Enhanced growth and total fatty acid production of microalgae under various lighting conditions induced by flashing light

Abstract

Microalgae are gaining importance as a source of high‐value bioproducts. However, data regarding optimization of algal productivity via variation of environmental factors are lacking. Here, we evaluated a novel lighting method for the enhancement of biomass and total fatty acid (TFA) productivities during algal cultivation. We cultivated six different algal strains (Chlorella vulgaris KCTC AG10002, Acutodesmus obliquus KGE18, Uronema sp. KGE03, Micractinium reisseri KGE19, Fragilaria sp., and Spirogyra sp.) under various lighting conditions—continuous light (CL), light‐dark cycle (LD), and continuous dark (CD)—with or without additional flashing light. We monitored dry cell weight (DCW) and TFA concentrations during cultivation. For each algal strain, the growth rate showed markedly different responses to the various lighting modes. The growth rates of C. vulgaris KCTC AG10002 (1.34‐fold DCW increase, LD with flash), A. obliquus KGE18 (5.16‐fold DCW increase, LD with flash), Uronema sp. KGE03 (2.77‐fold DCW increase, CL with flash), and M. reisseri KGE19 (1.52‐fold DCW increase, CL with flash) markedly increased in response to flashing light. Additionally, in some algal strains cultivated under the LD mode, the flashing light treatment induced increased TFA concentrations (C. vulgaris, 1.19‐fold increase; A. obliquus, 2.59‐fold increase; and M. reisseri, 3.31‐fold increase). Phytohormone analysis of M. reisseri revealed increases in growth rate and TFA concentrations, associated with phytohormone induction via flashing light (e.g. 2.93‐fold increase in gibberellic acid); hence, flashing light can promote substantial alterations in algal metabolism.

Microalgae: A Promising Source of Valuable Bioproducts

“…On the other hand, Chandra et al [ 64 ] established that the content of both linoleic and α-linolenic acids increases together with an increase in light intensity, which is a continuous lighting condition for an optimal photoperiod. Choi et al [ 65 ] studied the dependence of biomass productivity and total fatty acid content in microalgae on various lighting conditions (continuous light, light-dark cycle, continuous darkness and continuous darkness with additional flashing light). The analysis found that the use of flashing light significantly increased the growth rate of Chlorella vulgaris and the concentration of fatty acids in the biomass.…”

Impact of Cultivation Condition and Media Content on Chlorella vulgaris Composition

“…On the other hand, a later study has shown that flashing lights could significantly increase the total fatty acid (TFA) content of C. vulgaris in addition to its growth rate either the lighting period was continuous or cycling (light-dark). 28 On the other hand, Zhao and colleagues showed that red light wavelength at the intensity of 1200-1600 μmol/m 2 /s is optimum for microalgal growth. 29 More studies regarding light impact on microalgae growth and production are summarized in Table 1.…”

Effect of Electrical Ground Connection on Plant Growth

“…The plant growth hormone (IAA) was analyzed by the HPLC‐UV/Vis detector (YL9100 HPLC system, YL9120 UV/Vis Detector, Young Lin Instrument, Anyang, Korea). For the analysis of IAA, 15 days of cultivated whole plant (plant body and root) extracts were prepared using methanol . For the PCR‐DGGE analysis of the rhizobacteria of the plants, soil samples near the plant root surface were collected .…”