Luna-Flores Carlos H, Palfreyman Robin W, Krömer Jens O, Nielsen Lars K, Marcellin Esteban
Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane, Qld, Australia.
Dow Centre for Sustainable Engineering and Innovation, The University of Queensland, Brisbane, Qld, Australia.
Biotechnol J. 2017 Feb;12(2). doi: 10.1002/biot.201600120. Epub 2016 Oct 20.
Traditionally derived from fossil fuels, biological production of propionic acid has recently gained interest. Propionibacterium species produce propionic acid as their main fermentation product. Production of other organic acids reduces propionic acid yield and productivity, pointing to by-products gene-knockout strategies as a logical solution to increase yield. However, removing by-product formation has seen limited success due to our inability to genetically engineer the best producing strains (i.e. Propionibacterium acidipropionici). To overcome this limitation, random mutagenesis continues to be the best path towards improving strains for biological propionic acid production. Recent advances in next generation sequencing opened new avenues to understand improved strains. In this work, we use genome shuffling on two wild type strains to generate a better propionic acid producing strain. Using next generation sequencing, we mapped the genomic changes leading to the improved phenotype. The best strain produced 25% more propionic acid than the wild type strain. Sequencing of the strains showed that genomic changes were restricted to single point mutations and gene duplications in well-conserved regions in the genomes. Such results confirm the involvement of gene conversion in genome shuffling as opposed to long genomic insertions.
传统上，丙酸是从化石燃料中提取的，而近年来，丙酸的生物生产受到了关注。丙酸杆菌属物种将丙酸作为其主要发酵产物。其他有机酸的产生会降低丙酸的产量和生产率，这表明通过基因敲除副产物的策略是提高产量的合理解决方案。然而，由于我们无法对最佳生产菌株（即丙酸丙酸杆菌）进行基因工程改造，去除副产物形成的效果有限。为了克服这一限制，随机诱变仍然是改善生物生产丙酸菌株的最佳途径。新一代测序技术的最新进展为了解改良菌株开辟了新途径。在这项工作中，我们对两种野生型菌株进行基因组改组，以产生一种更好的丙酸生产菌株。利用新一代测序技术，我们绘制了导致表型改善的基因组变化图谱。最佳菌株产生的丙酸比野生型菌株多25%。菌株测序表明，基因组变化仅限于基因组中保守区域的单点突变和基因重复。这些结果证实了基因转换参与了基因组改组，而不是长基因组插入。
