Efeitos de coagulação na colheita de hidrólise de biomassa de S. platensis sobre a hidrólise enzimática

Abstract

Microalgae are an alternative to fossil fuels, as they can be applied in the production of biofuels. The environmental and technical advantages are proven, showing that the productivity of microalgae, when compared to traditional crops (corn and soybean, for example), is higher. However, one of the problems in production is the high cost and the harvesting of biomass is one of the most costly stages. In this way, finding more suitable and viable methods becomes necessary. One of the indicated processes for separation is the use of coagulants. In the case of ethanol production, which involves enzymatic and fermentative processes, many factors can affect the conversion efficiency into product. Therefore, the objective of this work was to study the separation of Spirulina platensis with different coagulants and their influence on enzymatic hydrolysis processes. Cultures of Spirulina platensis LEB 52 were performed in raceways, in semi-continuous mode. The microalgae harvest was carried out with 11 types of coagulants, these being organic and inorganic, and a comparison with the centrifugation method. For the determination of the best harvesting condition, central compound designs were performed, varying two factors (pH and concentration) at two levels. With the ideal harvest conditions for each coagulant, it followed the application on a larger scale, characterization of the biomass was carried out regarding the carbohydrate, protein, ash, moisture content and SEM/EDS analysis. The biomass was broken by the freezing and thawing method followed by enzymatic hydrolysis of carbohydrates and proteins. The coagulants were efficient in separating the biomass, reaching efficiencies up to 99.5%. In the chemical characterization, high ash content was identified from the culture medium salts and retained coagulant. Ferric aluminum sulphate stood out in saccharification, converting approximately 37.52% of the carbohydrates into reducing sugar. In protein hydrolysis, low hydrolysis efficiencies were obtained (1.26 - 4.07%). The coagulation and flocculation process has a promising application area, for ease of large-scale application and high removal efficiencies. However, for use in biotechnological processes studies are suggested to separate biomass coagulants previously.