Study on extraction and characterization of new antibiotics violacein from engineered Escherichia coli VioABCDE-SD.

Abstract

To better understand the characteristic properties of violacein biosynthesized by engineered Escherichia coli VioABCDE-SD, a convenient and simplified method was designed to extract violacein and its stability, antimicrobial activity, and antioxidant capacity were analyzed. Different fromthetraditional extraction methods, ournew method is easierandlesstime consuming and can directly obtain violacein dry powder product with a higher extraction rate. Low temperature, darkcondition, neutral pH, reducing agents, Ba2+ , Mn2+ , Ni2+ , Co2+ , and some food additives of sucrose, xylose, and glucose were conducive tomaintainingitsstability. The violacein also exhibited surprisingly high bacteriostatic action against Gram-positive Bacillus subtilis, Deinococcus radiodurans R1, and Staphylococcus aureus and Gram-negative Pseudomonasaeruginosa, but no effect on E. coli. The violacein of VioABCDE-SD exhibited strong antioxidant activity, with the scavenging rate of 1,1-diphenyl-2-picrylhydrazyl free radicals reaching 60.33%, the scavenging efficiency of hydroxyl radical scavenging reaching 56.34%, and the total antioxidant capacity reaching 0.63U/mL. Violacein from VioABCDE-SD can be synthesized directionally with better stability, antibacterial, and antioxidant properties compared with that from the original strain Janthinobacterium sp. B9-8. Therefore, our study indicated that violacein from engineered E. coli VioABCDE-SD was a kind of new antibiotic with potential biological activities, which may havepotentialutilityinmultiple areas such as pharmacological, cosmetics, and healthy food industries.