一階段逆境培養雨生紅球藻

Abstract

蝦紅素是一種具有極高經濟價值的紅色天然類胡蘿蔔素，廣泛存在於鮭魚、蝦、蟹、鳥類的羽毛中，蝦紅素為目前最強的抗氧化劑，據科學家研究其抗氧化能力為β胡蘿蔔素的10倍、維生素E的500倍，所以，蝦紅素又被稱為超級維生素或是維生素X。蝦紅素在食品添加劑、水產養殖、化妝品、保健品和醫藥工業方面有廣闊的應用前景。 雨生紅球藻(Haematococcus pluvialis)是目前所知主要的自然蝦紅素產生來源，被認為是一種很有蝦紅素商業生產前景的微藻。光照強度、溫度、pH、鹽度和培養基等許多因素，都會影響到雨生紅球藻累積蝦紅素的含量。當雨生紅球藻暴露在不利的生長條件或環境壓力下，如營養源(氮或磷)缺乏、鹽度過高或強光照射下，會刺激綠色細胞開始轉變成紅色細胞，進行蝦紅素的累積。因為蝦紅素的累積必須在不利生長的環境下進行，因而發展出兩階段培養的方法來培養雨生紅球藻。於第一階段時，將藻培養於適合生長的環境下得到高的生物產量，接著在第二階段時，將藻暴露於不利生長的環境下刺激蝦紅素的累積得到最大量的蝦紅素產量。 本研究期望在雨生紅球藻的培養上，利用強光照通以高濃度二氧化碳10%，亦或是15%，相當於電廠排放廢氣之二氧化碳濃度，發展出雨生紅球藻一階段生產蝦紅素之培養方法，同時利用藻之減碳能力達到降低電廠排放廢氣二氧化碳濃度的目的。結果顯示，當雨生紅球藻培養於光度150 μEm-2s-1 通以 10% CO2時，經過18天的培養，從起始細胞密度0.02 g/L增長到1.07 g/L，且蝦紅素獲得量為4.482 mg，優於兩階段培養對照組所獲得細胞密度0.56 g/L及蝦紅素獲得量0.775 mg；當起始細胞密度提高10倍至0.2 g/L，通以200 μEm-2s-1及15% CO2時，經過14天的培養，細胞密度增長至1.13 g/L同樣優於高起始細胞密度的兩階段培養獲得量0.26 g/L，且蝦紅素獲得量為3.410 mg。 由實驗結果可知，經由高光照及通入高濃度二氧化碳之雨生紅球藻一階段逆境生產蝦紅素培養法在獲得之生物量或是蝦紅素含量都明顯優於兩階段培養生產蝦紅素方法。

Haematococcus pluvialis is the most important source of natural astaxanthin which has the ability of antioxidative activity higher than β-carotene and vitamin E. Astaxanthin is a high-value-added product. Currently, the culture method of commercial Haematococcus pluvialis for producing astaxanthin is a two – stage mode. In this study, one-stage cultivation of Haematococcus pluvialis using stressful conditions: high light intensity (150 μEm-2s-1) and high CO2 concentration (10%) was developed to increase cell density from 0.02 to 1.07 g/L after 18-day culture. The amount of extracted astaxanthin was 4.482 mg. By contrast, the astaxatnthin extract amount 0.775 mg by a conventional two-stage culture which had initial cell density grew from 0.02 to 0.56 g/L under atmospheric CO2 concentration and low light intensity (25 μEm-2s-1) for 18 days and then switch to a second stage with high light intensity 300 μEm-2s-1 for 7 days to induce the accumulation of astaxanthin. When CO2 concentration elevated to 15% and light intensity increased to 200 μEm-2s-1, cell density increased from 0.2 g/L to 1.13 g/L and the obtained astaxanthin was 3.410 mg. Our results demonstrate that one-stage cultivation of Haematococcus pluvialis under stressful conditions for the production of high yield of astaxanthin is innovative approach compared to the conventional two-stage culture method. In addition, the high concentration of 15% CO2, discharged CO2 concentration from power plant, employed for the one-stage microalgae culture can be sequestered to a lower emission concentration for alleviate global warming effect.