Far‐red light (720 or 740 nm) improves growth and changes the chemical composition of Chlorella vulgaris

Abstract

Research ArticleFar-red light (720 or 740 nm) improves growth and changes the chemical composition of Chlorella vulgaris Far-red (FR) light is crucial for the efficiency of photosynthesis and photomorphogenetic activity. This study investigated whether FR light at different wavelengths affects the Chlorella vulgaris biomass growth rate and chemical composition. For this purpose, FR was added to the blue-red (R) light at the wavelength of 720 nm (BRFR 720 L [blue + R + FR 720 nm light]) or 740 nm (BRFR 740 L [blue + R + FR 740 nm light]). BRFR 740 L allowed both higher growth rate and increased amount of total biomass compared to BRFR 720 L (blue + R + FR 720 nm light). The chemical composition of C. vulgaris biomass, analyzed by FT-Raman spectroscopy on lyophilized cells, significantly correlated with the applied FR component. The differences in lipid, carotenoid, and chlorophyll contents were particularly evident and all were higher in BRFR 740 L. Fluorescence emissions spectra of C. vulgaris cells were measured in the range 420-800 nm in the cuvette equipped with a magnetic stirrer preventing sedimentation of the cells during measurement. In the blue-green range (420-650 nm) fluorescence emission spectra indicated that changes in the chemical composition of phenolic compounds in the algae depended on the wavelength of FR used in LED matrices. This work showed that the use of FR of a wavelength 740 nm in the bioreactor's light source significantly improves biomass production of C. vulgaris cultures. IntroductionThe light, among the many factors influencing the growth and metabolism of the algae, is one of the most important but also most highly variable parameter. It has been shown that the spectral composition of light that exerts a positive influence on the growth of a particular strain of algae is not necessarily beneficial for growth of another strain [1]. Hence the importance of the selection of spectral composition of light. Both higher and lower plants have developed many photoreceptors to estimate the intensity of the wavelength and the direcCorrespondence: Prof. Andrzej Skoczowski (amskoczowski@gmail .com), Institute of Biology, Pedagogical University of Cracow, ul. Podchorążych 2, PL 30-084 Cracow, Poland.Abbreviations: BR, blue + red light; Chl, chlorophyll; F450, blue fluorescence; F530, green fluorescence; F690, red chlorophyll fluorescence; F735, far-red chlorophyll fluorescence; F450/F530, ratio of the blue to green fluorescence; F450/F690, fluorescence ratio blue/red; F450/F735, fluorescence ratio blue/far-red; F690/F735, chlorophyll fluorescence ratio red/far-red; FR, far-red; R, red light; WL, white light tion of the light [2,3]. Red (R) and blue light plays an important role in the photosynthesis and photomorphogenesis, thus influencing the development and metabolism of autotrophic plants. The essential light requirement of the photosynthesis process is the PAR (photosynthetically active radiation) range, that is from 400 to 700 nm (the end of absorption spectrum of the chlorophyll [Chl]). H...

Far‐red dependent changes in the chemical composition of Spirulina platensis

“…, in terrestrial plants, several cinnamic acids (ferulic, sinapsis, and caffeic acid) are responsible for the so‐called F450, whereas the F530 is attributed to compounds such as berberine, quercetin, and riboflavin. Similar shifts in the fluorescence spectra, suggesting changes in the composition of phenolic compounds, were observed previously during the growth of Chlorella vulgaris culture .…”

“…According to Lang et al [41], in terrestrial plants, several cinnamic acids (ferulic, sinapsis, and caffeic acid) are responsible for the so-called F450, whereas the F530 is attributed to compounds such as berberine, quercetin, and riboflavin. Similar shifts in the fluorescence spectra, suggesting changes in the composition of phenolic compounds, were observed previously during the growth of Chlorella vulgaris culture [34,42]. Fluorescence emission spectra can produce many relevant information regarding plant responses to changing growth conditions, for example, the intensity and/or spectrum of light, temperature, and nutrient deficiency.…”

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