Sphagnum founder material used for the restoration of rewetted bogs and installation of Sphagnum paludiculture areas can be provided by submerged cultivation in photobioreactors (PBRs). This study represents the first investigation of the photoautotrophic cultivation of Sphagnum palustre L. in different PBRs at laboratory scale. One commercially available reactor - a 60 L flat-panel bioreactor - along with three self-developed PBRs - a 3 L wave-bag bioreactor, a 10 L bottle bioreactor and a 50 L tank bioreactor - were used. Using an inorganic Sphagnum medium, artificial light, and CO2 enriched air, the moss morphology, biomass productivity, specific power input and specific light availability were determined. The results suggest that the wave-bag bioreactor is not suitable for Sphagnum cultivation, while for the bubble columns, a minimum superficial gas velocity ug and specific power input (PG/VL), as well as specific light intensity (Ispec), are decisive process parameters. Submerse, photoautotrophic production of Sphagnum palustre L. in a bubble column PBR is highly feasible (0.14 +/- 0.03 g L- 1 d-1), and this reactor type shows potential for Sphagnum founder material production for peatland rewetting due to its simplicity and low pneumatic power input (9.9 W m- 3).

This study examines the dual benefits of microalgae cultivation for wastewater treatment and the enhancement of polylactic acid‐based biocomposites. Using Desmodesmus sp. in a photobioreactor, both batch and continuous operations achieve total nitrogen (TN) and total phosphorus (TP) removal rates of up to 99.9%, maintaining TN and TP levels below 0.02 mg L⁻¹ in the effluent, aligning with European discharge standards. Continuous cultivation increases biomass productivity from 0.102 to 0.43 g L⁻¹ day⁻¹, a 322% improvement over batch operations. Nutrient starvation followed by reintroduction to nutrient‐rich wastewater induces hyper‐compensation luxury uptake, with P‐enriched cells accumulating 1.33% intracellular P within six hours — 21% higher than natural accumulation. The results reveal that luxury phosphorus uptake in microalgae follows a triphasic system of uptake and storage, challenging the previously suggested biphasic model. When incorporated into Poly lactic acid (PLA), the biomass enhances versatility, offering potential replacement of inorganic P in industrial applications, particularly flame retardants. Pyrolysis and cone calorimetry confirm the thermal and fire‐retardant benefits, with a 20% reduction in peak heat release rate and increased char yield. This work highlights microalgae's role in sustainable biocomposites, supporting wastewater treatment, nutrient recovery, and CO₂ sequestration.

This study aimed to investigate the operation of a 1000L microalgae-based membrane photobioreactor system in a greenhouse for continuous secondary wastewater treatment using Desmodesmus sp., a green microalgae strain originally isolated from a German sewage plant. The research spanned both summer and winter seasons, seeking to comprehend key trends and optimization strategies. Maintaining low cell concentrations in the photobioreactor during periods of light inhibition proved advantageous for nutrient uptake rates. Effective strategies for enhancing algae-based wastewater treatment included cell mass recycling, particularly during periods of high light availability. In comparison to conventional continuous cultivation methods, employing cell recycling and high dilution rates during times of abundant light, alongside using low cell concentrations and dilution rates during light inhibition, resulted in an 80 % and 10 % increase in overall biomass productivity during summer and winter, respectively. Furthermore, nitrogen/phosphorus (N/P) removal rates exhibited a 23 % improvement during winter, while remaining unchanged in summer.

Conventional wastewater treatment (WWT) is not able to recycle nutrients from the wastewater (WW) directly. Microalgae integrate the valuable nutrients nitrogen and phosphorus within their biomass very efficiently, making them predestined for an application in WWT. Nevertheless, microalgae-based processes are driven by natural sunlight as energy source, making a continuous process mode during day and night difficult. The aim of this study was therefore to investigate metabolic activities of the continuously cultivated microalgae Chlorella vulgaris at light and dark periods (16 h,8 h) with focus on nutrient uptake during night from a synthetic WW. Varying the dilution rate D (D = 0.0-1.0 d-1 in 0.1 d-1-steps) causes different limitations for algae growth. Nutrient limitations at low D's cause maximum accumulation of intracellular storage components (sum of carbohydrates and lipids) of ~70 % of dry biomass, starch is converted to lipids at the absence of light. From middle to high D's, the growth rate is determined by light limitation, reducing the intracellular storage components to ~20 % of dry biomass. Complete nutrient uptake is measurable up to D = 0.5 d-1, marking the maximum operating point for wastewater purification. At that point, cells are characterised by high protein (up to 57%DBM) and pigment (up to 6.9%DBM) quotas. During the night, the build-up of proteins at the degradation of intracellular storage components is furthermore visible. Applying the concept of active biomass (cells without storage components), a constant cellular protein (~68%ABM) and nitrogen quota (11.94%ABM) was revealed. A nitrogen spiking experiment clearly showed nitrogen uptake and proliferation during the night period. Based on the experimental data, a window of operation for a continuous WWT process was designed, allowing the hypothesis that continuous WWT using microalgae during day and night operation is possible without the supplementation of artificial light. This revealed the system's capacity to treat WW throughout 24 h applying cell recycling and storage of carbohydrate-rich biomass. At the end of the night, protein-rich biomass is available for further valorisation.

