Candy Waste to Produce Bioplastics and Natural Pigments Using Haloarchaea From the Salt Flats of Alicante County (Spain)

The haloarchaeon Haloferax mediterranei (halophilic microorganism) has been used as a cell factory to produce the natural pigment called bacterioruberin (BR) and the biodegradable biopolymer termed poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV). During the last two decades, these two biomolecules have been revealed as promising tools in different sectors due to biological activities in the case of BR, or due to biodegradable plastic properties shown by PHBV. Both molecules can be produced at the same time by the same microorganism, but modulating nutritional conditions or using engineered strains, the production of one of them can be improved at the detriment of the other. To make the upscaling of the production economically feasible, residues from candy industries have been used as nutrients for the cells to grow and to produce these two highly marketed biomolecules. Thus, a circular economy-based process has been optimised in which, thanks to the metabolic versatility of the microorganism and biotechnological approaches, residues from other industries have been valorised to produce natural compounds following eco-friendly practices.