Light Intensity Conditions Research Articles

Predictive Population Dynamics of Escherichia coli O157:H7 and Salmonella enterica on Plants: a Mechanistic Mathematical Model Based on Weather Parameters and Bacterial State.

Weather affects key aspects of bacterial behavior on plants but has not been extensively investigated as a tool to assess risk of crop contamination with human foodborne pathogens. A novel mechanistic model informed by weather factors and bacterial state was developed to predict population dynamics on leafy vegetables and tested against published data tracking Escherichia coli O157:H7 (EcO157) and Salmonella enterica populations on lettuce and cilantro plants. The model utilizes temperature, radiation, and dew point depression to characterize pathogen growth and decay rates. Additionally, the model incorporates the population level effect of bacterial physiological state dynamics in the phyllosphere in terms of the duration and frequency of specific weather parameters. The model accurately predicted EcO157 and S. enterica population sizes on lettuce and cilantro leaves in the laboratory under various conditions of temperature, relative humidity, light intensity, and cycles of leaf wetness and dryness. Importantly, the model successfully predicted EcO157 population dynamics on 4-week-old romaine lettuce plants under variable weather conditions in nearly all field trials. Prediction of initial EcO157 population decay rates after inoculation of 6-week-old romaine plants in the same field study was better than that of long-term survival. This suggests that future augmentation of the model should consider plant age and species morphology by including additional physical parameters. Our results highlight the potential of a comprehensive weather-based model in predicting contamination risk in the field. Such a modeling approach would additionally be valuable for timing field sampling in quality control to ensure the microbial safety of produce. IMPORTANCE Fruits and vegetables are important sources of foodborne disease. Novel approaches to improve the microbial safety of produce are greatly lacking. Given that bacterial behavior on plant surfaces is highly dependent on weather factors, risk assessment informed by meteorological data may be an effective tool to integrate into strategies to prevent crop contamination. A mathematical model was developed to predict the population trends of pathogenic E. coli and S. enterica, two major causal agents of foodborne disease associated with produce, on leaves. Our model is based on weather parameters and rates of switching between the active (growing) and inactive (nongrowing) bacterial state resulting from prevailing environmental conditions on leaf surfaces. We demonstrate that the model has the ability to accurately predict dynamics of enteric pathogens on leaves and, notably, sizes of populations of pathogenic E. coli over time after inoculation onto the leaves of young lettuce plants in the field.

The purification performance of S doped g-C3N4 photocatalyst with outstanding reduction efficiency over Cr(VI) under the actual underwater transmission light

Cr(VI) existed in the industrial wastewater which has high biological toxicity has become one of the main pollution sources at present, and it is also difficult to remove from the wastewater because of its chemical stability. In this work, a raspberry-like sulfur doped carbon nitride photocatalyst (SCNx) with significant high reduction performance over Cr(VI) was prepared by solvothermal process. The BET data showed that the specific surface area of SCN4 was 3.75 times that of g-C3N4. Meanwhile, sulfur doping successfully reduce the band gap, which significantly improve the effective photoelectron density on the surface of the material, thus enhance its reduction ability. On this basis, the reduction activity of the SCNx to Cr(VI) in actual underwater environment was further investigated. Results show that SCNx still has good removal performance under weak light intensity and weak UV conditions. At 20 cm depth where ultraviolet spectral is attenuated 86.2%, the removal rate of SCN4 over Cr(VI) can still reach 58.1%. This research demonstrated that through S-doping and morphology control modification, carbon nitride can remain high photoreaction activity in the underwater weak light and weak UV environment, thus realize the efficient reduction treatment of Cr(VI). The research demonstrated the feasibility of heavy metal water treatment, and indicate a possible direction for the future practical application of heavy metal water purification.

