Exploring the potential of microalgae in the recycling of dairy wastes

Culturing microalgae using dairy-wastes offers the opportunity of producing valuable biomass for different industrial applications. The capability of four Chlorella species and a recombinant Chlamydomonas reinhardtii strain to mixotrophically grow in wastewaters from an Italian dairy factory was investigated. A robust algal growth could be efficiently sustained in these wastes, despite the abundance of d-Lactose (~4% w/v), that could not be metabolized by any microalgal species. Non axenic cocultivation of microalgae together with microbial communities from the dairy wastes resulted in a marked decrease of their pollution load, thus reducing the necessity of expensive treatments before their discharge in the municipal sewage system. Microalgae cultivated using dairy-wastes were characterized by a lipid content ranging from 12% to 21% (w/w), with Auxenochlorella protothecoides reaching the highest lipid productivity (~0.16 g/L/d) whereas the transplastomic C. reinhardtii strain expressing a thermostable β-glucosidase reached a recombinant enzyme productivity of 0.18 mg/L/d.