Pilot-scale outdoor photobioreactor culture of the marine dinoflagellate Karlodinium veneficum: Production of a karlotoxins-rich extract

Assessment of the marine microalga Chrysochromulina rotalis as bioactive feedstock cultured in an easy-to-deploy light-emitting-diode-based tubular photobioreactor

Marine microalgae have potential to be low-cost raw materials. This depends on the exploitation of different biomass fractions for high-value products, including unique compounds. Chrysochromulina rotalis, an under-explored haptophyte with promising properties, was the focus of this study. For the first time, C. rotalis was successfully cultivated in an 80 L tubular photobioreactor, illuminated by an easy-to-use light-emitting-diode-based system. C. rotalis grew without certain trace elements and showed adaptability to different phosphorus sources, allowing a significant reduction in the N:P ratio without compromising biomass yield and productivity. The design features of the photobioreactor provided a protective environment that ensured consistent biomass production from this shear-sensitive microalgae. Carotenoid analysis showed fucoxanthin and its derivatives as major components, with essential fatty acids making up a significant proportion of the total. The study emphasizes the tubular photobioreactor's role in sustainable biomass production for biorefineries, with C. rotalis as a valuable bioactive feedstock.

Life-cycle assessment of a microalgae-based fungicide under a biorefinery approach

The aim of this work was to perform a life-cycle analysis of the production process of a fungicide based on amphidinols. Two scenarios were evaluated: (1) biorefinery process -biofungicide, fatty acids and carotenoids were considered as co-products-, and (2) biofungicide as only product. Inventory data were taken and scaled-up from previous work on pilot-scale reactors, as well as lab-scale downstream equipment. A yearly production of 22,000 L of fungicide, was selected as the production objective. Despite, photosynthetic biomass is a sink of anthropogenic CO2, harvesting and downstream processing have large carbon footprints that exceed the biomass fixed carbon. Producing the biofungicide resulted in 34.61 and 271.33 ton of CO2e (15 years) for the Scenarios 1 and 2, respectively. Different commercial agricultural fungicides were compared with the microalgal fungicide. A lower impact of the microalgal product for most of the indicators, including carbon footprint, was shown.

Treatment of secondary urban wastewater with a low ammonium-tolerant marine microalga using zeolite-based adsorption

The low tolerance of marine microalgae to ammonium and hyposalinity limits their use in urban wastewater (UWW) treatments. In this study, using the marine microalga Amphidinium carterae, it is demonstrated for the first time that this obstacle can be overcome by introducing a zeolite-based adsorption step to obtain a tolerable UWW stream. The maximum ammonium adsorption capacities measured in the natural zeolite used are among the highest reported. The microalga grows satisfactorily in mixtures of zeolite-treated UWW and seawater at a wide range of proportions, both with and without adjusting the salinity, as long as the ammonium concentration is below the threshold tolerated by the microalgae (6.3 mg L^-1). A proof of concept performed in 10-L bubble column photobioreactors with different culture strategies, including medium recycling, showed an enhanced biomass yield relative to a control with no UWW. No noticeable effect was observed on the production of specialty metabolites.

Pathogens and predators impacting commercial production of microalgae and cyanobacteria

Production of phytoplankton (microalgae and cyanobacteria) in commercial raceway ponds and other systems is adversely impacted by phytoplankton pathogens, including bacteria, fungi and viruses. In addition, cultures are susceptible to productivity loss, or crash, through grazing by contaminating zooplankton such as protozoa, rotifers and copepods. Productivity loss and product contamination are also caused by otherwise innocuous invading phytoplankton that consume resources in competition with the species being cultured. This review is focused on phytoplankton competitors, pathogens and grazers of significance in commercial culture of microalgae and cyanobacteria. Detection and identification of these biological contaminants are discussed. Operational protocols for minimizing contamination, and methods of managing it, are discussed.

Karlodinium veneficum: Growth optimization, metabolite characterization and biotechnological potential survey

AIM OF THIS STUDY

The major aim of this work was to consistently optimize the production of biomass of the dinoflagellate Karlodinium veneficum and evaluate its extracts biotechnological potential application towards food, nutraceutical or/and pharmaceutical industries.