Characteristics of a New Halotolerant Arctic Strain of Carotenogenic Microalga <i>Halochlorella rubescens</i> NAMSU SBB-20

Green microalgae capable of accumulating secondary carotenoids are the most important objects of biotechnology, and the search for new strains with unique properties, in particular, those adapted to growth at low temperatures and high salinity in the environment, is an urgent task. The NAMSU SBB-20 microalga strain was isolated from an algal-bacterial biofilm found on the coast of the White Sea in the littoral zone of the Solovetsky Archipelago. Identification of the strain showed its belonging to the species Halochlorella rubescens P.J.L.Dangeard. The species H. rubescens was first described for the White Sea. Under conditions of high light intensity, ultrastructural changes in cells are shown, among which destruction of the photosynthetic apparatus and the formation of cytoplasmic and chloroplast lipid inclusions are noted. It was shown that the culture of the NAMSU SBB-20 strain is capable of acquiring an orange color under unfavorable growth conditions. An assessment was made of the effect of the composition of the medium and the intensity of illumination on the pigment composition of the algae. The highest absolute values of the accumulation of carotenoids were noted during cultivation in light with an intensity of 150 mol PAR quanta/m2/s on BG-11 media containing no source of phosphorus (15.66 0.18 mg/L) or nitrogen (15.95 0.56 mg/L). The described strain has a biotechnological potential due to the initial halotolerance and the accumulation of high values of secondary carotenoids in the biomass.

Investigation of tungsten halogen lamp for possible usage as heat source for testing solar collector

Artificial sunlight is a heat source in solar collector testing, where the light intensity and ambient conditions are controlled to provide uniformity in each test. In this study, twenty-five tungsten halogen lamps of 300 W 220 V were investigated for possible usage as the heat source. The experiment was conducted by varying the height of the lamps to the light field (Hd). The EN-12975–2 Standard was used to control the quality of the heat source on the light field. The results showed that the average light intensity (Iavg) decreased with an increase in Hd. When Hd was low, the %uniformity values (%uxy) met the criteria. The small light field area met the EN-12975–2 Standard better than the large area. A comparison of solar collector testing under a heat source from tungsten halogen lamps and natural sunlight was subsequently performed, and the experimental results were in accordance with the EN-12975–2 Standard. A single-channel flat plate solar collector was used as the test device and air was used as the working fluid. The experimental results revealed that the solar collector thermal efficiency (ηavg) trends were similar for both the heat source from tungsten halogen lamps and natural sunlight testing. A low %uxy resulted in a ηavg that was more similar to that of natural sunlight.

Enhancing fucoxanthin production in Phaeodactylum tricornutum by photo-fermentation

The aim of this study was to develop a technical system for high-efficient production of fucoxanthin by photo-fermentation of Phaeodactylum tricornutum. In a 5 L photo-fermentation tank, the effects of initial light intensity, nitrogen source and concentration as well as light quality on biomass concentration and fucoxanthin accumulation in P. tricornutum were investigated systematically under mixotrophic condition. The results showed that the biomass concentration, fucoxanthin content and productivity reached the highest level of 3.80 g/L, 13.44 mg/g and 4.70 mg/(L·d) under the optimal conditions of initial light intensity of 100 μmol/(m2·s), 0.02 mol TN/L of tryptone: urea (1:1, N mol/N mol) as mixed nitrogen source, and a mixed red/blue (R: B=6:1) light, 1.41, 1.33 and 2.05-fold higher than that before optimization, respectively. This study developed a key technology for enhancing the production of fucoxanthin by photo-fermentation of P. tricornutum, facilitating the development of marine natural products.

