The Environmental Biotechnology Group at the Geo- and Environmental Center of the University of Tübingen is recruiting two PhD candidates to join the GAIA-PRO project, an international collaboration with the University of Queensland. The group specializes in developing sustainable biotechnological platforms that harness microbial processes for future industrial applications, focusing on transforming gases and residues into valuable products. GAIA-PRO aims to create a modular system to convert hydrogen, syngas, and biogas into single-cell protein, offering a circular and climate-positive alternative to conventional feed and food production. The project integrates anaerobic and aerobic biotechnologies to maximize carbon capture and generate new protein sources. The two PhD positions each address distinct research challenges: one will investigate how oxygen-sensitive anaerobic microbes adapt to air exposure and engineer bioreactors to leverage this adaptation; the other will develop and study self-organizing, gas-fermenting granular microbial communities to enhance stability, gas transfer, and productivity in continuous systems. Both candidates will collaborate closely and work with international partners, gaining hands-on experience in modern bioreactor technology, microbial ecology, selection strategies, and sustainable process design. Applicants should have a Master’s degree in Environmental Biotechnology, Microbiology, Biochemical Engineering, or a related field, and be enthusiastic about microbial systems, gas fermentation, and the circular bioeconomy. The group values both experimental and conceptual skills, teamwork, and a willingness to learn. Experience with bioreactors, analytical instruments, and microbial cultivation is beneficial. Fluency in English is required, as it is the working language of the group. Successful candidates will join a collaborative, international team and work on a project with significant scientific and societal impact. The positions are funded for three years (TV-L E13, 65%), including health insurance and full university benefits. The preferred start date is February 1st, 2026, but is negotiable. The University of Tübingen encourages applications from underrepresented groups in science and is committed to equal opportunity and diversity. To apply, candidates should submit a single PDF containing a cover letter, CV, transcripts, diplomas, an overview of skills and techniques, and contact details for two references to the provided email address. Applications will be reviewed until the positions are filled. For more information, refer to the official job advertisement.