Optimising environmental factors for maximal lactate productivity in Synechocystis sp. PCC 6803 through a design of experiments approach

Genetic and metabolic engineering of Synechocystis sp. PCC 6803 has given rise to strains that produce a variety of bio-chemicals. Despite these successes, improvements in productivity metrics are required to achieve economically viable bio-production of carbon dioxide-derived compounds. Previously, environmental factors have been leveraged to increase product yields. Here, we optimise multiple environmental factors simultaneously using Design of Experiments (DOE) principles and find conditions that maximise L-lactate production. Light intensity, glycerol concentration, and light-dark cycle were found to be significant factors. Optimising these conditions resulted in a 6.3- and 7.4-fold increase in titre and yield. The results detailed here could have implications for metabolic engineering of, and bioprocesses using, Synechocystis sp. PCC 6803. In the future, DOE-mediated optimisation of environmental conditions could effectively maximise product titres from different production strains, or the enhanced conditions described here could be directly implemented in other metabolic engineering projects.