迦得拟微绿球藻异养培养产单细胞蛋白特性分析

Characteristic analysis of heterotrophic cultivation of Nannochloropsis gaditana for production of single cell proteins

为研究一株异养型迦得拟微绿球藻(Nannochloropsis gaditana)在通气搅拌培养条件下生长及产单细胞蛋白的情况,结合了不同生长阶段显微形态的分析,考察了pH对微藻生长的影响.结果表明:在碱性培养条件下(pH9)微藻囊泡相对松散,易解离成单细胞,从而减少营养物质的吸收,导致生物量和蛋白产率的下降;虽然较低的培养温度可以延长囊泡存在时间,但囊泡内单细胞繁殖速率下降,不利于菌体生长;较高的温度则会导致胞内酶活性下降及菌体过早衰亡,影响蛋白产率;通常,高搅拌速率可获得较高的体积传氧系数k La,提高溶氧水平,而当搅拌速率超过300 r/min,湍流漩涡长度接近囊泡的平均直径时,搅拌产生的水力学应力会对囊泡造成损伤.异养型迦得拟微绿球藻与传统的自养培养方式相比具有高效和高产的优势,因此,未来在高品质单细胞蛋白生产领域将具有广阔的应用前景.

The growth characteristic and single cell protein(SCP)production of a heterotrophic microalgal species,Nannochloropsis gaditana in air-sparging batch culture were studied in detail.The effect of pH on the microalgal growth was investigated in combination with microscopic morphological analysis in different growth stages.It was found that cultivation of microalgae in alkaline culture(pH9)could make the pectic tight-texture of microalgal vesicle loose and could be easily dissociated into single cells.The dissociation of microalgal vesicles may greatly reduced the absorption of nutrients and consequently result in the decline of both the biomass and SCP productivity.Although lower cultivation temperature could extend the existence of the vesicle,the single cellular propagation rate inside the vesicle may drop significantly.Higher temperature resulted in the inactivation of intracellular enzymes as well as the denaturation of tight structure of microalgal vesicle negatively had a contribution to dropping process of protein productivity.Generally,at higher agitation level,the greater volumetric mass transfer coefficient,k La could be achieved that highly improved the uptake of the oxygen.However,when the agitation rate was over 300 r/min,the damage caused by hydrodynamic stress could not be negligible because the turbulent eddy length scale would approach the average diameter of the vesicle.In conclusion,since the heterotrophic microalgal cultivation was efficient and highly-productive compared with the traditional autotrophic modes,it could be considered as a promising alternative for production of the quality SCP.