Mixotrophy in diatoms: Molecular mechanism and industrial potential

Abstract

Diatoms are microalgae well known for their high variability and high primary productivity, being responsible for about 20% of the annual global carbon fixation. Moreover, they are interesting as potential feedstocks for the production of biofuels and high‐value lipids and carotenoids. Diatoms exhibit trophic flexibility and, under certain conditions, they can grow mixotrophically by combing photosynthesis and respiration. So far, only a few species of diatoms have been tested for their mixotrophic metabolism; in some cases, they produced more biomass and with higher lipid content when grown under this condition. Phaeodactylum tricornutum is the most studied diatom species for its mixotrophic metabolism due to available genome sequence and molecular tools. However, studies in additional species are needed to better understand the conservation of this process in diatoms and its potential in industrial applications. Here, we describe the photosynthetic and respiratory pathways involved in mixotrophy and provide an overview of the trophic variability in diatoms. This review also highlights promising areas of industrial applications for diatoms when cultivated under mixotrophy.

Mixotrophy in a Local Strain of Nannochloropsis granulata for Renewable High-Value Biomass Production on the West Coast of Sweden

“…330401, Hilden, Germany) according to the manufacturer's instructions. Real-time quantitative reverse transcription-PCR (qRT-PCR) was performed in biological triplicate using the RT 2 Profiler PCR Array kit (Qiagen, cat.330231) in order to analyse the expression of 84 cell death genes in PC3 after exposure to the active fraction E. Plates were run on a ViiA7 (Applied Biosystems 384 well blocks, Waltham, MA, USA), Standard Fast PCR Cycling protocol with 10 µL reaction volumes. The cycling conditions used were 1 cycle initiation at 95.0 • C for 10 min, followed by amplification for 40 cycles at 95.0 • C for 15 s and 60.0 • C for 1 min.…”

“…It can be employed as a method to increase the productivity of microalgae that are cultivated in low light conditions. To minimize the additional cost of organic carbon supplementation, industrial wastewater and biodiesel waste (i.e., glycerol) are often used for algae cultivation and biomass production (as reviewed by Villanova et al 2021 [ 2 ]). The Eustigmatophyceae Nannochloropsis genus has been extensively used for biotechnological applications such as the production of biofuel [ 3 , 4 ] and fish feed [ 5 ].…”

“…Fatty acids have been reported using the LIPID MAPS shorthand notation[26]. Fatty acyl chains are indicated as C:N;O, where C is the number of carbon atoms, N is the number of double bond equivalents, and O is the number of additional oxygen atoms linked to the hydrocarbon chain 2. MGTS/A with a putative hydroperoxyhexadecenoic acid as a fatty acyl substituent, as revealed by a neutral loss of 34.0055 Da from the [M + H] + ion, arising from fragmentation of the hydroperoxy group.…”

Valorization of carbon dioxide (CO2) to enhance production of biomass, biofuels, and biorenewables (B3) in Chlorella saccharophilaUTEX247: a circular bioeconomy perspective

“…It has been observed that supplementation with an additional carbon source, especially CO 2 , enhances photosynthetic efficiency within a short period of time 49,50 . The absorption of sunlight through the antenna complex precedes the transfer of energy to reaction centers in light‐dependent processes 51 . Photosynthetic organisms employ non‐photochemical quenching (NPQ) processes to dissipate excess energy distributed in the Photosystem II and Photosystem I reaction centers.…”

“…49,50 The absorption of sunlight through the antenna complex precedes the transfer of energy to reaction centers in light-dependent processes. 51 Photosynthetic organisms employ non-photochemical quenching (NPQ) processes to dissipate excess energy distributed in the Photosystem II and Photosystem I reaction centers. Another key photosystem protective mechanism is the cyclic electron flow 52 around the PSI, which works to compensate for Adenosine triphosphate (ATP) deficiency by facilitating electron transfer from the PSI acceptor side to Plastoquinone (PQ), resulting in protons being translocated into the lumen without a net drop in Nicotinamide Adenine Dinucleotide Phosphate (NADP) (+) .…”