Production extraction and stabilization of lutein from microalgae

Abstract

Lutein is a type of carotenoids that can be found in plants microalgae and other photosynthetic organisms Lutein in human retina acts as a blue light filter to protect eyes from photochemical damage Lutein widely known as health supplement to reduce age-related macular degeneration (AMD) risk has been well developed with increasing demand over the years Lutein production from microalgae has been drawing numerous research interests over the past few years Microalgae show many advantages as lutein source over commercial lutein source (i e marigold flower) such as the high growth rate high lutein content no seasonal limitation and less labor-demand In this study lutein production from Chlorella sorokiniana MB-1 strain was examined The effects of gas sodium acetate concentrations and semi-batch operation on lutein content and lutein productivity were demonstrated First C sorokiniana MB-1 were grown on BG-11 medium with 1 0 g/L of sodium nitrate light intensity of 150 ?mol/m2/s and 0 1 vvm aeration rate Carbon dioxide (CO2) and air were used as feeding gas and another batch was cultivated without gas Undoubtedly C sorokiniana MB-1 accumulated highest lutein content and lutein productivity when fed with CO2 Optimal sodium acetate concentration was 6 0 mg/L resulting in maximal lutein content of 6 28 mg/g and lutein productivity of 3 06 mg/L/day To further enhance lutein accumulation semi-batch operation strategy was adopted Determination of optimal medium replacement ratio was first conducted The results show that 75% medium replacement ratio showed better efficiency in terms of lutein accumulation and was thus chosen for semi-batch cultivation Using semi-batch with eight cycles lutein productivity was much improved and reached up to 5 78 mg/L/d Lutein was then recovered by using both supercritical fluid extraction (SFE) and reduced pressure extraction method for comparison Better results were obtained using reduced pressure extraction while the highest recovery of lutein obtained from SFE was only 22% Moreover reduced pressure extraction can be applied at a lower temperature compared to conventional solvent extraction thus preventing lutein degradation In addition solvent can also be recovered using rotary evaporator therefore minimizing the consumption of organic solvent Recovery yield was found depending on the following parameters: pretreatment pressure solvent type extraction time and temperature Recovered lutein was measured using high-performance liquid chromatography (HPLC) High pressure cell disruption was chosen as pretreatment for being more effective than bead-beating The results show that tetrahydrofuran (THF) is the most effective solvent for lutein recovery With high pressure pretreatment THF and operation conditions of 850 mbar 25°C and 20 min about 87 0% lutein was recovered Almost full lutein recovery was achieved at longer extraction time (40 min) However since ethanol is more preferable in food processing extraction and optimization using ethanol is also conducted Using ethanol as solvent and under conditions of 450 mbar 35°C and 40 min 86 2% lutein was recovered The recovered lutein was then stabilized using vegetable oils Shelf-stability of lutein in olive oil and sunflower oil was studied Lutein suspended in oils were stored at 4 and 25°C Samples were analyzed at selected times and kinetic data were used to estimate lutein stability and half-life Samples were stored in dark and results showed that half-lives of lutein in olive oil at 4 and 25°C were 59 1 and 22 4 days respectively The corresponding results using sunflower oil at 4 and 25°C were 63 8 and 31 3 days respectively The reason behind the difference in stability could be the composition of antioxidant in the two type of oils Vegetable oils were proven capable of prolonging shelf-life of lutein compared to half-lives of lutein extracts in ethanol which only lasted for 16 7 and 11 1 days at 4 and 25°C respectively

Date of Award	2015 Aug 21
Original language	English
Supervisor	Jo-Shu Chang (Supervisor)