Novel cell-disruption combinations (autolytic incubation and hypotonic osmotic shock combined with HPH or pH12) were used to investigate the fundamental mass transfer of lipids and proteins from Nannochloropsis slurries (140 mg biomass/g slurry). Since neutral lipids exist as cytosolic globules, their mass transfer was directly dependent on disintegration of cell walls. Complete recovery was obtained with complete physical disruption. HPH combinations exerted more physical disruption and led to higher yields than pH12. In contrast, proteins exist as both cytosolic water-soluble fractions and cell-wall/membrane structural fractions and have a complex extraction behaviour. Mass transfer of cytosolic proteins was dependent on cell-wall disintegration, while that of structural proteins was governed by cell-wall disintegration and severance of protein linkage from the wall/membrane. HPH combinations exerted only physical disruption and were limited to releasing soluble proteins. pH12 combinations hydrolysed chemical linkages in addition to exerting physical disruption, releasing both soluble and structural proteins.

Microalgae were employed to remove nutrients from a pre-treated wastewater (so-called anaerobic membrane bioreactor effluent, AnMBR effluent) over a 24-day semi-continuous cultivation with varied N:P ratios. NH4+-N reduction percentage ranged from 68 to 94% with average removal rates varying from 8 to 26 mgN.L(-1)d(-1) at different stages. Total phosphorus was almost completely removed shortly after inoculation. Biomass productivity ranged from 0.13 to 0.19 g.L(-1)d(-1) during the cultivation. A submerged membrane-based filtration device was used to investigate the formation of biofouling, which occurred on the membrane surface during filtration and is considered as a bottleneck in downstream processing. Results indicated most severe fouling was caused by original microalgal suspension, compared to its individual fractions (cellular resuspensions, supernatant and AnMBR effluent). Irreversible fouling mainly occurred at the beginning of the filtration process; extracellular organic matter and cellular debris in the supernatant changed the fouling behavior more significantly than morphological properties of the algae cells; AnMBR effluent also led to a nonnegligible fouling effect. To minimize biofouling, TOC content in wastewater should be carefully controlled before and during cultivation. The current membrane can be proposed for long-term filtration, as irreversible fouling only occurred at the beginning and reversible fouling can be controlled effectively by backflushing and aeration. The biomass, characterized by relatively high protein and carbohydrate but low heavy metal content, indicated its potential as feeds and feedstock for bioenergy production. The present work provides novel insights into the coupling of wastewater treatment and fouling control, which has been rarely studied.

The moss Physcomitrella is an interesting production host for recombinant biopharmaceuticals. Here we produced MFHR1, a synthetic complement regulator which has been proposed for the treatment of diseases associated to the complement system as part of human innate immunity. We studied the impact of different operation modes for the production process in 5 L stirred-tank photobioreactors. The total amount of recombinant protein was doubled by using fed-batch or batch compared to semi-continuous operation, although the maximum specific productivity (mg MFHR1/g FW) increased just by 35%. We proposed an unstructured kinetic model which fits accurately with the experimental data in batch and semi-continuous operation under autotrophic conditions with 2% CO2 enrichment. The model is able to predict recombinant protein production, nitrate uptake and biomass growth, which is useful for process control and optimization. We investigated strategies to further increase MFHR1 production. While mixotrophic and heterotrophic conditions decreased the MFHR1-specific productivity compared to autotrophic conditions, addition of the phytohormone auxin (NAA, 10 µM) to the medium enhanced it by 470% in shaken flasks and up to 230% and 260%, in batch and fed-batch bioreactors, respectively. Supporting this finding, the auxin-synthesis inhibitor L-kynurenine (100 µM) decreased MFHR1 production significantly by 110% and 580% at day 7 and 18, respectively. Expression analysis revealed that the MFHR1 transgene, driven by the Physcomitrella actin5 (PpAct5) promoter, was upregulated 16 h after NAA addition and remained enhanced over the whole process, whereas the auxin-responsive gene PpIAA1A was upregulated within the first 2 hours, indicating that the effect of auxin on PpAct5 promoter-driven expression is indirect. Furthermore, the day of NAA supplementation was crucial, leading to an up to 8-fold increase of MFHR1-specific productivity (0.82 mg MFHR1/g fresh weight, 150 mg accumulated over 7 days) compared to the productivity reported previously. Our findings are likely to be applicable to other plant-based expression systems to increase biopharmaceutical production and yields.

