摘要
2-keto-D-gluconic acid(2-KGA)is a key precursor for synthesising vitamin C and isovitamin C.However,phage contamination is as constant problem in industrial production of 2-KGA using Pseudomonas fluorescens.Gluconobacter holds promise for producing 2-KGA due to impressive resistance to hypertonicity and acids,and high utilisation of glucose.In this study,the 2-KGA synthesis pathway was regulated to enhance production of 2-KGA and reduce accumulation of the by-products 5-keto-D-gluconic acid(5-KGA)and D-gluconic acid(D-GA)in the 2-KGA producer Gluconobacter japonicus CGMCC 1.49.Knocking out the ga5dh-1 gene from a competitive pathway and overexpressing the ga2dh-A gene from the 2-KGA synthesis pathway via homologous recombination increased the titre of 2-KGA by 63.81%in shake flasks.Additionally,accumulation of 5-KGA was decreased by 63.52%with the resulting G.japonicas-Δga5dh-1-ga2dh-A strain.Using an intermittent fed-batch mode in a 3 L fermenter,2-KGA reached 235.3 g L^−1 with a 91.1%glucose conversion rate.Scaling up in a 15 L fermenter led to stable 2-KGA titre with productivity of 2.99 g L^−1 h^−1,11.99%higher than in the 3 L fermenter,and D-GA and 5-KGA by-products were completely converted to 2-KGA.
基金
the National Key Research and Development Program of China(2017YFC1600403)
the National Natural Science Foundation of China(31830068,21822806)
the Fundamental Research Funds for the Central Universities(JUSRP51701A)
the National First-class Discipline Program of Light Industry Technology and Engineering(LITE2018-08)
the Distinguished Professor Project of Jiangsu Province.