Effect of Light Intensity on the Colony Development of <i>Lasius japonicus</i>（Hymenoptera: Formicidae）

In this study, we examined the effect of light intensity on colony development regulation in Lasius japonicus Santschi. Queens were collected soon after their nuptial flight in Okayama, Japan. They were reared under 16L-8D（16 h light, 8 h dark）and 12L-12D at 25°C with four light intensity conditions: 50, 200, 800, and 3000 lux. The queens started oviposition soon after collection. Thereafter, the larvae, pupae, and workers emerged under the 50–800 lux conditions； however, the hatching and larval development were suppressed under 3000 lux conditions, especially under the long-day photoperiod. Light intensity was also measured under the shelters where queens were found soon after their nuptial flight. Under the shelters, the median light intensities were between 2.4 lux and 1070.5 lux, which was low enough for the queens to develop colonies. These results suggest that queens start colony founding at places with low light intensity. The queens also likely control the rate of colony development by responding to the light intensity of the surrounding environment.

Suppression of the HOS1 Gene Affects the Level of ROS Depending on Light and Cold.

The E3 ubiquitin-protein ligase HOS1 is an important integrator of temperature information and developmental processes. HOS1 is a negative regulator of plant cold tolerance, and silencing HOS1 leads to increased cold tolerance. In the present work, we studied ROS levels in hos1Cas9Arabidopsis thaliana plants, in which the HOS1 gene was silenced by disruption of the open reading frame via CRISPR/Cas9 technology. Confocal imaging of intracellular reactive oxygen species (ROS) showed that the hos1 mutation moderately increased levels of ROS under both low and high light (HL) conditions, but wild-type (WT) and hos1Cas9 plants exhibited similar ROS levels in the dark. Visualization of single cells did not reveal differences in the intracellular distribution of ROS between WT and hos1Cas9 plants. The hos1Cas9 plants contained a high basal level of ascorbic acid, maintained a normal balance between reduced and oxidized glutathione (GSH and GSSG), and generated a strong antioxidant defense response against paraquat under HL conditions. Under cold exposure, the hos1 mutation decreased the ROS level and substantially increased the expression of the ascorbate peroxidase genes Apx1 and Apx2. When plants were pre-exposed to cold and further exposed to HL, the expression of the NADPH oxidase genes RbohD and RbohF was increased in the hos1Cas9 plants but not in WT plants. hos1-mediated changes in the level of ROS are cold-dependent and cold-independent, which implies different levels of regulation. Our data indicate that HOS1 is required to maintain ROS homeostasis not only under cold conditions, but also under conditions of both low and high light intensity. It is likely that HOS1 prevents the overinduction of defense mechanisms to balance growth.

Submerged macrophytes mediated remediation of molybdenum-contaminated sediments.

Molybdenum (Mo) sourced mainly from artificial activities is an emerging environmental concern whose remediation is seldom reported. This study screened the Mo-enriched macrophyte Vallisneria natans (Lour.) Hara due to its high enrichment factor (10.25). Phytoremediation (V. natans) and microorganism-assisted phytoremediation (V. natans-Serratia marcescens A2) efficiency were compared. S. marcescens A2 improved phytoremediation in the early stage, however, it reduced the total Mo removal rate by 8.42%. Further experiments were conducted to investigate the environmental factors (light intensity and overlying water flow rate) on the phytoremediation by V. natans. The optimal phytoremediation performance was achieved under a high overlying water flow rate (0.022cm·s-1) with intense light (60μmol·m-2·s-1) conditions. In addition, increasing the light intensity or flow rate increased the microbial communities' diversity in the sediment. Notably, the abundance of norank_f__Bacteroidetes_vadinHA17, related to Mo release in sediments, increased by 147.96% at optimal conditions. This study illustrated that the phytoremediation of Mo-contaminated sediments by V. natans is of practical potential.

