LED Light Wavelengths Research Articles

Effect of Different LED Light Wavelengths on Production and Quality of Pleurotus ostreatus Grown on Different Commercial Substrates

Artificial lighting, primarily employed in crop production, can also be applied to the cultivation of edible mushrooms to enhance productivity and quality. While UV radiation has predominantly been investigated in post-harvest treatments for edible mushrooms, the utilization of different light wavelengths during the cultivation phase remains largely unexplored for many mushroom species. This study aimed to assess the impact of three different light wavelengths 450 nm (B), 610 nm (R), and a combination of these two wavelengths (R + B) on the productive characteristics and quality of Pleurotus ostreatus, cultivated using three straw-based commercial substrates. It was observed that, except for yield, artificial light influenced mushroom growth. Specifically, the application of R light appeared to promote mycelium growth, whereas B light contributed to increase the diameter of fruiting bodies. Additionally, the concentration of vitamin D2 was higher under both B and R+B light treatments. Interestingly, the light treatments did not affect yield but impacted diameter and various chemical attributes such as EC, total soluble solids, and titratable acidity. In conclusion, exposure to different lighting affected Pleurotus ostreatus physiology and nutritional content.

In-vitro Approaches to Investigate the Detrimental Effect of Light on Dopaminergic Neurons

Our recent study revealed that fluorescent lamp light can penetrate deep into the brain of mice and rats leading to the development of typical histological characteristics associated with Parkinson’s disease such as the loss of dopamine neurons in the substantia nigra. Monochromatic LED lights were thus used in this work to deepen our knowledge on the effects of the major wavelength peaks of fluorescent light on mouse and human dopaminergic cells. In particular, we exposed immortalized dopaminergic MN9D neuronal cells, primary cultures of mouse mesencephalic dopaminergic cells and human dopaminergic neurons differentiated from induced pluripotent stem cells (hiPSC) to different LED light wavelengths. We found that chronic exposure to LED light reduced overall undifferentiated MN9D cell number, with the most significant effects observed at wavelengths of 485 nm and 610 nm. Moreover, LED light especially at 610 nm was able to negatively impact on the survival of mouse mesencephalic dopaminergic cells and of human dopaminergic neurons derived from hiPSC. Notably, differentiated MN9D dopaminergic cells, which closely resemble mature dopamine neuronal phenotype, acutely exposed for 3 h at 610 nm, showed a clear increase in ROS production and cytotoxicity compared to controls undifferentiated MN9D cells. These increases were even more pronounced by the co-treatment with the oxidative agent H2O2. Collectively, these findings suggest that specific wavelengths, particularly those capable of penetrating deep into the brain, could potentially pose an environmental hazard in relation to Parkinson's disease.

Application of an artificial neural network coupled to a genetic algorithm for the production of polyphenols in Parachlorella kessleri grown under mixotrophic conditions

Microalgae are vital sources of high-value compounds, like polyphenols. Boosting polyphenol production requires considering diverse factors and their impacts on synthesis. This study aims to optimise polyphenol yield in microalga Parachlorella kessleri using an artificial neural network coupled with a genetic algorithm (ANN-GA). P. kessleri was grown under mixotrophic conditions and subjected to 13 experimental treatments. Factors studied included glucose, NaNO3, KH2PO4, LED light wavelength, intensity, and photoperiod. Total polyphenol concentration was quantified with Folin-Ciocalteu reagent; the polyphenol profile was obtained via HPLC. A database was constructed for ANN training to predict polyphenol production. Developed models were compared using indicators: coefficient of determination (R2pred), Mean Absolute Error (MAE), and Mean Square Error (MSE). Optimal models were fine-tuned with a genetic algorithm and validated using randomised experiments. The optimal ANN architecture for P. kessleri polyphenol production is: 6 inputs, 4 hidden layers, 6 neurons per layer, one output. This design achieved high prediction accuracy (R2 = 0.93). The genetically algorithm-optimised ANN model has these conditions: 26.60 g/L glucose; 1.42 g/L NaNO3; 0.59 g/L KH2PO4; white light; 1000 lx light intensity; 12:12 photoperiod. In experimental validation, 28 mg gallic acid equivalents per gram dry weight (GAE/g DW) were obtained, surpassing all models. An ANN-GA optimisation procedure was used for the first time for polyphenol production in P. kessleri. The model under mixotrophic conditions showed higher polyphenol production than autotrophic conditions. Polyphenol composition in P. kessleri varied between autotrophic and mixotrophic cultures, indicating inducible polyphenol production. The ANN-GA approach for polyphenol production in P. kessleri proved effective, with potential for maximising other high-value microalgae metabolites.

