环绕式LED光质对蛋白核小球藻生长代谢影响

    Effects of wraparound LED light quality on the growth and metabolite of C. pyrenoidosa

    • 摘要: 微藻是一类生长速度快、环境适应能力强的单细胞自养生物,利用其生产的碳水化合物、蛋白质、油脂等已在食品、水产养殖、医疗保健等领域广泛应用,然而,高养殖成本始终是限制其产业化发展的难点之一。光源是微藻培养的重要环境因子,现有研究多报道波段及光照周期对微藻生长代谢的影响,其所用光源几乎均采用单侧排布,光在藻液中分布的均匀性和稳定性易受藻液光径、藻密度等影响。为研究环绕式LED光质对蛋白核小球藻生长代谢影响,该研究以商业化较成熟的微藻——蛋白核小球藻(Chlorella pyrenoidosa)为对象,将环绕式LED人工光源应用于微藻培养中,采用光强为100 μmol/(m2·s)的白、红、黄、绿、蓝、紫6种光质分别培养蛋白核小球藻21 d,每日监测藻液中生物量和光合色素含量变化,测定培养末期(D21)藻体中的蛋白质、油脂和碳水化合物含量及脂肪酸组成和丰度,分析不同波段光质对蛋白核小球藻生长代谢的影响。结果显示,相较于对照组(白光),绿光和蓝光分别培养蛋白核小球藻7 d和9 d后其生物量显著提高(P<0.05),培养末期(D21)绿光组和蓝光组的生物量分别提高了24.4%和8.0%(P<0.05);藻液中叶绿素a的变化趋势与生物量变化类似,但绿光组藻体中总光合色素质量分数却显著低于紫光组(P<0.05),可能与微藻对紫光的吸收利用率低有关(需要合成更多光合色素来获取光能);红光组中碳水化合物质量分数增加11.5%而油脂质量分数显著下降23.8%(P<0.05);蓝光最利于油脂累积,显著提升26.2%(P<0.05);紫光使蛋白核小球藻的碳分配从碳水化合物向蛋白质合成方向分流;脂肪酸分析表明,绿光和紫光最利于总脂肪酸累积,较对照组(39.5‰)分别提升20.1%和18.2%(P<0.05);绿光和蓝光更有利于多不饱和脂肪酸的合成。研究结果可为蛋白核小球藻胞内碳分配的优化调控提供有效的光源配置方案,为蛋白核小球藻的高效优质生产提供理论参考。

       

      Abstract: Microalgae are a type of single-cell autotrophic organisms with the advantages of fast growth rate and strong environmental adaptability. The carbohydrates, proteins, lipids produced by them have been widely used in food, aquaculture, healthcare and other fields. However, the high cost of cultivation has always been one of the difficulties for its industrial development. Light source is a critical environmental factor for microalgae cultivation. Existing studies have reported the effects of wavelength and photoperiod on the growth and metabolism of microalgae. Significantly, the light sources used in these studies almost are arranged on one side, and the uniformity and stability of the light distribution in the algal liquid are easily affected by the algal solution's optical diameter, algal density, and other factors. In this study, the commercial microalgae: C. pyrenoidosa was used as the research object, and the wraparound light emitting diode (LED) lights were adopted as an artificial light source for microalgae cultivation. Six light qualities of white, red, yellow, green, blue, and purple with a light intensity of 100 μmol/(m2·s) were applied to cultivate C. pyrenoidosa for 21 days. The biomass and photosynthetic pigment contents in the algal liquid were monitored daily. The protein, lipid, and carbohydrate contents in C. pyrenoidosa were determined, as well as the composition and abundance of fatty acids at the end of cultivation (D21), thereby to explore the dynamic patterns of six light qualities on the growth and metabolites of C. yrenoidosa. The results revealed that the growth rates of C. yrenoidosa cultured under green and blue LED were significantly higher than the control (white LED) from 7th and 9th day (P<0.05), respectively. At the end of cultivation (D21), the biomass in the green and blue groups increased by 24.4% and 8.0% as compared with the control, respectively. The trends of chlorophyll-a in algal liquid were similar to that of the biomass, but the total pigment of C. yrenoidosa in the green group was significantly lower than that of the purple group (P<0.05), which might be related to the low absorption and utilization rate of purple light by C. yrenoidosa (more photosynthetic pigments need to be synthesized to obtain light energy). Red LED could increase the carbohydrate content by 11.5% and reduce the lipid by 23.8% (P<0.05). Blue LED had the best positive effect on the lipid-accumulation, with a significant increment of 26.2% (P<0.05). Purple LED promoted carbon allocation from carbohydrates to protein synthesis in C. pyrenoidea. Fatty acid analysis indicated that green and purple LED significantly promoted total fatty acids (TFAs) synthesis (20.1% and 18.2%) as compared with the control group (39.5‰) (P<0.05). Moreover, green and blue LED were more conducive to the synthesis of polyunsaturated fatty acids. This study would not only provide an effective light source configuration scheme for the optimal regulation of intracellular carbon allocation of C. pyrenoidosa, but also provide some theoretical reference and technical support for the efficient and high-quality production of C. pyrenoidea.

       

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