PROTOTYPE OF THE INTERNET OF THINGS-BASED SWALLOW BUILDING MONITORING AND SECURITY SYSTEM

The Swallow nest production in a cultivation building have high commercial value. There are several factors that affect nest productivity such as light intensity, temperature and humidity conditions in the cultivation building. Better factors can be found in cultivation building that located far from residential area. However, this led to a risk of theft. Therefore, this study proposes a system that able to monitor the productivity factors and safety status of the building. System development uses a comparison method with black box testing. The system controller uses the Raspberry Pi B+ and the python programming language. Sensor Modules (GY-302, DHT-22, BME-280) are used to monitor light intensity, temperature and humidity. The security system uses sensor modules (LDR LM393, PIR HC-SR501 and SW-420) as flashlight, motion and vibration detectors. The black box testing result shows a good performance of the proposed system. The monitoring and security system can monitor the condition of swallow cultivation parameters and security status that can turn on alert alarms, send WhatsApp messages, store log data and send data to the website periodically according to the level of conditions that occur.

Response surface optimization of light conditions for organic matter accumulation in two different shapes of Arthrospira platensis.

Arthrospira platensis has attracted wide attention as a cyanobacteria with high nutritional value. In this research, the response surface method was used to study the effects of light cycle, light intensity and red-blue LED conditions on the growth and organic matter accumulation in spiral shaped strain A. platensis OUC623 and linear shaped strain A. platensis OUC793. The light conditions suitable for A. platensis OUC623 were as follows: growth (light time 12.01 h, light intensity 35.64 μmol/m2s, LED red: blue = 6.38:1); chlorophyll a (light time 12.75 h, light intensity 31.06 μmol/m2s, red: blue = 6.25:1); carotenoid (light time 13.12 h, light intensity 32.25 μmol/m2s, red: blue = 5.79:1); polysaccharide (light time 16.00 h, light intensity 31.32 μmol/m2s, blue: red = 6.24:1); protein (light time 12.18 h, light intensity 6.12 μmol/m2s, blue: red = 7.95:1); phycocyanin (light time12.00 h, light intensity 5.00 μmol/m2s, blue: red = 8.00:1). The light conditions suitable for A. platensis OUC793 were as follows: growth (light time 13.52 h, light intensity 40.22 μmol/m2s, red: blue = 5.98:1); chlorophyll a (light time 14.22 h, light intensity 44.96 μmol/m2s, red: blue = 5.94:1); carotenoid (light time 14.13 h, light intensity 44.50 μmol/m2s, red: blue = 6.02:1); polysaccharide (light time 16.00 h, light intensity 31.85 μmol/m2s, blue: red = 6.08:1); protein (light time12.00 h, light intensity 5.00 μmol/m2s, blue: red = 8.00:1); phycocyanin (light time12.01 h, light intensity 5.01 μmol/m2s, blue: red = 8.00:1). Under the theoretical optimal light conditions, compared with white LED, the growth rate, chlorophyll a, carotenoid, phycocyanin, protein and polysaccharide contents in strain 623 increased by 91.67%, 114.70%, 85.05%, 563.54%, 386.14%, 201.18%, and in strain 793 increased by 75.00%, 150.94%, 113.43%, 427.09%, 1284.71%, 312.38%, respectively. The two strains showed different advantages. Growth rate, chlorophyll a, polysaccharide, protein and phycocyanin content of strain 623 were higher than those of strain 793, while carotenoid was higher in strain 793. After optimization, both strains could reach a good growth state, and the growth rate and organic matter content were close. And then a 20 L photobioreactor was used to expand the culture of the two strains, validating the theoretical optimal light conditions of response surface method. This study laid the foundation for the establishment of optical conditions for organic matter accumulation in two different strains of A. platensis, which provided more options for meeting the industrialization needs of A. platensis.

Production of volatile organic iodine compounds by the marine cyanobacterium Calothrix parasitica under different light intensities

