Biomass Production and Ester Synthesis by In Situ Transesterification/Esterification Using the Microalga Spirulina platensis

The increasing energy demand and reduction in the availability of nonrenewable energy sources, allied with an increase in public environmental awareness, have stimulated a search for alternative energy sources. The present study was aimed at producing biomass from the microalga Spirulina platensis and at assessing in situ synthesis of alkyl esters via acid transesterification/esterification of biomass to produce biodiesel. Two alcohols (ethanol and methanol) and two cosolvents (hexane and chloroform) were tested, at different temperatures (30, 45, 60, 75, and 90°C) and reaction times (10, 20, 30, 60, and 120？min). The factorial analysis of variance detected an interaction between the factors ( ): temperature, reaction time, alcohol, and cosolvent. The best yields were obtained with the combination ethanol and chloroform at 60°C, after 30？min of reaction, and with hexane at 45°C, after 10？min of reaction. In situ transesterification/esterification of alga biomass to form esters for biodiesel production adds unconventional dynamics to the use of this feedstock. 1. Introduction The global concern about future availability of energy comes from national security, economic stability, and environmental sustainability issues [1, 2]. In this context, the demand for petroleum derivatives has increased, but the current concern about reduction in pollution and the energy crisis has stimulated the global biofuel market. The global economy keeps increasing and so does the need for clean, renewable energy sources [3]. In the sector of automotive fuels, the inclusion of renewable fuels, such as biodiesel, has several advantages, such as a reduction in pollution caused by exhaust emissions. Furthermore, biodiesel is an alternative to petroleum and contributes to regional development and social security, mainly in developing countries [4, 5]. A wide variety of feedstocks are currently used for biodiesel production, and microalgae have been considered a potentially useful and promising biodiesel source, because they are photosynthesizing organisms very efficient in the process of converting light into chemical energy [6–8]. In addition, microalgae stand out for presenting high productivity, exceeding that of any commercially produced plant in the world [9–11]. Microalgae have a life cycle of a few days and they may use CO2 from polluting companies as an input for photosynthesis, which helps decrease the emission of greenhouse gases; hence, microalgae may contribute significantly to the global energy matrix [9–11]. Microalgae contain lipids and fatty acids as membrane