A greater insight on the control of the interactions between microalgae and other microorganisms, particularly bacteria, should be useful for enhancing the efficiency of microalgal biomass production ...and associated valuable compounds. Little attention has been paid to the controlled utilization of microalgae-bacteria consortia. However, the studies of microalgal-bacterial interactions have revealed a significant impact of the mutualistic or parasitic relationships on algal growth. The algal growth, for instance, has been shown to be enhanced by growth promoting factors produced by bacteria, such as indole-3-acetic acid. Vitamin B12 produced by bacteria in algal cultures and bacterial siderophores are also known to be involved in promoting faster microalgal growth. More interestingly, enhancement in the intracellular levels of carbohydrates, lipids and pigments of microalgae coupled with algal growth stimulation has also been reported. In this sense, massive algal production might occur in the presence of bacteria, and microalgae-bacteria interactions can be beneficial to the massive production of microalgae and algal products. This manuscript reviews the recent knowledge on the impact of the microalgae-bacteria interactions on the production of microalgae and accumulation of valuable compounds, with an emphasis on algal species having application in aquaculture.
Carotenoids are among the most abundant natural pigments available in nature. These pigments have received considerable attention because of their biotechnological applications and, more importantly, ...due to their potential beneficial uses in human healthcare, food processing, pharmaceuticals and cosmetics. These bioactive compounds are in high demand throughout the world; Europe and the USA are the markets where the demand for carotenoids is the highest. The in vitro synthesis of carotenoids has sustained their large-scale production so far. However, the emerging modern standards for a healthy lifestyle and environment-friendly practices have given rise to a search for natural biocompounds as alternatives to synthetic ones. Therefore, nowadays, biomass (vegetables, fruits, yeast and microorganisms) is being used to obtain naturally-available carotenoids with high antioxidant capacity and strong color, on a large scale. This is an alternative to the in vitro synthesis of carotenoids, which is expensive and generates a large number of residues, and the compounds synthesized are sometimes not active biologically. In this context, marine biomass has recently emerged as a natural source for both common and uncommon valuable carotenoids. Besides, the cultivation of marine microorganisms, as well as the downstream processes, which are used to isolate the carotenoids from these microorganisms, offer several advantages over the other approaches that have been explored previously. This review summarizes the general properties of the most-abundant carotenoids produced by marine microorganisms, focusing on the genuine/rare carotenoids that exhibit interesting features useful for potential applications in biotechnology, pharmaceuticals, cosmetics and medicine.
The genus
Coccomyxa
comprises green microalgae, which can be found worldwide in remarkably versatile aquatic and terrestrial ecosystems including symbiotic associations with a number of different ...hosts. In this study, we describe a new species,
Coccomyxa onubensis
, based on 18S and ITS ribosomal DNA (rDNA) sequence data.
Coccomyxa onubensis
was isolated from acidic water, and its ability to adapt to a wide range of acidic and alkaline pH values and to high salinity was analyzed. The long-term adaptation capacity of the microalga to such extreme conditions was evaluated by performing continuous repeated batches at selected salt concentrations and pH values. Adapted cultures of
C. onubensis
were found to yield high biomass productivities from pH 2.5 to 9, with maximum yields at acidic pH between 2.5 and 4.5. Moreover,
C. onubensis
was also found to adapt to salinities as high as 0.5 M NaCl, reaching biomass productivities that were similar to those of control cultures. Ultrastructural analysis by transmission electron microscopy of
C. onubensis
cells adapted to high salinity showed a robust response to hyperosmotic shock. Thus,
C. onubensis
was found to be acidotolerant and halotolerant. High biomass productivity over a wide range of pH and salinities denotes
C. onubensis
as an interesting candidate for various biotechnological applications including outdoor biomass production.