METHODS AND RESULTS

A successful approach of biomass production of K. veneficum CCMP 2936 was optimized along with the chemical characterization of its metabolite profile. Several temperatures (12, 16, 20, 25, 30°C), L1 nutrient concentrations (0.5×, 2×, 2.5×, 3×) and NaCl concentrations (20, 25, 30, 40 g L^-1 ) were tested. The growth rate was maximum at 16°C, 2× nutrient concentration and 40 g L^-1 of NaCl; hence, these conditions were chosen for bulk production of biomass. Methanolic extracts were prepared, and pigments, lipids and phenolic compounds were assessed; complemented by antioxidant and anti-inflammatory capacities, and cytotoxicity. Fucoxanthin and derivatives accounted for 0.06% of dry weight, and up to 60% (w/w) of all quantified metabolites were lipids. Said extracts displayed high antioxidant capacity, as towards assessed via the NO^•- and ABTS^•+ assays (IC₅₀  = 109.09 ± 6.73 and 266.46 ± 2.25 µg_E  ml^-1 , respectively), unlike observed via the O₂ ^•- assay (IC₂₅ reaching 56.06 ± 5.56 µg_E  ml^-1 ). No signs of cytotoxicity were observed.

CONCLUSIONS

Karlodinium veneficum biomass production was consistently optimized in terms of temperature, L1 nutrient concentrations and NaCl concentration. In addition, this strain appears promising for eventual biotechnological exploitation.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work provides fundamental insights about the growth and potential of value-added compounds of dinoflagellate K. veneficum. Dinoflagellates, as K. veneficum are poorly studied regarding its biomass production and added-value compounds for potential biotechnological exploitation. These organisms are difficult to maintain and grow in the laboratory. Thus, any fundamental contribution is relevant to share with the scientific community.

An integrated approach for the efficient separation of specialty compounds from biomass of the marine microalgae Amphidinium carterae

An amphidinol-prioritized fractioning approach was for the first time developed to isolate multiple specialty metabolites such as amphidinols, carotenoids and fatty acids using the biomass of the marine microalgae Amphidinium carterae. The biomass was produced in a raceway photobioreactor and the exhausted culture media were reused, thus fulfilling sustainability criteria employing a circular economy concept. The integrated bioactive compounds-targeted approach presented here consisted of four steps with which recovery percentages of carotenoids, fatty acids and amphidinols of 97%, 82% and 99 %, respectively, were achieved. The proposed process was proved to be a better extraction system for this microalga than another based on a sequential gradient partition with water and four water-immiscible organic solvents (hexane, carbon tetrachloride, dichloromethane and n-butanol). The proposed process could be scaled-up as a commercial solid-phase extraction technology well-established for industrial bioprocesses.

Characterization of bubble column photobioreactors for shear-sensitive microalgae culture

The shear-sensitive marine algal dinoflagellate Karlodinium veneficum was grown in a cylindrical bubble column photobioreactor with an internal diameter of 0.044 m. Initial liquid height varied from 0.5 to 1.75 m, superficial gas velocities from 0.0014 to 0.0057 ms^-1, and nozzle diameter from 1 to 2.5 mm. Computational fluid dynamics was used to characterize the flow hydrodynamics and energy dissipation rates. Experimental gas holdup and volumetric mass transfer coefficient strongly depended on the liquid height and correlated well with the Froude number. Energy dissipation near the head space (ED_top) was one order of magnitude higher than the average energy dissipation in the whole reactor (ED_whole), and the value in the sparger zone (ED_spar) was one order of magnitude higher than ED_top. Cultures of K. veneficum were limited by CO₂ transfer at low ED_whole and severely stressed above a critical value of ED_whole.

Long-term culture of the marine dinoflagellate microalga Amphidinium carterae in an indoor LED-lighted raceway photobioreactor: Production of carotenoids and fatty acids

The feasibility of the long-term (>170 days) culture of a dinoflagellate microalga in a raceway photobioreactor is demonstrated for the first time. Amphidinium carterae was chosen for this study as it is producer of interesting high-value compounds. Repeated semicontinuous culture provided to be a robust operational mode. Different concentration levels of the f/2 medium nutrients (i.e. f/2×1-3) were assayed. The composition f/2×3 (N:P = 5), combined with a sinusoidal irradiance pattern (L/D = 24:0) with a 570 µE m^-2 s^-1 daily mean irradiance, maximized the biomass productivity (2.5 g m^-2 day^-1) and production rate of the valuable carotenoid peridinin (19.4 ± 1.35 mg m^-2 L^-1 with nearly 1% of the biomass d.w.). Several carotenoids and polyunsaturated fatty acids were also present in significant percentages in the harvested biomass (EPA, 1.69 ± 0.31% d.w.; DHA, 3.47 ± 0.24% d.w.), which had an average P-molar formulate of C_40.7O_21.2H_73.9N_3.9S_0.3P₁.