Fucoxanthin and docosahexaenoic acid production by cold-adapted Tisochrysis lutea.

Tisochrysis lutea is an important microalgal species for fucoxanthin and docosahexaenoic acid (DHA) production with an optimum cultivation temperature of approximately 30 °C. The aim of the present work was to develop a winter strain with high productivity at 15 °C. The response of the original strain to a decrease in temperature from 30 °C to 15 °C was investigated in continuous turbidostat experiments. This was followed by adaptation for >180 days at 15 °C and 2 rounds of sorting for cells with high chlorophyll fluorescence (top 5%) using fluorescence-activated cell sorting (FACS). For the original strain the productivity of biomass, fucoxanthin, and DHA decreased by 92 %, 98 % and 85 % respectively when decreasing the temperature from 30 °C to 15 °C. In the sorted cold-adapted 'winter strain', biomass, fucoxanthin, and DHA productivities were similar to those at 30 °C. In addition, the fucoxanthin concentration increased from 1.11 to 4.24 mg g-1 dry weight and the polar lipid fraction in total fatty acids increased from 21 % to 55 %. The winter strain showed a robust and stable phenotype after one year of cultivation, expanding the outdoor fucoxanthin and lipid production seasons for this species.

Improved fucoxanthin and docosahexaenoic acid productivities of a sorted self-settling Tisochrysis lutea phenotype at pilot scale.

This work aimed to select a Tisochrysis lutea phenotype with higher biomass and fucoxanthin productivities using fluorescence-activated cell sorting (FACS). A novel phenotype was obtained after 2 rounds of selection, based on high-fucoxanthin fluorescence. The resulting phenotype forms cell aggregates, has no flagella, and was stable after 15 months. Optimal temperature (30 °C) and light (300 µmol m-2 s-1) were obtained at laboratory scale, identical to the original strain. The biomass productivity was higher than the original strain: 1.9× at laboratory scale (0.4 L), and 4.5× under outdoor conditions (190 L). Moreover, compared to the original strain, the productivity of fucoxanthin increased 1.6-3.1× and docosahexaenoic acid 1.5-1.9×. These are the highest ever reported outdoor productivities, obtained with a robust new phenotype from a T. lutea monoculture isolated with FACS without genetic manipulation. The resulting phenotype shows high potential for industrial production.

Light spectra as triggers for sorting improved strains of Tisochrysis lutea.

It is known that microalgae respond to different light colors, but not at single-cell level. This work aimed to assess if different light colors could be used as triggers to sort over-producing cells. Six light spectra were used: red + green + blue (RGBL), blue (BL), red (RL), green (GL), blue + red (BRL) and blue + green (BGL). Fluorescence-activated cell sorting method was used to analyse single-cell fluorescence and sort cells. BGL and RGBL lead to the highest fucoxanthin production, while RL showed the lowest. Therefore, it was hypothesized that hyper-producing cells can be isolated efficiently under the adverse condition (RL). After exposure to all light colors for 14 days, the top 1% fucoxanthin producing cells were sorted. A sorted strain from RL showed higher (16-19%) growth rate and fucoxanthin productivity. This study showed how light spectra affected single-cell fucoxanthin and lipid contents and productivities. Also, it supplied an approach to sort for high-fucoxanthin or high-lipid cells.

The influence of day/night cycles on biomass yield and composition of Neochloris oleoabundans.

BACKGROUND: Day/night cycles regulate the circadian clock of organisms to program daily activities. Many species of microalgae have a synchronized cell division when grown under a day/night cycle, and synchronization might influence biomass yield and composition. Therefore, the aim of this study was to study the influence of day/night cycle on biomass yield and composition of the green microalgae Neochloris oleoabundans. Hence, we compared continuous turbidostat cultures grown under continuous light with cultures grown under simulated day/night cycles. RESULTS: Under day/night cycles, cultures were synchronized as cell division was scheduled in the night, whereas under continuous light cell division occurred randomly synchronized cultures were able to use the light 10-15% more efficiently than non-synchronized cultures. Our results indicate that the efficiency of light use varies over the cell cycle and that synchronized cell division provides a fitness benefit to microalgae. Biomass composition under day/night cycles was similar to continuous light, with the exception of starch content. The starch content was higher in cultures under continuous light, most likely because the cells never had to respire starch to cover for maintenance during dark periods. Day/night cycles were provided in a 'block' (continuous light intensity during the light period) and in a 'sine' (using a sine function to simulate light intensities from sunrise to sunset). There were no differences in biomass yield or composition between these two ways of providing light (in a 'block' or in a 'sine'). CONCLUSIONS: The biomass yield and composition of N. oleoabundans were influenced by day/night cycles. These results are important to better understand the relations between research done under continuous light conditions and with day/night cycle conditions. Our findings also imply that more research should be done under day/night cycles.

Sorting cells of the microalga Chlorococcum littorale with increased triacylglycerol productivity.

BACKGROUND: Despite extensive research in the last decades, microalgae are still only economically feasible for high valued markets. Strain improvement is a strategy to increase productivities, hence reducing costs. In this work, we focus on microalgae selection: taking advantage of the natural biological variability of species to select variations based on desired characteristics. We focused on triacylglycerol (TAG), which have applications ranging from biodiesel to high-value omega-3 fatty-acids. Hence, we demonstrated a strategy to sort microalgae cells with increased TAG productivity. RESULTS: 1. We successfully identified sub-populations of cells with increased TAG productivity using Fluorescence assisted cell sorting (FACS). 2. We sequentially sorted cells after repeated cycles of N-starvation, resulting in five sorted populations (S1-S5). 3. The comparison between sorted and original populations showed that S5 had the highest TAG productivity [0.34 against 0.18 g l(-1) day(-1) (original), continuous light]. 4. Original and S5 were compared in lab-scale reactors under simulated summer conditions confirming the increased TAG productivity of S5 (0.4 against 0.2 g l(-1) day(-1)). Biomass composition analyses showed that S5 produced more biomass under N-starvation because of an increase only in TAG content and, flow cytometry showed that our selection removed cells with lower efficiency in producing TAGs. CONCLUSIONS: All combined, our results present a successful strategy to improve the TAG productivity of Chlorococcum littorale, without resourcing to genetic manipulation or random mutagenesis. Additionally, the improved TAG productivity of S5 was confirmed under simulated summer conditions, highlighting the industrial potential of S5 for microalgal TAG production.