Microalgae have been widely recognized as a valuable source of natural, bioactive molecules that can benefit human health. Some molecules of commercial value synthesized by the microalgal metabolism ...have been proven to display anti-inflammatory activity, including the carotenoids lutein and astaxanthin, the fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), and sulphated polysaccharides. These molecules can accumulate to a certain extent in a diversity of microalgae species. A production process could become commercially feasible if the productivity is high and the overall production process costs are minimized. The productivity of anti-inflammatory molecules depends on each algal species and the cultivation conditions, the latter being mostly related to nutrient starvation and/or extremes of temperature and/or light intensity. Furthermore, novel bioprocess tools have been reported which might improve the biosynthesis yields and productivity of those target molecules and reduce production costs simultaneously. Such novel tools include the use of chemical triggers or enhancers to improve algal growth and/or accumulation of bioactive molecules, the algal growth in foam and the surfactant-mediated extraction of valuable compounds. Taken together, the recent findings suggest that the combined use of novel bioprocess strategies could improve the technical efficiency and commercial feasibility of valuable microalgal bioproducts production, particularly anti-inflammatory compounds, in large scale processes.
produce C50 carotenoids such as bacterioruberin, which are of biotechnological in-terest. This study aimed to analyze the effect of different environmental and nutritional conditions on the cellular ...growth and dynamics of carotenoids accumulation in
. The maximum production of carotenoids (40 µg·mL
) was obtained during the stationary phase of growth, probably due to nutrient-limiting conditions (one-step culture). By seven days of culture, 1 mL culture produced 22.4 mg of dry weight biomass containing 0.18 % (
/
) of carotenoids. On the other hand, carbon-deficient cultures (low C/N ratio) were observed to be optimum for C50 bacterioruberin production by
, but negatively affected the growth of cells. Thus, a two-steps process was evaluated for optimum carotenoids yield. In the first step, a nutri-ent-repleted culture medium enabled the haloarchaea to produce biomass, while in the second step, the biomass was incubated under osmotic stress and in a carbon-deficient medium. Under the conditions used, the obtained biomass contained 0.27% (
/
) of carotenoids after seven days, which accounts for 58.49 µg·mL
of carotenoids for a culture with turbidity 14.0.
produces C50 carotenoids that have strong antioxidant properties. The response surface methodology (RSM) tool helps to accurately analyze the most suitable conditions to maximize C50 carotenoids ...production by haloarchaea. The effects of temperature (15⁻50 °C), pH (4-10), and salinity (5⁻28% NaCl (
/
)) on the growth and carotenoid content of
were analyzed using the RSM approach. Growth was determined by measuring the turbidity at 600 nm. To determine the carotenoid content, harvested cells were lysed by freeze/thawing, then re-suspended in acetone and the total carotenoid content determined by measuring the absorbance at 494 nm. The analysis of carotenoids was performed by an HPLC system coupled with mass spectrometry. The results indicated the theoretical optimal conditions of 36.51 or 36.81 °C, pH of 8.20 or 8.96, and 15.01% or 12.03% (
/
) salinity for the growth of haloarchaea (OD600 = 12.5 ± 0.64) and production of total carotenoids (3.34 ± 0.29 mg/L), respectively. These conditions were validated experimentally for growth (OD600 = 13.72 ± 0.98) and carotenoid production (3.74 ± 0.20 mg/L). The carotenoid profile showed four isomers of bacterioruberin (89.13%). Our findings suggest that the RSM approach is highly useful for determining optimal conditions for large-scale production of bacterioruberin by haloarchaea.
Edible microalgae are marine or fresh water mesophilic species. Although the harvesting of microalgae offers an abundance of opportunities to the food and pharmaceutical industries, the possibility ...to use extremophilic microalgae as a food source for animals is not well-documented.
We studied the effects of dietary supplementation of a powdered form of the acidophilic microalga Coccomyxa onubensis on growth and health parameters of laboratory rats.
Four randomly organized groups of rats (n=6) were fed a standard diet (Diet 1, control) or with a diet in which 0.4% (Diet 2), 1.25% (Diet 3), or 6.25% (Diet 4) (w/w) of the standard diet weight was substituted with dried microalgae powder, respectively. The four groups of animals were provided ad libitum access to feed for 45 days.
