Study of the microalgae Spirulina platensis cultivation in whey and in wastewater from dairy industry as substrates

Abstract

Microalgae cultivation is a beneficial process due to the proteins production with high biological value for human and animal nutrition and other products generation such as pigments, lipids and vitamins. Microalgae can be used for various purposes including the biodiesel production. However, this production has a high cost, which can be decreased with an increase in biomass and oil productivity. Spirulina platensis is a filamentous photosynthetic cyanobacteria inhabiting media like soils, bogs, alkaline lakes and brackish, marine and sweet waters. It has been used as a food supplement because its high amounts of minerals and polyunsaturated fatty acids. It is also used as a source of vitamins. Recently, it was purified other nutrients and substances that biomass, some with great importance for the pharmaceutical industry. Studies about Spirulina have been done in various aspects such as profile bromatological in cells grown under different physicochemical conditions, diversification of nutrients sources for the cultivation and use of biomass in wastewater treatment. Microalgae use in wastewater treatment has been motivated by the ability they have to consume organic substances and inorganic nutrients from wastewater, besides the possibility of produced biomass reuse to generate energy and nutrients. The aim of this study is to obtain a culture medium for a efficient and economical microalgae production and at the same time to evaluate as the use of the wastewater coming from a cheese whey anaerobic treatment system as the need to add cheese whey "in natura" as a nitrogen source. The whey is the aquous portion of milk separates from the clot during conventional manufacturing of cheese or casein, which retains about 55% of the milk nutrients. Due to its high COD, the whey can not be dismissed without prior treatment. Spirulina platensis will be used, and, at first, it will be cultivated in Schlösser mineral medium. In the modified culture medium, it will be used the whey, either as "fresh" as coming from an baffled anaerobic treatment system. It will be also evaluated the needing for Schlösser medium addition. It will be used three elongated shape mini-tanks, constructed of PVC, each with a three liters volume. The culture will be stirred by rotating paddles. The temperature will be maintained at 30°C, illuminance between 1800 and 3000 lux by fluorescent lamps and depth of each tank at 10cm. With respect to the microalgae, it will be determine the cell concentration, pH, total lipids and proteins. Regarding the wastewater, it will be analyzed the nitrogen concentration, chemical oxygen demand (COD), acidity, alkalinity, pH, total dissolved solids (TDS) and dissolved volatile solids (SDV). In the experimental design and in the results analyze, initially it will be made a fully randomized experimental design, and to evaluate the addition of cheese whey, a 22 factorial design with central point, with the variables whey COD and illuminance. (AU)