Biosynthesis of D-danshensu from L-DOPA using engineered Escherichia coli whole cells

Efficient production of salvianic acid A from L-dihydroxyphenylalanine through a tri-enzyme cascade

Salvianic acid A (SAA), used for treating cardiovascular and cerebrovascular diseases, possesses several pharmacological properties. However, the current methods for the enzymatic synthesis of SAA show low efficiency. Here, we constructed a three-enzyme cascade pathway in Escherichia coli BL21 (DE3) to produce SAA from L-dihydroxyphenylalanine (L-DOPA). The phenylpyruvate reductase (LaPPR) from Lactobacillus sp. CGMCC 9967 is a rate-limiting enzyme in this process. Therefore, we employed a mechanism-guided protein engineering strategy to shorten the transfer distances of protons and hydrides, generating an optimal LaPPR mutant, LaPPRMu2 (H89M/H143D/P256C), with a 2.8-fold increase in specific activity and 9.3-time increase in kcat/Km value compared to that of the wild type. Introduction of the mutant LaPPRMu2 into the cascade pathway and the optimization of enzyme levels and transformation conditions allowed the obtainment of the highest SAA titer (82.6 g L-1) ever reported in vivo, good conversion rate (91.3%), excellent ee value (99%) and the highest productivity (6.9 g L-1 h-1) from 90 g L-1 L-DOPA in 12 h. This successful strategy provides a potential new method for the industrial production of SAA.

Coordinating caffeic acid and salvianic acid A pathways for efficient production of rosmarinic acid in Escherichia coli

Rosmarinic acid is a natural hydroxycinnamic acid ester used widely in the food and pharmaceutical industries. Although many attempts have been made to screen rate-limiting enzymes and optimize modules through co-culture fermentation, the titer of rosmarinic acid remains at the microgram level by microorganisms. A de novo biosynthetic pathway for rosmarinic acid was constructed based on caffeic acid synthesis modules in Escherichia coli. Knockout of competing pathways increased the titer of rosmarinic acid and reduced the synthesis of rosmarinic acid analogues. An L-amino acid deaminase was introduced to balance metabolic flux between the synthesis of caffeic acid and salvianic acid A. The ratio of FADH₂/FAD was maintained via the coordination of deaminase and HpaBC, which is responsible for caffeic acid synthesis. Knockout of menI, encoding an endogenous thioesterase, increased the stability of caffeoyl-CoA. The final strain produced 5780.6 mg/L rosmarinic acid in fed-batch fermentation, the highest yet reported for microbial production. The strategies applied in this study lay a foundation for the synthesis of other caffeic acid and rosmarinic acid derivatives.

Self-Sufficient In Vitro Multi-Enzyme Cascade for Efficient Synthesis of Danshensu from l-DOPA

Danshensu (DSS), a traditional Chinese medicine, is widely used for the treatment of cardiovascular and cancer diseases. Here, a one-pot multi-enzyme cascade pathway was designed for DSS synthesis from l-DOPA using tyrosine aminotransferase from Escherichia coli (EcTyrB) and d-isomer-specific 2-hydroxyacid dehydrogenase from Lactobacillus frumenti (LfD2-HDH). Glutamate dehydrogenase from Clostridium difficile (CdgluD) was also introduced for a self-sufficient system of α-ketoglutaric acid and NADH. Under optimal conditions (35 °C, pH 7.0, EcTyrB:LfD2-HDH:CdgluD = 3:2:1, glutamate:NAD⁺ = 1:1), 98.3% yield (at 20 mM l-DOPA) and space-time yield of 6.61 g L^-1 h^-1 (at 40 mM l-DOPA) were achieved. Decreased yields of DSS at elevated l-DOPA concentrations (100 mM) could be attributed to an inhibited CdgluD activity caused by NH₄⁺ accumulation. This developed multi-enzyme cascade pathway (including EcTyrB, LfD2-HDH, and CdgluD) provides an efficient and sustainable approach for the production of DSS from l-DOPA.

