Therapeutic applications of bacterial pigments: a review of current status and future opportunities

Anti-Melanogenic Activity of Undecylprodigiosin, a Red Pigment Isolated from a Marine Streptomyces sp. SNA-077

Bioassay and HPLC-UV guided fractionations of the crude extract of marine-derived Streptomyces sp. SNA-077 have led to the isolation of a red pigment, undecylprodigiosin (1). The chemical structure of undecylprodigiosin (1) was revealed by the interpretation of NMR and mass spectroscopic (MS) data. Further, anti-melanogenic effects of undecylprodigiosin (1) were investigated. First, the melanin contents of undecylprodigiosin (1)-treated B16 cells were evaluated. Furthermore, undecylprodigiosin (1) significantly inhibited the key enzymes involved in melanogenesis, including tyrosinase, tyrosinase related protein-1 (TYRP-1), and dopachrome tautomerase (DCT). The mRNA and protein expression levels of Microphthalmia-associated transcriptian factor (MiTF), a critical transcription factor for tyrosinase gene expression, were also suppressed by undecylprodigiosin (1) treatment in B16 analyses. Collectively, our results suggest for the first time that undecylprodigiosin (1), a potent component isolated from an extract of marine Streptomyces sp. SNA-077, critically exerts the anti-melanogenic ability for melanin synthesis.

Bacteria as a source of biopigments and their potential applications

From the prehistoric period, the utilization of pigments as colouring agents was an integral part of human life. Early people may have utilized paint for aesthetic motives, according to archaeologists. The pigments are either naturally derived or synthesized in the laboratory. Different studies reported that certain synthetic colouring compounds were toxic and had adverse health and environmental effects. Therefore, knowing the drawbacks of these synthetic colouring agents now scientists are attracted towards the harmless natural pigments. The main sources of natural pigments are plants, animals or microorganisms. Out of these natural pigments, microorganisms are the most important source for the production and application of bioactive secondary metabolites. Among all kinds of microorganisms, bacteria have specific benefits due to their short life cycle, low sensitivity to seasonal and climatic variations, ease of scaling, and ability to create pigments of various colours. Based on these physical characteristics, bacterial pigments appear to be a promising sector for novel biotechnological applications, ranging from functional food production to the development of new pharmaceuticals and biomedical therapies. This review summarizes the need for bacterial pigments, biosynthetic pathways of carotenoids and different applications of bacterial pigments.

Microbial pigments: Sources, current status, future challenges in cosmetics and therapeutic applications

Color serves as the initial attraction and offers a pleasing aspect. While synthetic colorants have been popular for many years, their adverse environmental and health effects cannot be overlooked. This necessitates the search for natural colorants, especially microbial colorants, which have proven and more effective. Pigment-producing microorganisms offer substantial benefits. Natural colors improve product marketability and bestow additional benefits, including antioxidant, antiaging, anticancer, antiviral, antimicrobial, and antitumor properties. This review covers the various types of microbial pigments, the methods to enhance their production, and their cosmetic and therapeutic applications. We also address the challenges faced during the commercial production of microbial pigments and propose potential solutions.

A comprehensive profiling of quorum quenching by bacterial pigments identifies quorum sensing inhibition and antibiofilm action of prodigiosin against Acinetobacter baumannii

Bacterial pigments represent a diverse group of secondary metabolites, which confer fitness advantages to the producers while residing in communities. The bioactive potential of such metabolites, including antimicrobial, anticancer, and immunomodulation, are being explored. Reckoning that a majority of such pigments are produced in response to quorum sensing (QS) mediated expression of biosynthetic gene clusters and, in turn, influence cell-cell communication, systemic profiling of the pigments for possible impact on QS appears crucial. A systemic screening of bacterial pigments for QS-inhibition combined with exploration of antibiofilm and antimicrobial action against Acinetobacter baumannii might offer viable alternatives to combat the priority pathogen. Major bacterial pigments are classified (clustered) based on their physicochemical properties, and representatives of the clusters are screened for QS inhibition. The screen highlighted prodigiosin as a potent quorum quencher, although its production from Serratia marcescens appeared to be QS-independent. In silico analysis indicated potential interactions between AbaI and AbaR, two major QS regulators in A. baumannii, and prodigiosin, which impaired biofilm formation, a major QS-dependent process in the bacteria. Prodigiosin augmented antibiotic action of ciprofloxacin against A. baumannii biofilms. Cell viability analysis revealed prodigiosin to be modestly cytotoxic against HEK293, a non-cancer human cell line. While developing dual-species biofilm, prodigiosin producer S. marcescens significantly impaired the fitness of A. baumannii. Enhanced susceptibility of A. baumannii toward colistin was also noted while growing in co-culture with S. marcescens. Antibiotic resistant isolates demonstrated varied responsiveness against prodigiosin, with two resistant strains demonstrating possible collateral sensitivity. Collectively, the results underpin the prospect of a prodigiosin-based therapeutic strategy in combating A. baumannii infection.

A Review of the Chemistry and Biological Activities of Natural Colorants, Dyes, and Pigments: Challenges, and Opportunities for Food, Cosmetics, and Pharmaceutical Application

Natural pigments are important sources for the screening of bioactive lead compounds. This article reviewed the chemistry and therapeutic potentials of over 570 colored molecules from plants, fungi, bacteria, insects, algae, and marine sources. Moreover, related biological activities, advanced extraction, and identification approaches were reviewed. A variety of biological activities, including cytotoxicity against cancer cells, antioxidant, anti-inflammatory, wound healing, anti-microbial, antiviral, and anti-protozoal activities, have been reported for different pigments. Considering their structural backbone, they were classified as naphthoquinones, carotenoids, flavonoids, xanthones, anthocyanins, benzotropolones, alkaloids, terpenoids, isoprenoids, and non-isoprenoids. Alkaloid pigments were mostly isolated from bacteria and marine sources, while flavonoids were mostly found in plants and mushrooms. Colored quinones and xanthones were mostly extracted from plants and fungi, while colored polyketides and terpenoids are often found in marine sources and fungi. Carotenoids are mostly distributed among bacteria, followed by fungi and plants. The pigments isolated from insects have different structures, but among them, carotenoids and quinone/xanthone are the most important. Considering good manufacturing practices, the current permitted natural colorants are: Carotenoids (canthaxanthin, β-carotene, β-apo-8'-carotenal, annatto, astaxanthin) and their sources, lycopene, anthocyanins, betanin, chlorophyllins, spirulina extract, carmine and cochineal extract, henna, riboflavin, pyrogallol, logwood extract, guaiazulene, turmeric, and soy leghemoglobin.

