Natascia Biondi

Microalgae for oil: strain selection, induction of lipid synthesis and outdoor mass cultivation in a low-cost photobioreactor.

Thirty microalgal strains were screened in the laboratory for their biomass productivity and lipid content. Four strains (two marine and two freshwater), selected because robust, highly productive and with a relatively high lipid content, were cultivated under nitrogen deprivation in 0.6‐L bubbled tubes. Only the two marine microalgae accumulated lipid under such conditions. One of them, the eustigmatophyte Nannochloropsis sp. F&M‐M24, which attained 60% lipid content after nitrogen starvation, was grown in a 20‐L Flat Alveolar Panel photobioreactor to study the influence of irradiance and nutrient (nitrogen or phosphorus) deprivation on fatty acid accumulation. Fatty acid content increased with high irradiances (up to 32.5% of dry biomass) and following both nitrogen and phosphorus deprivation (up to about 50%). To evaluate its lipid production potential under natural sunlight, the strain was grown outdoors in 110‐L Green Wall Panel photobioreactors under nutrient sufficient and deficient conditions. Lipid productivity increased from 117 mg/L/day in nutrient sufficient media (with an average biomass productivity of 0.36 g/L/day and 32% lipid content) to 204 mg/L/day (with an average biomass productivity of 0.30 g/L/day and more than 60% final lipid content) in nitrogen deprived media. In a two‐phase cultivation process (a nutrient sufficient phase to produce the inoculum followed by a nitrogen deprived phase to boost lipid synthesis) the oil production potential could be projected to be more than 90 kg per hectare per day. This is the first report of an increase of both lipid content and areal lipid productivity attained through nutrient deprivation in an outdoor algal culture. The experiments showed that this marine eustigmatophyte has the potential for an annual production of 20 tons of lipid per hectare in the Mediterranean climate and of more than 30 tons of lipid per hectare in sunny tropical areas. Biotechnol. Bioeng. 2009;102: 100–112.

Polyphasic study of Antarctic cyanobacterial strains

We isolated 59 strains of cyanobacteria from the benthic microbial mats of 23 Antarctic lakes, from five locations in two regions, in order to characterize their morphological and genotypic diversity. On the basis of their morphology, the cyanobacteria were assigned to 12 species that included four Antarctic endemic taxa. Sequences of the ribosomal RNA gene were determined for 56 strains. In general, the strains closely related at the 16S rRNA gene level belonged to the same morphospecies. Nevertheless, divergences were observed concerning the diversity in terms of species richness, novelty, and geographical distribution. For the 56 strains, 21 operational taxonomic units (OTUs, defined as groups of partial 16S rRNA gene sequences with more than 97.5% similarity) were found, including nine novel and three exclusively Antarctic OTUs. Sequences of Petalonema cf. involvens and Chondrocystis sp. were determined for the first time. The internally transcribed spacer (ITS) between the 16S and the 23S rRNA genes was sequenced for 33 strains, and similar groupings were observed with the 16S rRNA gene and the ITS, even when the strains were derived from different lakes and regions. In addition, 48 strains were screened for antimicrobial and cytotoxic activities, and 17 strains were bioactive against the gram‐positive Staphylococcus aureus, or the fungi Aspergillus fumigatus and Cryptococcus neoformans. The bioactivities were not in coincidence with the phylogenetic relationships, but rather were specific to certain strains.

Evaluation of Nostoc Strain ATCC 53789 as a Potential Source of Natural Pesticides

ABSTRACT The cyanobacterium Nostoc strain ATCC 53789, a known cryptophycin producer, was tested for its potential as a source of natural pesticides. The antibacterial, antifungal, insecticidal, nematocidal, and cytotoxic activities of methanolic extracts of the cyanobacterium were evaluated. Among the target organisms, nine fungi (Armillaria sp., Fusarium oxysporum f. sp. melonis, Penicillium expansum, Phytophthora cambivora, P. cinnamomi, Rhizoctonia solani, Rosellinia, sp., Sclerotinia sclerotiorum, and Verticillium albo-atrum) were growth inhibited and one insect (Helicoverpa armigera) was killed by the extract, as well as the two model organisms for nematocidal (Caenorhabditis elegans) and cytotoxic (Artemia salina) activity. No antibacterial activity was detected. The antifungal activity against S. sclerotiorum was further studied with both extracts and biomass of the cyanobacterium in a system involving tomato as a host plant. Finally, the herbicidal activity of Nostoc strain ATCC 53789 was evaluated against a grass mixture. To fully exploit the potential of this cyanobacterium in agriculture as a source of pesticides, suitable application methods to overcome its toxicity toward plants and nontarget organisms must be developed.

Cyanobacteria from benthic mats of Antarctic lakes as a source of new bioactivities

Aims:  To exploit the cyanobacterial diversity of microbial mats growing in the benthic environment of Antarctic lakes for the discovery of novel antibiotic and antitumour activities.

Advances in microalgal culture for aquaculture feed and other uses.

Abstract: The state of the art of microalgae biotechnology, particularly focusing on new culture techniques and actual and potential uses of microalgae in human and animal nutrition, in cosmetics and pharmaceutics, and for environmental applications, is described. Some examples of the worlds largest commercial plants in the field are presented. For the future, it is possible to foresee a huge increase in the demand for cultured algae, in terms of both quantity and diversity. For example, aquaculture will require new animal species and, consequently, new microalgae to fulfil their nutritional needs will be necessary. The production of algae for high–value markets (aquaculture, food supplements, nutraceuticals, pharmaceuticals) will be developed through the search for, isolation and cultivation of new algal strains endowed with the activity of interest. Algal biomass might become an important source of biofuels, especially if its production will be carried out in low-cost photobioreactors and associated with wastewater treatment and greenhouse gas abatement.