The design and optimization of photobioreactor(s) (PBR) benefit from the development of robust and quantitatively accurate computational fluid dynamics (CFD) models, which incorporate the complex interplay of fundamental phenomena. In the present work, we propose a comprehensive computational model for tubular photobioreactors equipped with glass sponges. The simulation model requires a minimum of at least three submodels for hydrodynamics, light supply, and biomass kinetics, respectively. First, by modeling the hydrodynamics, the light–dark cycles can be detected and the mixing characteristics of the flow (besides the mass transport) can be analyzed. Second, the radiative transport model is deployed to predict the local light intensities according to the wavelength of the light and scattering characteristics of the culture. The third submodel implements the biomass growth kinetic by coupling the local light intensities to hydrodynamic information of the CO2 concentration, which allows to predict the algal growth. In combination, the novel mesoscopic simulation model is applied to a tubular PBR with transparent walls and an internal sponge structure. We showcase the coupled simulation results and validate specific submodel outcomes by comparing the experiments. The overall flow velocity, light distribution, and light intensities for individual algae trajectories are extracted and discussed. Conclusively, such insights into complex hydrodynamics and homogeneous illumination are very promising for CFD-based optimization of PBR.

With its roots in kinetic theory, the lattice Boltzmann method (LBM) cannot only be used to solve complex fluid flows but also radiative transport in volume. The present work derives a novel Fresnel boundary scheme for radiative transport LBM, based on Fresnel's equation, which depicts the partly reflected radiation on surfaces. Driven from a boundary modeling and discussion on the microscopic level, incorporating Fresnel's equation, it is developed a boundary model for the mesoscopic radiative transport LBM. At an intermediate step, the Fresnel's equation is related to well known partial differential (Robin) equations, based on a bottom-up approach where the P1-Approximation is deployed. To connect the novel boundary scheme to the so derived target equation, a Chapman-Enskog expansion is examined in addition. Both techniques together, point out how to interpret microscopic modeling by the means of macroscopic expressions and as a consequence how, to chose simulation parameters according to the specific boundary. The numerical tests suggest that the proposed boundary is first order convergent. The paper closes with a showcase, where the novel boundary method for radiative transport LBM is applied to a setup with multiple LED spots.

Peat moss ( Sphagnum ) biomass is a promising bioresource to substitute peat in growing media with a renewable material. For sustainable production on a large scale, the productivity of Sphagnum mosses has to be increased by optimizing culture conditions. Optimization was achieved using fractional factorial design and response surface methodology based on central composite design to determine concentrations of eight factors leading to highest biomass yield. We improved a standard Sphagnum medium by reducing the concentrations of NH 4 NO 3 , KH 2 PO 4 , KCl, MgSO 4 , Ca(NO 3 ) 2 , FeSO 4 and a microelement solution up to 50 %. Together with a reduced sucrose concentration for Sphagnum fuscum , while it remained unchanged for Sphagnum palustre and Sphagnum squarrosum , moss productivities were enhanced for all tested species in shake flasks. Further upscaling to 5 L photobioreactors increased the biomass yield up to nearly 50-fold for S. fuscum , 40-fold for S. palustre and 25-fold for S. squarrosum in 24 days.

