超低温冷冻对螺旋藻光合及超微结构的影响

Effect of Cryopreservation on Photosynthesis and Ultrastructure of Spirulina maxima FACHB-438

本文通过正交实验优化了螺旋藻超低温保藏条件,结果表明,在所选择的这些实验条件中,对螺旋藻冻存效果影响最大的因子为:保护剂(甘油)浓度,其次为冻存速率,预冻温度,在冻存速率为1℃/min,预冻温度为-40℃,甘油浓度为10%的条件下,其冻存效果最佳。解冻后螺旋藻的超微结构表明:经超低温冷冻后,螺旋藻细胞外的胶鞘层变薄或者消失,细胞内的类囊体开始变得分散,排列不规则,聚集成束,有些出现断裂;螺旋藻的叶绿素荧光及77k荧光光谱分析表明,经超低温保藏后,螺旋藻的光合系统PSII受到一定的破坏,其Fv/Fm值明显低于未进行超低温保藏的,而其77k荧光光谱的峰位与未进行超低温保藏的相比没有明显差异,这表明超低温不会影响螺旋藻叶绿素和胡萝卜素的荧光光谱性质。而超低温保藏后,螺旋藻Fv/Fm值低的原因可能在于超低温损伤了藻细胞类囊体膜上的捕光色素蛋白复合体等,从而降低了捕获光能的能力,引起光合作用下降。

The cryopreserved conditions of Spirulina maxima were optimized through orthogonal experiment in this study. The results showed that the factors that influenced the cryopreservation of S. maxima ranged from protective agent(glycerin) concentration to precool temperature to cooling rate. The best cryopreserved condition of Spirulina was cooling rate at 1 ℃/min, precool temperature at-40 ℃ and glycerin concentration at 10%(v/v). The ultrastructure of post-thawed spirulina showed that the rubber sheath layer thinned or disappeared, intracellular thylakoids became scattered, irregularly arranged and gathered into a bundle, some appeared rupture comparing with that without cryopreservation. The chlorophyll fluorescence and 77 K fluorescence spectra of S. maxima showed that the photosynthetic system PSII of S. maxima was damaged after cryopreservation, and its Fv/Fm value was significantly lower than that of the non-cryopreserved, but the peak position of 77 K fluorescence spectra was not different from that of the non-cryopreserved, indicating that cryopreservation did not affect the fluorescence spectra of chlorophyll and carotene in S. maxima. After cryopreservation, the low Fv/Fm value of S. maxima may be due to the damage of light-harvesting pigment protein complexes on the thylakoid membranes of algal cells by cryopreservation, which reduced the ability of capturing the light energy, leading to the decrease of photosynthesis.