High-level production of microbial prodigiosin: A review

Copper(II) and Zinc(II) Complexes with Bacterial Prodigiosin Are Targeting Site III of Bovine Serum Albumin and Acting as DNA Minor Groove Binders

The negative environmental and social impacts of food waste accumulation can be mitigated by utilizing bio-refineries' approach where food waste is revalorized into high-value products, such as prodigiosin (PG), using microbial bioprocesses. The diverse biological activities of PG position it as a promising compound, but its high production cost and promiscuous bioactivity hinder its wide application. Metal ions can modulate the electronic properties of organic molecules, leading to novel mechanisms of action and increased target potency, while metal complex formation can improve the stability, solubility and bioavailability of the parent compound. The objectives of this study were optimizing PG production through bacterial fermentation using food waste, allowing good quantities of the pure natural product for further synthesizing and evaluating copper(II) and zinc(II) complexes with it. Their antimicrobial and anticancer activities were assessed, and their binding affinity toward biologically important molecules, bovine serum albumin (BSA) and DNA was investigated by fluorescence emission spectroscopy and molecular docking. The yield of 83.1 mg/L of pure PG was obtained when processed meat waste at 18 g/L was utilized as the sole fermentation substrate. The obtained complexes CuPG and ZnPG showed high binding affinity towards target site III of BSA, and molecular docking simulations highlighted the affinity of the compounds for DNA minor grooves.

Pigments from pathogenic bacteria: a comprehensive update on recent advances

Bacterial pigments stand out as exceptional natural bioactive compounds with versatile functionalities. The pigments represent molecules from distinct chemical categories including terpenes, terpenoids, carotenoids, pyridine, pyrrole, indole, and phenazines, which are synthesized by diverse groups of bacteria. Their spectrum of physiological activities encompasses bioactive potentials that often confer fitness advantages to facilitate the survival of bacteria amid challenging environmental conditions. A large proportion of such pigments are produced by bacterial pathogens mostly as secondary metabolites. Their multifaceted properties augment potential applications in biomedical, food, pharmaceutical, textile, paint industries, bioremediation, and in biosensor development. Apart from possessing a less detrimental impact on health with environmentally beneficial attributes, tractable and scalable production strategies render bacterial pigments a sustainable option for novel biotechnological exploration for untapped discoveries. The review offers a comprehensive account of physiological role of pigments from bacterial pathogens, production strategies, and potential applications in various biomedical and biotechnological fields. Alongside, the prospect of combining bacterial pigment research with cutting-edge approaches like nanotechnology has been discussed to highlight future endeavours.

Late-stage diversification of bacterial natural products through biocatalysis

Bacterial natural products (BNPs) are very important sources of leads for drug development and chemical novelty. The possibility to perform late-stage diversification of BNPs using biocatalysis is an attractive alternative route other than total chemical synthesis or metal complexation reactions. Although biocatalysis is gaining popularity as a green chemistry methodology, a vast majority of orphan sequenced genomic data related to metabolic pathways for BNP biosynthesis and its tailoring enzymes are underexplored. In this review, we report a systematic overview of biotransformations of 21 molecules, which include derivatization by halogenation, esterification, reduction, oxidation, alkylation and nitration reactions, as well as degradation products as their sub-derivatives. These BNPs were grouped based on their biological activities into antibacterial (5), antifungal (5), anticancer (5), immunosuppressive (2) and quorum sensing modulating (4) compounds. This study summarized 73 derivatives and 16 degradation sub-derivatives originating from 12 BNPs. The highest number of biocatalytic reactions was observed for drugs that are already in clinical use: 28 reactions for the antibacterial drug vancomycin, followed by 18 reactions reported for the immunosuppressive drug rapamycin. The most common biocatalysts include oxidoreductases, transferases, lipases, isomerases and haloperoxidases. This review highlights biocatalytic routes for the late-stage diversification reactions of BNPs, which potentially help to recognize the structural optimizations of bioactive scaffolds for the generation of new biomolecules, eventually leading to drug development.