Volatile organic iodine compounds (VOICs) that exist in the marine environment, such as diiodomethane (CH2I2), chloroiodomethane (CH2ClI), and bromoiodomethane (CH2BrI), are known to transport iodine from the ocean to the atmosphere. These VOICs play important roles in various atmospheric chemistry processes, such as ozone decomposition. So far, marine phytoplankton such as diatoms and chlorarachniophytes have been reported to produce these VOICs in the culture experiments. In this study, we examined the production of VOICs by the marine cyanobacterium Calothrix parasitica NIES-267 (axenic) cultured at 24 °C for several weeks. The effect of light intensity on the production of VOICs was also studied by irradiating the culture medium of C. parasitica with light at intensities of 60, 90, and 120 μmol photons m−2 s−1. In addition, incubation experiments with 13CH2I2 added to the culture medium were performed to evaluate the decrease of 13CH2I2 due to photolysis during incubation. The concentrations of VOICs in the culture medium were measured using a purge-and-trap gas chromatograph-mass spectrometer. The concentrations of VOICs in the culture medium increased during the exponential or stationary phase at each light intensity. During the exponential phase, the chlorophyll a-normalized production rates of CH2ClI and CH2BrI increased with increasing light intensity from 60 to 120 μmol photons m−2 s−1, while the chlorophyll a-normalized maximum production rate of CH2I2 was found to be 28 pmol (μg chlorophyll a) −1 d−1 at 90 μmol photons m−2 s−1. During the incubation period, 13CH2I2 was photodegraded by about 17% at 120 μmol photons m−2 s−1. The relative production rates were CH2I2 > CH2ClI > CH2BrI for all light conditions, and the relative amount of CH2I2 tended to decrease under high light intensity conditions (120 μmol photons m−2 s−1). These results suggest that the cyanobacterium C. parasitica could be one of the significant sources of VOICs such as CH2I2 in the marine environment, and that light intensity would be an important factor in estimating VOICs emissions from marine cyanobacteria.

Improvement of Lutein and Zeaxanthin Production in Mychonastes sp. 247 by Optimizing Light Intensity and Culture Salinity Conditions.

In this study, we sought to improve lutein and zeaxanthin production in Mychonastes sp. 247 and investigated the effect of environmental factors on lutein and zeaxanthin productivity in Mychonastes sp. The basic medium selection and N:P ratio were adjusted to maximize cell growth in one-stage culture, and lutein and zeaxanthin production conditions were optimized using a central composite design for two-stage culture. The maximum lutein production was observed at a light intensity of 60 μE/m2/s and salinity of 0.49%, and the maximum zeaxanthin production was observed at a light intensity of 532 μE/m2/s and salinity of 0.78%. Lutein and zeaxanthin production in the optimized medium increased by up to 2 and 2.6 folds, respectively, compared to that in the basic medium. Based on these results, we concluded that the optimal conditions for lutein and zeaxanthin production are different and that optimization of light intensity and culture salinity conditions may help increase carotenoid production. This study presents a useful and potential strategy for optimizing microalgal culture conditions to improve the productivity of lutein and zeaxanthin, which has applications in the functional food field.

Effect of Different Light Qualities and Intensities on the Yield and Quality of Facility-Grown Pleurotus eryngii.

Proper light is essential for the formation and development of macrofungi fruiting bodies. Currently, there are unclear treatment conditions, such as light quality and light intensity, in the production of Pleurotus eryngii in intensive cultivation facilities, which is not helpful to the formation and implementation of standardized production programs. The research discussed in this paper investigated the effects of different light quality and intensity conditions on the yield and quality of P. eryngii. The results showed that the yield and nutritional quality of the red light treatment samples were higher than those of the white light control, the commercial properties were good, and the energy consumption of the red LED light source was the lowest under the same light intensity. The results of this experiment further provide a reference for the energy-saving and high-quality cultivation of P. eryngii.

Facing energy limitations - approaches to increase basil (Ocimum basilicum L.) growth and quality by different increasing light intensities emitted by a broadband LED light spectrum (400-780 nm).

