鹽生杜氏藻對鹽度變化和滲透脅迫下的細胞反應(yīng)及其中性脂肪的積累
發(fā)布時間：2019-01-08 19:10
【摘要】：杜氏鹽藻是一種綠色微藻,能夠在鹽度極其廣泛的環(huán)境下生長并積累含有類胡蘿卜素的中性脂肪球,因此可以用來生產(chǎn)生物柴油和色素。杜氏鹽藻是迄今為止研究發(fā)現(xiàn)的最為耐鹽的真核生物,適合開放式的大規(guī)模培養(yǎng),具有廣泛的和潛在的工業(yè)應(yīng)用前景。杜氏鹽藻的另外一個重要的生物學(xué)特性是其無剛性細胞壁,有助于從其細胞中提取中性脂肪或類胡蘿卜素并進行生物煉制。這種藻類在細胞受到低鹽滲透脅迫或高鹽滲透脅迫時能夠迅速改變其體積和形狀。為了進一步開發(fā)和利用杜氏鹽藻生產(chǎn)生物柴油的實際應(yīng)用和研究鹽度對細胞生長和脂肪產(chǎn)生的影響,本論文通過改變培養(yǎng)基中氯化鈉的濃度分析了鹽度對于杜氏藻細胞的形態(tài)、生長以及中性脂質(zhì)積累情況的短期和長期影響。研究結(jié)果發(fā)現(xiàn):(1)在不同程度的鹽滲透脅迫下,細胞的大小與形態(tài)會發(fā)生明顯的變化。低鹽滲透脅迫下的細胞會迅速增大,而高鹽滲透脅迫下的細胞會迅速變小。這種現(xiàn)象說明了杜氏藻的特殊膜結(jié)構(gòu)能夠使其在不同鹽度的環(huán)境中使細胞迅速膨脹或收縮而避免細胞破裂,反映了其細胞內(nèi)離子濃度的變化。(2)鹽濃度對細胞生長速度和細胞最大生長量也有影響:鹽濃度越低,杜氏鹽藻的生長速率越快,細胞最大生長量越高;反之,鹽濃度越高,細胞生長速度越慢,細胞最大生長量越低。(3)將杜氏藻細胞從含有9%NaCl培養(yǎng)基中轉(zhuǎn)移到含有15%NaCl培養(yǎng)基中的細胞所積累的中性脂質(zhì)含量最高。然而在這種鹽脅迫條件下,杜氏藻生長緩慢,細胞分裂能力下降,但滲透脅迫并未對細胞造成致命性的傷害,細胞能自動調(diào)節(jié)體積以適應(yīng)這種變化。將杜氏藻從濃度為3%的NaCl培養(yǎng)基中轉(zhuǎn)移到濃度為9%的NaCl培養(yǎng)基后能迅速恢復(fù)生長并未能積累中性脂質(zhì),說明細胞在該濃度下的生長并未受到抑制。因此,杜氏鹽藻細胞的中性脂質(zhì)的積累應(yīng)該是建立在細胞生長受到抑制的基礎(chǔ)之上而獲得的。(4)在含有3%-15%NaCl濃度范圍內(nèi)分批培養(yǎng)的杜氏鹽藻的結(jié)果都顯示:營養(yǎng)元素的限制是減緩細胞分裂和抑制細胞生長的另一個重要因素,所有分批培養(yǎng)的細胞在進入了生長停滯期時都開始積累中性儲存脂質(zhì)。綜上所述,杜氏鹽藻只有在高鹽度滲透脅迫下,短期內(nèi)會引起細胞中中性脂質(zhì)的積累,且抑制細胞的分裂并造成細胞生長緩慢。盡管在高鹽度下生長的杜氏藻會積累中性脂質(zhì),但同時其緩慢的生長速度的也會影響細胞中中性脂肪的總產(chǎn)量。因此,工業(yè)化培養(yǎng)杜氏藻時建議在低鹽濃度條件下進行藻體細胞的培養(yǎng),等細胞生長進入到指數(shù)生長期后再將其轉(zhuǎn)移到高鹽濃度中,這樣既可獲得大量的藻細胞,又能收獲大量的中性脂肪。然而,這種培養(yǎng)方式周期較長,因此在探究利用微藻生產(chǎn)生物柴油領(lǐng)域的應(yīng)用前景時,最有待解決的問題是如何同時實現(xiàn)細胞生長量和單細胞脂質(zhì)產(chǎn)率的最大化。
[Abstract]:Dunaliella Salina is a green microalgae, which can grow and accumulate carotenoid neutral fat spheres in a very wide range of salinity, so it can be used to produce biodiesel and pigment. Dunaliella Salina is the most salt-tolerant eukaryote found so far. It is suitable for large-scale open culture and has wide and potential industrial application prospects. Another important biological characteristic of Dunaliella Salina is its non-rigid cell wall, which helps to extract neutral fat or carotenoid from its cells and biorefine them. The algae can change its size and shape rapidly under low salt osmotic stress or high salt osmotic stress. In order to further develop and utilize the application of Dunaliella Salina to produce biodiesel and to study the effect of salinity on cell growth and fat production, the morphology of Dunaliella sp. Cells was analyzed by changing the concentration of sodium chloride in culture medium. Short-and long-term effects of growth and neutral lipid accumulation. The results showed that: (1) under different degree of salt osmotic stress, the size and morphology of cells changed obviously. The cells under low salt osmotic stress will increase rapidly, while those under high salt osmotic stress will rapidly become smaller. This phenomenon shows that the special membrane structure of Dunaliella can cause the cells to expand or contract rapidly in different salinity environment to avoid cell rupture. (2) Salt concentration also affects the cell growth rate and the maximum cell growth: the lower the salt concentration, the faster the growth rate of Dunaliella Salina and the higher the cell growth; On the other hand, the higher the salt concentration, the slower the cell growth rate and the lower the maximum cell growth. (3) the higher the salt concentration, the higher the accumulation of neutral lipid in the cells transferred from the culture medium containing 9%NaCl to the medium containing 15%NaCl. However, under the condition of salt stress, the growth of Dunaliella was slow and the ability of cell division was decreased. However, osmotic stress did not cause fatal damage to the cells, and the cells could automatically adjust their volume to adapt to this change. When the algae was transferred from 3% NaCl medium to 9% NaCl medium, the growth of Dunaliella spp recovered rapidly and the neutral lipid was not accumulated, which indicated that the growth of the cells was not inhibited at this concentration. therefore The accumulation of neutral lipid in Dunaliella Salina cells should be based on the inhibition of cell growth. (4) the results of batch culture of Dunaliella Salina in the concentration range of 3%-15%NaCl showed that Nutrient restriction is another important factor in slowing cell division and inhibiting cell growth. All the cells cultured in batches began to accumulate neutral storage of lipid at the stage of growth stasis. In conclusion, only under high salinity osmotic stress, Dunaliella Salina can induce the accumulation of neutrophil lipid, inhibit cell division and slow cell growth. Although the growth of Dunaliella spp under high salinity will accumulate neutral lipid, but its slow growth rate will also affect the total production of cellular neutral fat. Therefore, it is suggested that the algae somatic cells should be cultured in low salt concentration, so that the cells grow into exponential growth period and then transfer to high salt concentration, so that a large number of algal cells can be obtained. And it can harvest a lot of neutral fat. However, this culture method has a long period of time, so the most important problem to be solved in exploring the application prospect of microalgae in biodiesel production is how to maximize both cell growth and single cell lipid yield.
