Polyhydroxyalkanoates and pigments coproduction by Arthrospira (Spirulina) platensis cultivated in crude glycerol

Valorization of industrial waste as an alternative carbon source for microalgae mixotrophic cultivation and co-production of high-value compounds are strategies to enhance the bioprocess revenue and make large-scale production of microalgae polyhydroxyalkanoates (PHAs) feasible, with these biopolymers as potential substitutes to conventional polymers, such as polypropylene (PP) and high-density polyethylene (HDPE). In this sense, the use of crude glycerol, a main byproduct of the biodiesel industry, is an alternative to reduce cultivation costs and, at the same time, to provide a biotechnological solution for the excess of this byproduct produced, approximately 10 wt% per biodiesel batch. Thus, this work evaluated the effect of pure and crude glycerol supplementation and nutrient depletion (N and P) on growth, total carotenoids, phycocyanin and PHAs content in Arthrospira platensis xenic cultures. The highest final biomass concentrations, 1.68 and 1.40 g L-1, and PHAs contents, 1.1 and 0.5 % were achieved by supplying a Zarrouk medium with 6.14 g L-1 of pure or crude glycerol, respectively. In spite of having its content reduced at 6.14 g L-1 of pure glycerol, phycocyanin still presents a reasonable content (4.2 %) in this condition and in crude glycerol at 3.07 g.L-1 attained the highest content (10.8 %). On the other hand, glycerol mixotrophic cultivations with simultaneous nutrient depletion (nitrogen or phosphorus) did not improve the accumulation of PHAs.