This study reports the use of hypotonic osmotic shock as a treatment step to enhance the recoveries of biofuel-convertible lipids and proteins from lipid-rich saltwater Nannochloropsis gaditana (N. gaditana) slurries (biomass content = similar to 140 mg biomass / g slurry, total lipid content = similar to 600 mg lipid /g biomass). The osmotic shock was induced through repeated washing of microalgal slurries with multiple batches of fresh water. Subjecting the slurries to 2 stages of freshwater washing resulted in a measurable damage to cell membranes (the uptake of membrane permeability marker increased by 6 folds), a partial loss of cell viability (only 64% of available cells were recoverable), and a minor release of free protein (similar to 2 wt% of available protein) from the biomass into the interstitial space of the slurries. Hypotonic osmotic shock was revealed to be ineffective in rupturing N. gaditana slurries (only 13 +/- 9% of available cells were ruptured after 2-stage washing) and, as such, had a limited prospect as a stand-alone cell disruption technology for the saltwater strain. The washing treatment, however, was found to be able to weaken the structural integrity of N. gaditana slurries and enhance the performance of subsequent mechanical or chemical cell disruption technologies when installed as a preparatory step. Applying the washing treatment prior to high-pressure homogenisation (HPH) and low solvent-to-biomass ratio hexane extraction (hexane : slurry = 1:1 w/w) for the recovery of biofuel-convertible lipids increased the extent of cell rupture from 28 +/- 8 to 46 +/- 19% of available cells and more than doubled neutral lipid yield from 25.1 +/- 2.0 to 64.6 +/- 4.9 wt% of available neutral lipid. Initial analysis revealed that the washing treatment had a minimal energy cost (similar to 6% of the total energy expenditure of downstream processing) and that its integration into HPH + hexane lipid recovery led to a 2.5 fold increase in the energy output of the biomass. Partnering the washing treatment with NaOH hydrolysis increased protein yield from 6.7 +/- 2.4 to 31.9 +/- 10.7 wt% of available protein.

Abstract The present work characterizes a submerged aerated hollow fiber polyvinylidene fluorid (PVDF) membrane (0.03 μm) device (Harvester) designed for the ultrafiltration (UF) of microalgae suspensions. Commercial baker's yeast served as model suspension to investigate the influence of the aeration rate of the hollow fibers on the critical flux (CF, Jc) for different cell concentrations. An optimal aeration rate of 1.25 vvm was determined. Moreover, the CF was evaluated using two different Chlorella cultures (axenic and non‐axenic) of various biomass densities (0.8–17.5 g DW/L). Comparably high CFs of 15.57 and 10.08 L/m/2/h were measured for microalgae concentrations of 4.8 and 10.0 g DW/L, respectively, applying very strict CF criteria. Furthermore, the Jc‐values correlated (negative) linearly with the biomass concentration (0.8–10.0 g DW/L). Concentration factors between 2.8 and 12.4 and volumetric reduction factors varying from 3.5 to 11.5 could be achieved in short‐term filtration, whereat a stable filtration handling biomass concentrations up to 40.0 g DW/L was feasible. Measures for fouling control (aeration of membrane fibers, periodic backflushing) have thus been proven to be successful. Estimations on energy consumption revealed very low energy demand of 17.97 kJ/m3 treated microalgae feed suspension (4.99 × 10−3 kWh/m3) and 37.83 kJ/kg treated biomass (1.05 × 10−2 kWh/kg), respectively, for an up‐concentration from 2 to 40 g DW/L of a microalgae suspension.

This chapter describes the process of designing photobioreactors (PBR). The most important thing is the mindset that a PBR transforms the given environmental conditions into favorable ones for the microalgae inside the reactor with respect to light, dissolved gases, nutrients and temperature. The tools for calculating this transformation are briefly outlined. The conditions for the microalgae are described in terms of kinetics in the first part of the chapter. Kinetics considers the relation between concentrations and turnover rates, giving the total amounts of the different energy and mass fluxes to supply the cells. In the central part of this treatise, a range of current solutions for PBR design are described and discussed. This includes numbers for regularly achieved productivities but also various pros and cons. Actually, there are still a lot of disadvantages that need to be stated. Innovative approaches to cope with these challenges are outlined. This supports the expectation that sustainable and economically viable microalgae production using closed PBRs will be possible in the near future.

