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Associations of grazer assemblages with worm-tubes vary according to random sites. nMDS plots of (a) densities, and (b) numbers per boulder, of mobile assemblages (grazers) on boulders with serpulimorph tubes (triangle) and without (circle).Results from PERMANOVA pairwise tests are shown under the plots; n = 10. https://doi.org/10.1371/journal.pone.0192579.g001 There is an error in the caption for Fig 6.

Microalgae are increasingly considered as sources of renewable feedstocks for industrial production, and microalgae production now focuses on the multiproduct microalgal biorefinery. However, such a biorefinery presents several bottlenecks that are mainly associated with downstream processes. This reduced downstream efficiency results from unsolved problems related to the culture strategy for the accumulation of different products – the protein versus lipid dilemma – and the dilute nature of the microalgal culture. We identify new trends and propose promising solutions for realizing microalgal biorefineries at industrial scale. New perspectives and challenges are identified in protein properties and in the integration and cooptimization of culture and downstream processes. The exploitation of a single microalgal product is unprofitable and generates undesirable waste, inspiring the biorefinery approach to microalgae production. Several thin culture systems are currently being proposed for intensifying the conversion of light into biomass. Downstream processing, and in particular the fractionation of microalgal components, remains the most expensive step limiting the practical implementation of microalgal biorefineries.

Microalgae produce a variety of compounds that are beneficial to human and animal health. Among these compounds are carotenoids, which are microalgal pigments with unique antioxidant and coloring properties. The objective of this review is to evaluate the potential of using microalgae as a commercial feedstock for carotenoid production. While microalgae can produce some of the highest concentrations of carotenoids (especially astaxanthin) in living organisms, there are challenges associated with the mass production of microalgae and downstream processing of carotenoids. This review discusses the synthesis of carotenoids within microalgae, their physiological role, large-scale cultivation of microalgae, up- and down-stream processing, commercial applications, natural versus synthetic carotenoids, and opportunities and challenges facing the carotenoid markets. We emphasize legal aspects and regulatory challenges associated with the commercial production of microalgae-based carotenoids for food/feed, nutraceutical and cosmetic industry in Europe, the USA, the People’s Republic of China, and Japan. This review provides tools and a broad overview of the regulatory processes of carotenoid production from microalgae and other novel feedstocks.

Microalgae culture collections may contain unexplored strains with great biotechnological potential. Through sampling, identification, characterization, and maintenance of local strains, part of the work described here led to the establishment of the first public Swiss microalgae culture collection, AlgoScope. The potential biotechnological applications of 7 strains from among over 120 native strains were suggested based on growth parameters and biochemical composition. Under standardized growth conditions, Tetradesmus obliquus FAM 27852 and FAM 27855, Chloroidium saccharophilum FAM 27962, Chlorella vulgaris FAM 27965, Stichococcus sp. FAM 27986, Desmodesmus sp. FAM 28090, and Tetranephris brasiliensis FAM 28097 had growth rates of 0.24 d −1 –0.80 d −1 and biomass productivities of 0.24 g L −1 d −1 –0.73 g L −1 d −1 . Proteins, lipids, carbohydrates, and ashes ranged from 32.88 to 53.54%, 9.69–18.08%, 9.32–23.94%, and 3.17–5.51%, respectively. All strains had a similar amino acid composition, containing all essential amino acids. In contrast, the fatty acid composition varied among strains, but, in general, the fatty acids were rich in PUFAs (23.83–53.49% of total fatty acids). Overall, C. saccharophilum FAM 27962 and T. brasiliensis FAM 28097 showed great potential for use in the animal feed sector.

Biofilm-based algal cultivation has received increased attention as a potential platform for algal production and other applications such as wastewater treatment. Algal biofilm cultivation systems represent an alternative to the suspension-based systems that have yet to become economically viable. One major advantage of algal biofilm systems is that algae can be simply harvested through scraping and thus avoid the expensive harvesting procedures used in suspension-based harvesting such as flocculation and centrifugation. In recent years, an assortment of algal biofilm systems have been developed with various design configurations and biomass production capacities. This review summarizes the state of the art of different algal biofilm systems in terms of their design and operation. Perspectives for future research needs are also discussed to provide guidance for further development of these unique cultivation systems.

