Mixotrophic cultivation of green algal aggregates boost photobiological hydrogen production.

To achieve long-term and efficient photobiological hydrogen production by green algal aggregates remains a challenge. Herein, we demonstrated that mixotrophic cultivation of green algal aggregates can greatly increase the hydrogen production of Chlorella pyrenoidosa by 37 times, and the period of the hydrogen production was up to 21 days with a hydrogen yield of 14.97 mmol L−1. We found that glucose enabled the green algal culture flocculated by cationic etherified starch anaerobic overall, while the algal cells remained highly active. Therefore, long-term effective hydrogen production by green algae was realized. The simplicity and low cost of the method, which requires only cationic etherified starch and glucose, gives it a good potential for scale-up applications and a positive impact on the energy and environment fields. [Display omitted] • A new strategy of mixotrophic cultivation increased the H 2 production by 37 times. • H 2 production was prolonged to 21 days by supplementation with 50 mM glucose. • Large green algal aggregates up to 1000 μm were formed. • Algal aggregates were wholly anaerobic while maintaining high cellular activity. [ABSTRACT FROM AUTHOR]