Banca de QUALIFICAÇÃO: RENATA ANDREIA DOS SANTOS

Production of pigments by co-cultivation of Serratia marcescens and Tetradesmus obliquous and evaluation of their

photoprotective potential

Bacteria, Microalgae, Pigments, Co-culture, Biosurfactant.

Natural products such as microbial pigments and biosurfactants have attracted attention because they are non-toxic, sustainable and renewable. However, the production of biopigments and biosurfactant is still limited, due to low yield and high production costs. Serratia marcescens and Tetradesmus obliquus were investigated for the production of prodigiosin, carotenoid, chlorophyll and biosurfactant, in cocultivation as a strategy to minimize production time and cost. The production of these biomolecules was carried out in monoculture and co-culture using alternative media as a sustainable strategy in order to compare the cultivation method. Monoculture of T. obliquus was carried out in BG 11 medium and BG 11 medium, supplemented with wheat bran (5%) and 5% post-frying soybean oil (OSPF). This last culture medium was also used for the monoculture of S. marcescens. Co-cultivation of S. marcescens with T. obliquus was carried out in BG 11 medium and BG 11 medium, supplemented with 5% wheat bran and 5% OSPF. The cellular concentration, specific growth rate and maximum cellular productivity of the microorganisms were analyzed daily over a period of 10 days, as well as the concentrations of carotenoid pigments, chlorophyll and prodigiosin. The microalgae T. obliquous in monoculture in the standard BG 11 medium showed a higher concentration of cells (Xmax = 398 ± 3 104 cells mL−1), with an Xmax value three times higher than the other cultivation conditions; specific growth speed (µmax = 0.131 d−1), maximum cell productivity (PX = 34.63 104 cells mL−1) and carotenoid 36 mg/g and chlorophyll 248 mg/g. The bacterium S. marcescens obtained greater growth in co-culture with T. obliquous in BG11, wheat bran and OSPF with an Xmax cell growth (18 ± 1 104 cells mL−1), maximum specific growth rate (µmax = 0.071 d −1) and cell productivity (PX = 19 104 cells mL−1), as well as a carotenoid value of 19 mg/g, chlorophyll 34 mg/g and prodigiosin 760 mg/g. It is worth noting that prodigiosin production was greater in co-culture than in monoculture. To obtain the biodispersant, the microorganisms were cultivated in monoculture and coculture for 48 h, using wheat bran and OSPF as substrates. After fermentation, surface tension and oil dispersion area (ODA) were evaluated in cell-free liquids and, from the best condition, interfacial tension and emulsification index were analyzed. The biosurfactant was isolated by acid precipitation and subjected to preliminary characterization (Zeta potential and FTIR spectroscopy) and stability and phytotoxicity tests. The results demonstrated that co-cultivation presented the best condition for biodispersant production, with excellent values of surface tension (26.6 mN/m), ODA (50.24 cm2), interfacial tension (1.0 mN/m) and emulsification index (96%). The yield of the biomolecule produced was 1.75 g/L, which was anionic and lipopeptide in nature. The biosurfactant was stable at alkaline pH (8-12) and in a wide range of temperatures (0-100 ºC) and salinity (5-15% NaCl), as well as being non-toxic to cucumber (Cucumis sativus) and lettuce (Lactuca) seeds. sativa). Therefore, cocultivation with S. marcescens and T. obliquus represents an innovative technology in the production of pigments and biodispersant for application in the industrial area, using agri-food substrates that makes the process less expensive, in addition to minimizing the environmental impact.