In a South Korean lab, a humble bacterium has learned to paint with all the colors of the rainbow, offering a natural alternative to synthetic colorants.
Walk down any supermarket aisle and you'll be greeted by a rainbow of artificial colors—vibrant red sodas, electric orange snacks, and brilliant blue candies. These synthetic colorants, derived from petroleum, have raised health concerns and environmental questions for decades. But what if we could harness nature's own palette instead? Thanks to a remarkable scientific breakthrough, researchers have successfully engineered Escherichia coli bacteria to produce the entire spectrum of rainbow colorants naturally. This colorful revolution promises to transform how we add color to our food, cosmetics, and medicines while replacing petroleum-based chemistry with sustainable biological solutions.
For over a century, synthetic colorants have dominated our color landscape. From the vibrant red of amaranth to the sunny yellow of tartrazine, these laboratory creations offered unprecedented stability, intensity, and affordability compared to their natural counterparts.
However, growing evidence suggests potential health risks including allergic reactions and behavioral changes in children have led to increased scrutiny and regulatory action 1 . Beyond health concerns, the production of synthetic colorants poses environmental challenges, including petroleum dependence and pollution from manufacturing processes.
The search for natural alternatives has been challenging. Traditional natural colorants—such as beet juice red, turmeric yellow, and spirulina blue—often suffer from limited stability, weaker coloring power, and higher costs. Some natural colors fade with heat, light, or changes in pH, making them unsuitable for many applications. The quest for a complete palette of natural colorants has remained elusive—until now.
Nature produces an extraordinary array of colorful molecules, but two families of compounds stand out for their rainbow potential: carotenoids and violacein derivatives. Carotenoids are pigments found in many plants and microorganisms, responsible for the bright reds, oranges, and yellows in carrots, tomatoes, and saffron. Violacein is a vibrant purple pigment produced by certain bacteria, which can be modified to create green, blue, and navy hues 1 8 .
What makes these natural pigments special isn't just their color—it's their potential health benefits. Many carotenoids function as antioxidants in the human body, helping to neutralize harmful free radicals. Similarly, violacein and its derivatives show promising antibacterial, antiviral, and anti-inflammatory properties 9 . Unlike synthetic colorants that may pose health risks, these natural alternatives might actually benefit our wellbeing while adding color to our products.
| Color Category | Specific Pigment | Production Level | Traditional Sources |
|---|---|---|---|
| Red | Astaxanthin | 322 mg/L | Shrimp, salmon, microalgae |
| Orange | β-carotene | 343 mg/L | Carrots, sweet potatoes |
| Yellow | Zeaxanthin | 218 mg/L | Corn, saffron, goji berries |
| Green | Proviolacein | 1.42 g/L | Bacterial fermentation |
| Blue | Prodeoxyviolacein | 0.844 g/L | Bacterial fermentation |
| Navy | Violacein | 6.19 g/L | Chromobacterium violaceum |
| Purple | Deoxyviolacein | 11.26 g/L | Modified bacterial strains |
Table 1: The rainbow of natural colorants produced by engineered E. coli, with production levels achieved through metabolic engineering and membrane optimization strategies 1 9 .
Astaxanthin: 322 mg/L
β-carotene: 343 mg/L
Zeaxanthin: 218 mg/L
Proviolacein: 1.42 g/L
Prodeoxyviolacein: 0.844 g/L
Violacein: 6.19 g/L
Deoxyviolacein: 11.26 g/L
E. coli may be infamous for causing food poisoning, but scientists have long recognized its potential as a microscopic workhorse. With its well-understood genetics and rapid growth, E. coli serves as an ideal platform for industrial biotechnology. Through metabolic engineering—the science of rewiring cellular processes—researchers can transform these simple bacteria into efficient factories for valuable chemicals 8 .
