Photon up‐conversion increases biomass yield in Chlorella vulgaris

Abstract

Photon up-conversion, a process whereby lower energy radiations are converted to higher energy levels via the use of appropriate phosphor systems, was employed as a novel strategy for improving microalgal growth and lipid productivity. Photon up-conversion enables the utilization of regions of the solar spectrum, beyond the typical photosynthetically active radiation, that are usually wasted or are damaging to the algae. The effects of up-conversion of red light by two distinct sets of up-conversion phosphors were studied in the model microalgae Chlorella vulgaris. Up-conversion by set 1 phosphors led to a 2.85 fold increase in biomass concentration and a 3.2 fold increase in specific growth rate of the microalgae. While up-conversion by set 2 phosphors resulted in a 30% increase in biomass and 12% increase in specific intracellular neutral lipid, while the specific growth rates were comparable to that of the control. Furthermore, up-conversion resulted in higher levels of specific intracellular reactive oxygen species in C. vulgaris. Up-conversion of red light (654 nm) was shown to improve biomass yields in C. vulgaris. In principle, up-conversion can be used to increase the utilization range of the electromagnetic spectrum for improved cultivation of photosynthetic systems such as plants, algae, and microalgae.

Shifting the Sun: Solar Spectral Conversion and Extrinsic Sensitization in Natural and Artificial Photosynthesis

“…Consequently, up‐conversion has been proposed for sensitizing photocatalysis at TiO 2 , Bi 2 WO 6 , α‐Fe 2 O 3 , CdS, and other semiconductor surfaces and, more recently, also to increase the photosynthetic activity in pumpkin leaf thylakoids . and Chlorella vulgaris microalgae …”

Promoting the Growth of Mung Bean Plants through Uptake and Light Conversion of NaYF4:Yb,Er@CDs Nanocomposites

“…NaYF 4 :Yb,Er is deemed to be a high-efficient UC material and has the ability to transform NIR light into visible light (mainly green and red light) via multiple-photon absorption. , NaYF 4 :Yb,Er UCNPs have been extensively applied to many fields, such as displays, optical storage, photovoltaic devices, bioimaging, anti-counterfeiting, and so on. − However, the application of NaYF 4 :Yb,Er UCNPs as light conversion materials for improving plant photosynthesis efficiency has not been reported, though this idea has been proposed. , In general, NaYF 4 :Yb,Er UCNPs show stronger green UC emissions than red UC emissions due to the different population of electrons in the corresponding levels of Er 3+ ions. , As mentioned above, red light is one of the most important light types for photosynthesis because it can be absorbed by chloroplasts. Therefore, it is highly desirable to explore NaYF 4 :Yb,Er UCNPs with enhanced red UC emissions and investigate their utility as light conversion materials in plants.…”

“…33−36 However, the application of NaYF 4 :Yb,Er UCNPs as light conversion materials for improving plant photosynthesis efficiency has not been reported, though this idea has been proposed. 30,37 In general, NaYF 4 :Yb,Er UCNPs show stronger green UC emissions than red UC emissions due to the different population of electrons in the corresponding levels of Er 3+ ions. 36,38 As mentioned above, red light is one of the most important light types for photosynthesis because it can be absorbed by chloroplasts.…”

Energy Pooling Upconversion in Organic Molecular Systems

“…The efficiency of photochemical processes in biological systems also suffers as a result of a mismatch of existing and desired frequencies of light. For instance, microalgae used in energy harvesting strategies do not efficiently utilize the red end of the solar spectrum for biomass production . An analogous issue confronts those involved in the design of solar panels because a large swath of the solar spectrum reaches earth at frequencies too low to be utilized by existing photovoltaic technology …”