Pseudomonas aeruginosa's greenish-blue pigment pyocyanin: its production and biological activities

A subject of great interest is the bioprospecting of microorganisms and their bioactive byproducts, such as pigments. Microbial pigments have various benefits, including being safe to use due to their natural makeup, having therapeutic effects, and being produced all year round, regardless of the weather or location. Pseudomonas aeruginosa produces phenazine pigments that are crucial for interactions between Pseudomonas species and other living things. Pyocyanin pigment, which is synthesized by 90-95% of P. aeruginosa, has potent antibacterial, antioxidant, and anticancer properties. Herein, we will concentrate on the production and extraction of pyocyanin pigment and its biological use in different areas of biotechnology, engineering, and biology.

Production of bioactive β-carotene by the endophytic bacterium Citricoccus parietis AUCs with multiple in vitro biological potentials

BACKGROUND

Although microalgae and plants are traditionally used for obtaining natural pigments, overexploitation and overharvesting threaten them. Bacteria represent a superior alternative for the production of pigments due to their ability to produce greater amounts in a short time without seasonal restrictions; furthermore, bacterial pigments have a wide range of uses and are safe and biodegradable. This study is the first on the production of ß-carotene as a promising bioactive agent from endophytic bacteria.

RESULTS

The yellow pigment produced by the endophytic bacterium Citricoccus parietis AUCs (NCBI accession number: OQ448507.1) was extracted by methanol and then purified and identified. One band was obtained by TLC analysis, which was identified as ß-carotene based on its spectroscopic and chromatographic characteristics. The pigment exhibited remarkable antibacterial, antioxidant and antidiabetic activities.

CONCLUSIONS

This research may serve as a valuable starting point for exploiting C. parietis AUCs as a potent source of ß-carotene for biomedical therapies. To validate the findings of this research, in vivo studies must be performed.

Antibacterial, antibiofilm, and anti-quorum sensing activities of pyocyanin against methicillin-resistant Staphylococcus aureus: in vitro and in vivo study

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) infections are considered a major public health problem, as the treatment options are restricted. Biofilm formation and the quorum sensing (QS) system play a pivotal role in S. aureus pathogenicity. Hence, this study was performed to explore the antibacterial effect of pyocyanin (PCN) on MRSA as well as its effect on MRSA biofilm and QS.

RESULTS

Data revealed that PCN exhibited strong antibacterial activity against all test MRSA isolates (n = 30) with a MIC value equal to 8 µg/ml. About 88% of MRSA biofilms were eradicated by PCN treatment using the crystal violet assay. The disruption of MRSA biofilm was confirmed using confocal laser scanning microscopy, which showed a reduction in bacterial viability (approximately equal to 82%) and biofilm thickness (approximately equal to 60%). Additionally, the disruption of the formation of microcolonies and the disturbance of the connection between bacterial cells in the MRSA biofilm after PCN treatment were examined by scanning electron microscopy. The 1/2 and 1/4 MICs of PCN exerted promising anti-QS activity without affecting bacterial viability; Agr QS-dependent virulence factors (hemolysin, protease, and motility), and the expression of agrA gene, decreased after PCN treatment. The in silico analysis confirmed the binding of PCN to the AgrA protein active site, which blocked its action. The in vivo study using the rat wound infection model confirmed the ability of PCN to modulate the biofilm and QS of MRSA isolates.

CONCLUSION

The extracted PCN seems to be a good candidate for treating MRSA infection through biofilm eradication and Agr QS inhibition.

De novo biosynthesis of carminic acid in Saccharomyces cerevisiae

Carminic acid is a natural red dye extracted from the insect Dactylopius coccus. Due to its ideal dying effect and high safety, it is widely used in food and cosmetics industries. Previous study showed that introduction of polyketide synthase (OKS) from Aloe arborescens, cyclase (ZhuI) and aromatase (ZhuJ) from Streptomyces sp. R1128, and C-glucosyltransferase (UGT2) from D. coccus into Aspergillus nidulans could achieve trace amounts of de novo production. These four genes were introduced into Saccharomyces cerevisiae, but carminic acid was not detected. Analysis of the genome of A. nidulans revealed that 4'-phosphopantetheinyl transferase (NpgA) and monooxygenase (AptC) are essential for de novo biosynthesis of carminic acid in S. cerevisiae. Additionally, endogenous hydroxylase (Cat5) from S. cerevisiae was found to be responsible for hydroxylation of flavokermesic acid to kermesic acid. Therefore, all enzymes and their functions in the biosynthesis of carminic acid were explored and reconstructed in S. cerevisiae. Through systematic pathway engineering, including regulating enzyme expression, enhancing precursor supply, and modifying the β-oxidation pathway, the carminic acid titer in a 5 L bioreactor reached 7580.9 μg/L, the highest yet reported for a microorganism. Heterologous reconstruction of the carminic acid biosynthetic pathway in S. cerevisiae has great potential for de novo biosynthesis of anthraquinone dye.

Insight into Green Extraction for Roselle as a Source of Natural Red Pigments: A Review

Roselle (Hibiscus sabdariffa L.) is a source of anthocyanins as red pigments that is extensively farmed in tropical and subtropical regions, including Indonesia, Malaysia, China, Thailand, Egypt, Mexico, and West India. The roselle plant contains a variety of nutrients, including anthocyanins, organic acids, pectin, etc. Due to the toxicity and combustibility of the solvents, traditional extraction methods for these compounds are restricted. Obtaining pure extracts is typically a lengthy procedure requiring many processes. Supercritical carbon dioxide (ScCO₂) extraction as a green technology is rapidly improving and extending its application domains. The advantages of this method are zero waste production, quicker extraction times, and reduced solvent consumption. The ScCO₂ extraction of natural pigments has great promise in food, pharmaceuticals, cosmetics, and textiles, among other uses. The ScCO₂ technique for natural pigments may also be advantageous in a variety of other contexts. Due to their minimal environmental risk, the high-quality red pigments of roselle rich in anthocyanins extracted using ScCO₂ extraction have a high sustainability potential. Therefore, the objective of this review is to increase knowledge related to the natural colorant of roselle as a substitute for chemically manufactured colorants using ScCO₂ as a green method. This article covers ScCO₂ extraction, particularly as it relates to the optimization of pigments that promote health. This article focuses on the high extraction efficiency of ScCO₂ extraction. Natural colorants extracted via ScCO₂ are regarded as safe compounds, especially for human consumption, such as novel functional food additives and textile and pharmaceutical colors.

