Illumination Cycle Research Articles

Photoswitchable CENP-E Inhibitor Enabling the Dynamic Control of Chromosome Movement and Mitotic Progression.

Interfering with mitosis is a potential cancer therapy strategy. However, the lack of controllability of antimitotic drugs in cell growth suppression causes severe side effects and limits their clinical utility. Herein, we developed an azobenzene-based photoswitchable inhibitor of CENP-E, a mitotic kinesin required for chromosome transportation. The new inhibitor enabled reversible photoswitching of CENP-E activity with ∼10-fold change in IC50 between cis and trans photoisomerization states both in vitro and in living cells. It also enabled repeatable photoswitching of CENP-E-dependent chromosome congression and hence mitotic progression with UV/vis light illumination cycles. Using this technique, we could specify the exact process of mitotic progression in which CENP-E plays an indispensable role. Our data demonstrate the power of a photochemical approach for highly controllable mitotic interference as well as for discovery of precise molecular functions in dynamic cellular processes.

Performance, Object, and Private Devotion: The Illumination of Thomas Butler’s Books of Hours

This article considers the major cycles of illumination in two Books of Hours belonging to Thomas Butler, seventh Earl of Ormond (c.1424–1515). The article concludes that the iconography of the two manuscripts reflects the personal and familial piety of the patron and was designed to act as a tool in the practice of devotion.

In-Situ Growth and Immobilization of CdS Nanoparticles onto Functionalized MoS2 : Preparation, Characterization and Fabrication of Photoelectrochemical Cells.

A facile strategy for the controllable growth of CdS nanoparticles at the periphery of MoS2 en route the preparation of electron donor-acceptor nanoensembles is developed. Precisely, the carboxylic group of α-lipoic acid, as addend of the modified MoS2 obtained upon 1,2-dithiolane functionalization, was employed as anchor site for the in situ preparation and immobilization of the CdS nanoparticles in an one-pot two-step process. The newly prepared MoS2 /CdS hybrid material was characterized by complementary spectroscopic, thermal and microscopy imaging means. Absorption spectroscopy was employed to register the formation of MoS2 /CdS, by observing a broad shoulder centered at 420 nm due to CdS nanoparticles, while the excitonic bands of MoS2 were also evident. Moreover, based on the efficient quenching of the characteristic fluorescence emission of CdS at 725 nm by the presence of MoS2 , strong electronic interactions at the excited state between the two species within the ensemble were identified. Photoelectrochemical assays of MoS2 /CdS thin-film electrodes revealed a prompt, steady and reproducible anodic photoresponse during repeated on-off cycles of illumination. A significant zero-current photopotential of -540 mV and an anodic photocurrent of 1 μA were observed, underlining improved charge-separation and electron transport from CdS to MoS2 . The superior performance of the charge-transfer processes in MoS2 /CdS is of direct interest for the fabrication of photoelectrochemical and optoelectronic devices.

Solar-assisted fabrication of dimpled 2H-MoS2 membrane for highly efficient water desalination

Solar-driven evaporation has been proposed as an efficient way to harvest solar energy for water treatment and desalination. However, the complex preparation process and the degradation of photothermal absorbers restrict their practical applications in solar thermal technology. Herein, a solar-assisted fabrication of three-dimensional dimpled MoS2 membrane (DMM-SA) with an open macroporous (1–2 μm) network is fabricated by folding and overlapping nanosheets under solar illumination. DMM-SA exhibits superior water permeability (334–461 LMH/bar) and extraordinary chemical and structural stability. Compared to the 1T and mixed-phase DMM-SA samples, 2H-DMM-SA floating on the water surface generates high heat localization and achieves high evaporation efficiencies of 83.8 ± 0.8% and 91.5 ± 1.1% at 1 and 3 sun illumination, respectively. After multiple illumination and regeneration cycles, 2H-DMM-SA presents high water evaporation and salt rejection performance. After desalination, the salinity level of permeate water is far below the World Health Organization (WHO) standard. Numerical simulations verify that the inner spaces between two nanosheets and the nanochannels contribute to the high bulk water and vapor fluxes during desalination. The facile and efficient design of 3D 2H-DMM-SA provides a novel avenue for seawater utilization by harvesting solar energy.

