Screening of microalgae strains for efficient biotransformation of small molecular organic acids from dark fermentation biohydrogen production wastewater

Dark fermentation biohydrogen production is a rapidly advancing and well-established field. However, the accumulation of volatile organic acid (VFAs) byproducts hinder its practical applications. Microalgae have demonstrated the ability to efficiently utilize VFAs while also treating waste gases and other nutrient elements. Integrating microalgae cultivation with dark fermentation is a promising approach. However, low VFAs tolerance and slow VFAs consumption restrict their application. To find suitable wastewater treatment microalgae, this work screened eight microalgae strains from five family. The results demonstrated that Chlamydomonas reinhardtii exhibited significant advantages in VFAs utilization, achieving a maximum removal of 100% for acetate and 52.5% for butyrate. Among the tested microalgae strains, CW15 outperformed in terms of photobioreactor adaptability, VFAs utilization, biomass productivity, and nutrient removal, making it the most promising microalgae for practical applications. This research demonstrates the feasibility of integrating microalgae cultivation with dark fermentation and providing a viable technical solution for integrated-biorefining.