Carotenoid metabolism: New insights and synthetic approaches

Carotenoids are well-known isoprenoid pigments naturally produced by plants, algae, photosynthetic bacteria as well as by several heterotrophic microorganisms. In plants, they are synthesized in plastids where they play essential roles in light-harvesting and in protecting the photosynthetic apparatus from reactive oxygen species (ROS). Carotenoids are also precursors of bioactive metabolites called apocarotenoids, including vitamin A and the phytohormones abscisic acid (ABA) and strigolactones (SLs). Genetic engineering of carotenogenesis made possible the enhancement of the nutritional value of many crops. New metabolic engineering approaches have recently been developed to modulate carotenoid content, including the employment of CRISPR technologies for single-base editing and the integration of exogenous genes into specific "safe harbors" in the genome. In addition, recent studies revealed the option of synthetic conversion of leaf chloroplasts into chromoplasts, thus increasing carotenoid storage capacity and boosting the nutritional value of green plant tissues. Moreover, transient gene expression through viral vectors allowed the accumulation of carotenoids outside the plastid. Furthermore, the utilization of engineered microorganisms allowed efficient mass production of carotenoids, making it convenient for industrial practices. Interestingly, manipulation of carotenoid biosynthesis can also influence plant architecture, and positively impact growth and yield, making it an important target for crop improvements beyond biofortification. Here, we briefly describe carotenoid biosynthesis and highlight the latest advances and discoveries related to synthetic carotenoid metabolism in plants and microorganisms.

Biological control of melanin biosynthesis pathway on prolific and pleochromatic induction of Lasiodiplodia theobromae

To obtain a kind of microbial pigment with high yield and variety coloration by regulating the pigment synthesis pathway in this experiment, Lasiodiplodia theobromae was used to induce pigment secretion by prolific inducing factors (tyrosinase, Cu²⁺, stilbene glycoside) and pleochromatic inducing factors (L-tyrosine, L-cysteine, tricyclazole). The results showed that through single factor and compound culture, the most reasonable inducing formula was 150 ku/L tyrosinase, while tricyclazole at 10 mg/L for 30 days had a maximum color difference of 42.92 NBS with a reddish-brown color in 10 days. The melanin content increased gradually with the extension of culture time, and the pleochromatic inducing group was up to 3.47 mg/mL, higher than that of the prolific inducing group. However, the poor solubility of purified melanin with a diameter of 100-200 nm was observed in conventional solvents. Through effective induction, it is expected that L. theobromae can secrete melanin stably and be widely used in printing, dyeing, electronics, and the chemical industry.

A purified and lyophilized Pseudomonas aeruginosa derived pyocyanin induces promising apoptotic and necrotic activities against MCF-7 human breast adenocarcinoma

BACKGROUND

Pyocyanin, a specific extracellular secondary metabolite pigment produced by Pseudomonas aeruginosa, exhibits redox activity and has toxic effects on mammalian cells, making it a new and potent alternative for treating cancer. Breast cancer (BC) treatment is now defied by acquired and de novo resistance to chemotherapy, radiation, or targeted therapies. Therefore, the anticancer activity of purified and characterized pyocyanin was examined against BC in our study.

RESULTS

The maximum production of pyocyanin (53 µg/ml) was achieved by incubation of the highest pyocyanin-producing P. aeruginosa strain (P32) in pH-adjusted peptone water supplemented with 3% cetrimide under shaking conditions at 37 °C for 3 days. The high purity of the extracted pyocyanin was proven by HPLC against standard pyocyanin. The stability of pyocyanin was affected by the solvent in which it was stored. Therefore, the purified pyocyanin extract was lyophilized to increase its shelf-life up to one year. Using the MTT assay, we reported, for the first time, the cytotoxic effect of pyocyanin against human breast adenocarcinoma (MCF-7) with IC₅₀ = 15 μg/ml while it recorded a safe concentration against human peripheral blood mononuclear cells (PBMCs). The anticancer potential of pyocyanin against MCF-7 was associated with its apoptotic and necrotic activities which were confirmed qualitatively and quantitively using confocal laser scanning microscopy, inverted microscopy, and flow cytometry. Caspase-3 measurements, using real-time PCR and western blot, revealed that pyocyanin exerted its apoptotic activity against MCF-7 through caspase-3 activation.

CONCLUSION

Our work demonstrated that pyocyanin may be an ideal anticancer candidate, specific to cancer cells, for treating MCF-7 by its necrotic and caspase-3-dependent apoptotic activities.

Bioactive Compounds from Endophytic Bacteria Bacillus subtilis Strain EP1 with Their Antibacterial Activities

Endophytic bacteria boost host plant defense and growth by producing vital compounds. In the current study, a bacterial strain was isolated from the Boswellia sacra plant and identified as Bacillus subtilis strain EP1 (accession number: MT256301) through 16S RNA gene sequencing. From the identified bacteria, four compounds-1 (4-(4-cinnamoyloxy)phenyl)butanoic acid), 2 (cyclo-(L-Pro-D-Tyr)), 3 (cyclo-(L-Val-L-Phe)), and 4 (cyclo-(L-Pro-L-Val))-were isolated and characterized by 1D and 2D NMR and mass spectroscopy. Moreover, antibacterial activity and beta-lactam-producing gene inhibition (δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine synthetase (ACVS) and aminoadipate aminotransferase (AADAT)) assays were performed. Significant antibacterial activity was observed against the human pathogenic bacterial strains (E. coli) by compound 4 with a 13 ± 0.7 mm zone of inhibition (ZOI), followed by compound 1 having an 11 ± 0.7 mm ZOI. In contrast, the least antibacterial activity among the tested samples was offered by compound 2 with a 10 ± 0.9 mm ZOI compared to the standard (26 ± 1.2 mm). Similarly, the molecular analysis of beta-lactam inhibition determined that compounds 3 and 4 inhibited the two genes (2- to 4-fold) in the beta-lactam biosynthesis (ACVS and AADAT) pathway. From these results, it can be concluded that future research on these compounds could lead to the inhibition of antibiotic-resistant pathogenic bacterial strains.