Attractiveness of four wavelengths of LED light: UV (385 nm), violet (405 nm), blue (450 nm), and red (660 nm) for seven species of natural enemies

Recently, the positive phototaxis exhibited by natural enemies such as Nesidiocoris tenuis (Hemiptera: Miridae) and Orius sauteri (Hemiptera: Anthocoridae) has been explored to enhance pest control efficiency in agriculture, mainly in Korea and Japan. Here, we evaluated the responses of seven natural enemies: Aphidius colemani, Asobara japonica (Hymenoptera: Braconidae), Chrysoperla carnea (Neuroptera: Chrysopidae), Harmonia axyridis, Illeis koebelei (Coleoptera: Coccinellidae), Nabis stenoferus (Hemiptera: Nabidae), and O. minutus (Hemiptera: Anthocoridae), to different wavelengths of LED light (i.e., 385, 405, 450, and 660 nm) to clarify the potential of phototaxis for behavioral manipulation of natural enemies. Also, we assessed how mating status and gender affected the responses of A. colemani and O. minutus using a video tracking system, EthoVision® XT. Overall, wavelengths of 385 and 405 nm were highly attractive to natural enemies, except for C. carnea and N. stenoferus. Unmated females of A. colemani moved greater distances than mated ones, the latter remaining significantly longer in the zone illuminated with UV light compared to the zone illuminated with white light. Adult O. minutus of both sexes remained longer under UV light than under white light. Therefore, the use of UV or near-UV lighting should serve to increase the retention time of natural enemies near light sources and might be useful to retain these and other natural enemies in specific agricultural contexts for better control of pests.

Concurrent purification of phycobiliproteins from Leptolyngbya sp. and their selective enhancement in response to different wavelengths of LED light

The present study identifies freshwater cyanobacterium Leptolyngbya sp. CMSACR2013 as a potential producer of phycobiliproteins. Concurrent purification of phycobiliproteins using the three-stage ammonium sulfate precipitation technique was employed to recover phycocyanin and phycoerythrin simultaneously. This was followed by anion exchange chromatography, resulting in an analytical grade C-phycoerythrin (Purity = 4.6) and reactant grade C-phycocyanin (Purity = 3.5). Moreover, to understand the relative pigment production in Leptolyngbya sp., the cultures were exposed to different wavelengths of LED lights and cultivated for 28 days. C-phycoerythrin content was higher under green light (74.77 mg L−1). In contrast, C-phycocyanin and C-allophycocyanin were higher under red light (72.94 mg L−1 and 63.50 mg L−1). The results also revealed the highest biomass content under red light (2.20 g L−1). These results suggest exploiting the complementary chromatic adaptation exhibited by the strain to improve the selective accumulation of phycobiliproteins.

In-door germination and seedling growth of green and red lettuce under LED-light spectrum and subsequent effect on baby leaf lettuce

The spectrum and intensity of light play a significant role in the primary and secondary metabolism of plants. Low intensity can make the photosynthetic process less efficient, while inadequate spectrum can impair plant growth and quality. This study investigates the effect of different LED light spectra at low intensity on germination and growth of lettuce (Lactuca sativa L.) seedlings under a temperature-controlled chamber and the subsequent impact on mature plants grown in a greenhouse under natural light. The purpose was to reach a commercial plant seedling using a low amount of energy to achieve the yield potential in a shorter period. The experiment was carried out in three trials. In trial 1, the effect of different LED light wavelengths [100% blue (B); 100% red (R); mixed light 1 (52% blue, 27% green and 21% red) (BGR1), and mixed light 2 (29% blue, 53% green and 17% red and 1% far red) (BGR2)] at low intensity (55 μmol m–2 s–1 and 12 h light photoperiod) and darkness (control) on germination of two lettuce cultivars [‘Levistro’ (green) and ‘Carmolí’ (red)] was evaluated in a controlled temperature chamber (20±1.2°C). In trial 2, the effect of the same light conditions of the first experiment on agronomic characteristics and pigment contents of lettuce seedlings compared to the natural light (control: 451±66 μmol m–2 s–1) were evaluated. In trial 3, the seedlings developed under different LED light wavelengths were transplanted to evaluate the subsequent effect on the growth of baby lettuce cultivated hydroponically in the greenhouse under natural light. The results of this study show that red wavelength reduced germination percentage, while lights with a higher blue component (B and BGR1) accelerated germination and increased the number of germinated seeds in ‘Levistro’. Red also delayed germination and decreased the number of germinated seeds in ‘Carmolí’ compared to darkness. Seedlings of ‘Levistro’ had a higher fresh weight (FW) than ‘Carmolí’. In addition, FW increased under BGR2 and R, which coincided with the highest number of leaves and leaf length. Nevertheless, fresh weight was higher under BGR2 and B after transplanting, coinciding with the highest number of leaves. A higher blue component of the light (B and BGR1) increased the dry matter percentage (DMP) of seedlings, but there was no significant difference after transplanting. Chlorophyll (CHL) a and b content increased under BGR2; however, the highest CHL a/b ratio was observed under BGR1 in ‘Levistro’ and B in ‘Carmolí’, but it was higher after transplanting when seedlings were grown under B. The anthocyanin (ANT) content of ‘Carmolí’ seedlings was promoted by a higher blue component of the light (B and BGR1) but significantly increased under natural light (control) at the highest intensity. This work shows that varying the spectrum at low intensity can positively modify the growth and biochemical characteristics of lettuce seedlings, although the effect depends on the cultivar. This modification improves the performance of plants during greenhouse growth after transplanting, especially seedlings grown under B and BGR2. Highlights - Blue light enhanced germination and increased the number of germinated seeds of green lettuce. - High blue component lights improved the morphology, dry matter percentage, and chlorophyll a/b ratio of lettuce seedlings. - Blue and full-spectrum lights applied to lettuce seedlings affect fresh weight after transplanting. - The anthocyanin content of seedlings was stimulated by blue light at 55 μmol m–2 s–1, but even more so by PAR of natural light at 451 μmol m–2 s–1.