Broadband-absorbing WO3-x nanorod-decorated wood evaporator for highly efficient solar-driven interfacial steam generation

The design and synthesis of solar steam generation materials is a green and promising approach to produce freshwater from seawater or contaminated water. Here, we develop a highly efficient and stable bilayer evaporator by assembling WO3-x nanorods (WO3-x NRs) onto a wood surface. Due to the broad-band absorption of the WO3-x NRs and the multiscatter of the incident light caused by the wood, the prepared solar evaporator with unique light trapping structures shows a high solar absorption (~94.0%). Additionally, combining with the merits of rapid water transport and heat localization, the energy conversion efficiency of the evaporator reaches as high as 82.5% under one sun irradiation and shows a stable water generation capability during long-term illumination cycles, which is one of the best performance compared with other wood-based materials and oxygen-defected tungsten oxide. The evaporator also shows great performance towards the evaporation of seawater and contaminated water, indicating great potential application. This work can provide reference for designing other high photothermal conversion system.

Fabrication of multifunctional closed-surface SiO2-TiO2 antireflective thin films

Multifunctional thin films with superhydrophilicity, broadband antireflective performance, humidity resistance and outstanding mechanical robustness are essential as for their wide applications. However, so far, it remains a big challenge to take into consideration all these properties simultaneously due to the structural contradiction. Herein, we develop an effective dip-coating process to prepare hybrid thin films with mechanical robustness, high transmittance, super-durable moisture resistance, excellent photocatalytic activity and durable superhydrophilicity. Three different nanoparticles were deposited sequentially to construct the above thin film and the maximum transmittance of this particular thin film reached ∼96.0%. The film surface showed an excellent superhydrophilicity (water contact angle ≈3.0°), and antifogging property. The superhydrophilic thin film could keep its property for more than 20 days. The transformation from hydrophilicity to superhydrophilicity of the thin film could be readily realized by UV irradiation. Moreover, its self-cleaning property could be retained after reduplicative storage and UV illumination cycles. Sponge washing test, water drop impact, pencil hardness test and tape peeling test revealed that the thin film possessed outstanding mechanical robustness. Methylene blue photodegradation was chose to weigh the photocatalytic activity of the hybrid thin film. In addition, the thin film shows excellent humidity-resistance at high temperature, and the excellent performance is due to its closed-surface structure. The closed-surface multifunctional thin films pave way toward use in solar cells, high-rise architecture windows under severe climate conditions.

The Protective Effects of Blue Light-Blocking Films With Different Shielding Rates: A Rat Model Study.

PurposeTo examine light emitting diode (LED)-induced retinal photochemical damage and assess the protective performance of blue light-shielding films with different shielding rates in Sprague-Dawley rats (SD rats).MethodsSD rats were randomly divided into five groups: blank control (group I), white LED illumination (group II), and white LED illumination combined with shielding of blue light of wavelength 440 nm at 40%, 60%, and 80% (groups III, IV, and V). The illumination was 200 lux. All animals underwent electroretinography (ERG), hematoxylin-eosin (H&E) staining, immunohistochemical (IHC) staining, and transmission electron microscopy (TEM) observation after 14 days of dark-adaptation before illumination, after 14 days of cyclic illumination, and after 14 days of darkness for recovery following illumination.ResultsERG showed retinal functional loss after LED light exposure. However, retinal cell function was partly recovered after a further 2 weeks of dark adaptation. H&E staining and TEM revealed increases in photoreceptor cell death after illumination. IHC staining demonstrated that oxidative stress was associated with retinal injury. Although retinal light injury was discovered in the LED light-exposure groups, shielding 60% of blue light of wavelength 440 nm (bandwidth 20 nm) protected retinas.ConclusionsCyclic illumination of low light intensity (200 lux) for 14 days produced retinal degeneration; shielding 60% of blue light may protect retinas from light damage.Translational RelevanceThis study found the effective shielding rate that could protect retinas from light damage when shielding specific narrow-band harmful blue light; thus providing a more normative method for protecting eyes from blue light hazard.