Based on the current trend towards broad-bandwidth LED light spectra for basil productions in multi-tiered controlled-environment horticulture, a recently developed white broad-bandwidth LED light spectrum (400-780 nm) including far-red wavelengths with elevated red and blue light fractions was employed to cultivate basil. Four Ocimum basilicum L. cultivars (cv. Anise, cv. Cinnamon, cv. Dark Opal and cv. Thai Magic) were exposed to two different rising light intensity conditions (ILow and IHigh). In dependence of the individual cultivar-specific plant height increase over time, basil cultivars were exposed to light intensities increasing from ~ 100 to ~ 200 µmol m-2 s-1 under ILow, and from 200 to 400 µmol m-2 s-1 under IHigh (due to the exponential light intensity increases with decreasing proximity to the LED light fixtures). Within the first experiment, basils' morphological developments, biomass yields and time to marketability under both light conditions were investigated and the energy consumptions were determined to calculate the basils' light use efficiencies. In detail, cultivar-dependent differences in plant height, leaf and branch pair developments over time are described. In comparison to the ILow light conditions, IHigh resulted in accelerated developments and greater yields of all basil cultivars and expedited their marketability by 3-5 days. However, exposure to light intensities above ~ 300 µmol m-2 s-1 induced light avoidance responses in the green-leafed basil cultivars cv. Anise, cv. Cinnamon and cv. Thai Magic. In contrast, ILow resulted in consumer-preferred visual qualities and greater biomass efficiencies of the green-leafed basil cultivars and are discussed as a result of their ability to adapt well to low light conditions. Contrarily to the green-leafed cultivars, purple-leafed cv. Dark Opal developed insufficiently under ILow, but remained light-tolerant under IHigh, which is related to its high anthocyanin contents. In a second experiment, cultivars' volatile organic compound (VOC) contents and compositions over time were investigated. While VOC contents per gram of leaf dry matter gradually decreased in purple-leafed cv. Dark Opal between seedling stage to marketability, their contents gradually increased in the green cultivars. Regardless of the light treatment applied, cultivar-specific VOC compositions changed tremendously in a developmental stage-dependent manner.

A high-efficiency mixotrophic photoelectroactive biofilm reactor (MPBR) for enhanced simultaneous removal of nutrients and antibiotics by integrating light intensity regulation and microbial extracellular electron extraction

The performance of a mixotrophic photoelectroactive biofilm reactor (MPBR) was improved in order to achieve enhanced simultaneous removal of multiple aqueous pollutants and the production of valuable biomass. The MPBR was optimized by integrating the regulation of light intensity (3000, 8000 and 23000 lux) and microbial extracellular electron extraction (using an electrode at −0.3, 0 and 0.3 V). Results showed that the MPBR operated at a high light intensity (23000 lux) with a potential of −0.3 V (Coulomb efficiency (CE) of 9.65%) achieved maximum pollutant removal efficiencies, effectively removing 65% NH4+-N, 95% PO43--P and 52% sulfadiazine (SDZ) within 72 h, exhibiting an increase by 30%, 56% and 26% compared to an MPBR operated at the same light intensity but without an externally applied potential. The use of an electrode with an applied potential of −0.3V was most suitable for the extraction of photosynthetic electrons from the photoelectroactive biofilm, in which Rhodocyclaceae was highly enriched, effectively alleviating photoinhibition and thereby enhancing N, P assimilation and SDZ degradation under high light conditions. A maximum lipid content of 409.28 mg/g was obtained under low light intensity (3000 lux) conditions with an applied potential of 0.3 V (CE 9.08%), while a maximum protein content of 362.29 mg/g was obtained at a low light intensity (3000 lux) and 0 V (CE 10.71%). The selective enrichment of Chlorobium and the subsequent enhanced conversion of excess available carbon under low light and positive potential stimulation conditions, were responsible for the enhanced accumulation of proteins and lipids in biomass.