​​Functional Lentil Sprouts Produced under Different Led Light Wavelengths Conditions

Advances in innovative agricultural technology could allow to satisfice the production of fresh foods. The use of light emitting diodes (LEDs) indoor farming production could, modify biological responses increasing the functional value of vegetable food like lentil sprouts, offering higher antioxidants content and to promote the bioavailability of their nutrients. Lentil growth under blue, violet, green, orange and red light in a dark growing chamber. As internal and external controls, seeds were germinated under white and natural (outdoor) light. Morphological, physiological and biochemical variables were evaluated. Green light enlarged the sprouts stem, reduced the biomass and the concentration of chlorophyll. Violet and white lights increased the protein concentration. Blue wavelength increased the seeds germination, concentration of β-carotenes, phenolic compounds and the antioxidant activity. The experimental evidence suggest blue LED light could be useful to produce functional lentil sprouts with a high nutritional value.

UV-LED lights enhance the establishment and biological control efficacy of Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae).

The zoophytophagous mirid Nesidiocoris tenuis (Hemiptera: Miridae) is one of the biological control agents against the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae), a major pest of greenhouse crops. The successful establishment of a biological control agent and its co-occurrence with the target pests increases the efficacy of biological control programs in greenhouses. In this study, we explored the effects of different wavelengths of LED light on establishment of N. tenuis in laboratory condition, with the goal of enhancing the biological control of B. tabaci in greenhouse crops. Nesidiocoris tenuis was most strongly attracted by LED light at a wavelength of 385 nm. This same wavelength was also highly attractive to B. tabaci in Y-tube experiments with lights of specific wavelengths provided is each arm of the apparatus. In trials in growth chambers, we verified the attraction of N. tenuis to 385 nm wavelength. When LED light at a wavelength of 385 nm was used in a growth chamber for 6 hours out of 24 hours, it significantly increased the remaining number of N. tenuis in growth chamber and level of predation compared to treatment with white LED light or without LED light. In conclusion, UV-LED light at a wavelength of 385 nm attracts both B. tabaci and N. tenuis. Thus, it would be used for enhancing early establishment of this mirid bug, better spatial congruence of both mirid bug and whitefly, and better control of the whitefly.

Effects of light quality and photoperiod on growth and photosynthetic pigment content of a Rhodophyta, Gloiopeltis furcata

The objective of the present study was to determine the optimal incubation conditions for Gloiopeltis furcata culture. Three experiments, each lasting 30 days, were conducted to study the effects of photoperiod (6:18, 8:16, 12:12, 14:10, and 16:8 h light/dark), different wavelengths of LED light (blue, green, yellow, red, and white), and solar radiation filtered through different plastic films (blue, green, yellow, red, and white) on the growth and photosynthetic pigment content of G. furcata. The results of these experiments demonstrated that the growth rate of G. furcata was significantly higher under 14:10 and 16:8 light/dark than under 6:18 and 8:16 light/dark, while the pigment content of G. furcata was significant higher under 6:18 and 8:16 than under 14:10 and 16:8 light/dark. The growth rate of G. furcata was the lowest when the algae were exposed to blue LED and the highest under yellow LED illumination, while the phycobiliprotein content was the highest under blue LED and the lowest under yellow LED. Solar radiation filtered through different plastic films had no significant effect on the growth rate of G. furcata, but affected its pigment content. The results indicate that a photoperiod of 12 h or more of light and yellow LED are the optimal parameters for culturing of G. furcata thalli on land.

