L-cysteine is a naturally occurring sulfur-containing amino acid bearing a reactive thiol group. It plays vital roles in maintaining cellular redox homeostasis and synthesizing bioactive compounds, thus gaining widespread attention and broad applications in: food, pharmaceutical, cosmetic and feed industries. Currently, its industrial production mainly relies on keratin hydrolysis, which causes serious environmental and safety concerns. By contrast, biocatalytic and microbial fermentation have emerged as sustainable and safe alternatives. This review systematically summarizes current bioproduction strategies for L-cysteine, covering biocatalytic pathways and metabolic engineering of microbial cell factories. We further elaborate the metabolic pathways, regulatory networks, and transport systems of L-cysteine in three mainstream microbial chassis, including Escherichia coli, Corynebacterium glutamicum, and Pantoea ananatis. Core production bottlenecks and targeted metabolic engineering solutions are also comprehensively discussed. Finally, future prospects for sustainable industrial L-cysteine production are proposed.
Ming-Li Zhao, Di Wu, Yu-Ting Liao et al.· Critical Reviews in Biotechn...· 0 citations
Ginsenoside Rh2, a potential anticancer agent originally isolated from the medicinal plant Panax ginseng, has low natural abundance and is difficult to extract, making biosynthetic production a promising alternative. UDP-glycosyltransferases (UGTs) that specifically catalyze protopanaxadiol (PPD) glycosylation to produce Rh2 have been widely identified in plants and microorganisms. In this study, we report that Barbarea vulgaris UGT73C21 effectively catalyzes this reaction. The enzyme was expressed in Escherichia coli and purified to electrophoretic homogeneity via Ni2⁺-affinity chromatography. It exhibited optimal activity at pH 8.0 (100 mM HEPES) and 45 °C. Mn2⁺, Mg2⁺, and Ca2⁺ significantly enhanced enzyme activity, whereas other tested metal ions reduced it. The kinetic parameters Km, Vmax, kcat, and kcat/Km were determined as 231.92 μM, 5.68 μM min-1, 0.053 s-1, and 228 M-1 s-1, respectively. In a reaction containing 0.2 mg/mL UGT73C21, 1 mM PPD, and 5 mM UDP-Glucose in HEPES buffer (pH 8.0), 0.55 mM Rh2 was produced within 1 h, corresponding to a 55% conversion rate. These results demonstrate that B. vulgaris UGT73C21 is an efficient biocatalyst for ginsenoside Rh2 biosynthesis.
Fan Xu, Yu-Ting Liao, Yulei Zhang et al.· Enzyme and Microbial Technol...· 0 citations
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