Sichuan Pepper Recognition in Complex Environments: A Comparison Study of Traditional Segmentation versus Deep Learning Methods

At present, picking Sichuan pepper is mainly undertaken by people, which is inefficient and presents the possibility of workers getting hurt. It is necessary to develop an intelligent robot for picking Sichuan peppers in which the key technology is accurate segmentation by means of mechanical vision. In this study, we first took images of Sichuan peppers (Hanyuan variety) in an orchard under various conditions of light intensity, cluster numbers, and image occlusion by other elements such as leaves. Under these various image conditions, we compared the ability of different technologies to segment the images, examining both traditional image segmentation methods (RGB color space, HSV color space, k-means clustering algorithm) and deep learning algorithms (U-Net convolutional network, Pyramid Scene Parsing Network, DeeplabV3+ convolutional network). After the images had been segmented, we compared the effectiveness of each algorithm at identifying Sichuan peppers in the various types of image, using the Intersection Over Union(IOU) and Mean Pixel Accuracy(MPA) indexes to measure success. The results showed that the U-Net algorithm was the most effective in the case of single front-lit clusters light without occlusion, with an IOU of 87.23% and an MPA of 95.95%. In multiple front-lit clusters without occlusion, its IOU was 76.52% and its MPA was 94.33%. Based on these results, we propose applicable segmentation methods for an intelligent Sichuan pepper-picking robot which can identify the fruit in images from various growing environments. The research showed good accuracy for the recognition and segmentation of Sichuan peppers, which suggests that this method can provide technical support for the visual recognition of a pepper-picking robot in the field.

Efficient Co-production of Docosahexaenoic Acid Oil and Carotenoids in Aurantiochytrium sp. Using a Light Intensity Gradient Strategy.

Aurantiochytrium is a promising source of docosahexaenoic acid (DHA) and carotenoids, but their synthesis is influenced by environmental stress factors. In this study, the effect of different light intensities on the fermentation of DHA oil and carotenoids using Aurantiochytrium sp. TZ209 was investigated. The results showed that dark culture and low light intensity conditions did not affect the normal growth of cells, but were not conducive to the accumulation of carotenoids. High light intensity promoted the synthesis of DHA and carotenoids, but caused cell damage, resulting in a decrease of oil yield. To solve this issue, a light intensity gradient strategy was developed, which markedly improved the DHA and carotenoid content without reducing the oil yield. This strategy produced 30.16g/L of microalgal oil with 15.11g/L DHA, 221µg/g astaxanthin, and 386µg/g β-carotene. This work demonstrates that strain TZ209 is a promising DHA producer and provides an efficient strategy for the co-production of DHA oil together with carotenoids.

Development of a Crop Spectral Reflectance Sensor

In this study, a low-cost, self-balancing crop spectral reflectance sensor (CSRS) was designed for real-time, nondestructive monitoring of the spectral reflectance and vegetation index of crops such as tomato and rapeseed. The sensor had a field of view of 30°, and a narrow-band filter was used for light splitting. The filter’s full width at half-maximum was 10 nm, and the spectral bands were 710 nm and 870 nm. The sensor was powered by a battery and used WiFi for communication. Its software was based on the Contiki operating system. To make the sensor work in different light intensity conditions, the photoelectric conversion automatic gain circuit had a total of 255 combinations of amplification. The gimbal of the sensor was mainly composed of an inner ring and an outer ring. Under the gravity of the sensor, the central axis of the sensor remained vertical, such that the up-facing and down-facing photosensitive units stayed in the horizontal position. The mechanical components of the sensor were designed symmetrically to facilitate equal mass distribution and to meet the needs of automatic balancing. Based on the optical signal transmission process of the sensor and the dark-current characteristics of the photodetector, a calibration method was theoretically deduced, which improved the accuracy and stability of the sensor under different ambient light intensities. The calibration method is also applicable for the calibration of other crop growth information sensors. Next, the standard reflectance gray scale was taken as the measurement variable to test the accuracy of the sensor, and the results showed that the root mean square error of the reflectance measured by the sensor at 710 nm and 870 nm was 1.10% and 1.27%, respectively; the mean absolute error was 0.95% and 0.89%, respectively; the relative error was below 4% and 3%, respectively; and the coefficient of variation was between 1.0% and 2.5%. The reflectance data measured by the sensor under different ambient light intensities suggested that the absolute error of the sensor was within ±0.5%, and the coefficients of variation at the two spectral bands were 1.04% and 0.39%, respectively. With tomato and rapeseed as the monitoring targets, the proposed CSRS and a commercial spectroradiometer were used to measure at the same time. The results showed that the reflectance measured by the two devices was very close, and there was a linear relationship between the normalized difference vegetation index of the CSRS and that of the commercial spectroradiometer. The coefficient of determination (R2) for tomato and rapeseed were 0.9540 and 0.9110, respectively.

