Microalgal AstaP is a natural solubilizer of astaxanthin with broad binding ability for carotenoids and related compounds

An ependymin-related blue carotenoprotein decorates marine blue sponge

“…The carotenoid-free apoprotein was obtained by gently mixing the protein solution with diethyl ether and acetone ( 44 ). The colorless apoprotein separated into the aqueous phase, and detached orange carotenoids separated into the organic phase.…”

“…Next, the apoprotein was tested for its selective binding of carotenoids ( 44 ). The apoprotein fully recovered the blue color by reconstitution with AXT and MXT, but the color recovery was incomplete with AXT or MXT alone ( Fig.…”

“…AXT and MXT were extracted from the purified EPD-BCP1 as described previously. Canthaxanthin and fucoxanthin were extracted from microalgal AstaP-orange1and blown alga Eisenia sp., respectively ( 18 , 44 ). Briefly, the crude extracted pigments were dissolved in hexane and were separated by silica gel HPTLC with concentrate zone (Merck; catalog no.…”

“…The extracted carotenoids were further collected by C18-HPLC. The authenticity of the purified carotenoids was determined based on the absorption spectra obtained using an HPLC photodiode array detector, HPLC retention times, and molecular masses from high-resolution LC–MS analysis in comparison with those of standard compound ( 18 , 19 , 44 ). Apo-EPD-BCP1 was used for reconstitution assays after removing the organic solvents under an N 2 gas stream.…”

“…Apo-EPD-BCP1 was used for reconstitution assays after removing the organic solvents under an N 2 gas stream. Apoprotein (dissolved in 50 mM Tris–HCl buffer [pH 7.5]) and a small amount of carotenoid solutions (dissolved in acetone) were mixed together and incubated overnight on ice ( 44 ). Unbound insoluble carotenoids were removed by centrifugation for 5 min at 15,000 g , and the trace amounts of free carotenoids were removed by brief extraction with diethyl ether followed by removing the residual diethyl ether under an N 2 gas stream.…”