College of Marine Life Sciences, Ocean University of China, Yushan Road, No. 5, Qingdao, China.
College of Marine Life Sciences, Ocean University of China, Yushan Road, No. 5, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 266003, China.
Int J Biol Macromol. 2019 Jul 1;132:701-709. doi: 10.1016/j.ijbiomac.2019.04.007. Epub 2019 Apr 3.
Overexpression of the optimized Vitreoscilla hemoglobin (VHb) gene and the native flavohemoglobin (FHb) gene in Aureobasidium melanogenum P16 rendered a V6 strain and a F44 strain to overproduce pullulan compared to that produced by their wild type strain P16. The capacity to bind CO and oxygen in the V6 strain and the F44 strain was also obviously enhanced. At the same time, the transcriptional levels of the relevant genes were also increased in the V6 strain and the F44 strain and the fused vgbop + the gene encoding GFP and FHb gene + the gene encoding GFP were also actively expressed. During a 10-liter fermentation, the P16 strain produced only 72.0 ± 1.0 g/L pullulan, the yield was 0.77 g/g of sucrose, the productivity was 0.5 ± 0.01 g/L/h and only 79.4% of the total sugar was used. In contrast, the strain V6 yielded 102.3 ± 1.8 g/L of pullulan, the yield was 0.89 g/g of sucrose, the productivity was 0.7 ± 0.01 g/L/h and 96.0% of total sugar was used while 101.4 ± 2.9 g/L of pullulan was accumulated in the culture of the strain F44, the yield was 0.88 g/g of sucrose, the productivity was 0.7 ± 0.02 g/L/h and 96.4% of total sugar was utilized. These data strongly demonstrated that the concentration of pullulan, yield, productivity and sugar utilization were greatly enhanced by overexpression of the VHb and FHb. But their cell growth was almost the similar.
优化的血晶朊（VHb）基因和天然细胞色素 b5 基因（FHb）在出芽短梗霉 P16 中的过表达使 V6 菌株和 F44 菌株相对于其野生型菌株 P16 能够过量生产普鲁兰。V6 菌株和 F44 菌株结合 CO 和氧气的能力也明显增强。同时，V6 菌株和 F44 菌株中相关基因的转录水平也有所增加，融合基因 vgbop+编码 GFP 的基因和 FHb 基因+编码 GFP 的基因也得到了有效表达。在 10 升发酵中，P16 菌株仅生产了 72.0±1.0g/L 的普鲁兰，产率为 0.77g/g 蔗糖，生产力为 0.5±0.01g/L/h，仅使用了总糖的 79.4%。相比之下，菌株 V6 产生了 102.3±1.8g/L 的普鲁兰，产率为 0.89g/g 蔗糖，生产力为 0.7±0.01g/L/h，总糖利用率为 96.0%，而菌株 F44 的培养物中积累了 101.4±2.9g/L 的普鲁兰，产率为 0.88g/g 蔗糖，生产力为 0.7±0.02g/L/h，总糖利用率为 96.4%。这些数据有力地证明了通过过表达 VHb 和 FHb，普鲁兰的浓度、产率、生产力和糖利用率得到了极大的提高。但它们的细胞生长几乎是相同的。
