This paper advances an anticipatory governance framework to investigate and prepare for the potential implications of an emerging technology. Within the growing domain of synthetic biology, we draw on an end-to-end assessment of biosynthetic menthol that incorporates consideration of multiple dimensions of production and use. Based on documentary analysis, available data, and interviews, our approach unfolds in three steps. First, we map the sociotechnical transition in menthol production, comparing existing agricultural and chemical production methods with new biosynthetic processes - or what we call the biological (bio) turn. Second, we explore the rationales, promises and expectations of menthol's bio-turn and explore the drivers of transition so as to clarify which goals and values innovation is addressing. Third, we reflect on the opportunities and challenges of such a transition to put forward an agenda for responsible innovation and anticipatory governance. The bio-turn in menthol is analysed through five responsible innovation dimensions: the potential distribution of benefits and burdens; social resilience; environmental sustainability; infrastructure and business models; and public perception and public interest. We consider the implications of our analysis both for the responsible development and application of synthetic biology for menthol and for the broader assessment and sociotechnical construction of emerging technologies.