Blue and White LED Lights Enhance Biosynthesis of Rosmarinic Acid in Cell Culture of Agastache rugosa

Agastache rugosa, an herbaceous Korean perennial, contains pharmacologically important phenylpropanoids such as tilianin and rosmarinic acid. However, the knowledge of biosynthesis of phenylpropanoids from A. rugosa is limited. Therefore, a study was conducted to develop an efficient protocol for in vitro regeneration of A. rugosa and to investigate the influence of three different LED light wavelengths (white, blue and red) on the biosynthesis of phenylpropanoids, including altered gene expression and variance in rosmarinic acid accumulation in calli. Transcription analyses revealed that white LED light enhances RAS expression; transcript levels were 15.7- and 10.4-fold higher for calli treated with white LED light than for those treated with red and blue light, respectively. Similarly, HPPR and C4H were also more highly expressed under blue and white LED light. In addition, HPLC quantification assays indicated that the highest levels of rosmarinic acid accumulate in calli treated with blue, red and white light (in that order) one week after cultivation. Together, our gene expression and HPLC quantification results provide evidence that rosmarinic acid in A. rugosa increases with the application of various wavelengths of LED light.

Blue light enhances astaxanthin biosynthesis metabolism and extraction efficiency in Haematococcus pluvialis by inducing haematocyst germination

Haematococcus pluvialis accumulates large amounts of astaxanthin during its haematocyst stage. Cyst germination is a biological pretreatment method for improved astaxanthin extraction with potential to replace energy-intensive homogenizer-based mechanical cell cracking methods. The present study demonstrates effects of different LED light wavelengths on haematocyst germination and on its astaxanthin biosynthesis pathway. Blue light enhanced the germination efficiency and slowed the nitrogen consumption rate, resulting in significantly higher astaxanthin content and improved extractability compared with white and red lights, that also had lower germination rates. After 5 days, the total astaxanthin extractability under blue light was 4.0 and 6.7 times higher than for white and red lights, respectively. The blue light receptor gene phot was significantly induced which upregulated the biosynthesis pathway genes psy and pds, as well as dgat1 and dgat2d. Hence, blue light triggers germination and astaxanthin biosynthesis, providing a strategy for improved extraction while modulating higher biosynthesis during germination.

Combined effects of LED lights and chicken manure on Neochloris oleoabundans growth

In this study a photobioreactor prototype is presented for the culture growth of microalgae model organism Neochloris oleoabundans by using chicken manure waste as feedstock along with the optimum combination of led light wavelengths and light intensity. Particularly interesting results are observed on the strains fed by chicken manure medium under the proper combination of red and blue LED light illumination, the microalgal growth resulted comparable with the strains fed by the costly commercial microalgal growth medium (BG 11 medium). Cell concentration, optical density, growth rate, cell size, total lipid and photosynthetic pigment content have been monitored during a time-course experiment. The data suggest that there are difficulties due to white light diffusion into the dark chicken medium, which leads to a generally lower intensity scattered along all wavelengths; blue or combined red and blue lights resulted in a higher irradiation density, affecting microalgae cell growth.

Influence of nutrients and LED light intensities on biomass production of microalgae Chlorella vulgaris

Microalgae are viable sources of biological compounds for biodiesel production. In this study, effects of various types of nitrogen sources and nutrients concentrations in the growth medium and different LED light wavelengths and intensities on biomass production of green algae Chlorella vulgaris were investigated. Warm white light with 80 µmol/m2/sec light intensity was determined as the optimal light for biomass production. The results indicated that microalgae growth with urea as nitrogen source was higher than that of other nitrogen sources such as sodium nitrate, ammonium carbonate and ammonium chloride. Maximum biomass concentration (1.37 g/L) was obtained under the following media compositions: urea 0.25 g/L, K2HPO4 0.04 g/L, MgSO4· 7H2O 0.06 g/L, and ammonium ferric citrate 0.01 g/L. Microalgae growth data under the different light wavelengths and intensities were fitted with a mathematical model.

