The idea that the Earth system self-regulates itself in a habitable state was proposed in the 1970s by James Lovelock, later on formalized as the Daisyworld model using a two-species system interacting with their environment. The potential for testing this conceptual framework in an experimental way is limited by its scale. To fill this gap, here we propose an explicit test tube-scale implementation for a microbial synthetic Daisyworld using an engineered community where pH as the external, abiotic control parameter. The computational modelling of this system shows robust self-regulation within a broad range of conditions, limited by tipping points, This synthetic Daisyworld allows exploring multiple scenarios of self-regulation that include the role of parasites, fluctuations or biodiversity and can help developing an experimental path to Earth Systems Science.