A 30-frames/s, $252\times144$ SPAD Flash LiDAR With 1728 Dual-Clock 48.8-ps TDCs, and Pixel-Wise Integrated Histogramming

A 252 × 144 single-photon avalanche diode (SPAD) pixel sensor, called Ocelot, is reported for light detection and ranging (LiDAR). The sensor, fabricated in the 180-nm CMOS technology, features 1728 12-bit time-to-digital converters (TDCs) with 48.8-ps resolution (LSB). Each 126 pixels in a half-column are connected to six TDCs through a collision detection bus, which enables effective sharing of resources, and consequently a fill factor of 28% with a pixel pitch of 28.5 μm. The columnparallel TDCs, based on dual-clock architecture, exhibit a DNL of +0.48/-0.48 LSB and an INL of +0.89/-1.67 LSB; they are dynamically reallocated in a scalable daisy chain approach that enables a maximum of five photon detections per illumination cycle per half-column. The sensor can operate in timecorrelated single-photon counting (TCSPC) and single-photon counting (SPC) modes, while peak detection (PD) and partial histogramming (PH) are included in the operation of the sensor. The PD and PH modes are enabled by the first implementation of integrated histogramming for a full array via 3.32-Mb SRAMbased PH readout (PHR) scheme providing a 14.9-to-1 compression. Telemetry measurements up to 50 m achieve an accuracy of 8.8 cm and worst-case precision of 1.4 mm (σ). A flash LiDAR using direct time of flight (dTOF) and based on Ocelot is demonstrated, achieving depth imaging at short distances with a frame rate of 30 frames/s, employing an ultra-low power laser with an average power of 2 mW and peak power of 0.5 W.

Microarray analysis of high light intensity stress on hydrogen production metabolism of Rhodobacter capsulatus

Biohydrogen obtained from purple non sulfur bacteria (PNSB) is an environmentally friendly alternative for hydrogen production. PNSB can be employed in large scale outdoor photobioreactors to produce hydrogen by photofermentation with sunlight as the light source. In external environmental conditions, however, bacteria can experience stress due to high light intensities, which can inhibit or slow down hydrogen production. Previous studies with other PNSB showed varying responses to light intensities (above 4000 lux), in some cases improving, and in others adversely affecting hydrogen production.In this study, Rhodobacter capsulatus, a PNSB species that produce hydrogen efficiently from dark fermenter effluents containing acetate, was used to investigate the effects of high light intensity stress on the hydrogen production metabolism at the gene expression level. A microarray analysis was carried out using a custom-design Affymetrix GeneChip TR_RCH2a520699F. R. capsulatus DSM1710 was grown under a cyclic illumination of 2000 and 7000 lux (12 h light/12 h dark) in a hydrogen production medium having 30 mM acetate and 2 mM glutamate, and was exposed to a high light intensity (10,000 lux) for 1 h in the middle of a light period. The results reveal that photosynthetic reaction center genes were down-regulated in order to protect the photosynthetic membrane from damage. On the other hand, the expression of nitrogenase and electron transport system genes were enhanced by high light intensity. These results show that a high light intensity stress drives R. capsulatus to direct gene expression towards hydrogen production, which supports the hypothesis that hydrogen production is a way for the disposal of excess reducing equivalents to maintain the internal redox balance.

Moonlight cycles synchronize oyster behaviour.

Organisms possess endogenous clock mechanisms that are synchronized to external cues and orchestrate biological rhythms. Internal timing confers the advantage of being able to anticipate environmental cycles inherent in life on Earth and to prepare accordingly. Moonlight-entrained rhythms are poorly described, being much less investigated than circadian and circannual rhythms synchronized by sunlight. Yet focus on these lunar rhythms is highly relevant to understanding temporal organization of biological processes. Here, we investigate moonlight cycle effects on valve activity behaviour of the oyster Crassostrea gigas. Our results show that oysters modulate valve behaviour according to both intensity and direction of the lunar illumination cycle. As a consequence, valve opening amplitude is significantly increased at third quarter Moons (decreasing lunar illumination) compared with first quarter Moons (increasing lunar illumination) despite identical lunar illumination, and this indicates that oyster modulation of valve behaviour by moonlight cycles is not a direct response to lunar illumination. We propose that oysters use moonlight cycles to synchronize behaviour and also other physiological and ecological aspects of this benthic mollusc bivalve.

Preparation of WO3 thin films by dip film-drawing for photoelectrochemical performance

Abstract Here we report the WO3 thin films on F-doped SnO2 conducting glass (FTO) substrates which were prepared by using dip film-drawing method. Dip film-drawing was a simple, convenient, economical method and in large-scale to prepare photoanodes for future applications. The FTO substrates were dipped in tungstic acid solution then film-drawn included 3, 6, 9, 12 and 15 times for prepared different thicknesses of WO3 thin film photoanodes. Then the photoanodes were employed as the electrodes in photoelectrochemical property measurements, which include scan linear sweep, repeated on/off illumination cycles, electrochemical impedance spectroscopy and incident photon to current conversion efficiency, respectively. The results showed that the WO3 thin films dipped 9 times with 175 nm thicknesses had the best photoelectrochemical performance of 0.067 mA·cm−2 at 1.23 V versus RHE.

