Process optimization involving critical evaluation of oxygen transfer, oxygen uptake and nitrogen limitation for enhanced biomass and lipid production by oleaginous yeast for biofuel application
Process optimization involving critical evaluation of oxygen transfer, oxygen uptake and nitrogen limitation for enhanced biomass and lipid production by oleaginous yeast for biofuel application
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DOI：
10.1007/s00449-018-1939-7
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发表时间：
2018-08-01
影响因子：
3.8
通讯作者：
Sen, Ramkrishna
中科院分区：
文献类型：
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作者：
Chopra, Jayita;Sen, Ramkrishna
产油酵母中的脂质积累通常是由氮饥饿引起的，而氧饱和度会影响生物量的增长。系统的摇瓶研究有助于确定正确的氮源，并将其吸收动力学与不同氧饱和度条件下的脂质生物合成联系起来，对于解决生物加工相关问题非常重要，这些问题预计会在发酵罐规模生产中发生。在本研究中，使用预先优化的氮源和在混合培养基中配制的两阶段接种物，在摇瓶中研究了吉里蒙假单胞菌在不同 C:N 比率和氧转移条件（以 k (L) a 评估）下的脂质生物积累。在初始C:N和k(L)a分别为60:1和0.6 min(-1)、生物量比生长率为0.11 h(-1)的最佳条件下，摇瓶研究中获得的最大脂质浓度为10.8 +/- 0.5 g L-1。将这些最佳摇瓶条件转化为 3.7 L 搅拌釜反应器，产生的生物量和脂质浓度为 16.74 +/- 0.8 和 8 +/- 0.4 g L-1。通过气相色谱法获得的脂质脂肪酸甲酯 (FAME) 谱被发现适合生物柴油应用。我们坚信，研究中采用的基于理性方法的实验设计将有助于实现高细胞密度，改善脂质积累，并最大限度地减少生物反应器水平操作过程中工艺优化的工作，从而降低研发相关成本。
Lipid accumulation in oleaginous yeast is generally induced by nitrogen starvation, while oxygen saturation can influence biomass growth. Systematic shake flask studies that help in identifying the right nitrogen source and relate its uptake kinetics to lipid biosynthesis under varying oxygen saturation conditions are very essential for addressing the bioprocessing-related issues, which are envisaged to occur in the fermenter scale production. In the present study, lipid bioaccumulation by P. guilliermondii at varying C:N ratios and oxygen transfer conditions (assessed in terms of k (L) a) was investigated in shake flasks using a pre-optimized N-source and a two-stage inoculum formulated in a hybrid medium. A maximum lipid concentration of 10.8 +/- 0.5 g L-1 was obtained in shake flask study at the optimal condition with an initial C:N and k (L) a of 60:1 and 0.6 min(-1), respectively, at a biomass specific growth rate of 0.11 h(-1). Translating these optimal shake flask conditions to a 3.7 L stirred tank reactor resulted in biomass and lipid concentrations of 16.74 +/- 0.8 and 8 +/- 0.4 g L-1. The fatty acid methyl ester (FAME) profile of lipids obtained by gas chromatography was found to be suitable for biodiesel application. We strongly believe that the rationalistic approach-based design of experiments adopted in the study would help in achieving high cell density with improved lipid accumulation and also minimize the efforts towards process optimization during bioreactor level operations, consequently reducing the research and development-associated costs.