产的可能挑战和建议。随着更多关于有益细菌多方面作用的证据的出现，将这些发现纳入藻类生物技术的发展将至关重要。
