氮源对盐藻生长及细胞物质组成的影响

The Effect of Nitrogen Supply on the Growth and Cell Chemical Composition of Dunaliella salina

杜氏盐藻(Dunaliella salina)细胞内含有大量的蛋白质、多糖、甘油、脂类、β-胡萝卜素等物质,不仅是水产养殖育苗常用的饵料,而且在食品、医药和保健品等日常生活用品中具有独特的经济价值。研究常见氮源形式和浓度对盐藻生长和细胞物质组成的影响,探索适宜于不同培养目的的氮源供给方式,可为盐藻的大量培养、开发应用提供依据。文章针对NaNO_3、NH_4Cl和CH_4N_2O等3种不同形式及200、600和1 800μmol·L^(-1)等3种不同浓度的氮源,研究了不同的氮源供给条件下杜氏盐藻的生长情况和细胞的物质组成。结果表明,盐藻生长可利用所测试的3种氮源。就氮源形式而言,最终生物量表现为CH_4N_2O≥NaNO_3>NH_4Cl,盐藻更偏好有机氮源CH_4N_2O;就氮源浓度而言,最终生物量表现为1 800μmol·L^(-1)≥600μmol·L^(-1)>200μmol·L^(-1),600μmol·L^(-1)以上的浓度上升对于进一步提高生物量没有显著性贡献。在200μmol·L^(-1)时,有机氮源CH_4N_2O比无机氮源NaNO_3、NH_4Cl更有利于盐藻生长。氮源形式对盐藻细胞中蛋白质含量的影响不显著,但显著地影响细胞中糖和脂肪的积累。有利于糖积累的氮源形式表现为NH_4Cl≥NaNO_3>CH_4N_2O,而有利于脂肪积累的氮源形式表现为NH_4Cl≥NaNO_3≥CH_4N_2O。高氮源浓度有利于盐藻细胞蛋白质的积累,但对糖和脂肪的积累效果不显著,对盐藻细胞糖和脂肪的积累最佳的氮源是200μmol·L^(-1) NH_4Cl。针对以脂肪为目标物质的盐藻培养,推荐采用二段培养方案,即在第一段培养时采用200μmol·L^(-1) CH_4N_2O为氮源,以获得较大的生物量;在第二段培养时采用200μmol·L^(-1) NH_4Cl,以提高单位细胞的脂肪含量。

Due to the high contents of proteins,sugars,glyceryl,lipids andβ-carotene,Dunaliella salina has been frequently used asfood for larval rearing of fishes,shrimps and shellfishes,and has special values for the industries of foods,pharmaceuticals andhealth care.The research on the effects of source and concentration of nitrogen against growth and cell chemical composition of D.salina will clarify the optimal nitrogen supply strategy for various expectations of culture.The results will promote the large scaleculture,exploration and utilization for D.salina.In this study,growth and cell chemical composition of D.salina were studied withnitrogen supplied by NaNO3,NH4Cl or CH4N2O as nitrogen source with concentration of200μmol·L-1,600μmol·L-1,or1800μmol·L-1.The results showed that D.salina was able to use all3kinds of nitrogen sources.The biomass growths of D.salinacultured in different nitrogen sources ranged in a descending sequence as CH4N2O≥NaNO3>NH4Cl,which indicates D.salina preferorganic nitrogen source of CH4N2O.The difference of nitrogen concentration led to various biomass growths of D.salina in adescending sequence as1800μmol·L-1≥600μmol·L-1>200μmol·L-1.The increase of nitrogen concentration higher than600μmol·L-1resulted in non-significant enhancement of biomass growths.The organic nitrogen CH4N2O achieved the higher biomass incomparison with inorganic nitrogen of NaNO3and NH4Cl under the concentration of200μmol·L-1.The sources of nitrogensignificantly affected both contents of sugar and lipid,but the same was not happened for the content of protein.In terms of sugarand lipid accumulations,the beneficial ranking of nitrogen source is NH4Cl≥NaNO3>CH4N2O and NH4Cl≥NaNO3≥CH4N2O,respectively.The higher nitrogen concentrations led to the significantly higher contents for protein but not for sugar or lipid.Theoptimal nitrogen supply for D.salina to accumulate sugar and lipid is200μmol·L-1NH4Cl.To achieve high total lipid production ofD.salina,the two-stage culture was proposed.With the purpose of producing high biomass and high lipid content per cell in first andsecond stages,respectively,the nitrogen supply was proposed to switched from200μmol·L-1CH4N2O in first stage to200μmol·L-1NH4Cl in the second stage.