A near-zero waste treatment system for food processing wastewater was developed and studied. The wastewater was treated using an anaerobic membrane bioreactor (AnMBR), polished using an outdoor photobioreactor for microalgae cultivation (three species were studied), and excess sludge was treated using hydrothermal carbonization. The study was conducted under arid climate conditions for one year (four seasons). The AnMBR reduced the total organic carbon by 97%, which was mostly recovered as methane (~57%) and hydrochar (~4%). Microalgal biomass productivity in the AnMBR effluent ranged from 0.25 to 0.8 g·L-1·day-1. Nitrogen (N) and phosphorous (P) uptake varied seasonally, from 18 to 45 mg·L-1·day-1 and up to 5 mg·L-1·day-1, respectively. N and P mass balance analysis demonstrated that the process was highly efficient in the recovery of nitrogen (~77%), and phosphorus (~91%). The performance of the microalgal culture changed among seasons because of climatic variation, as a result of variation in the wastewater chemistry, and possibly due to differences among the microalgal species. Effluent standards for irrigation use were met throughout the year and were achieved within two days in summer and 4.5 days in winter. Overall, the study demonstrated a near-zero waste discharge system capable of producing high-quality effluent, achieving nutrient and carbon recovery into microalgae biomass, and energy production as biogas and hydrochar.

Chemie Ingenieur TechnikVolume 92, Issue 9 p. 1199-1199 Poster Development of a photobioreactor for large-scale mass production of peat moss Sphagnum palustre I. Melková, Corresponding Author I. Melková ingrida.melkova@kit.edu Karlsruhe Institute of Technology, Institute of Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanyCorrespondence: I. Melková (ingrida.melkova@kit.edu), Karlsruhe Institute of Technology, Institute of Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this authorC. Steinweg, C. Steinweg Karlsruhe Institute of Technology, Institute of Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this authorC. Posten, C. Posten Karlsruhe Institute of Technology, Institute of Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this author I. Melková, Corresponding Author I. Melková ingrida.melkova@kit.edu Karlsruhe Institute of Technology, Institute of Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanyCorrespondence: I. Melková (ingrida.melkova@kit.edu), Karlsruhe Institute of Technology, Institute of Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this authorC. Steinweg, C. Steinweg Karlsruhe Institute of Technology, Institute of Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this authorC. Posten, C. Posten Karlsruhe Institute of Technology, Institute of Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this author First published: 28 August 2020 https://doi.org/10.1002/cite.202055329AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume92, Issue9Special Issue: 10. ProcessNet-Jahrestagung und 34. DECHEMA-Jahrestagung der Biotechnologen 2020: Processes for FutureSeptember 2020Pages 1199-1199 RelatedInformation

Chemie Ingenieur TechnikVolume 92, Issue 9 p. 1371-1371 Poster Membrane-harvesting for optimized wastewater treatment using microalgae F. Ortiz Tena, Corresponding Author F. Ortiz Tena franziska.schwertner@kit.edu Karlsruhe Institute for Technology, Institute of Process Engineering in Life Sciences – Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanyCorrespondence: F. Ortiz Tena (franziska.schwertner@kit.edu), Karlsruhe Institute for Technology, Institute of Process Engineering in Life Sciences – Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this authorC. Steinweg, C. Steinweg Karlsruhe Institute for Technology, Institute of Process Engineering in Life Sciences – Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this authorC. Posten, C. Posten Karlsruhe Institute for Technology, Institute of Process Engineering in Life Sciences – Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this author F. Ortiz Tena, Corresponding Author F. Ortiz Tena franziska.schwertner@kit.edu Karlsruhe Institute for Technology, Institute of Process Engineering in Life Sciences – Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanyCorrespondence: F. Ortiz Tena (franziska.schwertner@kit.edu), Karlsruhe Institute for Technology, Institute of Process Engineering in Life Sciences – Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this authorC. Steinweg, C. Steinweg Karlsruhe Institute for Technology, Institute of Process Engineering in Life Sciences – Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this authorC. Posten, C. Posten Karlsruhe Institute for Technology, Institute of Process Engineering in Life Sciences – Bioprocess Engineering, Fritz-Haber-Weg 2, 76131 Karlsruhe, GermanySearch for more papers by this author First published: 28 August 2020 https://doi.org/10.1002/cite.202055487AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume92, Issue9Special Issue: 10. ProcessNet-Jahrestagung und 34. DECHEMA-Jahrestagung der Biotechnologen 2020: Processes for FutureSeptember 2020Pages 1371-1371 RelatedInformation