Optimization of Extraction of Natural Antimicrobial Pigments Using Supercritical Fluids: A Review

It has become increasingly popular to replace chemically synthesized compounds with natural counterparts mostly found in natural sources, such as natural pigments. The conventional extraction processes for these compounds are limited by the toxicity and flammability of the solvents. To obtain pure extracts, it is always a longer process that requires several steps. Supercritical fluid extraction (SFE) is a cutting-edge green technology that is continuously increasing and expanding its fields of application, with benefits such as no waste produced, shorter extraction time, automation, and lower solvent consumption. The SFE of natural pigments has high potential in food, textiles, cosmetics, and pharmaceuticals; there are a number of other applications that can benefit from the SFE technique of natural pigments. The pigments that are extracted via SFE have a high potential for application and sustainability because of their biological and antimicrobial properties as well as low environmental risk. This review provides an update on the SFE technique, specifically as it pertains to the optimization of health-promoting pigments. This review focuses on antimicrobial pigments and the high efficiency of SFE in extracting pure antimicrobial pigments. In addition, the optimal conditions, biological activities, and possible applications of each category are explained.

Natural Substrates and Culture Conditions to Produce Pigments from Potential Microbes in Submerged Fermentation

Pigments from bacteria, fungi, yeast, cyanobacteria, and microalgae have been gaining more demand in the food, leather, and textile industries due to their natural origin and effective bioactive functions. Mass production of microbial pigments using inexpensive and ecofriendly agro-industrial residues is gaining more demand in the current research due to their low cost, natural origin, waste utilization, and high pigment stimulating characteristics. A wide range of natural substrates has been employed in submerged fermentation as carbon and nitrogen sources to enhance the pigment production from these microorganisms to obtain the required quantity of pigments. Submerged fermentation is proven to yield more pigment when added with agro-waste residues. Hence, in this review, aspects of potential pigmented microbes such as diversity, natural substrates that stimulate more pigment production from bacteria, fungi, yeast, and a few microalgae under submerged culture conditions, pigment identification, and ecological functions are detailed for the benefit of industrial personnel, researchers, and other entrepreneurs to explore pigmented microbes for multifaceted applications. In addition, some important aspects of microbial pigments are covered herein to disseminate the knowledge.

Nature's palette: An emerging frontier for coloring dairy products

Consumers all across the world are looking for the most delectable and appealing foods, while also demanding products that are safer, more nutritious, and healthier. Substitution of synthetic colorants with natural colorants has piqued consumer and market interest in recent years. Due to increasing demand, extensive research has been conducted to find natural and safe food additives, such as natural pigments, that may have health benefits. Natural colorants are made up of a variety of pigments, many of which have significant biological potential. Because of the promising health advantages, natural colorants are gaining immense interest in the dairy industry. This review goes over the use of various natural colorants in dairy products which can provide desirable color as well as positive health impacts. The purpose of this review is to provide an in-depth look into the field of food (natural or synthetic) colorants applied in dairy products as well as their potential health benefits, safety, general trends, and future prospects  in food science and technology. In this paper, we listed a plethora of applications of natural colorants in various milk-based products.

Prodigiosin: a promising biomolecule with many potential biomedical applications

Pigments are among the most fascinating molecules found in nature and used by human civilizations since the prehistoric ages. Although most of the bio-dyes reported in the literature were discovered around the eighties, the necessity to explore novel compounds for new biological applications has made them resurface as potential alternatives. Prodigiosin (PG) is an alkaloid red bio-dye produced by diverse microorganisms and composed of a linear tripyrrole chemical structure. PG emerges as a really interesting tool since it shows a wide spectrum of biological activities, such as antibacterial, antifungal, algicidal, anti-Chagas, anti-amoebic, antimalarial, anticancer, antiparasitic, antiviral, and/or immunosuppressive. However, PG vehiculation into different delivery systems has been proposed since possesses low bioavailability because of its high hydrophobic character (XLogP3-AA = 4.5). In the present review, the general aspects of the PG correlated with synthesis, production process, and biological activities are reported. Besides, some of the most relevant PG delivery systems described in the literature, as well as novel unexplored applications to potentiate its biological activity in biomedical applications, are proposed.

Insight into the Progress on Natural Dyes: Sources, Structural Features, Health Effects, Challenges, and Potential

(1) Background: Dyes play an important role in food, medicine, textile, and other industries, which make human life more colorful. With the increasing demand for food safety, the development of natural dyes becomes more and more attractive. (2) Methods: The literature was searched using the electronic databases PubMed, Web of Science, and SciFinder and this scoping review was carried out following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). (3) Results: 248 articles were included in this review. This review summarizes the research progress on natural dyes in the last ten years. According to structural features, natural dyes mainly include carotenoids, polyphenols, porphyrins, and alkaloids, and some of the newest dyes are summarized. Some pharmacological activities of carotenoids, anthocyanin, curcumin, and betalains in the last 10 years are summarized, and the biological effects of dyes regarding illumination conditions. The disadvantages of natural dyes, including sources, cost, stability, and poor bioavailability, limit their application. Here, some feasible strategies (potential resources, biotechnology, new extraction and separation strategies, strategies for improving stability) are described, which will contribute to the development and utilization of natural dyes. (4) Conclusion: Natural dyes show health benefits and potential in food additives. However, it is necessary for natural dyes to pass toxicity tests and quality tests and receive many regulatory approvals before their final entry into the market as food colorants or as drugs.