Effects of various LED light wavelengths and intensities on microalgae-based simultaneous biogas upgrading and digestate nutrient reduction process

Biogas is a well-known, primary renewable energy source, but its utilizations are possible only after upgrading. The microalgae-based bag photo-bioreactor utilized in this research could effectively upgrade biogas and simultaneously reduce the nutrient content in digestate. Red light was determined as the optimal light wavelength for microalgae growth, biogas upgrading, and digestate nutrient reduction. In the range of moderate light intensities (i.e., 800, 1200, 1600, and 2000μmolm−2s−1), higher light intensities achieved higher biogas upgrade and larger digestate nutrient reduction. Methane content attained the highest value of 92.74±3.56% (v/v). The highest chemical oxygen demand, total nitrogen, and total phosphorus reduction efficiency of digestate were 85.35±1.04%, 77.98±1.84%, and 73.03±2.14%, respectively. Considering the reduction and economic efficiencies of the carbon dioxide content of biogas and digestate nutrient as well as the biogas upgrading standard, the optimal light intensity range was determined to be from 1200 to 1600μmolm−2s−1.

Effects of various LED light wavelengths and light intensity supply strategies on synthetic high-strength wastewater purification by Chlorella vulgaris

Chemical fertilizer agricultural wastewater is a typical high-strength wastewater that has dramatically triggered numerous environmental problems in China. The Chlorella vulgaris microalgae biological wastewater treatment system used in this study can effectively decontaminate the high-strength carbon and nitrogen wastewater under an optimum light wavelength and light intensity supply strategy. The descending order of both the dry weight for C. vulgaris reproduction and wastewater nutrient removal efficiency is red>white>yellow>purple>blue>green, which indicates that red light is the optimum light wavelength. Furthermore, rather than constant light, optimal light intensity is used for the incremental light intensity strategy. The phases for the optimal light intensity supply strategy are as follows: Phase 1 from 0 to 48h at 800μmolm(-2)s(-1); Phase 2 from 48 to 96h at 1,200μmolm(-2)s(-1); and Phase 3 from 96 to 144h at 1,600μmolm(-2)s(-1). Additionally, the optimal cultivation time is 144h.

Effects of various LED light wavelengths and intensities on the performance of purifying synthetic domestic sewage by microalgae at different influent C/N ratios

In Chinese rural areas, domestic sewage is one of the main sources of water pollution that may cause water eutrophication if directly discharged into natural waters without appropriate treatment. This study demonstrates that the microalgae Chlorella vulgaris can effectively remove nutrients from domestic sewage. In this process, red is the optimal light wavelength, with an intensity strategy as follows: Phase 1, 0–48h with 1000μmolm−2s−1; Phase 2, 48–96h with 1500μmolm−2s−1; Phase 3, 96–120h with 2000μmolm−2s−1; and Phase 4, 120–144h with 2500μmolm−2s−1. The optimal cultivation time was 144h. Nutrient removal efficiency was significantly affected by the light wavelength, light intensity, the effect of the interaction between light wavelength and intensity, as well as the effect of the interaction among light wavelength, light intensity, and influent C/N ratio. Moreover, the total nitrogen and total phosphorus removal efficiencies were significantly affected by the influent C/N ratio. In this study, the optimal influent C/N ratio is 5:1.

Susceptibility of Candida albicans to photodynamic therapy in a murine model of oral candidosis

In vivo studies of antimicrobial PDT in animal models of oral candidosis are scarce and the association of porphyrin and LED light has not been evaluated for in vivo photoinactivation of Candida. In this study the effectiveness of photodynamic therapy (PDT) on the inactivation of Candida albicans in vivo was evaluated. Seventy-one 6-week-old female Swiss mice were immunosuppressed, provided tetracycline to their drinking water, then orally swabbed with a suspension of C. albicans (10(7) CFU/mL). Four days after oral inoculation, PDT was performed on the dorsum of the tongue after topical administration of Photogem at 400, 500, or 1000 mg/L and followed 30 minutes later by illumination with LED light (305 J/cm(2)) at 455 or 630 nm (n = 5 each). After swabbing to recover yeast from the tongue, the number of surviving yeast cells was determined (CFU/mL) and analyzed by ANOVA and Holm-Sidak tests (P < .05). Animals were humanely killed, and the tongues surgically removed and processed for histological evaluation of presence of yeast and inflammatory reaction. PDT resulted in a significant reduction in C. albicans recovered from the tongue (P < .001) when compared with mice from the positive control group. There was no difference between the concentrations of Photogem and LED light wavelengths used. Histological evaluation of the tongue revealed that PDT causes no significant adverse effects to the local mucosa. PDT promoted significant reduction in the viability of C. albicans biofilm without harming the tongue tissue.