avaliação de um sistema de cultivo em fotobiorreatores para produção de biomassa de microalgas

Abstract

The Microalgae are the most effective photosynthetic organisms existing in the world and have been a focus of great interest for the benefits they can offer to the environment due to their enormous capacity to capture and use carbon dioxide (CO2) present in the atmosphere as one of the sources of nutrients, and their conversion into biomass highly rich in lipids, pigments, polyunsaturated fatty acids, amino acids like mycosporins, ficocoloids, sterols, amino acids and proteins, carbohydrates. The biomass produced has great interest for energy, food, pharmaceutical and cosmetics. Many microalgae also act as efficient bioremediation agents for household and agroindustrial waste, so that integrated microalgae culture systems promising for the production of biofuels coupled with effluent treatment can have several benefits, such as reducing costs in wastewater treatment with co-production of microalgal biomass, reducing costs with cultivation media, promoting nutrient removal and minimizing environmental impacts. In this context, the objective of this work was to evaluate a mix culture system in tubular photobioreactors, composing a system of 2000 liters of effective capacity36, built in acrylic tube and closed tanks, and studies related to the growth of the microalgae Selenastrum gracile (Chlorophyceae) cultivated in the photobioreactor, using alternative culture medium prepared from biocomposite hortifrútis extract. The cultivation lasted 14 days, with an exponential phase from the second to the eighth day. The maximum yield of biomass was 20 mg.L-1 for a maximum cell density of 5.49 x 103 cells.mL-1 . Data on the growth kinetics of S. gracile in the photobioreactor showed mean values of 0.44 for Max (maximum growth rate), 0.64 for ok (cell doubling per day of culture) and 1.64 for tg (generation time) in the exponential phase. Measurements of the photosynthetic efficiency performed in the exponential phase, using a mini-PAM showed excellent physiological state of the cell, with Fv / Fm value (photosynthetic efficiency) above 0.79. Photoinhibition of photosynthesis was observed at 13 p.m in the day, in a saturating light situation. High temperature between around 13:00 to 15:00 hours also reduced the rate of photosynthesis. OJIP transients also show a decrease in Fm during the hours of greater illumination. The alternative medium used proved effective for the mass culture of this species in photobioreactor