Bacterial Pigments: Prodigiosin, Violacein, Pyocyanin, etc.

There are several well-studied bacterial pigments but these are not introduced in market because of its antimicrobial and eventual toxic activity, as is the case of prodigiosin and violacein. However, these pigments may have niche food uses (e.g., avoid fungal proliferation on the surface of meat products) or nonfood uses, as in textiles. At the other side, some bacteria produce harmless carotenoids. Examples of bacterial pigments produced using fermentation are presented in Table 4.8.

Prodigiosins are a class of tripyrrole antibiotic pigments produced by several microorganisms such as Serratia marcescens and Hahella chejuensis. These substances received recent renewed attention because of its reported immunosuppressant and anticancer properties (Williamson et al. 2006; Gulani et al. 2012) and potential involvement in the reduction of algal proliferation in algal blooms (Kwon et al. 2010). Serratia cultures produce almost 500 mg/L of prodigiosin in 2 days, at 30 °C. Giri et al. (2004) obtained excellent production in peanut seed broth (38.75 g/L), which indicated that peanut (and perhaps soy) processing residues could be an adequate substrate for the pigment.

Violacein is a purple diindole-pyrrole pigment derived from tryptophan. It is soluble in ethanol, and its biosynthesis and potential uses are still being studied. The same applies to the blue phenazine pigment pyocyanin, produced by Pseudomonas aeruginosa. Pyocyanin is a highly reactive metabolite which, being toxic to mammal

Table 4.8 Selected pigments produced by bacteria

Microorganism

Molecule

Culture medium

Xmax

(g/L)

Pmax

(mg/L)

References

Serratia marcescens

Prodigiosin

Maltose and

–

535

Gulani et al.

peanut

(2012)

oil based

Serratia marcescens

Prodigiosin

Powdered

–

39,000

Giri et al.

peanut

(2004)

medium

Hahella chejuensis,

Prodigiosin

Sucrose and

–

2,600

Kim et al.

mutant

peptone

(2008)

based

Chromobacterium violaceum

Violacein

Glucose and peptone

21

430

Mendes et al. (2001)

based

Paracoccus carotinifaciens

Astaxanthin, canthaxanthin

Glucose and peptone

–

25–40

(mg/g)

Hirschberg

et al. (1999);

based

Tanaka et al.

(2011)

cells, cannot be used in foods; however, it is possible that its conjugation to proteins in leather and other materials may stabilize it, permitting its use as a textile pigment. Paracoccus carotinifaciens is a bacterium which accumulates a mix of carotenoids.

Recent patents cover proprietary isolates and mutant strains, and although the carotenoid content is not superior to that of selected microalgae, the specific growth rate is probably high, as common in bacteria. This biomass hit market relatively quickly and is already permitted as a fish feed supplement in the USA.
 
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