Indigo formation by microorganisms expressing styrene monooxygenase activity

Area of Science:

• Microbiology
• Biotechnology
• Biocatalysis

Background:

• The structural similarity between styrene and indole suggests potential for microbial transformation.
• Styrene monooxygenase (SMO) is a key enzyme in styrene degradation and a candidate for indole transformation.

Purpose of the Study:

• To investigate microbial transformation of indole to indigo using styrene-degrading bacteria.
• To identify the specific enzymes and conditions facilitating this biotransformation.

Main Methods:

• Screening of various styrene-degrading bacterial strains for indole transformation.
• Growth studies on solid and liquid media with indole and styrene as inducers.
• Enzyme activity characterization using SMO- and styrene oxide isomerase (SOI)-negative mutants.
• Analysis of indigo production rates under different growth conditions and nutrient supplements.

Main Results:

• Two strains, Pseudomonas putida S12 and CA-3, demonstrated blue color formation from indole.
• Styrene was identified as a potent inducer for indole transformation, while indole was a poor inducer in liquid media.
• Both SMO and SOI were found to be crucial for the indole to indigo transformation.
• Arginine influenced indigo formation rates differently in the two strains, indicating strain-specific regulatory mechanisms.

Conclusions:

• Pseudomonas putida strains S12 and CA-3 can efficiently convert indole to high-purity indigo.
• The biotransformation is mediated by styrene monooxygenase (SMO) and styrene oxide isomerase (SOI).
• Understanding the induction and regulation of these enzymes is key for optimizing indigo production.