Antimicrobial and anti-virulence activities of 4-shogaol from grains of paradise against gram-negative bacteria: Integration of experimental and computational methods

ETHNOPHARMACOLOGICAL RELEVANCE

Bacterial resistance to antibiotics is a growing global concern, highlighting the urgent need for new antimicrobial candidates. Aframomum melegueta was traditionally used for combating urinary tract and soft tissue infections, which implies its potential as an antimicrobial agent.

AIM OF STUDY

This study was designed to explore the antibacterial and anti-virulence capabilities of 4-shogaol isolated from A. melegueta seeds versus gram-negative bacteria: Serratia marcescens, Klebsiella pneumoniae, Acinetobacter baumannii, and the clinically important pathogen Pseudomonas aeruginosa.

MATERIALS AND METHODS

4-Shogeol was isolated from A. melegueta seeds and its MICs were determined for Acinetobacter baumannii (ATCC-17978), Pseudomonas aeruginosa (ATCC-27853), Klebsiella pneumoniae (ATCC-700603), and Serratia marcescens clinical isolate. The anti-efflux activity and effect on the bacterial cell membrane for the compound were evaluated. Furthermore, the anti-virulence activities of the compound were evaluated. The effects of 4-shogeol at sub-MIC on bacterial motility, biofilm formation, and production of virulent enzymes and pigments were assessed. The anti-quorum sensing activities of 4-shogeol were evaluated virtually and by quantification its effect on the expression of quorum sensing encoding genes. The in vivo protection assay was conducted to evaluate the effect of 4-shogaol on the P. aeruginosa capacity to induce pathogenesis in mice. Finally, the effect of shogaol-antibiotics combination was assessed.

RESULTS

The research revealed that 4-shogaol's antibacterial action primarily involves disrupting the bacterial cell membrane and efflux pumps. It also exhibited significant anti-virulence effects by reducing biofilm development and repressing virulence factors production, effectively protecting mice against P. aeruginosa infection. Furthermore, when combined with antibiotics, 4-shogaol demonstrated synergistic effects, leading to reduced minimum inhibitory concentrations (MICs) against P. aeruginosa. Its anti-virulence properties were linked to its ability to disrupt bacterial quorum sensing (QS) mechanisms, as evidenced by its interaction with QS receptors and downregulation of QS-related genes. Notably, in silico analysis indicated that 4-shogaol exhibited strong binding affinity to different P. aeruginosa QS targets.

CONCLUSION

These findings suggest that 4-shogaol holds promise as an effective anti-virulence agent that can be utilized in combination with antibiotics for treating severe infections caused by gram-positive bacteria.

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.

Improving Bioprocess Conditions for the Production of Prodigiosin Using a Marine Serratia rubidaea Strain

The enormous potential attributed to prodigiosin regarding its applicability as a natural pigment and pharmaceutical agent justifies the development of sound bioprocesses for its production. Using a Serratia rubidaea strain isolated from a shallow-water hydrothermal vent, optimization of the growth medium composition was carried out. After medium development, the bacterium temperature, light and oxygen needs were studied, as was growth inhibition by product concentration. The implemented changes led to a 13-fold increase in prodigiosin production in a shake flask, reaching 19.7 mg/L. The conditions allowing the highest bacterial cell growth and prodigiosin production were also tested with another marine strain: S. marcescens isolated from a tide rock pool was able to produce 15.8 mg/L of prodigiosin. The bioprocess with S. rubidaea was scaled up from 0.1 L shake flasks to 2 L bioreactors using the maintenance of the oxygen mass transfer coefficient (kLa) as the scale-up criterion. The implemented parameters in the bioreactor led to an 8-fold increase in product per biomass yield and to a final concentration of 293.1 mg/L of prodigiosin in 24 h.

