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Mar Biotechnol (2011) 13:527535 DOI 10.1007/s10126-010-9323-x
ORIGINAL ARTICLE
Stress-Induced Changes in Optical Properties, Pigmentand Fatty Acid Content of Nannochloropsis sp.: Implications for Non-destructive Assay of Total Fatty Acids
Alexei Solovchenko & Inna Khozin-Goldberg &
Lee Recht & Sammy Boussiba
Received: 5 May 2010 /Accepted: 8 September 2010 /Published online: 30 September 2010 # Springer Science+Business Media, LLC 2010
Abstract In order to develop a practical approach for fast and non-destructive assay of total fatty acid (TFA) and pigments in the biomass of the marine microalga Nannochloropsis sp. changes in TFA, chlorophyll, and carotenoid contents were monitored in parallel with the cell suspension absorbance. The experiments were conducted with the cultures grown under normal (complete nutrient f/2 medium at 75 mol PAR photons/(m2s)) or stressful (nitrogen-lacking media at 350 mol PAR photons/(m2s)) conditions. The reliable measurement of the cell suspension absorbance using a spectrophotometer without integrating sphere was achieved by deposition of cells on glassfiber filters in the chlorophyll content range of 313 mg/L. Under stressful conditions, a 3050% decline in biomass and chlorophyll, retention of carotenoids and a build-up of TFA (1545 % of dry weight) were recorded. Spectral regions sensitive to widely ranging changes in carotenoid-to-chlorophyll ratio and correlated changes of TFA content were revealed. Employing the tight inter-correlation of stress-induced changes in lipid metabolism and rearrangement of the pigment apparatus, the spectral indices were constructed for non-destructive assessment of carotenoid-to-chlorophyll ratio (range 0.30.6; root mean square error (RMSE)=
0.03; r2=0.93) as well as TFA content of Nannochloropsis sp. biomass (range 5.045%; RMSE=3.23 %; r2=0.89) in the broad band 400550 nm normalized to that in chlorophyll absorption band (centered at 678 nm). The findings are discussed in the context of real-time monitoring of the TFA accumulation by Nannochloropsis cultures under stressful conditions.
Keywords Carotenoids . Microalgal biotechnology. Nannochloropsis . Photoadaptation . Non-destructive assay
AbbreviationsCar Carotenoid(s)
Chl Chlorophyll(s)
DW Biomass dry weight IS Integrating sphere PFD Photon Flux Density(T)FA (Total) fatty acids
Introduction
Up-scaling of microalgal photobiotechnology for the production of value-added products such as long-chain polyunsatu-rated fatty acids, storage triacylglycerols, and carotenoids (Car) requires fast and reliable techniques, preferably nondestructive, for on-line monitoring of the target products content and the state of algal culture. These techniques provide information, which is essential for timely and...