Grass pea (Lathyrus sativus L.) is commonly consumed in cooked, fermented, and roasted forms in Ethiopia. However, the impacts of household processing practices on its nutrients, antinutrients, and toxic compounds have not been adequately studied. Therefore, the effects of household processing and fermentation in the presence and absence of a phytase on the contents of β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP), myo-inositol phosphates, crude protein, minerals and the in vitro bioaccessibility were investigated. Fermentation exhibited a significant decline in β-ODAP (13.0–62.0%) and phytate (7.3–90.5%) irrespective of the presence of phytase. Pressure and pan cooking after discarding the soaking water resulted in a 27.0 and 16.2% reduction in β-ODAP. A 30% reduction in phytate was observed during germination followed by roasting. In addition, germination resulted in a significant (p < 0.05) increase in crude protein. Germination and germination followed by roasting resulted in the highest Fe bioaccessibilities (more than 25 fold higher compared to untreated samples) followed by pressure cooking and soaking. Processing also improved Zn bioaccessibilities by 50.0% (soaked seed without soaking water), 22.5% (soaked seed with soaking water), and 4.3% (germination). Thus, the processing technologies applied were capable of reducing the content of phytate (InsP6) and β-ODAP with a concomitant increase in mineral bioaccessibilities. Processing of grass peas could therefore contribute to their more widespread utilization.

Phaeodactylum tricornutum (P. triconutum) gained high interest for use in human nutrition. We aimed to investigate the effect of photoautotrophically cultivated Phaeodactylum tricornutum on genotoxicity, cytotoxicity, formation of reactive oxygen species and apoptosis in Caco-2 and HT-29 cells. Furthermore, the effect of processing (sonication, ball-milling) on these parameters was assessed.P. triconutum dose-dependently induced DNA strand breaks (2 µg dry matter/mL – 200 µg dry matter/mL) in both cell lines. These breaks can mostly be repaired after a recovery time of 2 h. Using processing methods did not affect the genotoxicity. We found that a lipophilic fraction, but not fucoxanthin, might be responsible for the DNA damage. Neither the P. triconutum preparations nor fucoxanthin affected cell proliferation or revealed an apoptotic or necrotic activity.In conclusion, P. triconutum showed a genotoxic potential in intestinal cells, mainly mediated by lipophilic constituents. Sonication and ball-milling might be considered as safe methods for processing of P. triconutum.

BACKGROUND:Microalgae species for industrialization are largely selected because of their high lipid and biomass productivity. Both marine and freshwater species exhibit variations in biochemical compositions (i.e. lipid, carbohydrate and protein accumulation in biomass) when cultivated under varyi ng environmental conditions. There is very little research available on the physiological responses of N. limnetica SAG 18.99 in terms of growth rates, biomass and lipid productivity when cultivated under variant nitrogen concentrations. OBJECTIVES:The objective of this research was to observe the physiological responses of Nannochloropsis limnetica (N. limnetica SAG 18.99) in terms of growth rates, biomass and neutral intracellular lipid when cultivated under variant nitrate concentrations. The null hypothesis was there is no significant difference in growth rate, biomass and neutral intracellular lipid productivity of N. limnetica SAG 18.99 cultivated under variant nitrate concentrations. METHODS:N. limnetica SAG 18.99 was cultivated under “normal nitrate” (3.53 M), “nitrate replete” (7.06 M), “moderate nitrate deplete” (1.765 M), and “high nitrate deplete” (0.8825 M) under the same conditions of light, pH, temperature and CO2 concentration over the duration of 14 days. The parameters measured during the cultivation were optical density to measure growth rates, flow-cytometry to measure cell concentrations/density, gravimetrical measurements for bio dry mass/biomass (BDM), ion chromatography measurements for ions/macronutrients, pH as well as sterility tests. All statistical analyses were performed using the SPSS software package (IBM statistics Version 23) and differences in data were considered significant at p < 0.05. RESULTS:Growth rates were statistically significant (p = 0.001). Therefore, the null hypothesis was rejected. Bio dry mass was not significant (p = 0.939). Therefore, the null hypothesis was accepted. Relative fluorescence data recorded for all of the four flasks was not significant (p = 0.112). Therefore, the null hypothesis was accepted. pH was not statistically significant (p > 0.05), which means it remained constant and, therefore, had no influence on the cultivation process. CONCLUSIONS:Biomass production exponentially increased in each of the four flasks throughout the cultivation. Relative fluorescence data recorded for all of the four flasks was the highest on the first couple of days during the lag phase and decelerated towards the end of the cultivation period. It was discovered that the success of the Nile red method in assessment of lipids is species dependent. Therefore, other gravimetric and chromatography methods (i.e. gas liquid chromatography, flow cytometry, low field nuclear magnetic resonance) must be employed together with or independent of it. Furthermore, the study recommends future researchers to look into the physiological responses of N. limnetica SAG 18.99 when cultivated under other macronutrient concentrations (i.e. phosphate) and variant environmental parameters (i.e. variations in light intensity, CO2).