In situ monitoring of chlorophyll a fluorescence in Nannochloropsis oceanica cultures to assess photochemical changes and the onset of lipid accumulation during nitrogen deprivation

Abstract

In situ chlorophyll a fluorescence measurements were applied to monitor changes in the photochemical variables of Nannochloropsis oceanica cultures under nitrogendeplete and nitrogen-replete (control) conditions. In addition, growth, lipid, fatty acid, and pigment contents were also followed. In the control culture, growth was promoted along with pigment content, electron transport rate (ETR), and polyunsaturated fatty acids, while total lipid content and fatty acid saturation level diminished. Under nitrogen-deplete conditions, the culture showed a higher deepoxidation state of the xanthophyll cycle pigments. Fast transients revealed a poor processing efficiency for electron transfer beyond Q A , which was in line with the low ETR due to nitrogen depletion. Lipid content and the de-epoxidation state were the first biochemical variables triggered by the change in nutrient status, which coincided with a 20% drop in the in situ effective quantum yield of PSII (ΔF'/F m '), and a raise in the V j measurements. A good correlation was found between the changes in ΔF'/F m ' and lipid content (r = −0.96, p < 0.01). The results confirm the reliability and applicability of in situ fluorescence measurements to monitor lipid induction in N. oceanica.

On-Line Monitoring of Biological Parameters in Microalgal Bioprocesses Using Optical Methods

“…(1) [42][43][44][45][46] (2) [47] (2) (a) [58] (2) (b) [57] Mass spectrometry Contamination On TOF mass spectrometer Grazer detection Expensive instruments…”

“…[28] [29] (r,g,b)/DWC: R 2 = 0.97-0.99 [28] Open container/biofilm, suspension [28] (r,b)/DWC: R 2 = 0.90-0.96 [29] Open container/suspension [29] Biomass Transmittance spectrum DWC/T 751 /T 676 : r = 0.51-0.93 [30] Microwells [30] Biomass Chlorophyll fluorometry DWC/Chl a fluorescence: r = 0.95 [35] Fiber probe in PBR bypass [35] [39] CC/T751/T676: r = 0.85-0.96 [30] Microwells [30] [30] [25] [56] [35] CC/HR,EC: R 2 = 0.99 [25] Open container [25] CC/OD560: R 2 = 0.992-0.999 [56] Flask bypass [56] CC/Chl a fluorescence: r = 0.92 [35] Fiber probe in PBR bypass [35] Viable Algal lipids/NMR signal: R 2 = 0.99 [52] Bleed [52] Lipids as %DW/QY(∆F /Fm ): r = −0.96 [46] In-situ fiber [46] Lipids predicted/observed: R 2 = 0.94 [31] Sampling [31] Fatty acids ISM/Image recognition DHA/cell diameter: R 2 = 0.98 (calibration) PBR in-situ probe [34] Protein Chlorophyll fluorometry Protein/Chl a fluorescence: r = 0.92 Fiber probe in PBR bypass [35] Carotenoids (C) VIS/NIR spectrum Predicted/observed C: r = 0.96 Fiber in sample [32] 2.1. Biomass Concentration Biomass concentration (BC, mostly expressed as dry weight concentration, DWC) is the basic biological variable in any microbial cultivation.…”

“…On-line measurements in light-adapted samples are rather infrequent (see Section 3.3 in [10]). Recent examples are the identification of failures of CO 2 supply by the in-situ, on-line monitoring of the PQY by a PAM fluorometer together with monitoring differences in dissolved oxygen concentration in two locations along an open outdoor TLC photobioreactor [45]; further estimation of biomass productivity in Chlorella cultivated in a TLC open outdoor PBR by simultaneous on-line measurement of irradiance and quantum yield by a PAR sensor and a PAM fluorometer with fiber optics both submerged in the culture [44]; and identification of the lipid accumulation onset in Nannochloropsis oceanica cultured in closed Roux bottles by measuring in situ the effective PSII quantum yield (∆F /F m ) and finding also a pronounced correlation between the effective quantum yield and the lipid content [46].…”

“…Carneiro et al [46] could identify the onset of lipid accumulation in N. oceanica cultured in closed Roux bottles by in-situ monitoring of chlorophyll a fluorescence using a PAM fluorometer. The effective quantum yield of PSII (∆F /F m ) could be successfully correlated with the cell lipid content as %DWC.…”

Impact of Light Stress on the Synthesis of Both Antioxidants Polyphenols and Carotenoids, as Fast Photoprotective Response in Chlamydomonas reinhardtii: New Prospective for Biotechnological Potential of This Microalga

“…On the same extracts, the concentration of individual carotenoids was performed by reversed-phase Beckman System Gold HPLC (module 125 solvent) detector (DAD), model 168 Nouveau, column Luna, C8 (Phenomenex, Torrance, CA, USA), according to [17]. Carotenoids were identified by comparing the retention time and the spectrum with the standards, HPLC grade (Sigma-Aldrich, Louis, MO, USA).…”