Algal-bacterial cooperation improves algal photolysis-mediated hydrogen production.

In this study, bacterium Pseudomonas sp. strain D was proved to be the main partner assisting Chlamydomonas reinhardtii in improving photolysis-mediated H2 production and a good partner for promoting H2 production by the green algae Chlorella and Scenedesmus. In strain D partnered algal-bacterial co-culture, the relative O2 content in the headspace plus the dissolved oxygen in the culture medium were rapidly consumed by bacterial growth, resulting in a completely anaerobic environment that proved suitable for the activation of algal hydrogenase. Moreover, algal-bacterial cooperation was able to slow the reduction of chlorophyll, enhance starch accumulation, and maintain protein content, which are the potential factors whose control provides an opportunity for improving algal H2 production. This study systematically analyzed the main pathway responsible for H2 production by algal-bacterial cooperation and the potential mechanisms for improvement, and proposed an efficient and durable algal-bacterial cooperation system for improving photolysis-mediated H2 production by green algae.