Emerging from the field of synthetic biology, biosynthetic substitutes of natural products have been framed as offering a more sustainable means of production. ‘Lab-grown’ meat has received most attention, yet it is botanical and plant-based compounds which represent the majority of current R&D. As innovation moves from scientific hype to commercial reality, my paper explores the emerging biosynthesis industry building on 3 years of multi-sited-ethnographic fieldwork tracing both the global governance of synthetic biology at the UN Convention on Biological Diversity (CBD) and through the lens of one biosynthetic product: the sweet herb known as stevia. I adopt assemblage theory to map the (trans)forming relations between sites in Paraguay, Brazil, USA, Europe as well as the locations of CBD conferences connecting indigenous peoples, farmers, scientists, activists, entrepreneurs, policy-makers and corporates. Conceptually, assemblage frameworks account for the contingent and non-linear processes of innovation, the coalescing of actors, actants, artefacts, and ideas as an incoherent whole. Theoretically, assemblage thinking helps determine the durability of biosynthesis and its interaction and effects on other socio-technical assemblages. My paper presents early evidence that the ‘biosynthesis assemblage’ around stevia is indeed stabilising. The durability of this assemblage has significant implications for technological pathway ‘lock in’ as small farmers are disincentivised to continue cultivating crop-stevia. Despite being framed by Oxfam amongst others as a cash crop well-suited for ‘sustainable livelihoods’ of small farmers, stevia is representative of many other high-value crops grown in the Global South that are the target of biosynthesis innovations in the Global North. Aside from at the UN CBD, biosynthesis has received little governance or academic scrutiny neither for the sustainability claims of its proponents, nor in terms of the continuation of a technological trajectory rooted in the transfer of valuable (genetic) materials from Global South to North.