Stabilization of Natural Canthaxanthin Produced by DietzianatronolimnaeaHS-1 in Niosomes

Canthaxanthin (an orange-red xantophyll) is a superior antioxidant with widespreadapplications (Gharibzahedi et al., 2013a; Hojjati et al., 2012; Nasri Nasrabadi and Razavi2010; Tanaka et al., 2012). Recently production of this pigment from biological resources,especially microorganisms are preferred, owing to problems of seasonal and geographicvariability and use of agricultural waste and industrial wastewater as substrates (Gharibzahediet al., 2013b; Hojjati et al., 2011). As most food matrices are water-soluble, many efforts weredirected to the formulation of lipophilic pigments (mainly carotenoids) into water-solubleformulations (Socaciu, 2007). On the other hand, processing and preservation of productscontaining this pigment are extremely difficult due to their high sensitivity to operational andenvironmental conditions such as pH, light, O2, temperature, and etc (Seyedrazi et al., 2011).In order to overcome the solubility and instability problems of these bioactive compounds,encapsulation has become an important tool (Santos and Meireles, 2010). Niosomes aremicroscopic lamellar structures (Shirsandet al., 2012) and can be used as carriers ofamphiphilic and lipophilic substances (Akhilesh et al., 2012). The objective of this studyfirstly was to formulate niosomes with good properties and higher entrapment efficiency.Secondly, this study was also directed to evaluate the effects of different environmentalparameters such as time, temperature, pH and light on the degradation of naturalcanthaxanthin incorporated in niosomes.The strain of bacterium Dietzia natronolimnaea HS-1 (DSM 44860) used in this work wasfirst cultured in Yeast Malt agar (4 days, 28°C) and then transferred into Erlenmeyer flaskscontaining Glucose Peptone Yeast extract medium (180 rpm, 28 °C, 7 days). The mediumwere centrifuged and cell pellets were re-suspended in pure ethanol to extract the pigment.The carotenoid extract was subsequently centrifuged, filtered and analysed by HPLC (Hojjatiet al., 2014). Niosomes were prepared by thin film hydration method and sonication ofniosomal dispersions with various span 60 to cholesterol ratio (120:80, 100:100 and 80:120μmol). The effect of temperature (4, 25, 40°C), pH (3, 5, 7) and light on size, size distribution,zeta potential, entrapment efficiency and morphological characterization over storage wereevaluated. Data analysis was carried out using SAS statistical software. Comparison amongthe means was made using the Duncan’s multiple-range analysis at probability value of 0.05.The HPLC analysis of ethanol extract revealed that canthaxanthin was more than 90% oftotal carotenoids produced by Dietzia natronolimnaea HS-1. The results showed a meandiameter of niosomes in the range 160-177 nm. All formulations showed a negative surfacecharge and entrapment efficiency in the range 77.2–81.2%. Niosome prepared with span 60 incombination with cholesterol at a ratio of 100:100 was found to produce small and uniformvesicle size with high stability and entrapment efficiency over storage. The TEM micrographconfirmed the formation of niosomes. All the niosomes showed spherical unilamellarvesicular structure with size less than 200 nm, which correlated with the results of DLSmeasurements. According to the present study, Light, low pH and high temperatures weredrastic factors to the stability of canthaxanthin incorporated in niosomes due to theaccelerated changes in double bonds existed in the chain of carotenoids. Samples weredegraded in all conditions over storage, especially in light. The entrapment efficiency ofcanthaxanthin in niosomes decreased by an increase in time or temperature. Cholesteroldecreased the degradation of canthaxanthin during storage by adding rigidity to niosomes.This present study has demonstrated the stability enhancement of canthaxanthin in niosomes.Concluding the above mentioned results, canthaxanthin can be incorporated and stabilizedwell in niosomes prepared with span 60 and cholesterol at equimolar ratio. Although thisstudy provided better stability for canthaxanthin than our previously published data, furtherwork is needed to improve canthaxanthin maintenance