MICROBIAL PIGMENTS AND DYES
Natural pigments and dyes can be obtained from 3 major sources. That includes-
We have discussed all these 3 sources in great detail in our previous posts of ECO-FRIENDLY SERIES. But there is one more category that has been used as a natural and sustainable alternative for synthetic chemical dyes. The category belongs to – Microbes and Fungus.
COLORS FROM MICROBES ??? Yes, sounds a bit strange! But they are used to impart natural color to the fabric or any other element when treated rightly.
WHAT ARE MICROBIAL PIGMENTS?
These are color imparting substances that are obtained from Bacterias and Fungi. New studies and development in the color industry, opens up new possibilities of extracting dyes from Microbes.
Microbial dye is certainly a recent approach. A large number of different species of bacteria, yeast, mold and algae are used to produce pigments for economical dyes.
These pigments overcome the disadvantages of plant-based pigments such as –
- Non-availability of plants throughout the year
- Color extraction from endangered species
- Color fading
- Pigment stability and solubility
- Fabric dependency of colors.
ADVANTAGES OF MICROBIAL PIGMENTS
Microbial pigments are becoming popular worldwide due to :
- Rapid growth of microbes in cheaper medium
- Easy processing and color extraction
- Independence of weather conditions
- Antioxidant, antimicrobial and anticancer properties
- Broad area of application mainly in food, dairy, printing, textile and pharmaceutical industries
MICROORGANISMS USED AS PIGMENTS
The significant source of colors in microorganisms are carotenoids which are yellow, orange, red or purple pigments used as nutrient supplements, food, pharmaceutical, and cosmetic industries as dyes/colorants.
Carotenoids can be produced by numerous microorganisms. Few of them are:
1. Micrococcus Bacteria
Micrococcus is a gram positive Bacteria found in soil, water and dust belonging to Micrococcaceae family. Micrococcus roseus is the bacteria used for extraction of the carotenoid pigment with antimicrobial, antioxidant, anticancer, and anti-inflammatory properties. Isolated colonies on a TSA plate are circular, 1.0–1.5 mm in size, slightly convex, smooth, and pink in color.
2. Chromobacter Violaceum
Chromobacterium violaceum is a Gram-negative bacteria of Rhizobiaceae family. It is a saprophyte found in soil and water in tropical and subtropical areas.
Violet colonies of Chromobacterium violaceum
The pigment produced from the violet colony is violacein [3-(1, 2-dihydro-5-(5-hydroxy-1H-indol-3-yl)-2-oxo-3H-pyrrol-3-ilydene)-1, 3-dihydro-2H-indol-2-one] which have a strong bactericidal, trypanocidal, tumoricidal, mycobactericidal and antioxidant activity.
Rhodotorula is a genus of single-cell yeasts. Colonies of Rhodotorula can be found in air, soil, lakes, ocean water, milk and fruit juice. They create pigmented colonies of pink to red color.
Rhodotorula mucilaginosa colonies on sabouraud agar
These hues of Reds are carotenoid compounds produced by the yeast; these natural dyes can be extracted from Rhodotorula /Rhodosporidium and used in the food and vitamin industries.
4. Monascus – Red Yeast
Monascus purpureus is a species of mold that is purple-red in color and thus popularly known as Red yeast.
This fungus is used in the form of red yeast rice, of China called as angkak. Red yeast rice has been used as staple food and food additive for centuries in Asia and Indonesia. In Japan red rice is known as beni-koji and its pigments are widely used for food coloring.
Monascus species are known to produce well-known azaphilone pigments . In fact, various pigments derivatives with improved color range of orange-red to violet-red can be produced by Monascus fermentation in the presence of different amino acid .
5. Phaffia – Pink Yeast
Phaffia rhodozyma is a pink yeast discovered by Herman Phaff in 1960. One of the most remarkable features of P. rhodozyma is the pink to orange color of its colonies due the production of carotenoid pigments.
The main carotenoid pigment produced by P. rhodozyma is astaxanthin, a compound not formed by any other yeast species. Astaxanthin is economically important because it is an aquaculture feed component needed for pigmentation of fish and crustaceans.
6. Sarcina Bacteria
Sarcina is a gram positive, non-motile bacteria , spherical in shape and are various members of the genus are found in soil, mus, cereal seeds and may be found in the skin and large intestine.
They produce yellow color pigment carotenoid by nature. Studies are going on with the mechanism of photo‐protection by the carotenoid pigments of Sarcina lutea and three induced mutants.
PIGMENTS OF FUTURE
Microbial pigments are renewable and sustainable sources of natural pigments. These are more reliable than Plant-based sources due to their wide presence and fast bacterial growth. Natural dyes are biodegradable and disposing of them doesn’t cause pollution. However, using these sources as food colorants may not be suggestive due to their harmful effects on the human body when consumed. They may cause allergies and inflammation with exceptions such as carmine found in lipsticks, will not cause harm or health problems when ingested.
A large number of different species of bacteria, yeast, mold and algae produce pigments for economical dyes. Further studies will surely open up more possibilities of Microbial sources as a cheap alternative to plant-based dyes.