The phycoerythrin-deficient strain (green phenotype) of Hypnea musciformis (Rhodophyta) originated from a green branch, which had arisen as a spontaneous mutation in a wild plant (brown phenotype) collected from the Brazilian coast. The present study describes the growth responses to irradiance, photoperiod and temperature variations, pigment contents, and photosynthetic characteristics of the brown and green strains of H. musciformis. The results showed that growth rates increased as a function of irradiance (up to 40 μmol photons m −2 s −1 ) but, with further increase in irradiance (from 40 to 120 μmol photons m −2 s −1 ), became light-saturated and remained almost unchanged. The highest growth rates of the brown and green strains were observed in temperatures of 20-25°C under long (14:10 h LD) and short (10:14 h LD) photoperiods. The brown strain had higher growth rates than the green strain in the short photoperiod, which could be related to the high concentrations of phycobiliproteins. Phycoerythrin was not detected in the green strain. The brown strain had higher concentrations of allophycocyanin and phycoerythrin in the short photoperiod while the green strain had higher concentrations of phycocyanin. The brown strain presented higher photosynthetic efficiency (α), and lower saturation parameter (I k ) and compensation irradiance (I c ) than the green strain. The brown strain exhibited the characteristics of shade-adapted plants, and its higher value of photosynthetic efficiency could be attributed to the higher phycoerythrin concentrations. Results of the present study indicate that both colour strains of H. musciformis could be selected for aquaculture, since growth rates were similar (although in different optimal light conditions), as the green strain seems to be adapted to higher light levels than the brown strain. Furthermore, these colour strains could be a useful experimental system to understand the regulation of biochemical processes of photosynthesis and metabolism of light-harvesting pigments in red algae.

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Considering these compositions, both algae species were determined to have sources of protein, essential amino acids and carbohydrates similar to the edible seaweeds Laminaria japonica and Palmaria palmata.

Renewable energy has attracted significant interest in recent years as a result of sustainability, environmental impact, and socio-economic considerations. Given existing technological knowledge and based on projections relating to biofuels derived from microalgae, microalgal feedstock is considered to be one of the most important renewable energy sources potentially available for industrial production. Therefore, this review examines microalgal bioethanol technology, which converts biomass from microalgae to fuel, the chemical processes involved, and possible ways of increasing the bioethanol yield, such as abiotic factors and genetic manipulation of fermenting organisms.

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2012Influence of temperature, light and nutrients on the growth rates of the macroalga Gracilaria domingensis in synthetic seawater using experimental design JOURNAL OF APPLIED PHYCOLOGY, DORDRECHT, v. 24, n. 6, pp. 1419-1426, DEC, 2012 Abstract In the present study, the daily relative growth rates (DRGR, in percent per day) of the red macroalga Gracilaria domingensis in synthetic seawater was investigated for the combined influence of five factors, i.e., light (L), temperature (T), nitrate (N), phosphate (P), and molybdate (M), using a statistical design method. The ranges of the experimental cultivation conditions were T, 18-26°C; L, 74-162 μmol photons m −2 s . In additional, these growth rate values are close to the growth rate values in natural medium (von Stosch medium), i.e., 6.5-7.0% d −1. The results analyzed by the ANOVA indicate that the factors N and T are highly significant linear terms, X L , (α00.05). On the other hand, the only significant quadratic term (X Q ) was that for L. Statistically significant interactions between two different factors were found between T vs. L and N vs. T. Finally, a two-way (linear/quadratic interaction) model provided a quite reasonable correlation between the experimental and predicted DRGR values (R adjusted 2 00.9540).

Abstract:In Brazil, Hypnea musciformis is the main raw material for carrageenan production and the knowledge of nitrogen and phosphorus metabolism in algae is critical for the success of cultivation because these elements can limit seaweed productivity. Thus, the objective of this study was to evaluate the effects of nitrate (zero to 100 µM) and nitrate plus phosphate (zero to 25 µM) availabilities on the growth, the contents of photosynthetic pigments (phycobiliproteins and chlorophyll a) and proteins, and the photosynthesis and respiration of the brown (BR) and light green (LG) strains of H. musciformis. The results revealed metabolic differences between the colour strains of H. musciformis for nitrogen metabolism: upon nitrate addition, the LG strain stored nitrogen mainly as proteins, while the BR strain stored it as proteins and pigments. Moreover, the respiration of the LG strain and the photosynthesis of the BR strain increased with nitrate concentrations, indicating that the BR strain fixed more photosynthetic carbon than the LG strain. Keywords:colour strain Hypnea nitrate phosphate photosynthesis IntroductionThe genus Hypnea (Gigartinales, Rhodophyta) includes about fi fty species that are distributed in warm water areas (Masuda et al., 1997), of which six species are known in Brazil (Schenkman, 1986;Nunes, 2005). Hypnea musciformis (Wulfen in Jacqu.) J. V. Lamour. is a species with wide geographical distribution along the Brazilian coast and is the main raw material for carrageenan production (Oliveira, 1998). Carrageenan is a sulfated polysaccharide widely used in the food and pharmaceutical industries; it also has antiviral activity, inhibiting, for example, HSV and HIV (Neushul, 1990).The concern with the impoverishment of natural beds of H. musciformis led to several investigations, which found that there are large variations in biomass and carrageenan yields during the year related to seasonality (Schenkman, 1989;Faccini & Berchez, 2000;Ramos et al., 2006). Since the carrageenan production from natural populations is very variable, studies were undertaken to determine the best conditions for H. musciformis cultivation in the laboratory, and in the ocean (Faccini & Berchez, 2000; Reis et al., 2003; Schenkman, 1989). However, few studies evaluated the nutrient requirements of this species.Nitrogen is considered to be the primary limiting nutrient for algal growth in marine ecosystems. Thus, the success of seaweed cultivation requires a knowledge of the nitrogen requirements of the algae (Hanisak, 1990). In the absence of this nutrient, many algae present the following changes: hair formation (DeBoer & Whoriskey, 1983;O'Connor & West, 1991); a decrease in growth (Hwang et al., 1987;Collén et al., 2004); a decrease in the contents of soluble proteins and phycobiliproteins (Collén et al., 2004); a decrease in the nitrate, nitrite and aminoacid contents of the thallus (Hwang et al., 1987); a decrease in photosynthesis and in the activities of enzymes involved in carbon metabolism (Collén et al., 2004) ...

Dictyota menstrualis (Hoyt) Schnetter, Hörning & Weber-Peukert (Dictyotales, Phaeophyceae) was studied for the production of oil-based bioproducts and co-products. Experiments were performed to evaluate the effect of carbon dioxide (CO2) concentration, under nitrogen (NO3 (-)) limiting and saturation conditions, on growth rate (GR), photosynthesis, as well as nitrate reductase (NR), carbonic anhydrase (CA), and Rubisco activities. In addition, the biochemical composition of D. menstrualis under these conditions was estimated. GR, protein content, and N content in D. menstrualis were higher in treatments containing NO3 (-), irrespective of CO2 addition. However, when CO2 was added to medium saturated with NO3 (-), values of maximum photosynthesis, Rubisco, and NR activity, as well as total soluble carbohydrates and lipids, were increased. CA activity did not vary under the different treatments. The fatty acid profile of D. menstrualis was characterized by a high content of polyunsaturated fatty acids, especially the omega-3 fatty acids, making it a possible candidate for nutraceutical use. In addition, this species presented high GR, photosynthetic rate, and fatty acid content, highlighting its economic importance and the possibility of different biotechnological applications.