Biotechnological applications of mangrove plants and their isolated compounds in medicine-a mechanistic overview

Mangrove plants, also known as halophytes, are ecologically important plants that grow in various tropical and subtropical intertidal regions. Owing to the extreme abiotic and biotic stressful conditions they thrive in, these plants produce unique compounds with promising pharmacological propensities. Mangroves are inhabited by an astronomical number of fungal communities which produce a diverse array of extracellular degradative enzymes, namely: amylase, cellulase, xylanase, pectinase, cholesterol oxidase, etc. Such enzymes can be isolated from the mangrove fungi and harnessed for different biotechnological applications, for example, as replacements for chemical catalysts. Mangrove microbes attract considerable attention as they shelter the largest group of marine microorganisms that are resistant to extreme conditions and can produce novel biogenic substances. Vaccines developed from mangrove microbes may promise a safe future by developing effective immunization procedures with a minimum of economic burden. Interestingly, mangroves offer an exciting opportunity for synthesizing nanoparticles in a greener way as these plants are naturally rich in phytochemicals. Rhizophora mucronata Lam., Avicennia officinalis L. and Excoecaria agallocha L. are capable of synthesizing nanoparticles which have evolved recently as an alternative in various industries and are used for their biomedical application. Besides, the phytoconstituents isolated from mangrove plants, such as: gallic acid, galactose, lupeol, catechins, carotenoids, etc., were explored for various biological activities. These compounds are used in the pharmaceutical and nutraceutical industries to produce antimicrobial, antioxidant, anticancer, antidiabetic, and other therapeutic agents. The present review provides information on the biotechnological potentials of mangrove plants and their bioactive compounds as a new source of novel drugs, enzymes, nanoparticles and therapeutically important microbial pigments. Thus, this review forms a base of support and hasten the urgent research on biomedical applications of mangroves.

Antimicrobial Food Packaging Based on Prodigiosin-Incorporated Double-Layered Bacterial Cellulose and Chitosan Composites

Nowadays, food packaging systems have shifted from a passive to an active role in which the incorporation of antimicrobial compounds into biopolymers can promote a sustainable way to reduce food spoilage and its environmental impact. Accordingly, composite materials based on oxidized-bacterial cellulose (BC) and poly(vinyl alcohol)-chitosan (PVA-CH) nanofibers were produced by needleless electrospinning and functionalized with the bacterial pigment prodigiosin (PG). Two strategies were explored, in the first approach PG was incorporated in the electrospun PVA-CH layer, and TEMPO-oxidized BC was the substrate for nanofibers deposition (BC/PVA-CH_PG composite). In the second approach, TEMPO-oxidized BC was functionalized with PG, and afterward, the PVA-CH layer was electrospun (BC_PG/PVA-CH composite). The double-layer composites obtained were characterized and the nanofibrous layers displayed smooth fibers with average diameters of 139.63 ± 65.52 nm and 140.17 ± 57.04 nm, with and without pigment incorporation, respectively. FTIR-ATR analysis confirmed BC oxidation and revealed increased intensity at specific wavelengths, after pigment incorporation. Moreover, the moderate hydrophilic behavior, as well as the high porosity exhibited by each layer, remained mostly unaffected after PG incorporation. The composites’ mechanical performance and the water vapor transmission rate (WVTR) evaluation indicated the suitability of the materials for certain food packaging solutions, especially for fresh products. Additionally, the red color provided by the bacterial pigment PG on the external surface of a food packaging material is also a desirable effect, to attract the consumers’ attention, creating a multifunctional material. Furthermore, the antimicrobial activity was evaluated and, PVA-CH_PG, and BC_PG layers exhibited the highest antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa. Thus, the fabricated composites can be considered for application in active food packaging, owing to PG antimicrobial potential, to prevent foodborne pathogens (with PG incorporated into the inner layer of the food packaging material, BC/PVA-CH_PG composite), but also to prevent external contamination, by tackling the exterior of food packaging materials (with PG added to the outer layer, BC_PG/PVA-CH composite).

Bacterial Carotenoids: Extraction, Characterization, and Applications

Natural carotenoids are secondary metabolites that exhibit antioxidant, anti-inflammatory, and anti-cancer properties. These types of compounds are highly demanded by pharmaceutical, cosmetic, nutraceutical, and food industries, leading to the search for new natural sources of carotenoids. In recent years, the production of carotenoids from bacteria has become of great interest for industrial applications. In addition to carotenoids with C40-skeletons, some bacteria have the ability to synthesize characteristic carotenoids with C30-skeletons. In this regard, a great variety of methodologies for the extraction and identification of bacterial carotenoids has been reported and this is the first review that condenses most of this information. To understand the diversity of carotenoids from bacteria, we present their biosynthetic origin in order to focus on the methodologies employed in their extraction and characterization. Special emphasis has been made on high-performance liquid chromatography-mass spectrometry (HPLC-MS) for the analysis and identification of bacterial carotenoids. We end up this review showing their potential commercial use. This review is proposed as a guide for the identification of these metabolites, which are frequently reported in new bacteria strains.

Multi-target drug with potential applications: violacein in the spotlight

The aim of the current review is to address updated research on a natural pigment called violacein, with emphasis on its production, biological activity and applications. New information about violacein's action mechanisms as antitumor agent and about its synergistic action in drug delivery systems has brought new alternatives for anticancer therapy. Thus, violacein is introduced as reliable drug capable of overcoming at least three cancer hallmarks, namely: proliferative signaling, cell death resistance and metastasis. In addition, antimicrobial effects on several microorganisms affecting humans and other animals turn violacein into an attractive drug to combat resistant pathogens. Emphasis is given to effects of violacein combined with different agents, such as antibiotics, anticancer agents and nanoparticles. Although violacein is well-known for many decades, it remains an attractive compound. Thus, research groups have been making continuous effort to help improving its production in recent years, which can surely enable its pharmaceutical and chemical application as multi-task compound, even in the cosmetics and food industries.

Evaluation of antioxidant potential of pigments extracted from Bacillus spp. and Halomonas spp. isolated from mangrove rhizosphere

The present study aimed to isolate different pigment-producing bacteria from the mangrove rhizosphere habitat and to extract their pigments for evaluating their antioxidant and sun-protective properties. Three pigment-producing bacterial cultures were isolated from soil samples and were identified by morphological analysis and 16S rDNA sequencing. The pigments were isolated by the solvent extraction method and named as MZ (Pink), Orange, and Yellow. They were characterized by Fourier Transform Infrared (FTIR) and UV-Vis spectroscopy. The sun protection factor (SPF) values of these pigments were then determined using the Mansur equation. The total polyphenol content was estimated by the Folin-Ciocâlteu method, and the antioxidant activity of the pigments was determined using DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (ferric reducing antioxidant power), and ABTS (2,2-azinobis-3-ethyl-enzothiazoline-6-sulfonic acid) assays. The in vitro antioxidant potential of the pigments in the presence of oxidative stress (H₂O₂) was confirmed in the mouse macrophage cell line RAW264.7 by using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The pigment-producing bacterial isolates were identified as Bacillus infantis (MZ), Halomonas spp. (Orange), and Bacillus spp. (Yellow). The pigments were found to be carotenoid in nature, and the SPF values were in the range of 3.99 to 5.22. All three pigments had high polyphenol content (22 to 48 μg tannic acid equivalent) and showed significant antioxidant properties in both chemical and cell line-based studies. The results of this study indicate that these pigments have the potential to be used as an antioxidant agent and can be further developed as a pharmaceutical compound.

