Abstract：
In the present study, cellulose purified from finger millet agricultural waste is subjected to enzymatic hydrolysis, and the hydrolysate (predominantly glucose) is used as a carbon source supplement in the media for the mixotrophic growth of Chlamydomonas reinhardtii. Interestingly, a switch between excess starch production and excess lipid (triacylglycerols, TAG) production occurs by a small change in hydrolysate concentration in the media. Starch production increased 4.5-fold with respect to the photoautotrophic control, with a glucose concentration of 3 mg/mL in the media after hydrolysate addition. This culture had TAG production enhancement by 1.5-fold. However, mixotrophic cultivation with 4 mg/mL glucose concentration in the media with hydrolysate addition resulted in TAG productivity enhancement by 4.2-fold compared to control and starch amount increase of 1.3-fold. The organic carbon source (glucose) and the inorganic carbon source (citrate ions) in the hydrolysate together played a role in this delicate switching between starch and lipid pathways. Proteins, starch, and TAG molecules are analyzed in the microalgal cells grown under different conditions with FTIR spectroscopy, a rapid, high-throughput method of biomolecular estimation. High-resolution single-cell AFM studies of the cell wall structure reveal enhanced corrugations in surface morphology during mixotrophic growth with cellulose hydrolysate, illustrating an adaptive mechanism with improved mechanical stress management. Lipid droplet morphology at the single-cell level points to two distinct mechanisms of lipid accumulation: one in which the lipids are segregated as droplets, and the other in which lipid molecules are uniformly dispersed in the cytosol as unresolved, ultra-small droplets. The present study therefore analyzes both the bulk and the single-cell level changes when cellulose hydrolysate is used as a carbon source for Chlamydomonas reinhardtii mixotrophic cultivation, which serves a four-fold purpose: value from waste, fixation of atmospheric CO2, production of lipids for biodiesel, and starch for bioethanol.
摘要：
在本研究中,从手指小米农业废物中纯化的纤维素经过酶水解，和水解产物（主要是葡萄糖）用作培养基中的碳源补充剂，用于莱茵衣藻的兼养生长。有趣的是,过量淀粉生产和过量脂质(三酰甘油，TAG）的产生是通过培养基中水解产物浓度的微小变化而发生的。相对于光合自养控制，淀粉产量增加了4.5倍，在添加水解产物后,培养基中的葡萄糖浓度为3mg/mL。该培养物的TAG产量提高了1.5倍。然而,与对照组相比，在培养基中添加4mg/mL葡萄糖浓度的混合营养培养使TAG生产率提高了4.2倍，淀粉量增加了1.3倍。水解产物中的有机碳源（葡萄糖）和无机碳源（柠檬酸根离子）一起在淀粉和脂质途径之间的这种微妙转换中起作用。蛋白质,淀粉，用FTIR光谱分析在不同条件下生长的微藻细胞中的TAG分子，一个快速的，高通量生物分子估算方法。细胞壁结构的高分辨率单细胞AFM研究揭示了纤维素水解产物在混合营养生长过程中表面形态的波纹增强，说明了一种具有改进的机械应力管理的自适应机制。单细胞水平的脂滴形态指向两种不同的脂质积累机制：一种是脂质分离为液滴，另一种是脂质分子均匀分散在细胞溶质中，超小液滴。因此，本研究分析了当纤维素水解物用作衣藻混合营养培养的碳源时，体积和单细胞水平的变化，它有四个目的:废物的价值，固定大气中的二氧化碳，生产生物柴油的脂类，和用于生物乙醇的淀粉。
