Produção de bio-óleo empregando microalgas em diferentes meios de cultivo

Abstract

Microalgae are photosynthetic unicelular microorganism present in aquatic environments and soil. Microalgae have more productivity than oilseeds, being approximately 89.9% over the palm and 99.2% compared to soybean. Microalgae produce a bio-oil that can be classified as a raw material for biofuel production. The use of microalgae to bio-oil producion can be a potential economic alternative to other sources of fuel. The microalgae cultive occur in open ponds or photobioreactors in systems. The microalgae biomass can be for the most diverse applications such as the production of lipids and use in biofertilizers. In this paper were evaluate the bio-oil production using the Scenedesmus sp. microalgae in fermentation medium containing salts. The Scenedesmus sp. was chosen from the microalgae Spirulina platensis, Chlorella sp. and Nannochoropsis oculata, good oil production, no need to add vitamins in the middle and ease in growing to be cultivated in fresh water. The cultivation occurred in vertical planes reactors in acrylic, useful volume 3 L with 0.7 vvm aeration system, temperatura 23 ± 1 °C and artificial illumination with 3 fluorescent lamps of 20 W, subjected to a photoperiod of 12 hours. Preliminary tests determined that the best way of microalgae cultive Scenedesmus sp., in order to produce bio-oil, using inoculum was 10% of total volume, aged 12 days of culture without the vitamins addition, getting 0.121 g of oil produced per reactor, the lipid content of 18.15% and final biomass concentration at 0.221 g/L. It was found that changes in the concentration of macro-and micronutrients medium proposed in the literature do not favor the production of bio-oil, except for ZnSO4 7H2O and MnCl2 4H2O micronutrients. Were evaluated the influence of the concentration of ZnSO4 7H2O and MnCl2 4H2O in a central composite design (CCD). The joint analysis of the variables through the analysis of the CCD and response surfaces showed that the lipids production is favored when working with 0.06 g/L of ZnSO4 7H2O and 0.5 g/L MnCl2 4H2O, reaching in a production of 0.141 g of bio-oil, lipid content of 47.5% and biomass 0.099 g/L, representing a 161.7% improvement in lipid content and 16.9% in volume oil produced and 55.32% reduction in the dry biomass concentration.