Department of Chemistry, Umeå University, 901 87 Umeå, Sweden.
Molecules. 2019 Sep 5;24(18):3237. doi: 10.3390/molecules24183237.
Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy is a simple, cheap, and fast method to collect chemical compositional information from microalgae. However, (semi)quantitative evaluation of the collected data can be daunting. In this work, ATR-FTIR spectroscopy was used to monitor changes of protein, lipid, and carbohydrate content in seven green microalgae grown under nitrogen starvation. Three statistical methods-univariate linear regression analysis (ULRA), orthogonal partial least squares (OPLS), and multivariate curve resolution-alternating least squares (MCR-ALS)-were compared in their ability to model and predict the concentration of these compounds in the biomass. OPLS was found superior, since it i) included all three compounds simultaneously; ii) explained variations in the data very well; iii) had excellent prediction accuracy for proteins and lipids, and acceptable for carbohydrates; and iv) was able to discriminate samples based on cultivation stage and type of storage compounds accumulated in the cells. ULRA models worked well for the determination of proteins and lipids, but carbohydrates could only be estimated if already determined protein contents were used for scaling. Results obtained by MCR-ALS were similar to ULRA, however, this method is considerably easier to perform and interpret than the more abstract statistical/chemometric methods. FTIR-spectroscopy-based models allow high-throughput, cost-effective, and rapid estimation of biomass composition of green microalgae.
衰减全反射-傅里叶变换红外（ATR-FTIR）光谱学是一种从微藻中收集化学成分信息的简单、廉价且快速的方法。然而，（半）定量评估所收集的数据可能会令人望而却步。在这项工作中，ATR-FTIR 光谱学被用于监测在氮饥饿条件下生长的七种绿藻中蛋白质、脂质和碳水化合物含量的变化。三种统计方法——单变量线性回归分析（ULRA）、正交偏最小二乘（OPLS）和多变量曲线分辨-交替最小二乘法（MCR-ALS）——在其建模和预测生物量中这些化合物浓度的能力方面进行了比较。OPLS 被发现更优越，因为它：i）同时包含这三种化合物；ii）很好地解释了数据中的变化；iii）对蛋白质和脂质具有出色的预测准确性，对碳水化合物的预测准确性可接受；iv）能够根据培养阶段和细胞中积累的储存化合物的类型来区分样品。ULRA 模型在确定蛋白质和脂质方面效果良好，但如果使用已经确定的蛋白质含量进行缩放，则可以估计碳水化合物。MCR-ALS 获得的结果与 ULRA 相似，然而，这种方法比更抽象的统计/化学计量方法更容易执行和解释。基于 FTIR 光谱学的模型允许对绿藻的生物量组成进行高通量、经济高效和快速估计。