Discovery and therapeutic implications of bioactive dihydroxylated phenolic acids in patients with severe heart disease and conditions associated with inflammation and hypoxia

Our initial studies detected elevated levels of 3,4-dihydroxyphenyllactic acid (DHPLA) in urine samples of patients with severe heart disease when compared with healthy subjects. Given the reported anti-inflammatory properties of DHPLA and related dihydroxylated phenolic acids (DPAs), we embarked on an exploratory multi-centre investigation in patients with no urinary tract infections to establish the possible pathophysiological significance and therapeutic implications of these findings. Chinese and Caucasian patients being treated for severe heart disease or those conditions associated with inflammation (WBC ≥ 10×10⁹/L or hsCRP ≥ 3.0mg/L) and/or hypoxia (PaO₂ ≤ 75mmHg) were enrolled; their urine samples were analyzed by HPLC, HPLC-MS, GC-MS and biotransformation assays. DHPLA was detected in urine samples of patients, but undetectable in healthy volunteers. Dynamic monitoring of inpatients undergoing treatment showed their DHPLA levels declined in proportion to their clinical improvement. In DHPLA-positive patients' fecal samples, Proteus vulgaris and P. mirabilis were more abundant than healthy volunteers. In culture, these gut bacteria were capable of reversible interconversion between DOPA and DHPLA. Furthermore, porcine and rodent organs were able to metabolize DOPA to DHPLA and related phenolic acids. The elevated levels of DHPLA in these patients suggest bioactive DPAs are generated de novo as part of a human's defense mechanism against disease. Because DHPLA isolated from Radix Salvia miltiorrhizae has a multitude of pharmacological activities, these data underpin the scientific basis of this medicinal plant's ethnopharmacological applications as well as highlighting the therapeutic potential of endogenous, natural or synthetic DPAs and their derivatives in humans.

Efficient Production of 3′-Sialyllactose by Single Whole-Cell in One-Pot Biosynthesis

Sialyllactose (SL) is one of the most important acidic oligosaccharides in human milk, which plays an important role in the health of infants. In this work, an efficient multi-enzyme cascade was developed in a single whole cell to produce 3′-SL. We constructed two compatible plasmids with double cloning sites to co-express four genes. Different combinations were assessed to verify the optimal catalytic ability. Then, the conversion temperature, pH, and stability under the optimal temperature and pH were investigated. Moreover, the optimal conversion conditions and surfactant concentration were determined. By using the optimal conditions (35 °C, pH 7.0, 20 mM polyphosphate, 10 mM cytidine monophosphate (CMP), 20 mM MgCl2), 25 mL and 4 L conversion systems were carried out to produce 3′-SL. Similar results were obtained between different volume conversion reactions, which led the maximum production of 3′-SL to reach 53 mM from 54.2 mM of sialic acid (SA) in the 25 mL system and 52.8 mM of 3′-SL from 53.8 mM of SA in the 4 L system. These encouraging results demonstrate that the developed single whole-cell multi-enzyme system exhibits great potential and economic competitiveness for the manufacture of 3′-SL.

Biosynthesis of Putrescine from L-arginine Using Engineered Escherichia coli Whole Cells

Putrescine, a biogenic amine, is a highly valued compound in medicine, industry, and agriculture. In this study, we report a whole-cell biocatalytic method in Escherichia coli for the production of putrescine, using L-arginine as the substrate. L-arginine decarboxylase and agmatine ureohydrolase were co-expressed to produce putrescine from L-arginine. Ten plasmids with different copy numbers and ordering of genes were constructed to balance the expression of the two enzymes, and the best strain was pACYCDuet-speB-speA. The optimal concentration of L-arginine was determined to be 20 mM for this strain. The optimum pH of the biotransformation was 9.5, and the optimum temperature was 45 °C; under these conditions, the yield of putrescine was 98%. This whole-cell biocatalytic method appeared to have great potential for the production of putrescine.

Production of rosmarinic acid with ATP and CoA double regenerating system

Rosmarinic acid (RA), as a hydroxycinnamic acid ester of caffeic acid (CA) and 3,4-dihydroxyphenyllactic acid (3,4-DHPL), is a phenylpropanoid-derived plant natural product and has diverse biological activities. This work acts as a modular platform for microbial production using a two-cofactor (ATP and CoA) regeneration system to product RA based on a cell-free biosynthetic approach. Optimal activity of the reaction system was pH 8 and 30 °C. Total turnover number for ATP and CoA was 820.60 ± 28.60 and 444.50 ± 9.65, respectively. Based on the first hour data, the RA productivity reached 320.04 mg L-1 h-1 (0.889 mM L-1 h-1).