Adverse effects of strong light and nitrogen deficiency on cell viability, photosynthesis, and motility of the red-tide dinoflagellate Karenia mikimotoi

:The dinoflagellate Karenia mikimotoi is a red tide–forming alga that causes serious damage to aquaculture in coastal areas around the world. Its eco-physiological characteristics have been investigated extensively but conditions associated with declines of red tides of K. mikimotoi remain unknown. In the present study, we investigated the effects of light and nutrients on the viability, activity of photosystem II (PSII), and motility of K. mikimotoi. Cells were incubated under low (100 μmol photons m−2 s−1 on a 12:12 light:dark cycle of illumination) or high irradiance (1000 μmol photons m−2 s−1) for 4 h in the middle of the photoperiod, in different media. Under low light, most cells survived for about 1 month in media depleted of nitrogen (N) and phosphorus (P), similar to their survival pattern in complete medium. However, when cells that had been pre-incubated in N-depleted medium for 7 d were incubated under high light in an N-depleted medium, cell density and PSII activity declined within a few days. In P-depleted and complete media, there were no significant differences in cell density and PSII activity between low and high light, at least for 10 d. Furthermore, PSII activity was much more sensitive to photoinhibition in N-depleted than in complete medium. The rhythm of diurnal vertical migration of K. mikimotoi was observed in very low light (10 μmol photons m−2 s−1) in different media. The rhythm became obscure in N- and P-depleted media; in fact, most cells stayed in the surface layer all day in N-depleted medium. Moreover, cells accumulating in surface layers in N- and P-depleted media descended very little, even when irradiated with high light. These observations suggest that N-deficiency might trap cells in the surface layer and increase their susceptibility to photoinhibition of PSII, possibly leading to cell death. The combination of N-deficiency and high light thus appears to be an important factor that determines the decline of red tides of K. mikimotoi.

Phototrophic production of heterologous diterpenoids and a hydroxy-functionalized derivative from Chlamydomonas reinhardtii

Photosynthetic microalgae harbor enormous potential as light-driven green-cell factories for sustainable bio-production of a range of natural and heterologous products such as isoprenoids. Their capacity for photosynthesis and rapid low-input growth with (sun)light and CO2 is coupled to a robust metabolic architecture structured toward the generation of isoprenoid pigments and compounds involved in light capture, electron transfer, and radical scavenging. Metabolic engineering approaches using eukaryotic green microalgae have previously been hampered mainly by low-levels of nuclear transgene expression. Here, we employed a strategy of optimized transgene design which couples codon optimization and synthetic intron spreading for the expression of heterologous plant enzymes from the algal nuclear genome. The diterpenoids casbene, taxadiene, and 13R(+) manoyl oxide were produced after expressing heterologous diterpene synthases and enzymes participating in the 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway which were all targeted to the algal chloroplast. Additionally, a truncated and soluble plant microsomal cytochrome P450 monooxygenase was functionally expressed and able to hydroxylate 13R(+) manoyl oxide when directed into the chloroplasts. The heterologous diterpenoids were found to be excreted from the cells and accumulate in dodecane solvent-culture overlays. It was shown that the algal cell could tolerate significant metabolic pull towards diterpenoids without loss of native pigments. Using an algal strain producing 13R(+) manoyl oxide as a model, diterpenoid production was shown to be highest in photoautotrophic cultivations using CO2 as the sole carbon source and day:night illumination cycles. Up to 80 mg 13R(+) manoyl oxide per gram cell dry mass (CDM) could be produced from C. reinhardtii in a 7 day batch cultivation with a sustained maximal productivity of 22.5 mg gcdm−1 d−1 over 3 consecutive days. Collectively the results presented here suggest that green algal cells have remarkable potential for the heterologous production of non-native isoprenoids and support the use of these hosts for (sun)light driven bioproduction concepts.

Two-Dimensional Flexible Bilayer Janus Membrane for Advanced Photothermal Water Desalination

Solar water evaporation is thought to be a promising solution to address the issues of global water scarcity. However, it is particularly difficult to achieve an idealized photothermal conversion membrane with all of the required structure characteristics such as wide spectrum absorption, ultrathin and porous, low thermal conductivity, and ease to scale up, thus leading to reduced water evaporation efficiency. Here, we designed a large-area bilayer Janus film by assembling gold nanorod (AuNR) onto the interconnected single-walled carbon nanotube (SWNT) porous film. The combined characteristics of high solar spectrum absorption, enhanced photothermal performance, thermal insulating feature, interconnected porous structure, and excellent mechanical performance enable the bilayer Janus film with a nearly 94% water evaporation efficiency under 5 kW m–2 solar irradiation and stable water generation capability during long-term illumination cycles as a water desalination membrane. Construction of the bilayer Jan...

