Grechanik Vera I, Bol'shakov Maksim A, Tsygankov Anatoly A
Institute of Basic Biological Problems Russian Academy of Sciences - Separate Division of Federal Research Center "Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
Biochemistry (Mosc). 2025 Jul;90(7):921-933. doi: 10.1134/S0006297925600929.
Some microalgae are capable of light-dependent hydrogen production after a period of anaerobic adaptation, thus performing biophotolysis of water. The rate of hydrogen production the start of illumination has the rate equal to the maximum rate of photosynthesis. However, this process is short-lived: oxygen produced during photosynthesis quickly inactivates the key enzyme of biophotolysis, hydrogenase, and inhibits its expression. To date, approaches have been developed to achieve sustained hydrogen production by microalgae. The most studied are those based on transferring microalgae to nutrient-deficient conditions. However, it is known that hydrogen production under nutrient deficiency is always accompanied by the decrease in activity of photosystem II (PSII). Several mechanisms for suppression of PSII activity have been described in the literature, and there is no consensus on which mechanism is the determining one. The aim of this work was to test the hypothesis that realization of a particular mechanism of PSII suppression depends not only on the type of stress but also on the growth conditions. For this purpose, the photoautotrophic culture of the microalga was grown under nitrogen or sulfur deficiency under different light regimes, and realization of the following mechanisms of PSII activity suppression was analyzed: over-reduction of the plastoquinone pool (coupled with over-reduction of the entire photosynthetic electron transport chain), decoupling of PSII (based on the kinetics of ascorbate accumulation and the JIP test) with water-oxidizing complex, violaxanthin cycle, anaerobic stress associated with the creation of a reducing redox potential of the culture suspension. It was found that the key mechanism determining hydrogen production is the over-reduction of the plastoquinone pool. Other mechanisms are also realized under various conditions but do not show clear correlation with hydrogen production. The obtained results indicate that induction of stress through starvation of cultures is a convenient approach for studying hydrogen production by microalgae, but due to the low activity of PSII, it is impractical. New approaches are required to create industrial systems based on microalgae, allowing full realization of their photosynthetic potential.
一些微藻在经过一段时间的厌氧适应后能够进行光依赖型产氢，从而实现水的生物光解。光照开始时的产氢速率与光合作用的最大速率相等。然而，这个过程是短暂的：光合作用过程中产生的氧气会迅速使生物光解的关键酶——氢化酶失活，并抑制其表达。迄今为止，已经开发出了实现微藻持续产氢的方法。研究最多的是基于将微藻转移到营养缺乏条件下的方法。然而，众所周知，营养缺乏条件下的产氢总是伴随着光系统II（PSII）活性的降低。文献中描述了几种抑制PSII活性的机制，但对于哪种机制起决定性作用尚无共识。这项工作的目的是检验这样一个假设，即PSII抑制的特定机制的实现不仅取决于胁迫类型，还取决于生长条件。为此，在不同光照条件下，使微藻的光合自养培养物在氮或硫缺乏的条件下生长，并分析了以下PSII活性抑制机制的实现情况：质体醌库的过度还原（与整个光合电子传递链的过度还原相关）、PSII与水氧化复合物的解偶联（基于抗坏血酸积累动力学和JIP测试）、紫黄质循环、与培养悬浮液还原氧化还原电位的产生相关的厌氧胁迫。结果发现，决定产氢的关键机制是质体醌库的过度还原。其他机制在各种条件下也会实现，但与产氢没有明显的相关性。所得结果表明，通过培养物饥饿诱导胁迫是研究微藻产氢的一种便捷方法，但由于PSII活性较低，不切实际。需要新的方法来创建基于微藻的工业系统，以充分发挥其光合潜力。
