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Biotechnology advances have allowed bacteria, yeasts, plants, mammalian and insect cells to function as heterologous protein expression systems. Recently, microalgae have gained attention as an innovative platform for recombinant protein production, due to low culture media cost, compared to traditional systems, as well as the fact that microalgae such as Chlamydomonas reinhardtii are considered safe (GRAS) by the Food and Drug Administration (FDA). Previous studies showed that recombinant protein production in traditional platforms by semicontinuous process increased biomass and bio product productivity, when compared to batch process. As there is a lack of studies on semicontinuous process for recombinant protein production in microalgae, the production of recombinant mCherry fluorescent protein was evaluated by semicontinuous cultivation of Chlamydomonas reinhardtii in bubble column photobioreactor. This semicontinuous cultivation process was evaluated in the following conditions: 20%, 40%, and 60% culture portion withdrawal. The highest culture withdrawal percentage (60%) provided the best results, as an up to 161% increase in mCherry productivity (454.5 RFU h-1 - Relative Fluorescence Unit h-1 ), in comparison to batch cultivation (174.0 RFU h-1 ) of the same strain. All cultivations were carried out for 13 days, at pH 7, temperature 25°C and, by semicontinuous process, two culture withdrawals were taken during the cultivations. Throughout the production cycles, it was possible to obtain biomass concentration up to 1.36 g L-1 .

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Abstract Microalgae are aquatic unicellular microorganisms that can be found both in freshwater and marine systems; are capable of photosynthesis; and can grow as individual cells or associated in chains or small colonies. Microalgae cultivation has gained large momentum among researchers in the past decades due to their ability to produce value metabolites, remarkable photosynthetic efficiency, and versatile nature. The wide technological potential, and thus increasing amount of scattered knowledge, may become the very first barrier that a post graduating student, or any non-specialist reader, will face when introduced to the subject. In this review paper, we access the core aspects of microalgae technology, covering their main characteristics, and comprehensively presenting the main features of their various cultivation modes and biological activity from metabolites.

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Biorefineries have the potential to meet a significant part of the growing demand for energy, fuels, chemicals and materials worldwide. Indeed, the bio-based industry is expected to play a major role in energy security and climate change mitigation during the 21th century. Despite this, there are challenges related to resource consumption, processing optimization and waste minimization that still need to be overcome. In this context, microalgae appear as a promising non-edible feedstock with advantages over traditional land crops, such as high productivity, continuous harvesting throughout the year and minimal problems regarding land use. Importantly, both cultivation and microalgae processing can take place at the same site, which increases the possibilities for process integration and a reduction in logistic costs at biorefinery facilities. This review describes the actual scenario for microalgae biorefineries integration to the biofuels and petrochemical industries in Brazil, while highlighting the major challenges and recent advances in microalgae large-scale production.

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Despite microalgae recently receiving enormous attention as a potential source of biodiesel, their use is still not feasible as an alternative to fossil fuels. Recently, interest in microalgae has focused on the production of bioactive compounds such as polyunsaturated fatty acids (PUFA), which provide microalgae a high added value. Several considerations need to be assessed for optimizing PUFA production from microalgae. Firstly, a microalgae species that produces high PUFA concentrations should be selected, such as Nannochloropsis gaditana, Isochrysis galbana, Phaeodactylum tricornutum, and Crypthecodinium cohnii, with marine species gaining more attention than do freshwater species. Closed cultivation processes, e.g., photobioreactors, are the most appropriate since temperature, pH, and nutrients can be controlled. An airlift column with LEDs or optical fibers to distribute photons into the culture media can be used at small scale to produce inoculum, while tubular and flat panels are used at commercial scale. Depending on the microalgae, a temperature range from 15 to 28 °C and a pH from 7 to 8 can be employed. Relevant conditions for PUFA production are medium light irradiances (50-300 µmol photons m(-2) s(-1)), air enriched with (0-1 % (v/v) CO2, as well as nitrogen and phosphorous limitation. For research purposes, the most appropriate medium for PUFA production is Bold's Basal, whereas mixotrophic cultivation using sucrose or glucose as the carbon source has been reported for industrial processes. For cell harvesting, the use of tangential flow membrane filtration or disk stack centrifugation is advisable at commercial scale. Current researches on PUFA extraction have focused on the use of organic solvents assisted with ultrasound or microwaves, supercritical fluids, and electroporation or are enzyme assisted. Commercial-scale extraction involves mainly physical methods such as bead mills and expeller presses. All these factors should be taken into account when choosing a PUFA production system, as discussed in this review.

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O gênero Spirulina, devido às suas qualidades nutricionais (alto teor protéico, baixo teor de gordura e alto teor de ácido -linolênico), tem sido considerado muito promissor para a alimentação humana e animal. Spirulina major foi cultivada em escala laboratorial, com o objetivo de determinar a temperatura e o pH ótimos de cultivo, visando uma maior produção de biomassa. Os cultivos foram realizados em sistema fechado, em meio de cultura Guillard-F2, com agitação constante (100rpm), com fotoperíodo de 12 horas, por 8 dias. Foram testadas quatro diferentes temperaturas (20, 25, 30 e 35°C) e quatro valores de pH do meio de cultivo (7,0; 8,0; 9,0 e 10,0). A biomassa obtida era filtrada e seca a 55°C. Os resultados obtidos mostram que a temperatura ótima de cultivo é 30°C e que ocorre uma maior produção de biomassa em pH 8,0. (AU)

The Spirulina genera has great nutritional qualities such as high protein content, low fat and high -Iinolenic acid content, and has been considered a great promising ingredient for human and animal feeding. Spirulina major was cultivated in laboratory scale with the objective of determining the optimal growth temperature and the pH for a greater biomass production. The cultivations were carried out in a closed system, Gillard's F2 medium, constant agitation (100rpm), 12-hour photoperiod, for 8 days. Different temperatures were tested (20°, 25°, 30°, and 35°C), and four pH values of culture medium (7.0; 8.0; 9.0, and 10.0). The resulting biomass was filtered and dried at 55°C. The results showed that 30°C is the best growth temperature, and the largest biomass production occurs at pH 8.0. (AU)

La clase de Spirulina, debido a sus calidades nutricionales (alto contenido proteico, bajo contenido de gordura y alto contenido de ácido -linolénico) ha sido considerado muy promisorio para la alimentación animal y humana. La Spirulina major fue cultivada en escala laboratorial con el objetivo de determinar la temperatura y el pH excelentes de cultivo, buscando una mayor producción de biomasa. Los cultivos fueron realizados en sistema cerrado, en medio de cultura Guillard-F2, con agitación constante (100rpm), con fotoperíodo de 12 horas, por 8 días. Fueron testadas cuatro diferentes temperaturas (20, 25, 30 y 35ºC) y cuatro valores de pH del medio de cultivo (7,0; 8,0; 9,0 e 10,0). La biomasa conseguida fue fi ltrada y seca a 55ºC. Los resultados conseguidos demuestran que la temperatura excelente de cultivo es de 30ºC y que ocurre una mayor producción de biomasa en pH 8,0.(AU)

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