PigmentQuantification.md

Pigment quantification

Each culture (300 µL) was sampled after 72 hours at the end of the growth experiment. The sample was centrifuged at 14,000 g for 5 minutes and 4°C. The supernatant was discarded and the pellet was resuspended in 100 μl water. The samples were frozen at -80°C until further processing. 900 μl of 100% methanol were added to the sample and the sample was mixed by vortexing. After incubation in the dark under gentle agitation for 1 h at 4°C the sample was centrifuged at 14,000 g for 5 minutes. The supernatant was transferred into a cuvette and an absorbance spectrum was measured from 400 nm to 750 nm. The absorbance spectra were divided by the OD750 or CDW and the amount of chlorophyll a in the sample was quantified by the absorbance maximum of chlorophyll a at 665 nm (A665nm) using following equation (Lichtenthaler and Buschmann 2001):

Chlorophyll content[μg/ml]=12.66 μg/ml * A665 nm

The amount of carotenoids in the sample was quantified by the absorbance maximum of the sum of carotenoids at 470 nm (A470nm) and a correction term considering absorbance of chlorophyll a at 470 nm (c(Chl a): concentration of chlorophyll a in the sample) using following Equation (Lichtenthaler and Buschmann 2001):

Carotenoid content[mg/ml]=(1000 μg/ml * A470 nm−1.91 * c(Chl))/225