VALORIZATION OF SOLID WASTES FROM THE BREWERY AND BIODIESEL INDUSTRIES FOR THE BIOPRODUCTION OF NATURAL DYES

This study aims to assess a new approach for concomitant valorization of two industrial wastes - raw glycerin and spent brewer’s yeast - for the bioproduction of valuable carotenoids. Microbial pigments have numerous applications in the food and cosmetic industries. First, four cultures of yeasts were screened using pure glycerol and either (NH4)2SO4 or urea as carbon and nitrogen sources, respectively. The ability of the best performing culture to accumulate carotenoids was investigated in a medium in which only wastes were supplemented as carbon and nitrogen sources. All the fermentations were carried out in 500 mL-Erlenmeyer flasks containing 150 mL of the medium. Microbial culture was incubated at 30 °C and 150 rpm for 120 h. Particularly, R. marina was the strain with the biggest potential to produce total carotenoids (up to 420 μg g-1). The four major carotenoid pigments identified by LCAPCI-MS were β-carotene, γ-carotene, torulene, and torularhodin. All fermentation assays and all the determinations were performed in triplicate. Results show that the bioprocess proposed in this work is technically and environmentally feasible, and sustainable. The simultaneous use of raw glycerin and spent brewer’s yeast for the production of carotenoids by R. marina is reported for the first time.