Metabolites from halophilic bacterial isolates Bacillus VITPS16 are cytotoxic against HeLa cells

The present study was aimed at evaluating the cytotoxic potential of selected halophilic bacterial metabolites. The use of the metabolomics approach in identifying the unexplored bioactive metabolites from halophilic bacterial isolate reduces time and complex experiments. In our study, we used UV/Visible spectroscopy, LC-MS/MS, and NMR to identify the metabolites present in the methanolic extract of the halophilic bacterium Bacillus VITPS16. MTT assay revealed that metabolite fractions (S1-79.61% and S2-85.74%) possess cytotoxic activity. Colonogenic assay confirmed the cytotoxic potential of the fractions and apoptosis assays showed that 83.37% of the cells undergo apoptosis at 10 mg/mL concentration (MF-S2). The DNA binding studies revealed the metabolite fraction interacts with DNA resulting in cytotoxicity. The study states that MF- S2 induced an antiproliferative effect that led to apoptosis through DNA binding as one of the possible pathways. The toxicity analysis using zebrafish indicated that the metabolite fractions are non-toxic even at 10 mg/mL concentration. Fraction MF-S2 is found to contain phosphoethanolamines, glycerophospholipids, sphingolipids, apocarotenoid, enigmol and its analogue, ankaflavin and flavonoid type of metabolites, which have been previously reported to have anti-cancer activity.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02724-9.

Ecological and Biotechnological Aspects of Pigmented Microbes: A Way Forward in Development of Food and Pharmaceutical Grade Pigments

Microbial pigments play multiple roles in the ecosystem construction, survival, and fitness of all kinds of organisms. Considerably, microbial (bacteria, fungi, yeast, and microalgae) pigments offer a wide array of food, drug, colorants, dyes, and imaging applications. In contrast to the natural pigments from microbes, synthetic colorants are widely used due to high production, high intensity, and low cost. Nevertheless, natural pigments are gaining more demand over synthetic pigments as synthetic pigments have demonstrated side effects on human health. Therefore, research on microbial pigments needs to be extended, explored, and exploited to find potential industrial applications. In this review, the evolutionary aspects, the spatial significance of important pigments, biomedical applications, research gaps, and future perspectives are detailed briefly. The pathogenic nature of some pigmented bacteria is also detailed for awareness and safe handling. In addition, pigments from macro-organisms are also discussed in some sections for comparison with microbes.

An Overview on Industrial and Medical Applications of Bio-Pigments Synthesized by Marine Bacteria

Marine bacterial species contribute to a significant part of the oceanic population, which substantially produces biologically effectual moieties having various medical and industrial applications. The use of marine-derived bacterial pigments displays a snowballing effect in recent times, being natural, environmentally safe, and health beneficial compounds. Although isolating marine bacteria is a strenuous task, these are still a compelling subject for researchers, due to their promising avenues for numerous applications. Marine-derived bacterial pigments serve as valuable products in the food, pharmaceutical, textile, and cosmetic industries due to their beneficial attributes, including anticancer, antimicrobial, antioxidant, and cytotoxic activities. Biodegradability and higher environmental compatibility further strengthen the use of marine bio-pigments over artificially acquired colored molecules. Besides that, hazardous effects associated with the consumption of synthetic colors further substantiated the use of marine dyes as color additives in industries as well. This review sheds light on marine bacterial sources of pigmented compounds along with their industrial applicability and therapeutic insights based on the data available in the literature. It also encompasses the need for introducing bacterial bio-pigments in global pigment industry, highlighting their future potential, aiming to contribute to the worldwide economy.

Patents on Violacein: A Compound with Great Diversity of Biological Activities and Industrial Potential

BACKGROUND

This review outlines to envisage the current impact of violacein-derivative materials in several technological areas through patents.

METHODS

A comprehensive examination up to day patent databases on violacein demonstrated the relevance of this pigment, as well as the pertinent topics related to its technological development in order to obtain adaptable new pharmaceuticals, cosmetics and new quality fiber materials, together with others applications of violacein in different areas.

RESULTS

At present time, there is no efficient and economical feasible technique for violacein preparation at industrial scale. Many attempts have been developed but none have achieved the big challenge of being effective and inexpensive process. However, some potential applications of violacein in fields like biomedicine make the pigment worth to continuous the investigations. Particularly, violacein patents covering from biosynthesis to different applications were reported recently.

CONCLUSION

As unique pigment, violacein has been used in distinct areas of specialties, such as in medical and industrial fields. Then, this review through patents provides an update on violacein innovations useful for researchers working in an expandable and interesting field of biotechnology with natural pigments.

Production of Tyrian purple indigoid dye from tryptophan in Escherichia coli

Tyrian purple, mainly composed of 6,6'-dibromoindigo (6BrIG), is an ancient dye extracted from sea snails and was recently demonstrated as a biocompatible semiconductor material. However, its synthesis remains limited due to uncharacterized biosynthetic pathways and the difficulty of regiospecific bromination. Here, we introduce an effective 6BrIG production strategy in Escherichia coli using tryptophan 6-halogenase SttH, tryptophanase TnaA and flavin-containing monooxygenase MaFMO. Since tryptophan halogenases are expressed in highly insoluble forms in E. coli, a flavin reductase (Fre) that regenerates FADH₂ for the halogenase reaction was used as an N-terminal soluble tag of SttH. A consecutive two-cell reaction system was designed to overproduce regiospecifically brominated precursors of 6BrIG by spatiotemporal separation of bromination and bromotryptophan degradation. These approaches led to 315.0 mg l^-1 6BrIG production from tryptophan and successful synthesis of regiospecifically dihalogenated indigos. Furthermore, it was demonstrated that 6BrIG overproducing cells can be directly used as a bacterial dye.

