Utilização de vinhaça no cultivo de Chlorella sp.

Abstract

In the face of future scarcity of energy resources derived from oil and its derivatives, coupled with the environmental impacts caused by rampant consumption of natural resources, it is necessary to search for a renewable and clean energy. In the meantime, there are microalgae with potential of biofuel production due to its high growth rate and productivity capacity of lipids and carbohydrates. However, the high cost of maintenance still prevents its manufacture. In this way, the present work aims to increase the production of microalgae using vinasse which is a residue of highly nutritious sugarcane industry and a polluter, and reusing waste from the own cultivation as a nutritional supplement to the culture medium. The microalgae Chlorella sp. was grown in a modified Bold's Basal Medium (BBM), supplemented with 5, 10 and 15% of vinasse and residues of cultivations with different concentrations in what they were reused at maximum of three times. The adopted cultivation system was the mixotrophic. Calculations were made to obtain the specific maximum speed of growth and the generation times of cultivations supplemented with vinasse and cultivation waste. Also, it was calculated the removals of Chemical Oxygen Demand (COD) of cultivations supplemented with vinasse. For the next step, it was quantified the reducing sugars and lipids of biomass cultivated with 10% of vinasse and without supplementation. It was verified that the cultivation supplemented with 5 and 10% of vinasse showed higher cell density than the unsupplemented cultivation. The maximum growth rates and generation times of cultivations with 5 and 10% of vinasse were very close whereas cultivation supplemented with 15% of vinasse showed growth inhibition. The removals of COD were high and averaged at 85%. The use of cultivation residue has favored the microalgae growth, presenting best results for the cultures supplemented with second reuse waste, in particular cultures supplemented with residues derived from a culture with addition of vinasse. The biomass of cultivated Chlorella sp. with supplementation of 10% of vinasse showed 11.50% lipids, 0.33% of reducing sugars. Further studies should be performed to better characterize the biomass to check the influence of the medium supplementation with vinasse in the production of proteins and total carbohydrates.