Color change in the Sargassum crab, Portunus sayi: response to diel illumination cycle and background albedo

Floating mats of Sargassum macroalgae provide a model system for studying multiple aspects of animal coloration. The endemic crab Portunus sayi has heterogeneous yellow and brown patterning, which matches its algal background. We show that by fluctuating the chromatophores underneath its transparent carapace, the crab can alter its coloration within hours in response to diel variability in the ambient light field and to changes in background reflectance. Held in a naturalistic illumination and temperature regime, P. sayi displayed a distinct diel cycle of coloration, being pale at night and darker during the day. Individuals under constant illumination showed a modified cycle, retaining their nocturnal shading but becoming significantly paler during day time. On monochromatic black, grey, and white surfaces, crabs showed an ability to change coloration in response to their backgrounds, as integrated reflectance (ΣR) of crabs generally followed background albedo. This study expands on earlier work which revealed that P. sayi utilizes a distinct camouflage strategy from other cryptic Sargassum crabs to achieve background color matching in the view of predators. Dynamic color change in this species may play roles including photoprotection and enhancing camouflage in a unique marine environment.

Route Fidelity during Marine Megafauna Migration

The conservation and protection of marine megafauna require robust knowledge of where and when animals are located. Yet, our ability to predict animal distributions in space and time remains limited due to difficulties associated with studying elusive animals with large home ranges. The widespread deployment of satellite telemetry technology creates unprecedented opportunities to remotely monitor animal movements and to analyse the spatial and temporal trajectories of these movements from a variety of geophysical perspectives. Reproducible patterns in movement trajectories can help elucidate the potential mechanisms by which marine megafauna navigate across vast expanses of open-ocean. Here, we present an empirical analysis of humpback whale (Megaptera novaeangliae), great white shark (Carcharodon carcharias) and northern elephant seal (Mirounga angustirostris) satellite telemetry-derived route fidelity movements in magnetic and gravitational coordinates. Our analyses demonstrate that: 1) humpback whales, great white sharks and northern elephant seals are capable of performing route fidelity movements across millions of square kilometers of open ocean with a spatial accuracy of better than 150 km despite temporal separations as long as 7 years between individual movements; 2) route fidelity movements include significant (p<0.05) periodicities that are comparable in duration to the lunar cycles and semi-cycles; 3) latitude and bedrock-dependent gravitational cues are stronger predictors of route fidelity movements than spherical magnetic coordinate cues when analysed with respect to the temporally dependent moon illumination cycle. We further show that both route fidelity and non-route fidelity movement trajectories, for all three species, describe overlapping in-phase or antiphase sinusoids when individual movements are normalised to the gravitational acceleration present at migratory departure sites. Although these empirical results provide an inductive basis for the development of testable hypotheses and future research questions, they cannot be taken as evidence for causal relations between marine megafauna movement decisions and geophysical cues. Experiments on model organisms with known sensitivities to gravity and magnetism, complemented by further empirical observation of free-ranging animals, are required to fully explore how animals use discrete, or potentially integrated, geophysical cues for orientation and navigation purposes.

Keeping the light energy constant — Cultivation of Chlorella sorokiniana at different specific light availabilities and different photoperiods

Microalgae cultivation is strongly dependent on light availability. Sunlight is the natural energy source for algae cultivation processes, but its fluctuation during the day and the natural day-night-rhythm mean an increasing challenge for an efficient algae production. Additionally, different seasons lead to unequal photoperiods and their influence on the productivity has not been determined in detail yet.Therefore, we investigated the growth of Chlorella sorokiniana at different light intensities and illumination cycles of 24h/0h (light/dark), 16/8h and 12/12h. The light integral, more exactly the amount of photons per gram biomass and day (specific light availability) was kept constant during 24h to ensure the comparability of the results of the different photoperiods. During the cultivation in repeated fed-batch mode, the productivity and biomass yield on light of Chlorella sorokiniana were determined to characterize the growth.During the night phase a biomass loss occurred, which was independent of the night temperature and the specific light availability on the day before, but increased with higher biomass concentration. A higher biomass yield on light during the shorter photoperiods led to an improved gross productivity compared to the continuous illumination, especially at a biomass concentration above 4gL−1. This compensated for the night loss; therefore, the net productivity (during one day) was independent of the photoperiod. In order to determine an optimal process window biomass yield on light and productivity have to be considered. They are diametric with respect to the specific light availability and furthermore dependent on the biomass concentration. The optimal combination of biomass yield on light and productivity could be achieved with a biomass concentration below 4gL−1 during 24/0 illumination and with a biomass concentration below 7gL−1 during shorter photoperiods; the specific light availability should be as high as possible.