Optimization of light intensity and color temperature in the cultivation of Chlorella vulgaris culture using the Surface Response Method

Microalgae have an important role as a source of biomass in producing energy. One type of microalgae that has the potential to be developed is Chlorella vulgaris. Several factors that affect the growth and biomass production of Chlorella vulgaris microalgae are color temperature and light intensity because they play an important role in the photosynthesis process. This study aims to influence the effect of light and color temperature and optimize these parameters using Response Surface Methodology (RSM). Two independent variables were varied: light intensity 200, 400, 600, 800, 1000 lux and color temperature 3000, 4000, 5000, and 6000 K. The results showed that the average value of Chlorella vulgaris growth was higher along with higher light intensity. At a color temperature of 4000 K, the highest biomass yield and the most negligible biomass production were found at 6000 K. At a color temperature of 4000 K, it is feasible to apply it as an alternative lighting source in the production of Chlorella vulgaris. The combination of light intensity and color temperature shows that the specific growth rate and doubling time have opposite trends where high values produce low values and vice versa. Growth in dark conditions, the specific growth rate was 0.0026 day-1, and the optimal light intensity at 600 lux treatment. ANOVA evaluation showed that color temperature greatly affected growth. Based on the optimization, the optimal specific growth rate of 00751day-1 with the conditions of light intensity and color temperature of 556 lux and 4152 K, respectively.

Potential for the Production of Carotenoids of Interest in the Polar Diatom Fragilariopsis cylindrus.

Carotenoid xanthophyll pigments are receiving growing interest in various industrial fields due to their broad and diverse bioactive and health beneficial properties. Fucoxanthin (Fx) and the inter-convertible couple diadinoxanthin–diatoxanthin (Ddx+Dtx) are acknowledged as some of the most promising xanthophylls; they are mainly synthesized by diatoms (Bacillariophyta). While temperate strains of diatoms have been widely investigated, recent years showed a growing interest in using polar strains, which are better adapted to the natural growth conditions of Nordic countries. The aim of the present study was to explore the potential of the polar diatom Fragilariopsis cylindrus in producing Fx and Ddx+Dtx by means of the manipulation of the growth light climate (daylength, light intensity and spectrum) and temperature. We further compared its best capacity to the strongest xanthophyll production levels reported for temperate counterparts grown under comparable conditions. In our hands, the best growing conditions for F. cylindrus were a semi-continuous growth at 7 °C and under a 12 h light:12 h dark photoperiod of monochromatic blue light (445 nm) at a PUR of 11.7 μmol photons m−2 s−1. This allowed the highest Fx productivity of 43.80 µg L−1 day−1 and the highest Fx yield of 7.53 µg Wh−1, more than two times higher than under ‘white’ light. For Ddx+Dtx, the highest productivity (4.55 µg L−1 day−1) was reached under the same conditions of ‘white light’ and at 0 °C. Our results show that F. cylindrus, and potentially other polar diatom strains, are very well suited for Fx and Ddx+Dtx production under conditions of low temperature and light intensity, reaching similar productivity levels as model temperate counterparts such as Phaeodactylum tricornutum. The present work supports the possibility of using polar diatoms as an efficient cold and low light-adapted bioresource for xanthophyll pigments, especially usable in Nordic countries.