Found 3 results
Article
06 February 2024Bio-Based Production of Uroporphyrin in Escherichia coli
Uroporphyrin (UP) is a porphyrin compound with medical applications and a key precursor for heme biosynthesis. However, there is no biosynthetic strategy for UP production. In this study, we present a novel bioprocess for enhanced production of UP in engineered Escherichia coli. We first implemented the Shemin/C4 pathway heterologously in an E. coli strain with an enlarged intracellular pool of succinyl-CoA. Using a plasmid with the trc promoter regulating the expression of a synthesized gene operon, the effects of key pathway genes, including hemA, hemB, hemC, and hemD, on UP biosynthesis were characterized. By cultivating the resulting engineered E. coli strains in a batch bioreactor with 30 g/L glycerol under aerobic conditions, up to 901.9 mg/L UP was produced. Most of the synthesized UP was extracellularly secreted with a high purity more than 80 wt%, facilitating its downstream purification. The study paves the way for large-scale bio-based production of UP using synthetic biology and metabolic engineering strategies.
Article
22 May 2023Fed-batch Self-regulated Fermentation of Glucose to Co-produce Glycerol and 1,3-propanediol by Recombinant Escherichia coli
As important bio-chemicals, glycerol and 1,3-propanediol (1,3-PDO) have been widely used in numerous fields, e.g., polymers, cosmetics, foods, lubricants, medicines, and so on. Bio-based 1,3-PDO is generally produced from glycerol or glucose by natural or recombinant strains, during which organic acids are always co-produced. In this work, acetic acid was also co-produced when 1,3-PDO was obtained from glucose by a recombinant strain of E. coli MG1655. Usually, a base was added to adjust the fermentation pH, resulting in the accumulation of organic salts and difficulty in the next down streaming process. Herein, a novel strategy was developed to consume the produced acetic acid by cells self in fed-batch self-regulated fermentation. The recombinant E. coli cells produced 48.33 g/L glycerol and 61.27 g/L 1,3-PDO with a total mass yield of 45.6% and without any other byproducts at the end of 5 fed-batch fermentations. The initial buffer pH, glucose concentration, pulse feeding sugar amount, time for a single batch fermentation and reducing acid were investigated by a series of comparative experiments. This fed-batch self-regulated fermentation has potential for the co-production of 1,3-PDO and glycerol, and will highlight the subsequent modification of recombinant E. coli strain by synthetic biology.
Article
10 May 2023Development of a New 1,2,4-butanetriol Biosynthesis Pathway in an Engineered Homoserine-producing Strain of Escherichia coli
1,2,4-butanetriol (BT) is a compound of high interest with applications in pharmaceutical and materials. In this work, we designed a novel biosynthetic pathway for BT from glucose via a nonessential amino acid homoserine. This non-natural pathway used an engineered phosphoserine transaminase (SerCR42W/R77W) to achieve the deamination of homoserine to 4-hydroxy-2-oxobutanoic acid (HOBA). Three consecutive enzymes including a lactate dehydrogenase, a 4-hydroxybutyrate CoA-transferase and a bifunctional aldehyde/alcohol dehydrogenase are used to catalyze HOBA to BT. To enhance the carbon flux to homoserine, a homoserine-producing Escherichia coli was developed by improving the overexpression of two relevant key genes metL and lysC (V339A). The simultaneous overexpression of the genes encoding these enzymes for the homoserine-derived BT pathway enabled production of 19.6 mg/L BT from glucose in the homoserine-producing E. coli.
