Recebido em 22/11/11; aceito em 5/7/12; publicado na web em 31/8/12 BIODIESEL DERIVED FROM MICROALGAE: ADVANCES AND PERSPECTIVES. Microalgae are a promising source of raw material for biodiesel production. This review discusses the latest developments related to the application of microalgae biomass for biodiesel production. Characterization of fatty acid of microalgae and comparisons with other sources of raw materials and processes are presented. Furthermore, technological perspectives and approaches for growing microalgae in photobioreactors, microalgal oil extraction techniques, and procedures for synthesizing biodiesel are reviewed.Keywords: microalgae; biofuel; fatty acid. INTRODUÇÃOO biodiesel tem sido objeto de grande atenção nos últimos anos, devido aos impactos e passivos ambientais, além dos altos preços do diesel oriundo de fontes fósseis. O biodiesel é produzido a partir de biomassas renováveis, pela transesterificação de triglicerídeos com alcoóis de cadeia curta, produzindo ésteres monoalquílicos de ácidos graxos de cadeia longa. As principais vantagens deste combustível devem-se ao fato do mesmo ser biodegradável, não tóxico e renová-vel. Além disso, o biodiesel pode ser misturado ao diesel fóssil em qualquer proporção. 1,2A matéria-prima utilizada na síntese de biocombustível contribui para a maior porção nos custos da produção de biodiesel. Em geral, a procura por fontes alternativas e economicamente viáveis tem sido o principal foco de pesquisadores da área. Assim, a fonte ideal para a produção de biocombustível depende principalmente da sua disponibilidade e do seu custo. 1 O biodiesel pode ser produzido a partir de diferentes fontes, como óleos vegetais (soja, palma, girassol, algodão, amendoim e outros), gordura animal e pelo reuso de óleo (proveniente de fritura). 1,3 No entanto, a procura por novas fontes para a produção de biocombustí-veis não se limita a óleos vegetais e gordura animal, mas também de microalgas.3 Estudos recentes indicam que o biodiesel pode ser obtido a partir de microalgas, devido à facilidade de seu cultivo, quantidade intracelular de lipídios, viabilidade de manipulação genética das vias metabólicas, duplicação da biomassa em um curto período de tempo e possibilidade de controlar estas condições. Neste sentido, é emergente a aplicação de microalgas como fonte alternativa para a produção de biodiesel. 4,5 As microalgas são organismos aquáticos, que crescem em ambientes de águas doce e salgada. Estas podem usar diferentes metabolismos energéticos para manutenção de suas estruturas, como fotossíntese, respiração e fixação/assimilação de nitrogênio, o que torna algumas espécies organismos únicos, com amplo espectro de aplicação tecnológica. 6,7 A biomassa de microalgas contém três componentes principais: carboidratos, proteínas e lipídios.5,8 Sabendo-se que para constituir uma matéria-prima de biodiesel, esta deve ser rica em ácido graxo, uma microalga com um teor de proteínas muito alto e baixo teor de lipídios não seria útil como matéria-prima para biocombustíveis. A ...

Currently, algae and algae products are extensively applied in the pharmaceutical, cosmetic and food industries. Algae are the main organisms that take up and store heavy metals. Therefore, the use of compounds derived from algae by the pharmaceutical industry should be closely monitored for possible contamination. The pollution generated by heavy metals released by industrial and domestic sources causes serious changes in the aquatic ecosystem, resulting in a loss of biological diversity and a magnifi cation and bioaccumulation of toxic agents in the food chain. Since algae are at the bottom of the aquatic food chain, they are the most important vector for transfer of pollution to upper levels of the trophic chain in aquatic environments. Moreover, microalgae are also used for the bioremediation of wastewater, a process that does not produce secondary pollution, that enables effi cient recycling of nutrients and that generates biomass useful for the production of bioactive compounds and biofuel.

In this work, the use of ultraviolet radiation combined with microwave-assisted wet digestion (MW-UV) was applied for digestion of seaweed samples and further determination of As, Cd and Pb by inductively coupled plasma mass spectrometry (ICP-MS). In the proposed method, UV radiation was generated in situ by electrodeless Cd discharge lamps inserted into digestion quartz vessels. This approach increased the digestion efficiency allowing lower consumption of acids. The feasibility of using diluted acid solution (0.5 to 7 mol L À1 HNO 3 ) was evaluated for relatively higher sample masses (up to 800 mg). The efficiency of digestion was evaluated taking into account the residual carbon content and residual acidity in digests. Under the selected conditions, it was possible to digest up to 700 mg of sample using a nitric acid solution as diluted as 2 mol L À1 HNO 3 allowing an efficiency of digestion higher than 77% (considering the total C content in the sample) and acidity as low as 0.19 mol L À1 that is convenient for ICP-MS measurements. The accuracy of the proposed MW-UV method was evaluated by the digestion of two certified reference materials of aquatic plant (BCR 060 and BCR 670) and by comparison with the results obtained after digestion by microwave-assisted wet digestion in a high pressure system using concentrated HNO 3 (MW-AD). The results obtained by the proposed method did not present difference (t-test, 95% confidence level) with the certified values and with results obtained after seaweed sample digestion using the MW-AD method. Using 700 mg of sample, the limit of detection was 0.005, 0.001, and 0.012 mg g À1 for As, Cd, and Pb, respectively. A clear advantage of the proposed method over classical approaches is that only diluted solution was necessary and it is possible to digest a relatively high sample mass, that is important to minimize the generation of laboratory residues and to improve the limits of detection, respectively.

World-wide, invertebrates are found in most drinking water networks; however, limited data and information are available on the occurrence of invertebrates throughout the purification process.During this investigation, temporal and spatial variations in the invertebrate composition occurring throughout a conventional Drinking Water Purification Plant (DWPP) and the abiotic drivers responsible for their occurrence were investigated. Samples destined for invertebrate and water quality analyses were collected and multivariate statistical analysis was performed on the data obtained. Copepoda, Rotatoria, Cladocera, Ostracoda and Diptera were the dominant groups found in the source water and occurred throughout the purification process. A higher total biomass occurred throughout the purification process, in particular after sedimentation and filtration, compared with the total biomass entering the DWPP. The water quality variables measured were within the optimum ranges of invertebrates. The present study proved the theory that purification plants are an important source of invertebrates occurring in the drinking water distribution network.Strategies should be implemented to improve coagulation (by using coagulants/flocculants to increase the pH above 10.5), flocculation, sedimentation (by removing sludge and algae) and filtration (by optimizing filter bed maintenance) and general filter house 'housekeeping'.