Production and Potential Applications of Bioconversion of Chitin and Protein-Containing Fishery Byproducts into Prodigiosin: A Review

The technology of microbial conversion provides a potential way to exploit compounds of biotechnological potential. The red pigment prodigiosin (PG) and other PG-like pigments from bacteria, majorly from Serratia marcescens, have been reported as bioactive secondary metabolites that can be used in the broad fields of agriculture, fine chemicals, and pharmacy. Increasing PG productivity by investigating the culture conditions especially the inexpensive carbon and nitrogen (C/N) sources has become an important factor for large-scale production. Investigations into the bioactivities and applications of PG and its related compounds have also been given increased attention. To save production cost, chitin and protein-containing fishery byproducts have recently been investigated as the sole C/N source for the production of PG and chitinolytic/proteolytic enzymes. This strategy provides an environmentally-friendly selection using inexpensive C/N sources to produce a high yield of PG together with chitinolytic and proteolytic enzymes by S. marcescens. The review article will provide effective references for production, bioactivity, and application of S. marcescens PG in various fields such as biocontrol agents and potential pharmaceutical drugs.

Antibacterial Potential and Apoptosis Induction by Pigments from the Endophyte Burkholderia sp. WYAT7

Pigment from the endophyte Burkholderia sp. WYAT7 isolated from the medicinal plant Artemisia nilagirica (Clarke) Pamp. was extracted. The antibacterial efficacy of the crude pigment Y was assessed as a source of antibiotic against both Gram-positive and Gram-negative bacterial pathogens. The pigment Y exhibited a significant level of antibacterial activity against the tested pathogens Salmonella typhi (MTCC 733), Staphylococcus aureus (MTCC 1430), Pseudomonas aeruginosa (MTCC 2453), Klebsiella pneumoniae (MTCC 432), Escherichia coli (MTCC 1610), Salmonella paratyphi (3220), Bacillus subtilis (441) and Acinetobacter baumannii (12,889). The minimum inhibitory concentration of crude pigment extract Y for most of the bacterial pathogens tested was below or equal to 0.25 µg/mL and the minimum bactericidal concentration was below or equal to 0.5 µg/mL. In the cytotoxicity evaluation, crude pigment Y exhibited less toxicity toward normal cells lines (L929). Crude pigment extract Y also showed powerful anticancer activity toward melanoma cancer cells (A375). The IC₅₀ value obtained was 68.08 µg/mL. Acridine orange (AO) and ethidium bromide (EB) double staining of cells treated with the pigment helped in the morphological assessment of nuclear condensation, apoptotic bodies and live cells. The DNA fragmentation analysis and caspase-9 quantification in the pigment-treated A375 cells determined the apoptosis activity mediated by the crude pigment extract Y. The compounds in the crude pigment extract Y was identified by HR-LCMS analysis. Further studies on the active compounds can lead to a rise in new drugs for cancer treatment and also against rising antibacterial resistant pathogens.

Fluviispira multicolorata gen. nov., sp. nov. and Silvanigrella paludirubra sp. nov., isolated from freshwater habitats

Strain 33A1-SZDP^T was isolated from a small creek located in Puch, Austria. Strain SP-Ram-0.45-NSY-1^T was obtained from a small pond located in Schönramer Moor, Germany. 16S rRNA gene sequence similarities between the type strain of Silvanigrella aquatica, currently the only member of the family Silvanigrellaceae, and strains 33A1-SZDP^T and SP-Ram-0.45-NSY-1^T of 94.1 and 99.1 %, respectively, suggested affiliation of the two strains with this family. Phylogenetic reconstructions with 16S rRNA gene sequences and phylogenomic analyses with amino acid sequences obtained from 103 single-copy genes suggested that the strains represent a new genus and a new species in the case of strain 33A1-SZDP^T (=JCM 32978^T=DSM 107810^T), and a new species within the genus Silvanigrella in the case of strain SP-Ram-0.45-NSY-1^T (=JCM 32975^T=DSM 107809^T). Cells of strain 33A1-SZDP^T were motile, pleomorphic, purple-pigmented on agar plates, putatively due to violacein, and showed variable pigmentation in liquid media. They grew chemoorganotrophically and aerobically and tolerated salt concentrations up to 1.2 % NaCl (v/w). The genome size of strain 33A1-SZDP^T was 3.4 Mbp and the G+C content was 32.2 mol%. For this new genus and new species, we propose the name Fluviispira multicolorata gen. nov., sp. nov. Cells of strain SP-Ram-0.45-NSY-1^T were motile, pleomorphic, red-pigmented and grew chemoorganotrophically and aerobically. They tolerated salt concentrations up to 1.1 % NaCl (v/w). The genome size of strain SP-Ram-0.45-NSY-1^T was 3.9 Mbp and the G+C content 29.3 mol%. For the new species within the genus Silvanigrella we propose the name Silvanigrella paludirubra sp. nov.

Ameliorating process parameters for zeaxanthin yield in Arthrobacter gandavensis MTCC 25325

The present study aims to escalate the production of prophylactic agent zeaxanthin using a screened potential bacterial isolate. For this purpose, a freshwater bacterium capable of producing zeaxanthin was isolated from Bor Talav, Bhavnagar. The 16S rRNA sequence confirmed the isolate as Arthrobacter gandavensis. The bacterium was also submitted to Microbial Type Culture Collection, CSIR-Institute of Microbial Technology, Chandigarh, India, with the accession number MTCC 25325. The chemo-metric tools were employed to optimise the influencing factors such as pH, temperature, inoculum size, agitation speed, carbon source and harvest time on zeaxanthin yield. Thereafter, six parameters were narrowed down to three factors and were optimised using the central composite design (CCD) matrix. Maximum zeaxanthin (1.51 mg/g) was derived when A. gandavensis MTCC 25325 was grown under pH 6.0, 1.5% (w/v) glucose and 10% (v/v) inoculum size. A high regression coefficient (R²= 0.92) of the developed model indicated the accurateness of the tested parameters. To the best of our knowledge, this is the first report on tailoring the process parameters using chemo-metric optimisation for escalating the zeaxanthin production by A. gandavensis MTCC 25325.