Microalgae and cyanobacteria are diverse groups of organisms with great potential to benefit societies across the world. These organisms are currently used in food, feed, pharmaceutical and cosmetic industries. In addition, a variety of novel compounds are being isolated. Commercial production of photosynthetic microalgae and cyanobacteria requires cultivation on a large scale with high throughput. However, scaling up production from lab-based systems to large-scale systems is a complex and potentially costly endeavor. In this review, we summarise all aspects of large-scale cultivation, including aims of cultivation, species selection, types of cultivation (ponds, photobioreactors, and biofilms), water and nutrient sources, temperature, light and mixing, monitoring, contamination, harvesting strategies, and potential environmental risks. Importantly, we also present practical recommendations and discuss challenges of profitable large-scale systems associated with economical design, effective operation and maintenance, automation, and shortage of experienced phycologists.

Biological soil crusts (BSCs) are an important cover in arid desert landscapes, and have a profound effect on the CO sub(2) exchange in the desert system. Although a large number of studies have focused on the CO sub(2) flux at the soil-air interface, relatively few studies have examined the soil CO sub(2) concentration in individual layers of the soil profile. In this study, the spatiotemporal dynamics of CO sub(2) concentration throughout the soil profile under two typical BSCs (algae crusts and moss crusts) and its driving factors were examined in a revegetated sandy area of the Tengger Desert from Mar 2010 to Oct 2012. Our results showed that the mean values of the vertical soil CO sub(2) concentrations under algal crusts and moss crusts were 600-1,200 mu mol/mol at the 0-40 cm soil profiles and increased linearly with soil depth. Daily CO sub(2) concentrations showed a single-peak curve and often had a 1-2 h time delay after the maximum soil temperature. During the rainy season, the mean soil CO sub(2) concentration profile was 1,200-2,000 mu mol/mol, which was 2-5 times higher as compared to the dry season (400-800 mu mol/mol). Annually, soil moisture content was the key limiting factor of the soil CO sub(2) concentration, but at the daily time scale, soil temperature was the main limiting factor. Combined with infiltration depth of crusted soils, we predicted that precipitation of 10-15 mm was the most effective driving factor in arid desert regions.

The use of fossil fuels has been strongly related to critical problems currently affecting society, such as: global warming, global greenhouse effects and pollution. These problems have affected the homeostasis of living organisms worldwide at an alarming rate. Due to this, it is imperative to look for alternatives to the use of fossil fuels and one of the relevant substitutes are biofuels. There are different types of biofuels (categories and generations) that have been previously explored, but recently, the use of microalgae has been strongly considered for the production of biofuels since they present a series of advantages over other biofuel production sources: (a) they don’t need arable land to grow and therefore do not compete with food crops (like biofuels produced from corn, sugar cane and other plants) and; (b) they exhibit rapid biomass production containing high oil contents, at least 15 to 20 times higher than land based oleaginous crops. Hence, these unicellular photosynthetic microorganisms have received great attention from researches to use them in the large-scale production of biofuels. However, one disadvantage of using microalgae is the high economic cost due to the low-yields of lipid content in the microalgae biomass. Thus, development of different methods to enhance microalgae biomass, as well as lipid content in the microalgae cells, would lead to the development of a sustainable low-cost process to produce biofuels. Within the last 10 years, many studies have reported different methods and strategies to induce lipid production to obtain higher lipid accumulation in the biomass of microalgae cells; however, there is not a comprehensive review in the literature that highlights, compares and discusses these strategies. Here, we review these strategies which include modulating light intensity in cultures, controlling and varying CO 2 levels and temperature, inducing nutrient starvation in the culture, the implementation of stress by incorporating heavy metal or inducing a high salinity condition, and the use of metabolic and genetic engineering techniques coupled with nanotechnology.