An Ultrathin Flexible 2D Membrane Based on Single‐Walled Nanotube–MoS2 Hybrid Film for High‐Performance Solar Steam Generation

AbstractSolar steam generation is achieved by localized heating system using various floating photothermal materials. However, the steam generation efficiency is hindered by the difficulty in obtaining a photothermal material with ultrathin structure yet sufficient solar spectrum absorption capability. Herein, for the first time, an ultrathin 2D porous photothermal film based on MoS2 nanosheets and single‐walled nanotube (SWNT) films is prepared. The as‐prepared SWNT–MoS2 film exhibits an absorption of more than 82% over the whole solar spectrum range even with an ultrathin thickness of ≈120 nm. Moreover, the SWNT–MoS2 film floating on the water surface can generate a sharp temperature gradient due to the localized heat confinement effect. Meanwhile, the ultrathin and porous structure effectively facilitates the fast water vapor escaping, consequently an impressively high evaporation efficiency of 91.5% is achieved. Additionally, the superior mechanical strength of the SWNT–MoS2 film enables the film to be reused for atleast 20 solar illumination cycles and maintains stable water productivity as well as high salt rejection performance. This rational designed hybrid architecture provides a novel strategy for constructing 2D‐based nanomaterials for solar energy harvesting, chemical separation, and related technologies.

A damping circadian clock drives weak oscillations in metabolism and locomotor activity of aphids (Acyrthosiphon pisum)

Timing seasonal events, like reproduction or diapause, is crucial for the survival of many species. Global change causes phenologies worldwide to shift, which requires a mechanistic explanation of seasonal time measurement. Day length (photoperiod) is a reliable indicator of winter arrival, but it remains unclear how exactly species measure day length. A reference for time of day could be provided by a circadian clock, by an hourglass clock, or, as some newer models suggest, by a damped circadian clock. However, damping of clock outputs has so far been rarely observed. To study putative clock outputs of Acyrthosiphon pisum aphids, we raised individual nymphs on coloured artificial diet, and measured rhythms in metabolic activity in light-dark illumination cycles of 16:08 hours (LD) and constant conditions (DD). In addition, we kept individuals in a novel monitoring setup and measured locomotor activity. We found that A. pisum is day-active in LD, potentially with a bimodal distribution. In constant darkness rhythmicity of locomotor behaviour persisted in some individuals, but patterns were mostly complex with several predominant periods. Metabolic activity, on the other hand, damped quickly. A damped circadian clock, potentially driven by multiple oscillator populations, is the most likely explanation of our results.

Investigation of lipid production by nitrogen-starved Parachlorella kessleri under continuous illumination and day/night cycles for biodiesel application

This study aims to investigate the triacylglycerol (TAG) productivity of Parachlorella kessleri grown under continuous illumination and to investigate its metabolism in simulated day/night cycles in order to estimate the feasibility of a large-scale production in outdoor solar photobioreactors. The strain was chosen for its ability to accumulate large amounts of triacylglycerol during nitrogen starvation. Several protocols of nitrogen starvation were tested in continuous illumination as well as in simulated day/night cycles. Sudden and progressive nitrogen starvation conditions have enhanced the TAG concentration and productivity of P. kessleri reaching up to 48 dry wt% and 4.4 × 10−3 kg m−2 day−1, respectively. Microalgal cell metabolism was significantly affected by the day/night illumination cycles. The energy-rich compounds (TAGs and carbohydrates) were accumulated by P. kessleri during the photoperiods and partly consumed during the dark to sustain the microalgae vitality. This TAG oxidation ultimately led to a 26% decrease in TAG productivity in cultures exposed to day/night cycles compared to ones exposed to continuous illumination of equal 24-h average photon flux density. The results can dictate the optimal time for harvesting cells for recovering the largest amount of TAGs.