Repeated nitrogen starvation doesn't affect lipid productivity of Chlorococcum littorale.

In the present work we wanted to know what happens during time to biomass and lipid productivities of Chlorococcum littorale repeatedly subjected to N-starvation. Experiments were done using repeated cycles of batch-wise N run-out (after 2days N=0). Two different cycles were used: repeated short-starvation (6days of N=0) over a total period of 72days and repeated long-starvation (13days of N=0) over a total period of 75days. Batches (using fresh inocula) were done separately as control. Shorter and longer periods of starvation showed no differences in biomass productivities and PSII quantum yield evolution. The repeated short-starvation-batches showed the same lipid productivities as the control short-starvation batches. Most importantly, the biomass lipid content was the same between control and repeated-batches. Altogether, the results point to C. littorale as a resilient and stable strain, with potential to be used under semi continuous cultivation.

Rapid method to screen and sort lipid accumulating microalgae.

The present work established an efficient staining method for fluorescence activated cell sorting (FACS) with Chlorococcum littorale maintaining cellular viability. The method was designed to detect high-lipid cells and to guarantee cellular viability. BODIPY505/515 (BP) was more suitable to FACS when compared to Nile red. The optimum concentrations were 0.4 µg ml(-1) of BP, 0.1% DMSO or 0.35% ethanol. Both ethanol and DMSO were equally efficient and assured cellular viability after the staining and sorting. Here a method is presented to rapidly screen and sort lipid rich cells of C. littorale with FACS, which can be used to produce new inoculum with increased cellular lipid content.

Comparing the use of different domestic wastewaters for coupling microalgal production and nutrient removal.

The streams from municipal wastewater treatment plants (WWTP) have been considered a valuable medium for mass cultivation of algal biomass. The aim of this work is to test and compare the performance of Chlorella vulgaris on several streams from five stages, from two different WWTP. The results showed biomass yields ranging from 39 to 195mg dry-weightl(-1)days(-1). The best performance as biomass production was obtained with the centrate (effluent from drying the anaerobic sludge). After testing a wide range of N/P ratios with centrate, the highest productivity and growth rates were obtained with the original N/P ratio (2.0) of this stream. The highest removal rates were of 9.8 (N) and 3.0 (P) mgl(-1)days(-1), in the centrate. Finally, this research also suggests that microalgal production seems to be a promising process when coupled to wastewater treatment.

Estudo sobre o estado de preservação das nascentes do rio Sapato, Lauro de Freitas-Ba / Study about the preservation state springs of Sapato river, Lauro de Freitas-BA

Poucos são os centros urbanos que desfrutam de fontes hídricas ainda intactas ou em bom estado de conservação. O objetivo deste estudo foi avaliar o estado atual de preservação das nascentes e as medidas de prevenção a danos ambientais do rio Sapato (Lauro de Freitas – BA), localizado na Região Metropolitana de Salvador (RMS). O trabalho foi desenvolvido por meio de levantamento de dados nos órgãos ambientais pertinentes, nos municípios de Salvador e Lauro de Freitas. Há poucas informações referentes ao rio Sapato. A única informação relevante é de que não há sistema de esgotamento sanitário em Lauro de Freitas. O zoneamento das nascentes evidenciou uma taxa alta de aterramento e de desvio do leito e das nascentes. Mas também mostrou riqueza e diversidade de flora e fauna. Concluiu-se que as nascentes encontram-se preservadas em Praia do Flamengo, porém altamente deterioradas em praia de Ipitanga, evidenciando a necessidade da implantação de programas de recuperação e preservação por parte da administração pública.

Perfil do albinismo oculocutâneo no estado da Bahia / Profile of oculocutaneos albinism in Bahia state

O albinismo é um conjunto heterogêneo de distúrbios genéticos que afeta a produção de melanina, podendo levar à hipopigmentação da pele, dos pêlos, cabelos e olhos. O objetivo deste trabalho foi analisar aspectos genéticos e agravos à saúde decorrentes do albinismo oculocutâneo. Foi feita uma amostragem de conveniência, utilizando-se como instrumento de coleta de dados questionários semi-estruturados aplicados a 40 probandos (23 mulheres e 17 homens) de famílias associadas a APALBA (Associação dos Portadores de Albinismo da Bahia). Os albinos eram filhos de pais normalmente pigmentados, portadores do alelo recessivo mutante. A maioria (65por cento) refere hereditariedade, com mais de um caso na família, e origem étnica predominantemente negra. A ocorrência do albinismo está associada a dificuldades e desvantagens, conseqüências do distúrbio genético e da segregação social. O diagnóstico usual do albinismo segue critérios clínicos, embora já existam métodos laboratoriais que identificam algumas mutações. A falta de assistência aos afetados contribui para a baixa da visão e a ocorrência de câncer de pele. O estudo indica a necessidade de um novo modelo de atendimento ao albino, com medidas de prevenção aos danos à saúde, que também incluam, nos casos indicados, testes laboratoriais com técnicas da biologia molecular que possam contribuir para o aconselhamento genético da condição.