Photobioreactors for Microalgal Biofuel Production

Many different PBR designs have been proposed for biofuel production, few of them have been tested at pilot-scale, none developed at the (large) scale necessary for a complete and correct evaluation. Thus the main issues that impact on the reactor’s performance (i.e., suitable construction materials, efficient mixing, heating/cooling, CO2 supply and oxygen removal), although explored at pilot level, still await evaluation at real scale. Although the main limitations of PBR are the high cost and the reduced scalability, with few exceptions, R&D on photobioreactor design is aimed at achieving high photosynthetic efficiencies and at pushing productivity beyond that currently attainable. The main strategies explored to this end are intensive mixing, light dilution via large external surfaces or internal light conducting structures. This chapter reviews and examined recent advances and innovations in photobioreactor design and operation.

Growth, photosynthetic efficiency, and biochemical composition of Tetraselmis suecica F&M-M33 grown with LEDs of different colors.

The effect of light quality on cell size and cell cycle, growth rate, productivity, photosynthetic efficiency and biomass composition of the marine prasinophyte Tetraselmis suecica F&M‐M33 grown in 2‐L flat panel photobioreactors illuminated with light emitting diodes (LEDs) of different colors was investigated. Biomass productivity and photosynthetic efficiency were comparable between white and red light, while under blue and green light productivity decreased to less than half and photosynthetic efficiency to about one third. Differences in cell size and number correlated with the cell cycle phase. Under red light cells were smaller and more motile. Chlorophyll content was strongly reduced with red and enhanced with blue light, while carotenoids and gross biomass composition were not affected by light quality. The eicosapentaenoic acid content increased under red light. Red light can substitute white light without affecting productivity of T. suecica F&M‐M33, leading to smaller and more motile cells and increased eicosapentaenoic acid content. Red LEDs can thus be profitably used for the production of this microalga for aquaculture. Biotechnol. Biotechnol. Bioeng. 2014;111: 956–964.

Oil and eicosapentaenoic acid production by the diatom Phaeodactylum tricornutum cultivated outdoors in Green Wall Panel (GWP®) reactors

Phaeodactylum tricornutum is a widely studied diatom and has been proposed as a source of oil and polyunsaturated fatty acids (PUFA), particularly eicosapentaenoic acid (EPA). Recent studies indicate that lipid accumulation occurs under nutritional stress. Aim of this research was to determine how changes in nitrogen availability affect productivity, oil yield, and fatty acid (FA) composition of P. tricornutum UTEX 640. After preliminary laboratory trials, outdoor experiments were carried out in 40‐L GWP® reactors under different nitrogen regimes in batch. Nitrogen replete cultures achieved the highest productivity of biomass (about 18 g m−2 d−1) and EPA (about 0.35 g m−2 d−1), whereas nitrogen‐starved cultures achieved the highest FA productivity (about 2.6 g m−2 d−1). The annual potential yield of P. tricornutum grown outdoors in GWP® reactors is 730 kg of EPA per hectare under nutrient‐replete conditions and 5,800 kg of FA per hectare under nitrogen starvation. Biotechnol. Bioeng. 2017;114: 2204–2210.

Thermal mud maturation: organic matter and biological activity

Many of the therapeutic and cosmetic treatments offered in spas are centred on mud therapy, to moisturize the skin and prevent skin ageing and rheumatic diseases. Thermal mud is a complex matrix composed of organic and inorganic elements which contribute to its functions. It is a natural product derived from the long mixing of clay and thermal water. During its maturation, organic substances are provided by the microalgae, which develop characteristic of the composition of thermal water.

Safety evaluations and lipid-lowering activity of an Arthrospira platensis enriched diet: A 1-month study in rats

Arthrospira platensis (A. platensis) is worldwide consumed as dietary supplement, but its use in the form of whole biomass for food purposes may raise toxicity concerns. The aim of this study was to preliminarily evaluate the safety of an A. platensis F&M-C256-enriched diet (20% (weight/weight) corresponding to 12g/kg body weight/day), administered to rats for 1month. A. platensis F&M-C256-enriched diet was well tolerated: behavior, body weight, food consumption and growth curves were not affected; no discomfort, no deaths and no physical signs related to the treatment were observed during the administration period; food daily consumption and apparent digestibility were comparable to those of the standard laboratory AIN-76 control diet. Daily water consumption and urine excretion were, on the contrary, significantly higher (27.18±1.24 vs 21.53±1.68ml and 12.63±0.99 vs 7.00±1.29ml respectively), probably because of a slight increase in sodium intake in rats fed A. platensis F&M-C256-enriched diet. Biochemical markers of kidney and liver function were not varied but a significant increase in cholesterol-HDL and a decreased plasma triglycerides level was observed in rats fed A. platensis F&M-C256-enriched diet. These last changes were associated with an increased fecal lipids excretion and liver PPAR-α gene expression. These results indicate that A. platensis F&M-C256 is likely safe and well tolerated even at a high dosage in rodents and suggest that it may represent a promising functional food for preventing or even for managing dyslipidemias.