Transcriptomic analysis of cell envelope inhibition by prodigiosin in methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading threat to public health as it is resistant to most currently available antibiotics. Prodigiosin is a secondary metabolite of microorganisms with broad-spectrum antibacterial activity. This study identified a significant antibacterial effect of prodigiosin against MRSA with a minimum inhibitory concentration as low as 2.5 mg/L. The results of scanning electron microscopy, crystal violet staining, and confocal laser scanning microscopy indicated that prodigiosin inhibited biofilm formation in S. aureus USA300, while also destroying the structure of the cell wall and cell membrane, which was confirmed by transmission electron microscopy. At a prodigiosin concentration of 1.25 mg/L, biofilm formation was inhibited by 76.24%, while 2.5 mg/L prodigiosin significantly reduced the vitality of MRSA cells in the biofilm. Furthermore, the transcriptomic results obtained at 1/8 MIC of prodigiosin indicated that 235and 387 genes of S. aureus USA300 were significantly up- and downregulated, respectively. The downregulated genes were related to two-component systems, including the transcriptional regulator LytS, quorum sensing histidine kinases SrrB, NreA and NreB, peptidoglycan biosynthesis enzymes (MurQ and GlmU), iron-sulfur cluster repair protein ScdA, microbial surface components recognizing adaptive matrix molecules, as well as the key arginine synthesis enzymes ArcC and ArgF. The upregulated genes were mainly related to cell wall biosynthesis, as well as two-component systems including vancomycin resistance-associated regulator, lipoteichoic acid biosynthesis related proteins DltD and DltB, as well as the 9 capsular polysaccharide biosynthesis proteins. This study elucidated the molecular mechanisms through which prodigiosin affects the cell envelope of MRSA from the perspectives of cell wall synthesis, cell membrane and biofilm formation, providing new potential targets for the development of antimicrobials for the treatment of MRSA.

Red bioactive pigment from Himalayan Janthinobacterium sp. ERMR3:09: optimization, characterization, and potential applications

Prodigiosin is a red pigment commonly produced as a secondary metabolite by Serratia marcescens. It exhibits inherent bioactivities, including antimicrobial and anticancer, with low to no toxic effects on normal cells. The present study investigates a bioactive prodigiosin production from an atypical, red-pigmented, potentially novel Janthinobacterium sp. ERMR3:09 isolated from a glacial moraine. Statistically optimized culture parameters, i.e., w/v 1.0% glucose and 0.08% peptone as carbon and nitrogen sources, temperature 20 °C, and media pH 7, resulted in a four-fold increase in the pigment yield. The upscaled production in an 8 L volume resulted in higher pigment production within a shorter period of 48 h. The ultra-performance liquid chromatography (UPLC) analysis validated the identity of the purified pigment as prodigiosin that showed thermostability at 75 °C for 3 h. Evaluation of antimicrobial activity showed potent inhibitory effects (> 50%) against the opportunistic pathogenic fungal and Gram-positive bacterial strains. The pigment showed significant cytotoxicity (p < 0.05) towards A549 and HeLa cell lines with IC50 values of 42.2 μM and 36.11 μM, respectively. The study demonstrated that microbial communities from extreme niches can be ideal sources of bioactive pigments with immense pharmaceutical potential vital for the development of non-synthetic therapeutic agents.

Microbial Pigments: Major Groups and Industrial Applications

Microbial pigments have many structures and functions with excellent characteristics, such as being biodegradable, non-toxic, and ecologically friendly, constituting an important source of pigments. Industrial production presents a bottleneck in production cost that restricts large-scale commercialization. However, microbial pigments are progressively gaining popularity because of their health advantages. The development of metabolic engineering and cost reduction of the bioprocess using industry by-products opened possibilities for cost and quality improvements in all production phases. We are thus addressing several points related to microbial pigments, including the major classes and structures found, the advantages of use, the biotechnological applications in different industrial sectors, their characteristics, and their impacts on the environment and society.

The Anti-Virulence Activities of the Antihypertensive Drug Propranolol in Light of Its Anti-Quorum Sensing Effects against Pseudomonas aeruginosa and Serratia marcescens

