Photoautotrophic production of polyhydroxyalkanoates in a synthetic mixed culture of and .

BACKGROUND

One of the major challenges for the present and future generations is to find suitable substitutes for the fossil resources we rely on today. Cyanobacterial carbohydrates have been discussed as an emerging renewable feedstock in industrial biotechnology for the production of fuels and chemicals, showing promising production rates when compared to crop-based feedstock. However, intrinsic capacities of cyanobacteria to produce biotechnological compounds are limited and yields are low.

RESULTS

Here, we present an approach to circumvent these problems by employing a synthetic bacterial co-culture for the carbon-neutral production of polyhydroxyalkanoates (PHAs) from CO. The co-culture consists of two -: -, in which the cyanobacterial strain fixes CO, converts it to sucrose, and exports it into the culture supernatant; and -, where this sugar serves as C-source for and is converted to PHAs that are accumulated in the cytoplasm. By applying a nitrogen-limited process, we achieved a maximal PHA production rate of 23.8 mg/(L day) and a maximal titer of 156 mg/L. We will discuss the present shortcomings of the process and show the potential for future improvement.

CONCLUSIONS

These results demonstrate the feasibility of mixed cultures of and for PHA production, making room for the cornucopia of possible products that are described for . The construction of more efficient sucrose-utilizing phenotypes and the optimization of process conditions will increase yields and productivities and eventually close the gap in the contemporary process. In the long term, the co-culture may serve as a platform process, in which is used as a chassis for the implementation of synthetic metabolic pathways for biotechnological production of value-added products.