C. onubensis biomass is rich in protein (44.60% of dry weight) and dietary fiber (15.73%), and has a moderate carbohydrate content (24.8%) and a low lipid content (5.4%) in which polyunsaturated fatty acids represent 65% of the total fatty acid. Nucleic acids are present at 4.8%. No significant difference was found in growth rates or feed efficiency ratios of the four groups of rats. Histological studies of liver and kidney tissue revealed healthy organs in control and C. onubensis-fed animals, while plasma hematological and biochemical parameters were within healthy ranges for all animals. Furthermore, animals fed a microalgae-enriched diet exhibited a statistically significant decrease in both blood cholesterol and triglyceride levels. The blood triglyceride content and very low density lipoprotein-cholesterol levels decreased by about 50% in rats fed Diet 4.
These data suggest that C. onubensis may be useful as a food supplement for laboratory animals and may also serve as a nutraceutical in functional foods. In addition, microalgae powder-supplemented diets exerted a significant hypocholesterolemic and hypotriglyceridemic effect in animals.
Agricultural fertilisers (NPKs) have been recognised as an alternative to make microalgae cultivation cheaper as well as simpler in terms of the preparation of the medium.
Botryococcus braunii
, a ...green microalga, has the almost unique capacity to accumulate and excrete large amounts of long-chain hydrocarbons and/or interesting groups of polysaccharides which can be further converted into bio-products. However, limitations in growth are currently hindering its industrial production. In this work, the use of different agricultural fertilisers (NPKs) was evaluated for the cultivation of two
B. braunii
races (A and B) in terms of productivity and final media labour and cost. Results corroborated that fertilisers-based media are easier to prepare and their prices are considerably lower compared to common culture media. At the same time, good growth performance and photosynthetic efficiency can be maintained and carbohydrate and hydrocarbon productivities can be further enhanced. However, special attention should be given to each particular strain since different behaviour in growth and metabolite production can be observed depending on the media composition. The significantly higher productivities obtained, together with the important reduction in media price when using commercial fertilisers and the advantages related to the easiness to prepare the culture media based on NPK fertilizers, represent an important achievement for the development of an industry based on these renewable products.
Haloarchaea are halophilic microorganisms belonging to the Archaea domain that inhabit salty environments (mainly soils and water) all around the world. Most of the genera included in this group are ...able to produce carotenoids at significant concentrations (even wild-type strains). The major carotenoid produced by the cells is bacterioruberin (and its derivatives), which is only produced by this kind of microbes. Nevertheless, the understanding of carotenoid metabolism in haloarchaea, its regulation, and the roles of carotenoid derivatives in this group of extreme microorganisms remains mostly unrevealed. Besides, potential biotechnological uses of haloarchaeal pigments are poorly explored. This work summarizes what it has been described so far about carotenoid production by haloarchaea, haloarchaeal carotenoid production at large scale, as well as the potential uses of haloarchaeal pigments in biotechnology and biomedicine.
The large-scale biomass production is an essential step in the biotechnological applications of microalgae. Coccomyxa onubensis is an acidophilic microalga isolated from the highly acidic waters of ...Río Tinto (province of Huelva, Spain) and has been shown to accumulate a high concentration of lutein (9.7 mg g−1dw), a valuable antioxidant, when grown at laboratory-scale. A productivity of 0.14 g L−1 d−1 was obtained by growing the microalga under outdoor conditions in an 800 L tubular photobioreactor. The results show a stable biomass production for at least one month and with a lutein content of 10 mg g−1dw, at pH values in the range 2.5–3.0 and temperature in the range 10–25 °C. Culture density, temperature, and CO2 availability in highly acidic medium are rate-limiting conditions for the microalgal growth. These aspects are discussed in this paper in order to improve the outdoor culture conditions for competitive applications of C. onubensis.
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