Dyeing textiles with bacteria is a novel and futuristic approach to coloring, fabrics. The novelty lies in the fact that they are eco-friendly and are not toxic to the environment. They can be scaled up with a small carbon footprint and with very little impact on the environment. Microbial pigments have successfully been synthesized and can be used for dyeing textiles. Several bacteria like Chromobacterium violaceum, Janthinobacterium lividum, Chromobacterium lividum, Pseudoalteromonas luteoviolacea, and Pseudomonas fluorescens have been explored as sources for bio pigments, for their possible use as a dyestuff for textile materials. Microbial dyes are a viable alternative to natural dyes and hence can be classified under natural dyes. Scientists can tune them genetically for maximal pigment production. The industry can thus produce clothing with a varied color palette from blue jeans to red scarfs through bioengineered microbes.
Importance of Bio Pigments:
The production volume of dyes and pigments has been estimated to increase at a compounded annual growth rate (CAGR) of 6% between 2017 and 2022. The growing demand for dyes, especially in the textile market, is estimated to increase from USD 7.34 billion in 2017 to USD 9.82 billion by 2022. Nevertheless, due to their adverse effects such as carcinogenicity, hypersensitivity, and other toxicological effects, many synthetic pigments are banned worldwide. Many organizations like the World Health Organization (WHO), the European Food Standards Authority (EFSA), and Food and Drug Administration (FDA) have established stringent regulations. Moreover, plant-derived pigments have many drawbacks such as seasonal variation (availability throughout the year), larger cultivable area, high manpower consumption, and complexity of extraction.
In such a situation, microorganisms such as bacteria and fungi offer an eco-friendly choice of natural pigments. The advantages of bio-pigments are manifold which includes diverse color compound production, ease of environmental acceptability (bio-degradable), and renewability, widely encouraged for its developmental strategies. Microorganisms such as Monascus purpureus, Serratia marcescens, Penicillium atrovenetum, Rhodotorula glutinis, Phaffia rhodozyma, Paecilomyces sp., Bacillus sp., and Achromobacter sp., have the ability to produce various types of pigments such as carotenoid, violacein, naphthoquinone, polyketides, flavin, melanin, monascins, and prodigiosin. Streptomyces coelicolor is a harmless bacteria and easy to grow. In addition, the pigments also display several biological advantages such as antimicrobial, antioxidant, and anticancer activities
Advantages of Bio pigments:
The use of microorganisms for the recovery of bio pigments is considered more advantageous than extraction from plants not only due to its independence from atmospheric and geographical conditions but also for the following reasons:
Production feasibility
higher stability to heat, light exposure, and pH variation, and high solubility in water as compared to plant pigments
some kinds of pigments, like aryl carotenoids, are only produced by microorganisms
using low-cost substrates, such as agro-industrial wastes
possibilities of using modern genetic engineering tools to express bio pigment production by industrially important species (e.g. Escherichia coli and Saccharomyces cerevisiae) compared to plants, microbial diversity has enormous unexplored potential, expanding the possibility to find novel molecules.
Bio Pigment Sources:
Pigments are mainly classified into three classes - synthetic pigments, plant-derived pigments, and microbial pigments. “Bio pigments” or microbial pigments are natural-colored substances produced by microorganisms, especially fungi and bacteria. Fungi are also known to produce pigments in different natural media – potato dextrose agar (PDA), corn extract agar (CEA), Jowar extract agar (JEA), rice extract agar (REA), and also two synthetic media – Sabouraud dextrose agar (SDA) medium and Czapek-Dox agar (CZA) medium. Fungal pigments are produced in the extracellular liquid medium and intracellular in the mycelia.
Colour palette of Bio Pigments:
Microorganisms produce a variety of pigments as listed below
Table 1: Colour palette produced by microorganisms
S.no | Color of Pigment | Name of the Coloring compound | Pigment producing Organisms |
|---|---|---|---|
1 | Orange-red | Astaxanthin | Xanthophyllomyces dendrorhous (Red Yeast) Haematococcus Pluvialis (alga ) Agrobacterium aurantiacum (Bacterium) |
2 | Red | Prodigiosin | Serratia marcescens, Vibrio psychoerythrus, Rugamonas Rubra, Streptoverticillium rubrireticuli, and other eubacteria |
3 | Golden Yellow | Staphyloxanthin, Zeaxanthin | Staphylococcus aureus |
4 | Purple | Violacein | Chromobacterium violaceum, Janthinobacterium lividum |
5 | Cream | Zeaxanthin | Bacillus Spp, Achromobacter |
6 | Yellow | Xanthomonadin | Flavobacterium sp, Xanthomonas oryzae |
7 | Blue-Green | Pyocyanin | Pseudomonas aeruginosa |
8 | Brown | Zeaxanthin | Bacillus |
Current limitation and future perspective:
Bio pigments are a good source of color for textile dyeing. However, certain limitations in the form of high-cost investment required for large-scale production; lower stability; shade variation due to operational parameters; less percentage of annual production; limited color palette; technological advancement, etc plague their widespread usage. For these pigments to replace the synthetic pigments, concentrated efforts are required by the researchers in terms of the easiest method of harvesting bacterial pigments, developing a low-cost process for the production of bacterial pigments.
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