Quercetin Glucoside Production by Engineered Escherichia coli

Area of Science:

• Metabolic Engineering
• Enzyme Technology
• Biotechnology

Background:

• Quercetin glucosides have potential health benefits.
• Enzymatic glycosylation using O-glucosyltransferases offers a sustainable production method.
• Escherichia coli is a versatile host for microbial production systems.

Purpose of the Study:

• To compare the efficacy of UGT73B3 and UGT84B1 in producing quercetin glucosides.
• To optimize conditions for enhanced glucoside production in E. coli.
• To achieve high-yield production of quercetin-3-glucoside (Q3G).

Main Methods:

• Engineered E. coli strains expressing UGT73B3 or UGT84B1 were utilized.
• Production was assessed at different temperatures and in various culture systems (shake flasks vs. bioreactors).
• A phosphoglucose isomerase (pgi) deletion mutant was employed to redirect glucose metabolism.

Main Results:

• UGT73B3 produced quercetin-3-glucoside (Q3G) optimally at 33°C, while UGT84B1 produced quercetin-7-glucoside optimally at 37°C.
• E. coli strains with a pgi deletion significantly increased Q3G concentrations.
• Bioreactor cultivation yielded higher Q3G formation compared to shake flasks due to improved oxygen transfer.
• A yield of 3.9 g/L Q3G was achieved in 56 hours using E. coli MEC367 (MG1655 pgi) expressing UGT73B3 under batch conditions with 30 g/L glucose.

Conclusions:

• UGT73B3 is more effective for Q3G production.
• Metabolic engineering strategies, including pgi deletion, enhance glucoside yields.
• Optimized fermentation conditions in bioreactors are crucial for high-titer production of valuable glucosides.