Simultaneous estimation of chlorophyll a and lipid contents in microalgae by three‐color analysis

Abstract

A method of rapid determination of chlorophyll a and lipid contents of microalgae based on colorimetric analysis of the digital images of the microalgae is proposed. The color variation of microalgae during cultivation is evaluated by the brightness of the three primary colors (red, green, and blue). The brightness values of the three primary colors are modeled as two linear correlation functions (RGB model) for microalgal chlorophyll a and lipid contents, respectively. The chlorophyll a and lipid contents predicted by the proposed model are compared with that determined by the standard methods. The good agreement of the model predictions with experimental results is demonstrated with a squared correlation coefficient (R(2)) of 0.99 for chlorophyll a and lipid. The reliability of the RGB model was verified in real cultivations of the microalgae in a photobioreactor. Growth dynamics, contents of chlorophyll a and lipid corresponded very well with previously reported studies.

Effect of Various Pretreatment for Extracting Intracellular Lipid fromNannochloropsis oculataunder Nitrogen Replete and Depleted Conditions

“…The chlorophyll content (mg/L) was estimated according to Su et al [14]. Two milliliters of culture broth was taken in centrifuge tube, ultrasonic for 10 min in ice bath with two milliliters of 90% methanol overnight.…”

Monitoring of Microalgal Processes

“…Pigments were measured online in a bypass in a spectrophotometer measuring cell [101,102]. Neutral lipids could be estimated by correlating lipid yield and PE during physiological stress using PAM fluorometry [130], Chl a and lipid contents were simultaneously estimated by three-color analysis in culture samples [36]. In that approach, the total fatty acid content was correlated with carotenoid-tochlorophyll ratio obtained by measuring absorbance spectra of a microalgal suspension [140,141], and the carotenoid and chlorophyll content were correlated with the color coordinates of a culture sample measured by a colorimeter [58].…”

“…Because of its inhibitory effect, oxygen must be continually removed by sparging the culture with air, usually enriched by CO 2 ; thus, O 2 removal, CO 2 supply, and pH control are combined in one step. Oxygen in the liquid phase can be measured by a Clark electrode, by an optical oxygen sensor [93], or by a luminescence optical DO electrode [94], either directly in the photobioreactor [18,36,58,[94][95][96] or in the degasser or a bypass [61]. Oxygen in the gas phase can be measured in outlet gas with a paramagnetic [19] or polarometric gas analyzer [48].…”

“…Measurement principles employed so far include optical methods as fluorescence spectrometry and flow cytometry (FC), Fourier transform infrared (FTIR), NIR, and Raman spectrometry, colorimetric detection by image analysis, submicroscale gas chromatography-mass spectrometry (GC-MS), nuclear magnetic resonance (NMR) and dielectrophoresis, as shown in recent reviews [7,8] and in a publication of the Algae Biomass Organization (ABO) Technical Standard Committee [9]. Attempts to adapt some of these high-throughput methods to online use have been made for Raman spectroscopy [35] and colorimetry [36] but, on the whole, this task is difficult.…”

Microalgae, a Potential Natural Functional Food Source – a Review

“…There is a chlorophyll c, which has a fully unsaturated porphyrin macrocycle and generally lacks chlorophyllides [Hosikian et al, 2010;Su et al, 2008].…”