Center for Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China.
School of Environmental and Biological Engineering, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China.
World J Microbiol Biotechnol. 2021 Apr 1;37(5):77. doi: 10.1007/s11274-021-03043-0.
Lipids produced by oleaginous microorganisms enrich the supply of feedstock for bio-fuel. In this study, a mutant (Mut) obtained by UV-nitrosoguanidine mutagenesis turned its colony color from orange-red to light-yellow and showed higher lipid productivity at 37 °C than the original strain Rhodotorula sp. U13N3 (Rht) in the glycerol medium. The metabolic changes between Mut and Rht in batch fermentation were investigated by transcriptomic and metabolomic profiling at the biomass accumulation (30 h) and lipid production (96 h) stages. The average base number in each strain was 5.80 × 10 ± 0.38 × 10 bp (mean ± SD) with 62.43% ± 0.13% GC ratio, and 7499 unigenes were assembled after Illumina sequencing. Moreover, 33 metabolites were quantified by H NMR-based profiling. The multi-omics results demonstrated that Mut showed increased glycerol transport and utilization capabilities especially at the first stage (30 h). Then the carbon flux shifted from the TCA cycle to lipid production (96 h). The increased lipid productivity of Mut was partially attributed to the down-regulation of mannitol biosynthesis. However, the mechanism for color change was elusive. At 96 h, the low level of cytosol glycerol probably restricted the lipid production. As a result, supplementation of glycerol in fed-batch fermentation remarkably improved the biomass, lipid production, and lipid content to 34.60 g/L, 25.72 g/L, and 74.3% (w/w dcw), respectively. The cell morphology implied that excessively prolonging the fermentation time was detrimental to the final lipid yield due to cell breakage. In conclusion, the Rhodotorula mutant provided a candidate strain for lipid production with glycerol as the carbon source.
产油微生物产生的脂质丰富了生物燃料的原料供应。在这项研究中，通过 UV-亚硝基胍诱变获得的一个突变体（Mut），其菌落颜色从橙红色变为浅黄色，在甘油培养基中，其 37°C 时的脂类生产力比原始菌株 Rhodotorula sp. U13N3（Rht）更高。在生物量积累（30h）和产脂（96h）阶段，通过转录组学和代谢组学分析研究了 Mut 和 Rht 在分批发酵过程中的代谢变化。每个菌株的平均碱基数为 5.80×10±0.38×10bp（平均值±SD），GC 比为 62.43%±0.13%，经 Illumina 测序后组装了 7499 个单体。此外，通过 H NMR 谱分析定量了 33 种代谢物。多组学结果表明，Mut 表现出增强的甘油运输和利用能力，特别是在第一阶段（30h）。然后，碳通量从 TCA 循环转移到脂类生产（96h）。Mut 较高的脂类生产力部分归因于甘露醇生物合成的下调。然而，颜色变化的机制尚不清楚。在 96h 时，胞质甘油水平较低可能限制了脂类的生产。因此，在分批补料发酵中补充甘油显著提高了生物量、脂类生产和脂类含量，分别达到 34.60g/L、25.72g/L 和 74.3%（w/w dcw）。细胞形态暗示由于细胞破裂，过度延长发酵时间不利于最终的脂类产量。总之，该罗德里西亚突变体为以甘油为碳源的脂类生产提供了候选菌株。