The process begins with genetic modification. Scientists introduce genes from other organisms into E. coli, enabling the bacteria to produce enzymes they wouldn't naturally have. For rainbow colorants, this means borrowing genes from colorful bacteria and plants. For instance, to produce carotenoids, researchers integrate enzymes from marigolds or algae. For violacein derivatives, they use genes from naturally purple-pigmented bacteria like Chromobacterium violaceum 9 .
Identify and isolate pigment-producing genes from natural sources
Insert genes into plasmids for introduction into E. coli
Introduce engineered plasmids into E. coli cells
Balance enzyme expression and remove metabolic bottlenecks
Scale up production in controlled bioreactors
Producing colorants inside bacteria is one thing; storing them in large quantities is another. Many natural colorants are hydrophobic molecules that accumulate in cell membranes. As production increases, these colorful chemicals can overwhelm the bacteria's storage capacity, ultimately limiting growth and production. This challenge led researchers to develop an innovative solution: membrane engineering 1 .
The groundbreaking experiment that enabled rainbow colorant production involved multiple sophisticated approaches:
This comprehensive approach represented a major advance in microbial production—not merely engineering the chemical production pathways but physically redesigning the cellular architecture to accommodate the valuable pigments.
The membrane engineering strategy achieved remarkable production levels across the color spectrum (as shown in Table 1). The most impressive results were for deoxyviolacein (purple), which reached 11.26 grams per liter—an exceptionally high titer for natural product biosynthesis 1 . Subsequent research has pushed this even further, with a 2025 study reporting deoxyviolacein production of 12.18 grams per liter 9 .
Perhaps the most significant finding was that these membrane engineering strategies could be generally applied to improve production of all seven rainbow colorants, not just one specific pigment. This suggests the approach could be valuable for manufacturing a wide range of hydrophobic natural products beyond colorants.
| Pigment Type | Base Production (mg/L) | With Membrane Engineering (mg/L) | Fold Improvement |
|---|---|---|---|
| Astaxanthin (Red) | 85 | 322 | 3.8x |
| β-carotene (Orange) | 95 | 343 | 3.6x |
| Zeaxanthin (Yellow) | 62 | 218 | 3.5x |
| Proviolacein (Green) | 380 | 1,420 | 3.7x |
| Prodeoxyviolacein (Blue) | 225 | 844 | 3.8x |
| Violacein (Navy) | 1,650 | 6,190 | 3.8x |
| Deoxyviolacein (Purple) | 2,950 | 11,260 | 3.8x |
Table 2: The dramatic improvement in colorant production achieved through membrane engineering strategies. Values are approximate and based on data from the research 1 .
Creating bacterial colorant factories requires specialized materials and reagents. Below are key components used in this cutting-edge research:
Table 3: Research reagents and essential materials used in metabolic engineering of E. coli for colorant production 1 9 .
The implications of this research extend far beyond laboratory curiosities. The food industry can benefit from natural alternatives to synthetic colorants like Red No. 40 and Yellow No. 5. The cosmetic industry can replace petroleum-derived pigments in makeup and skincare products. Even the textile industry could use these bio-based colorants for more sustainable clothing dyes 5 .
Natural alternatives to synthetic colorants in candies, beverages, and processed foods with potential health benefits.
Bio-based pigments for makeup, skincare, and personal care products with reduced environmental impact.
Sustainable dyes for clothing and fabrics that reduce water pollution from traditional dyeing processes.
Perhaps most excitingly, this research demonstrates a broader principle: through metabolic engineering, we can reprogram microorganisms to produce valuable compounds that would otherwise be scarce, expensive, or environmentally damaging to produce. The same strategies used to create rainbow colorants are now being applied to produce medicines, biofuels, and other precious chemicals 8 .
As research advances, we may see even more colors and improved production methods. Scientists are working on expanding the color palette further, improving stability of natural colorants, and reducing production costs. The day when we can enjoy a brightly colored candy or wear a vibrant shirt dyed with bacteria-produced pigments isn't far off. The rainbow future of natural colorants is bright—and it's brewing in a bacterial factory.