【學(xué)位授予單位】：沈陽農(nóng)業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：Q945.78
[Abstract]:Dunaliella Salina is a green microalgae, which can grow and accumulate carotenoid neutral fat spheres in a very wide range of salinity, so it can be used to produce biodiesel and pigment. Dunaliella Salina is the most salt-tolerant eukaryote found so far. It is suitable for large-scale open culture and has wide and potential industrial application prospects. Another important biological characteristic of Dunaliella Salina is its non-rigid cell wall, which helps to extract neutral fat or carotenoid from its cells and biorefine them. The algae can change its size and shape rapidly under low salt osmotic stress or high salt osmotic stress. In order to further develop and utilize the application of Dunaliella Salina to produce biodiesel and to study the effect of salinity on cell growth and fat production, the morphology of Dunaliella sp. Cells was analyzed by changing the concentration of sodium chloride in culture medium. Short-and long-term effects of growth and neutral lipid accumulation. The results showed that: (1) under different degree of salt osmotic stress, the size and morphology of cells changed obviously. The cells under low salt osmotic stress will increase rapidly, while those under high salt osmotic stress will rapidly become smaller. This phenomenon shows that the special membrane structure of Dunaliella can cause the cells to expand or contract rapidly in different salinity environment to avoid cell rupture. (2) Salt concentration also affects the cell growth rate and the maximum cell growth: the lower the salt concentration, the faster the growth rate of Dunaliella Salina and the higher the cell growth; On the other hand, the higher the salt concentration, the slower the cell growth rate and the lower the maximum cell growth. (3) the higher the salt concentration, the higher the accumulation of neutral lipid in the cells transferred from the culture medium containing 9%NaCl to the medium containing 15%NaCl. However, under the condition of salt stress, the growth of Dunaliella was slow and the ability of cell division was decreased. However, osmotic stress did not cause fatal damage to the cells, and the cells could automatically adjust their volume to adapt to this change. When the algae was transferred from 3% NaCl medium to 9% NaCl medium, the growth of Dunaliella spp recovered rapidly and the neutral lipid was not accumulated, which indicated that the growth of the cells was not inhibited at this concentration. therefore The accumulation of neutral lipid in Dunaliella Salina cells should be based on the inhibition of cell growth. (4) the results of batch culture of Dunaliella Salina in the concentration range of 3%-15%NaCl showed that Nutrient restriction is another important factor in slowing cell division and inhibiting cell growth. All the cells cultured in batches began to accumulate neutral storage of lipid at the stage of growth stasis. In conclusion, only under high salinity osmotic stress, Dunaliella Salina can induce the accumulation of neutrophil lipid, inhibit cell division and slow cell growth. Although the growth of Dunaliella spp under high salinity will accumulate neutral lipid, but its slow growth rate will also affect the total production of cellular neutral fat. Therefore, it is suggested that the algae somatic cells should be cultured in low salt concentration, so that the cells grow into exponential growth period and then transfer to high salt concentration, so that a large number of algal cells can be obtained. And it can harvest a lot of neutral fat. However, this culture method has a long period of time, so the most important problem to be solved in exploring the application prospect of microalgae in biodiesel production is how to maximize both cell growth and single cell lipid yield.
【學(xué)位授予單位】：沈陽農(nóng)業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：Q945.78
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