Medium pH influences citric acid and lipid production in oleaginous yeast Yarrowia lipolytica. Yarrowia lipolytica

The goal of this study is to find out how Yarrowia lipolytica W29’s transcriptome changes in response to different pHs in certain medium, where the production of citric acid and lipid vary significantly at different pHs. The changes in transcriptome will give us insight about the mechanism of citric acid and/or lipid production are regulated. We harvested Y. lipolytica cells from bioreactor cultures from three different pHs: 2.0, 4.0 and 6.0 in triplicates. We sequenced the mRNA by Illumina HiSeq 2500 and generated an average of 20 million reads for each sample. We did not find distinct gene expression changes for the enzymes right downstream the intersection where citrate is cleaved into acetyl-CoA. Instead, from gene ontology enrichment analysis, we observed proteins with transport activities were overrepresented in gene groups that were up-regulated higher pH conditions, where citric acid secretion is favored. Overall design: mRNA profiling of Yarrowia lipolytica W29 cells in pH 2.0, 4.0 and 6.0 bioreactors in triplicates, harvested at hour 50, sequenced by Illumina HiSeq 2500

本研究旨在探究解脂耶氏酵母（Yarrowia lipolytica）W29的转录组在特定培养基中响应不同pH条件的变化规律——该培养基中柠檬酸与脂质的产量随pH差异呈现显著变化。转录组的变化特征将为阐明柠檬酸和/或脂质合成的调控机制提供关键视角。我们从生物反应器培养体系中，于pH 2.0、4.0和6.0三个梯度条件下分别设置三次生物学重复，收集解脂耶氏酵母细胞。采用Illumina HiSeq 2500平台对样本的mRNA进行测序，每个样本平均生成2000万条reads。研究未发现柠檬酸裂解为乙酰辅酶A（acetyl-CoA）通路下游紧邻的酶存在显著基因表达差异。与之相反，通过基因本体（Gene Ontology, GO）富集分析发现，在柠檬酸分泌更具优势的高pH条件下，上调基因显著富集于编码具有转运活性蛋白的基因簇。总体实验设计：对pH 2.0、4.0和6.0的生物反应器培养的解脂耶氏酵母W29细胞开展mRNA表达谱分析，设置三次生物学重复，于培养第50小时收获样本，采用Illumina HiSeq 2500完成测序。