透明质酸具有保湿、润滑等多种生理功能,广泛应用于食品、医药和化妆品领域。目前透明质酸主要依赖于兽疫链球菌发酵生产。然而,遗传背景不清晰等问题,限制了兽疫链球菌作为底盘细胞的相关改造以及透明质酸发酵水平的提升。该研究首先对兽疫链球菌WSH-24的全基因组和转录组数据进行了测序分析,发现该菌株具有高效的糖酵解和乳酸合成能力,以及不完整的三羧酸循环和多种氨基酸合成途径的缺失。结合生长曲线分析,进一步明确该菌株为缬氨酸、谷氨酰胺、精氨酸和色氨酸4种氨基酸缺陷型。在此基础上,通过外源添加对应的氨基酸使透明质酸产量达到(2.65±0.02) g/L。其次,结合转录组测序数据,确定了维生素B5、维生素B7和维生素B12相关合成基因的转录水平过低。通过外源添加对应的维生素有效提高透明质酸的合成,使其产量达到(2.46±0.07) g/L。最后,通过培养基优化,在3 L发酵罐上透明质酸发酵质量浓度达到5.63 g/L,生产强度为0.31 g/(L·h),相较优化前提高了33.33%。该研究为进一步改造兽疫链球菌WSH-24奠定了基础,为透明质酸的产量提升提供了支撑。
Hyaluronic acid has a variety of physiological functions such as moisturizing and lubrication, and has been widely applied in food, medicine and cosmetics. Nowadays, the production of hyaluronic acid mainly relies on the fermentation of S. zooepidemicus. While, unclear genomic background limits the modification of S. zooepidemicus as a chassis cell and the improvement of hyaluronic acid fermentation yield. First, the genome-wide and transcriptome data of S. zooepidemicus WSH-24 were sequenced and analyzed in this study, and it was found that the strain had efficient glycolytic pathway and lactic acid synthesis capabilities, as well as incomplete tricarboxylic acid cycle and the absence of multiple amino acid synthesis pathways. Combined with the analysis of growth curves, this strain was further determined to be deficient in four amino acids: Valine, glutamine, arginine and tryptophan. On top of that, the yield of hyaluronic acid reached (2.65±0.02) g/L by exogenous addition of corresponding amino acids. Subsequently, combined with transcriptome sequencing data, the transcription level of vitamin B5, B7 and B12-related synthetic genes were determined to be low. To effectively improve the synthesis of hyaluronic acid, the yield of hyaluronic acid reached (2.46±0.07) g/L by exogenous addition of corresponding vitamins. Finally, by optimizing the media components, the fermentation concentration of hyaluronic acid increased to 5.63 g/L in a 3 L fermenter, and the production intensity was 0.31 g/(L·h) (33.33% higher than that before optimization). This study lays foundation for the further modification of S. zooepidemicus WSH-24, and provides support for hyaluronic acid on the increasing of yield.
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