Applications of Prodigiosin Extracted from Marine Red Pigmented Bacteria Zooshikella sp. and Actinomycete Streptomyces sp

This study is aimed to determine the distribution, diversity and bioprospecting aspects of marine pigmented bacteria (MPB) isolated from pristine Andaman Islands, India. A total of 180 samples including seawater, sediment, marine plants, invertebrates, and vertebrates were collected and investigated for isolating pigmented bacteria. Results revealed that sediment, invertebrates, and seawater samples were colonized with a greater number of pigmented bacteria pertains to 27.9 × 10³ CFU/mL, 24.1 × 10³ CFU/mL and 6.7 × 10³ CFU/mL respectively. Orange (21.6 × 10³ CFU/mL) and red (8.0 × 10³ CFU/mL) MPB were predominant than other pigmented bacteria. Fourteen potential MPB were selected based on their intense pigmentation and tested for bioactive nature and food colorant applications. Out of 14, two red pigmented strains BSE6.1 & S2.1 displayed potential multifaceted applications, such as antibacterial, antioxidant, food colorant, and staining properties. Brown pigmented strains CO8 and yellow pigmented strain SQ2.3 have displayed staining properties. Chemical characterization of red pigment using TLC, HP-LC, GC-MS, FT-IR and ¹H-NMR analysis revealed prodigiosin as a main chemical constituent. Pure form of prodigiosin compound fractions obtained from both the strains displayed effective antibacterial activity against different human pathogens. MIC and MBC assays revealed that S2.1 requires 300 µg and 150 µg, respectively, and BSE6.1 require 400 µg concentrations of pigment compound for complete inhibition of S. aureus subsp. aureus. On the basis of 16S rRNA sequence analysis, strains S2.1 and BSE6.1 were identified as Zooshikella sp. and Streptomyces sp. and assigned under the GenBank accession numbers: MK680108 and MK951781 respectively.

Engineered Microbes for Pigment Production Using Waste Biomass

Agri-food waste biomass is the most abundant organic waste and has high valorisation potential for sustainable bioproducts development. These wastes are not only recyclable in nature but are also rich sources of bioactive carbohydrates, peptides, pigments, polyphenols, vitamins, natural antioxidants, etc. Bioconversion of agri-food waste to value-added products is very important towards zero waste and circular economy concepts. To reduce the environmental burden, food researchers are seeking strategies to utilize this waste for microbial pigments production and further biotechnological exploitation in functional foods or value-added products. Microbes are valuable sources for a range of bioactive molecules, including microbial pigments production through fermentation and/or utilisation of waste. Here, we have reviewed some of the recent advancements made in important bioengineering technologies to develop engineered microbial systems for enhanced pigments production using agri-food wastes biomass/by-products as substrates in a sustainable way.

Fungal Pigments and Their Prospects in Different Industries

The public's demand for natural, eco-friendly, and safe pigments is significantly increasing in the current era. Natural pigments, especially fungal pigments, are receiving more attention and seem to be in high demand worldwide. The immense advantages of fungal pigments over other natural or synthetic pigments have opened new avenues in the market for a wide range of applications in different industries. In addition to coloring properties, other beneficial attributes of fungal pigments, such as antimicrobial, anticancer, antioxidant, and cytotoxic activity, have expanded their use in different sectors. This review deals with the study of fungal pigments and their applications and sheds light on future prospects and challenges in the field of fungal pigments. Furthermore, the possible application of fungal pigments in the textile industry is also addressed.

Targeting virulence factors as an antimicrobial approach: Pigment inhibitors

The fascinating and dangerous colored pathogens contain unique chemically pigmented molecules, which give varied and efficient assistance as virulence factors to the crucial reproduction and growth of microbes. Therefore, multiple novel strategies and inhibitors have been developed in recent years that target virulence factor pigments. However, despite the importance and significance of this topic, it has not yet been comprehensively reviewed. Moreover, research groups around the world have made successful progress against antibacterial infections by targeting pigment production, including our serial works on the discovery of CrtN inhibitors against staphyloxanthin production in Staphylococcus aureus. On the basis of the previous achievements and recent progress of our group in this field, this article will be the first comprehensive review of pigment inhibitors against colored pathogens, especially S. aureus infections, and this article includes design strategies, representative case studies, advantages, limitations, and perspectives to guide future research.

Multifaceted Applications of Microbial Pigments: Current Knowledge, Challenges and Future Directions for Public Health Implications

Microbial oddities such as versatile pigments are gaining more attention in current research due to their widely perceived applications as natural food colorants, textiles, antimicrobial activities, and cytotoxic activities. This indicates that the future generation will depend on microbial pigments over synthetic colorants for sustainable livelihood. Although several reviews have detailed the comprehensive applications of microbial pigments extensively, knowledge on several aspects of pigmented microbes is apparently missing and not properly reviewed anywhere. Thus, this review has been made to provide overall knowledge on biodiversity, distribution, pathogenicity, and ecological and industrial applications of microbial pigments as well as their challenges and future directions for food, industrial, and biomedical applications. Meticulously, this compendious review treatise on the pigments from bacteria, fungi, yeasts, and microalgae includes reports from the 1970s to 2018. A total of 261 pigment compounds produced by about 500 different microbial species are included, and their bioactive nature is described.

Pigments from Soil Bacteria and Their Therapeutic Properties: A Mini Review

Advancement in research on dyes obtained from natural sources e.g., plants, animals, insects and micro-organisms is widening the application of natural dyes in various fields. The natural dyes substituted their synthetic analogs at the beginning of twentieth century due to their improved quality, value, ease of production, ease of dyeing and some other factors. This era of dominance ended soon when toxic effects of synthetic dyes were reported. In the last few decades, pigments from micro-organisms especially soil derived bacteria is replacing dyes from other natural sources because of the increasing demand for safe, non-toxic, and biodegradable natural product. Apart from application in agriculture practices, cosmetics, textile, food and paper industries, bacterial pigments have additional biological activities e.g., anti-tumor, anti-fungal, anti-bacterial, immunosuppressive anti-viral, and many more which make them a potential candidate for pharmaceutical industry. Optimization of culture conditions and fermentation medium is the key strategies for large scale production of these natural dyes. An effort has been done to give an overview of pigments obtained from bacteria of soil origin, their dominance over dyes from other sources (natural and synthetic) and applications in the medical world in the underlying study.