Wastewater treatment through the activated sludge method demands a substantial amount of electricity for aeration. This high energy requirement has led to growing interest in innovative co-culture systems that combine microalgae with heterotrophic microorganisms—an approach that eliminates the need for aeration and significantly saves energy.
Researchers from Osaka Metropolitan University have found that these uncomplicated organisms create the optimal combination for enhancing the efficiency of wastewater treatment. The activated sludge method of treating wastewater relies on electricity to maintain oxygen flow that sustains bacteria and other organisms involved in processing the water.
Incorporating microalgae to perform photosynthesis, which generates oxygen, enhances energy efficiency; however, their growth is limited by low carbon dioxide levels. This is where the yeast Saccharomyces cerevisiae comes into play, as it produces carbon dioxide.
Associate Professor Ryosuke Yamada from the Graduate School of Engineering directed the team in exploring which blend of these microorganisms would yield the greatest efficiency in treating wastewater. For the first time, to the best of the researcher’s knowledge, the team discovered that the pairing of the green algae Chlamydomonas reinhardtii with yeast resulted in the highest efficiency.
One of the main reasons for the improved wastewater treatment performance of the combination of green algae and yeast was the increased expression of genes associated with the absorption of phosphate and ammonium ions in the green algae. As both the green algae Chlamydomonas reinhardtii and the yeast Saccharomyces cerevisiae are highly safe microorganisms, the establishment of their effective combination for wastewater treatment is highly significant.
“The green algae and yeast are highly safe for humans, especially considering that treated wastewater is discharged into the environment,” Professor Yamada explained. “These microorganisms can also accumulate useful compounds such as polysaccharides, fats, and oils in their cells and be used as microbial fertilizers, so it is possible to expect useful compounds to be produced at the same time as the wastewater is being treated.”
Journal reference:
- Miiku Takahashi, Yukino Karitani, Ryosuke Yamada, Takuya Matsumoto & Hiroyasu Ogino. Co-utilization of microalgae and heterotrophic microorganisms improves wastewater treatment efficiency. Applied Microbiology and Biotechnology, 2024; DOI: 10.1007/s00253-024-13309-w
