Department of Food Quality and Safety/National R&D Center for Chinese Herbal Medicine Processing, College of Engineering, China Pharmaceutical University, Nanjing, Jiangsu 211198, China.
Department of Food Quality and Safety/National R&D Center for Chinese Herbal Medicine Processing, College of Engineering, China Pharmaceutical University, Nanjing, Jiangsu 211198, China.
Int J Biol Macromol. 2023 Apr 1;233:123474. doi: 10.1016/j.ijbiomac.2023.123474. Epub 2023 Jan 30.
Phycocyanin, a natural blue colorant, derived from Spirulina platensis, is now widely used in the food industry. However, its main drawbacks are loss of color and denature of structure in an acidic environment. In this study, carboxylated chitosan (0.1 %-1 % w/v) was chosen as an additive in acid-denatured phycocyanin for preserving phycocyanin's blue color and natural structure. Zeta-potential and particle size revealed that the carboxylated chitosan with high negative charge adsorbed on phycocyanin and provided stronger electrostatic repulsion to overcome the protein aggregation. Ultraviolet-visible absorption spectrum and fluorescence spectroscopy showed that the carboxylated chitosan recovered the microenvironment of tetrapyrrole chromophores and β-subunits, which led the secondary structure changed and the trimers depolymerized into the monomers changed by the acidic environment. Furthermore, Fourier transform infrared spectroscopy revealed highly negatively charged carboxylated chitosan with the groups (NH, COOH and OH) could restored the microenvironment of tetrapyrrole chromophores and β-subunits of phycocyanin, and interact with phycocyanin through hydrogen bonding, NH bonding, ionic bonding and van der Waals, which led to a change in secondary structure and depolymerization of trimers into monomers. Our study demonstrated the carboxylated chitosan played a beneficial role in recovering the structure of acid-denatured phycocyanin and its blue color.
藻蓝蛋白是一种天然蓝色着色剂，来源于螺旋藻，现广泛应用于食品工业。然而，其主要缺点是在酸性环境中颜色损失和结构变性。在本研究中，选择羧甲基壳聚糖（0.1%-1%w/v）作为酸性变性藻蓝蛋白的添加剂，以保持藻蓝蛋白的蓝色和天然结构。Zeta 电位和粒径表明，带高负电荷的羧甲基壳聚糖吸附在藻蓝蛋白上，并提供更强的静电排斥力以克服蛋白质聚集。紫外-可见吸收光谱和荧光光谱表明，羧甲基壳聚糖恢复了四吡咯发色团和β亚基的微环境，导致酸性环境下发生的二级结构变化和三聚体解聚成单体。此外，傅里叶变换红外光谱表明，带高负电荷的羧甲基壳聚糖（NH、COOH 和 OH 基团）可以恢复藻蓝蛋白的四吡咯发色团和β亚基的微环境，并通过氢键、NH 键、离子键和范德华力与藻蓝蛋白相互作用，导致二级结构变化和三聚体解聚成单体。我们的研究表明，羧甲基壳聚糖在恢复酸性变性藻蓝蛋白的结构及其蓝色方面发挥了有益作用。
