Effect of Production Conditions on Efficiency and Properties ofNiosomes Incorporating Natural Canthaxanthin Produced byDietzia natronolimnaeaHS-1

Canthaxanthin is an orange-red xanthophyll with widespread applications in thepharmaceutical, cosmetic, medical, feed and food industries (Hojjati et al., 2014;Gharibzahedi, et al., 2013a). 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(Gharibzahedi, et al., 2013b). Processing and preservation of products containing this pigmentare extremely difficult due to their high sensitivity to operational and environmentalconditions such as pH, light, O2, temperature, and etc (Seyedrazi et al., 2011). In order toovercome the instability problem of these bioactive compounds, encapsulation has become animportant tool, helping to increase shelf life and protecting the biological properties of thematerial. Moreover encapsulation allows the controlled release of these functional pigmentsunder desired conditions (Santos and Meireles, 2010). Niosomes are microscopic lamellarstructures (Shirsandet al., 2012) and can be used as carriers of amphiphilic and lipophilicsubstances (Akhilesh et al., 2012). The intention of this study was to evaluate theeffectiveness of production conditions on incorporation of natural canthaxanthin in niosomes.The strain of bacterium Dietzia natronolimnaea HS-1 (DSM 44860) used in this workwas first cultured in Yeast Malt Agar (4 days, 28°C) and then transferred into Erlenmeyerflasks containing Glucose Peptone Yeast extract medium (180 rpm, 28 °C, 7 days). Themedium were centrifuged and cell pellets were resuspended in pure ethanol to extract thepigment. The carotenoid extract was subsequently centrifuged, filtered and analysed by HPLC(Hojjati et al., 2014). Niosomes were prepared by a thin film hydration method followed bysonication and the effect of rotational speed of rotary vacuum evaporator flask (100 and 150rpm), canthaxanthin concentration (0, 10 and 20 µg/ml), concentration of polyethylene glycol400 (0, 0.5 and 1 w/v%), surfactant type (tween 60, tween 80, span 60 and span 80) andsurfactant to cholesterol ratio (80:120, 100:100, 120:80, 140:60 µmol) on entrapmentefficiency and noisome properties such as average vesicle size, poly dispersibility index, zetapotential, and morphological characterization were evaluated. Data analysis was carried outusing SAS statistical software. Comparison among the means was made using the Duncan’smultiple range analysis at probability value of 0.05.The results of HPLC analysis showed that the amount of canthaxanthin produced by D.natronolimnaea HS-1 was at the highest possible (more than 90%) when compared with otherimportant wild canthaxanthin-producing strains. The results revealed that rotational speed of150 rpm, canthxanthin concentration of 20 g/ml, polyethylene glycol 400 concentration of1% (w/v) and span 60 to cholesterol ratio of 100:100 produced niosomes with higherentrapment efficiency (81.2±1.2) and smaller size (162±9nm). As the hydrophilic-lipophilicbalance (HLB) value and the alkyl chain length of non-ionic surfactants increased, theentrapment efficiency of canthaxanthin also increased. Though span 80 has lower HLB value,entrapment with span 80 didn’t change significantly (p>0.05) which may be attributed to thepresence of unsaturation in the chain. Utilization of span 60 with similar efficiency to span 80was chosen due to smaller and more uniform vesicle size (0.26±0.02). On the other hand, inPEG coated vesicles, some expected material is entrapped in the long PEG chains which canincrease the entrapment efficiency. Result of the current study showed that surfactant typeaffected zeta potential significantly (p<0.05) while there was no significant difference amongsamples prepared with different surfactant to cholesterol ratio (p>0.05). All of theformulations considered to be stable due to the zeta potential of ±30 mV or higher. Althoughthere was no significant difference between ethanol and chloroform as solvent, use of ethanolwas preferred because of adverse effects of other residual solvents on health. Unilamellarniosomes became unstable with an increase of cholesterol more than 120 µmol which mightbe due to the cholesterol crystal formation.Concluding the above mentioned results, canthaxanthin can be incorporated and stabilizedwell in niosomes prepared with span 60 and cholesterol at equimolar ratio. Vesicles obtainedfrom the surfactants with low HLB values gave higher entrapment efficiency. Moreover, thelength and saturation of alkyl chain of the surfactants and surfactant to cholesterol ratio wasan important consideration for high entrapment efficiency

کلیدواژه ها:

Canthaxanthin ، Dietzia natronolimnaea HS1 ، Nano ، Niosome ، Surfactant