The Impact of Light Spectrum and Intensity on the Growth, Physiology, and Antioxidant Activity of Lettuce (Lactuca sativa L.)

This study focused on the physiology, growth and antioxidant activity response of hydroponically grown lettuce (Lactuca sativa L.) under sole-source LED lighting of differing spectra. Lighting spectra were provided by differing combinations of LEDs of three different peak wavelengths, (Blue 435, Blue 450, and Red 663 nm) with ratios of B450/R663: 1.25 ± 0.1, B450/R663: 1.25 ± 0.1, and B450/R663 1:1 at two light intensities of photosynthetically active radiation (PAR) (270 μmol m−2 s−1 and 60 μmol m−2 s−1). A further experiment was conducted, in which Blue and Red LEDs were supplemented with Green (Blue 450, Red 663, and Green 520 nm) with ratios of B435/R663: 1.25 ± 0.1, B450/R663/G520: 1/0.73/0.26, and B450/R663: 1.25 ± 0.1. LED light intensities under the different spectra were adjusted to deliver the same level of PAR (270 ± 20 μmol m−2 s−1). Results from the first experiment showed that increased fraction of blue 435 nm in combination with red light at 663 nm at high irradiance enhanced the physiology of lettuce (i.e., significantly increased assimilation rate, stomatal conductance and transpiration rate) and increased the yield while having no significant effect on antioxidant activity. At the lower irradiance, the B435/R663 significantly increased antioxidant activity compared to other spectra. Results from the second experiment showed no significant effect of the spectra of LEDs on the physiology and yield of lettuce, but antioxidant activity was very significantly induced by B450/R663 at the ratio of 1.25 ± 0.1. However, the amount was still less than that obtained by B435/R663 1.25 ± 0.1 from the first experiment. This study indicates that LED light with a spectrum of B435/R663 at a ratio of 1.25 ± 0.1 significantly improves lettuce yield and antioxidant activity.</jats:p

The Impact of LED Lighting Spectra in a Plant Factory on the Growth, Physiological Traits and Essential Oil Content of Lemon Balm (Melissa officinalis)

With the recent development of LED lighting systems for plant cultivation, the use of vertical farming under controlled conditions is attracting increased attention. This study investigated the impact of a number of LED light spectra (red, blue, green and white) on the growth, development and essential oil content of lemon balm (Melissa officinalis), a herb and pharmaceutical plant species used across the world. White light and red-rich light spectra gave the best outputs in terms of impact on the growth and yield. For blue-rich spectra, the development and yield was lower despite having a significant impact on the photosynthesis activity, including Fv/Fm and NDVI values. For the blue-rich spectra, a peak wavelength of 450 mn was better than that of 435 nm. The results have practical value in terms of increased yield and the reduction of electricity consumption under controlled environmental conditions for the commercial production of lemon balm.</jats:p

Partial Purification and Characterization of Exo-Polygalacturonase Produced by Penicillium oxalicum AUMC 4153

Pectinase enzymes are important industrial enzymes having considerable applications in several industries, especially in food processing. Pectinases contribute 25% of global food enzyme sales. Therefore, the demand for a commercial enzyme with desirable characteristics and low production costs has become one of the great targets. Hence, this study aims to produce exo-polygalacturonase (exo-PG) using local fungal isolate Penicillium oxalicum AUMC 4153 by utilizing sugar beet manufacturing waste (sugar beet pulp) as a sole raw carbon source under shaken submerged fermentation, which is purified and characterized to optimize enzyme biochemical properties for industrial application. The purity of the obtained exo-PG was increased by about 28-fold, and the final enzyme yield was 57%. The partially purified enzyme was active at a broad range of temperatures (30–60 °C). The optimum temperature and pH for the purified exo-PG activity were 50 °C and pH 5. The enzyme was stable at a range of pH 3 to 6 and temperature 30–50 °C for 210 min. The values for Km and Vmax were 0.67 mg/mL, with polygalacturonic acid as substrate and 6.13 µmole galacturonic acid/min/mg protein, respectively. It can be concluded that purified exo-PG production by P. oxalicum grown on sugar beet waste is a promising effective method for useful applications.</jats:p