New method turns wastewater into valuable chemicals using sunlight

Prof. Gao Xiang and Prof. Lu Lu, leading a team from the Shenzhen Institute of Advanced Technology (SIAT) and the Harbin Institute of Technology, have introduced an innovative approach to transform wastewater contaminants into valuable chemicals using sunlight. Their study, featured in the journal Nature Sustainability. offers a promising avenue for sustainable and eco-friendly chemical manufacturing.

Traditional chemical manufacturing heavily relies on energy-intensive processes, and the emergence of semiconductor biohybrids, which combine efficient light-harvesting materials with living cells, represents a significant breakthrough in harnessing solar energy for chemical production. However, the key challenge has been finding a cost-effective and environmentally friendly method to scale up this technology.

In their research, the scientists set out to directly convert pollutants from wastewater into semiconductor biohybrids within the wastewater environment. This concept involves utilizing the organic carbon, heavy metals, and sulfate compounds present in wastewater as the raw materials for constructing these biohybrids, subsequently transforming them into valuable chemicals.

However, real industrial wastewater typically contains a complex mix of organic pollutants, heavy metals, and challenging-to-metabolize complex pollutants, often toxic to bacterial cells. It also features high levels of salt and dissolved oxygen, requiring bacteria with an aerobic sulfate reduction capacity, making it a challenging source for bacterial feedstock.

To tackle these obstacles, the researchers opted for Vibrio natriegens, a fast-growing marine bacterium known for its tolerance to high salt concentration and ability to utilize various carbon sources. They introduced an aerobic sulfate reduction pathway into V. natriegens and trained the engineered strain to efficiently use different metal and carbon sources to produce semiconductor biohybrids directly from wastewater.

Their primary target chemical was 2,3-butanediol (BDO), a valuable commodity chemical. By modifying V. natriegens, they produced hydrogen sulfide, a crucial component in facilitating the creation of CdS nanoparticles that effectively absorb light. These biocompatible nanoparticles enabled the in-situ development of semiconductor biohybrids, allowing non-photosynthetic bacteria to harness solar energy.

The results demonstrated that these sunlight-activated biohybrids significantly enhanced BDO production, surpassing yields achievable with bacterial cells alone. Moreover, the process showed scalability, achieving solar-driven BDO production on a substantial 5-liter scale using real wastewater.

Prof. Gao highlighted the benefits of this biohybrid platform, emphasizing its reduced carbon footprint, lower product costs, and overall smaller environmental impact compared to traditional bacterial fermentation and fossil fuel-based BDO production methods. Importantly, these biohybrids can be produced using a range of wastewater sources.

Source: Chinese Academy of Sciences

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