The Environmental Biotechnology Group at the Geo- and Environmental Center of the University of Tübingen is seeking two excellent PhD candidates to join our international and dynamic team of engineers, microbiologists, and biotechnologists within the GAIA-PRO project. Our group pioneers sustainable biotechnological platforms that link microbial processes to future industrial applications. We explore how microorganisms can transform gases and residues into valuable products. GAIA-PRO (Gas-to-Food for an Innovative and Advanced Circular Bioeconomy) is a joint German-Australian research project aiming to develop a modular platform to convert hydrogen, syngas, and biogas into single-cell protein - a sustainable, circular alternative to conventional feed and food production. The project combines anaerobic and aerobic biotechnologies to capture carbon and produce new forms of protein with near complete carbon capture for a climate-positive future. We offer two PhD positions, each exploring a different part of this challenge: PhD 1: Teach anaerobes to survive a breath of air. You will push oxygen-sensitive microbes to their limits, uncover how they adapt, and engineer bioreactors that turn this challenge into a design advantage. PhD 2: Make microbes build cities. You will develop and study gas-fermenting granular communities that organize themselves - boosting stability, gas transfer, and productivity in newly designed continuous systems. Both PhD candidates will work closely together and with our international partners at the University of Queensland, gaining hands-on experience with modern bioreactor technology, microbial ecology, selection strategies, and sustainable process design. We seek motivated and curious students with a Master’s degree in Environmental Biotechnology, Microbiology, Biochemical Engineering, or a related field, who are excited about microbial systems, gas fermentation, and the circular bioeconomy. You should enjoy both experimental and conceptual work, be eager to learn, and value teamwork. Experience with bioreactors, analytical instruments, and microbial cultivation is a plus. Good communication skills and fluency in English are essential, as it is the working language of our group. You will join a friendly, international, and highly collaborative team, working on a project that combines fundamental science with real-world impact. We offer two PhD positions (TV-L E13, 65%) for 3 years, including health insurance and full university benefits. The preferred start date is February 1st, 2026 (negotiable). The University of Tübingen is committed to equal opportunity and diversity; we particularly encourage applications from underrepresented groups in science.