Biocatalytic Indigo Synthesis From L-Tryptophan Using a Three-Step Cascade Without Cofactor Regeneration

Area of Science:

• Biotechnology
• Synthetic Biology
• Enzymatic Synthesis

Background:

• Current indigo production relies on petrochemicals, causing environmental concerns.
• Existing enzymatic methods for indigo synthesis often require expensive coenzymes like NAD(P)H, limiting scalability.

Purpose of the Study:

• To develop a novel, self-sufficient enzyme cascade for indigo biosynthesis from L-tryptophan.
• To create an NAD(P)H-independent pathway for sustainable indigo production.

Main Methods:

• Engineered a cascade starting with tryptophanase to convert L-tryptophan to indole and pyruvate.
• Coupled engineered bacterial tyrosine hydroxylase with pyruvate oxidase to utilize hydrogen peroxide in situ.
• Optimized cascade parameters for efficient indigo biosynthesis.

Main Results:

• Achieved a novel, NAD(P)H-independent enzymatic cascade for indigo production.
• Demonstrated the conversion of a reaction byproduct (pyruvate) into an essential oxidizing agent (hydrogen peroxide).
• Produced 0.25 mM indigo from 5 mM L-tryptophan, establishing a proof-of-principle.

Conclusions:

• The developed enzyme cascade provides a sustainable and cost-effective route for indigo production from renewable L-tryptophan.
• This NAD(P)H-independent system minimizes auxiliary inputs, offering an environmentally friendly alternative to petrochemical synthesis.