International audienceThe current inclination towards exploiting bacterial pigments for various coloring functions, like food, cloth, painting, cosmetics, pharmaceuticals, plastics etc. is a well-recognized aspect. Nevertheless, the current bacterial pigment productions are not effective to meet their industrial needs. Current research going on world over on bacterial pigments signify that genetic engineering for strain improvement, optimization of bioprocess modelling and utilizing cheap agro-industrial residues as substrates are key developmental strategies to maximize pigment production from bacteria. Incidentally the superior performance characteristics of the bacteria for producing differing colouring compounds and the environmental acceptability of bacterial pigments are very encouraging factors to promote higher pigment production taking advantage of the current developmental strategies. This paper evaluates the current advances in bacterial pigment production, its recovery and wide-ranging scope of its industrial applications and commercial viability

Violacein, violet pigment produced by Chromobacterium violaceum, has attracted much attention recently due to its pharmacological properties including antibacterial activity. The present study investigated possible antibacterial mode of action of violacein from C. violaceum UTM5 against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) strains. Violet fraction was obtained by cultivating C. violaceum UTM5 in liquid pineapple waste medium, extracted, and fractionated using ethyl acetate and vacuum liquid chromatography technique. Violacein was quantified as major compound in violet fraction using HPLC analysis. Violet fraction displayed bacteriostatic activity against S. aureus ATCC 29213 and methicillin-resistant S. aureus ATCC 43300 with minimum inhibitory concentration (MIC) of 3.9 μg/mL. Fluorescence dyes for membrane damage and scanning electron microscopic analysis confirmed the inhibitory effect by disruption on membrane integrity, morphological alternations, and rupture of the cell membranes of both strains. Transmission electron microscopic analysis showed membrane damage, mesosome formation, and leakage of intracellular constituents of both bacterial strains. Mode of action of violet fraction on the cell membrane integrity of both strains was shown by release of protein, K, and extracellular adenosine 5'-triphosphate (ATP) with 110.5 μg/mL, 2.34 μg/mL, and 87.24 ng/μL, respectively, at 48 h of incubation. Violet fraction was toxic to human embryonic kidney (HEK293) and human fetal lung fibroblast (IMR90) cell lines with LC value of 0.998 ± 0.058 and 0.387 ± 0.002 μg/mL, respectively. Thus, violet fraction showed a strong antibacterial property by disrupting the membrane integrity of S. aureus and MRSA strains. This is the first report on the possible mode of antibacterial action of violet fraction from C. violaceum UTM5 on S. aureus and MRSA strains.

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Natural yellowish-orange pigments are derived from bacteria, yeasts, fungi and microalgae, including Chryseobacterium, Monascus and Chlorella. The purpose of this review is to provide an overview of these pigments in various aspects towards exploiting them for numerous functions. These pigments are produced in various shades of yellow-orange and categorised as carotenoids, anthraquinones, zeaxanthin, flexirubin and other compounds. They served as alternative colourants to replace hazardous and toxic synthetic pigments. Researchers are in progress to increase the pigment yield by improving the strains genetically, optimising the fermentation process and utilising cheap agroindustrial waste to reduce the production cost. Yellowish-orange pigments are applied in food, pharmaceuticals, cosmetics and textile industries. This review summarises the current technology status and challenges, economics, biosyn-thesis of pigment, novel strategies for production of yellowish-orange pigments, biological properties of pigments and metabolic engineering of microorganism with a focus on applications of pigments in food, pharmaceutical, dyeing industries as well as on other applications.

Highlights 39• Liquid pineapple waste, a novel nutritious low cost growth medium. 40• Post-treatment of bacterial effluent for eco-friendly disposal. 41• Violet pigment stable at optimum conditions. 42• Violacein and deoxyviolacein isolated and characterized. 43• Crude violet pigment shows bioactivity. 44 • The first report on the production of violet pigment using liquid pineapple waste 45 medium. 46 47 48 Abstract 49 50 Synthetic pigments have been utilized in numerous industries including textile, cosmetic, 51 food and pharmaceuticals. However, the drawbacks of these pigments, namely toxicity 52 problems have kindle the interest in natural pigments. In view of this, the use of natural 53 pigments such as those from bacterial origin offers interesting alternative for industrial 54 application. However, large scale applications of natural pigments are often hindered by the 55 high production cost. This study evaluates on the feasibility of using liquid pineapple waste 56 for the production of violacein by a locally isolated Chromobacterium violaceum UTM5 both 57 in shake flask and 50 L bioreactor. The use of optimized growth parameters including culture 58 conditions, concentration of liquid pineapple waste and supplementation of L-tryptophan 59 resulted in violacein yield of 16256 ± 440 mg L -1 . Post treatment of the effluent effectively 60 reduced the COD, turbidity and TSS contents to less than 1 mg L -1 , 1.57 ± 0.2 NTU and 2.7 ± 61 0.6 mg L -1 respectively. Violet pigment exhibited good stability during the entire storage 62 period of 30 days at pH 7, temperature 25 -30 °C and under dark condition. The violet 63 pigment has a good antimicrobial activity against selected microorganisms. Of interest, the 64 pigment was active against Staphylococcus aureus ATCC 29213 and methicillin-resistant 65 Staphylococcus aureus (MRSA) ATCC 43300 with MIC value of 7.8 and 15.6 µg mL -1 , 66 respectively. However, the pigment is toxic to the V79-4 Chinese hamster lung cells with low 67 selectivity index. The purified compounds were determined as violacein and deoxyviolacein 68 using FT-IR, LC-MS and NMR respectively. Results confirmed the feasibility of using liquid 69 pineapple waste as a potential low cost growth medium for large-scale cultivation of violet 70 pigment using C. violaceum UTM5. Synthetic colours are mostly used in the food processing and cosmetic industries as natural 81 colorants are expensive, less stable and possess lower intensity. 1,2 Conversely, these 82 synthetic colorants have been or being banned due to their carcinogenicity, hyperallergenicity 83 and toxicological issues. Thus, natural pigments are progressively in an increasing demand as 84 they are biodegradable, non-toxic to humans and have precise differences in colour tones. 3,4 85 A wide range of pigment applications in fields of food, cosmetics, pharmaceuticals and 86 textiles has contributed to its escalating needs by colouring agents in many industries. 1 In 87 comparison to colorants extracted from plant and animals, microorganisms ...