Optimization of lutein production with mixotrophic cultivation of an indigenous microalga

  • 劉 振群

Student thesis: Master's Thesis


Lutein is a kind of carotenoids widely existing in plants microalgae and other photosynthetic organisms In addition to acting as photosynthetic pigments uptaking lutein can also effectively prevent aging retinal diseases cardiovascular diseases and chronic diseases Compared to conventional lutein production source (i e marigold petals) microalgae have emerged as a promising lutein producer due to their high growth rate no limitation of seasonal harvesting and most importantly high lutein content in microalgal biomass high lutein productivity and the structure of lutein in microalgae being the free form Therefore using microalgae as the lutein production sources has some advantages over marigold This study was to establish the platform technology on lutein production from the indigenous microalgal strains First several indigenous microalgal strains isolated from aquatic environments of Taiwan such as Chlorella sp Scenedesmus abundans GH-D11 Scenedesmus obliquus AS-6-1 and Chlorella sorokiniana HCH-2 were examined for their capabilities to accumulate lutein under mixotrophic cultivation The results show that the indigenous microalga Chlorella sp had the highest biomass and lutein productivity (1 10 mg/L/d and 2 79 mg/L/d respectively) In order to further enhance the performance of lutein productivity of Chlorella sp a series of systematic strategies were applied First four kinds of broth media (Basal MBM MBBM and BG-11) were used to examine the microalgae cell growth and lutein content of Chlorella sp The results show that BG-11 medium was more suitable for lutein production (2 96 mg/L/d) Furthermore since our previous work showed the performance of lutein production with Chlorella sp was markedly dependent on the concentration of sodium acetate and sodium nitrate which also further influenced the biomass productivity and harvest timing Therefore the response surface methodology (RSM) experimental design was used to optimize the composition of carbon and nitrogen source The simulated results based on RSM analysis predicted a maximal lutein productivity of 3 86 mg/L/d when adding 4 88 g/L of sodium acetate and 1 83 g/L of sodium nitrate This predicted value was confirmed with experiments conducted based on the optimized conditions The lutein productivity obtained from the confirmation experiments was 3 87 mg/L/d which is quite similar to the predicted one Finally in order to investigate the influence of trace elements in the medium on lutein productivity and avoid neglecting the main and interaction effects among those ions the two-level fractional factorial experimental design was applied to find out the significant factors Afterwards the steepest ascent method was used to locate the center for central composite designs Lastly the response surface methodology was employed for optimizing the trace composition The RSM analysis demonstrated a little improvement on lutein production as the productivity further increased to 4 10 mg/L/d with the optimal trace element composition of 51 mg/L calcium chloride dihydrate and 218 mg/L sodium chloride The investigation on the effect of light intensity shows that light intensity did not have significant effect on the performance of lutein production Also there was also no light inhibition on the cell growth Hence this strain may be feasible for outdoor cultivation Next the operation modes were studied (including semi-batch and semi-batch integrated with two-stage system) using optimal medium composition as mentioned above to improve the biomass productivity and lutein productivity The results of semi-batch system show that the maximal biomass productivity and maximal lutein productivity were 1 55 g/L/d and 5 51 mg/L/d respectively at 80% medium replacement ratio The results of semi-batch integrated with two-stage operation strategy demonstrated a maximal biomass productivity and maximal lutein productivity of 1 98 g/L/d and 7 62 mg/L/d respectively also occurred at a medium replacement ratio of 80% ratio Compared with the optimal condition of batch cultivation the lutein productivity was enhanced by 87% and to 86% respectively for semi-batch operation and semi-batch integrated with two-stage system
Date of Award2014 Aug 27
Original languageEnglish
SupervisorJo-Shu Chang (Supervisor)

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