Photoacclimation of Chlorella vulgaris to Red Light from Light‐Emitting Diodes Leads to Autospore Release Following Each Cellular Division

Abstract

The detailed light requirement for photosynthesis and photoautotrophic cell growth can be assessed using solid state technology. Advanced light-emitting diodes (LEDs), constructed with double-power double-heterostructure (DDH) gallium aluminum arsenide (GaAlAs) chips, were examined for their ability to support mass culture of the eucaryotic alga Chlorella vulgaris. LEDs with peak emittance of 680 nm (with half-power band width of 20 nm) were used as a sole light source for the cultivation of C. vulgaris. Fluorescent light (FL) served as a control. The final cell mass and specific cellular growth rate under LEDs were comparable to those obtained under full-spectrum light (FL). The narrow-spectrum monochromatic red light was found to reduce the average cell volume from 60 µm 3 to 30 µm 3 , and to make the size distribution and the per cell DNA distribution narrower, but did not affect the total biomass production. By switching light sources, the two distinct cell population states (obtained under red LEDs and FL, respectively) were found to be interchangeable. Two parametric flow cytometric analyses showed that the cells grown under red LED light had a more uniform DNA content at all cell sizes, as compared to cells grown under FL. These results show that the critical cell size for releasing autospores under red LED is smaller than that under FL. The number of autospores in one mother cell when grown under LED light appeared to be two, so that the mother cells break up after only one round of DNA replication. Although the solid state LED light source altered the cell cycle behavior of C. vulgaris, it can be used as an effective light source for autotrophic growth. Use of LEDs therefore promises to advance the current state of algal photobioreactors due to their efficiency, smallness, reliability, long lifetime, and desirable light characteristics.

Effects of light quality on the accumulation of phytochemicals in vegetables produced in controlled environments: a review

“…LEDs have been used in vegetable cultivation for more than 20 years, and Bula et al were the first investigators to use LEDs as the unique light source in the cultivation of lettuce . In the following years, increasing numbers of researchers conducted similar studies utilising LEDs for growth of kudzu, strawberry, Arabidopsis thaliana , and Chlorella vulgaris . In the 21st century, many countries, including the USA, Netherlands, China, South Korea, Japan and Lithuania, have conducted various studies on the application of LED light to crop cultivation, particularly in horticultural crop cultivation.…”

“…32 In the following years, increasing numbers of researchers conducted similar studies utilising LEDs for growth of kudzu, 33 strawberry, 34 Arabidopsis thaliana, 35 and Chlorella vulgaris. 36,37 In the 21st century, many countries, including the USA, Netherlands, China, South Korea, Japan and Lithuania, have conducted various studies on the application of LED light to crop cultivation, particularly in horticultural crop cultivation. Until recently, research concerning the effects of LED light on vegetables was mainly focused on varieties of lettuce, 38,39 cucumber, 40,41 tomato, 42 radish and spinach, 43 whereas research on field crops was focused on rice 44 and wheat.…”

Effect of different light spectra on the growth and productivity of acclimated Nannochloropsis sp. (Eustigmatophyceae)

“…By using selective wavelengths of incident light which are complementary or at least close to the maximum absorption of microalgae pigmentation, the use of other wavelengths which are poorly absorbed by the alga is avoided [1,27]. This added advantage is why many indoor microalgal photobioreactors are being designed and equipped with light emitting diodes (LEDs) which are currently the only efficient tool capable of emitting narrow bands of monochromatic light while including other advantages such as lower heat emission, higher conversion efficiency and also a much longer life-span when compared to common fluorescent or halogen lamps [7].…”

Photobioreactor cultivation strategies for microalgae and cyanobacteria

“…In a previous study, several lights used in PBRs were evaluated during microalgal cultivation and it was determined that AllnGaP II (aluminum indium gallium phosphide) emit light in the wavelength range of 600–700 nm and can convert electrical energy to photon energy at a 98% efficiency . Lee and Palsson concluded that Chlorella vulgaris cell size in cultures cultivated in red LED light was smaller (25–35 μm cell −1 ) than cells cultivated in fluorescent light (50–120 μm cell −1 ) . However, the cell density was similar from the two light sources.…”