The development of bacterial resistance is an increasing global concern that requires discovering new antibacterial agents and strategies. Bacterial quorum sensing (QS) systems play important roles in controlling bacterial virulence, and their targeting could lead to diminishing bacterial pathogenesis. In this context, targeting QS systems without significant influence on bacterial growth is assumed as a promising strategy to overcome resistance development. This study aimed at evaluating the anti-QS and anti-virulence activities of the β-adrenoreceptor antagonist propranolol at sub-minimal inhibitory concentrations (sub-MIC) against two Gram-negative bacterial models Pseudomonas aeruginosa and Serratia marcescens. The effect of propranolol on the expression of QS-encoding genes was evaluated. Additionally, the affinity of propranolol to QS receptors was virtually attested. The influence of propranolol at sub-MIC on biofilm formation, motility, and production of virulent factors was conducted. The outcomes of the propranolol combination with different antibiotics were assessed. Finally, the in vivo protection assay in mice was performed to assess propranolol's effect on lessening the bacterial pathogenesis. The current findings emphasized the significant ability of propranolol at sub-MIC to reduce the formation of biofilms, motility, and production of virulence factors. In addition, propranolol at sub-MIC decreased the capacity of tested bacteria to induce pathogenesis in mice. Furthermore, propranolol significantly downregulated the QS-encoding genes and showed significant affinity to QS receptors. Finally, propranolol at sub-MIC synergistically decreased the MICs of different antibiotics against tested bacteria. In conclusion, propranolol might serve as a plausible adjuvant therapy with antibiotics for the treatment of serious bacterial infections after further pharmacological and pharmaceutical studies.

Isolation and Characterization of a Serratia rubidaea from a Shallow Water Hydrothermal Vent

Microbial life present in the marine environment has to be able to adapt to rapidly changing and often extreme conditions. This makes these organisms a putative source of commercially interesting compounds since adaptation provides different biochemical routes from those found in their terrestrial counterparts. In this work, the goal was the identification of a marine bacterium isolated from a sample taken at a shallow water hydrothermal vent and of its red product. Genomic, lipidomic, and biochemical approaches were used simultaneously, and the bacterium was identified as Serratia rubidaea. A high-throughput screening strategy was used to assess the best physico-chemical conditions permitting both cell growth and production of the red product. The fatty acid composition of the microbial cells was studied to assess adaptation at the lipid level under stressful conditions, whilst several state-of-the-art techniques, such as DSC, FTIR, NMR, and Ultra-High Resolution Qq-Time-of-Flight mass spectrometry, were used to characterize the structure of the pigment. We hypothesize that the pigment, which could be produced by the cells up to 62 °C, is prodigiosin linked to an aliphatic compound that acts as an anchor to keep it close to the cells in the marine environment.

Growth Kinetics of Prodigiosin (Food Color) Produced by Novel Serratia marcescens bhu prodig Under Submerged Fermentation (SMF)

Prodigiosin is a promising food color due to its antibacterial, antimalarial, antimycotic characteristics, immunomodulating, and antitumor activities. Novel prodigiosin producing strain isolated from sugarcane field soil of Banaras Hindu University, India, characterized as Serratia marcescens bhu prodig by 16 sRNA. The effect of carbon, nitrogen source, and physical parameters (pH and temperature) on pigment yield was studied. The highest amount of pigment produced, which was 800.95 ± 0.05 mg/L, was detected when sorbitol and peptone were used as nitrogen and carbon source with pH 7 at 30 °C. The optimized condition scale-up in a bioreactor with a working capacity of 3.0 L, gave maximum pigment yield of 825 ± 0.05 mg/L with µ (Maximum specific growth rate), Yp/x, which represents the product yield coefficient, and Yp/s, which signifies the specific product yield coefficient and productivity of 0.3/h, 0.62, 0.80, and 0.02 g/L/h, respectively, after 72 h of cultivation in submerged fermentation (SMF). The isolated pigment was characterized as prodigiosin by the analysis of spectral data and GC-MS. The mass spectrophotometry investigation characterized pigment as 4-methoxy-5(5 methyl-4-pentyl-2H-pyrrol-2-ylidene)- 2,2-bipyrrole ring structure. The GC-MS chromatogram showed m/z of 323, representing prodigiosin. The prodigiosin yield and productivity obtained in the current finding were higher than in previous reports.

Relocating Glyceryl Trinitrate as an Anti-Virulence Agent against Pseudomonas aeruginosa and Serratia marcescens: Insights from Molecular and In Vivo Investigations

The problem of antibiotic resistance is a global critical public health concern. In light of the threat of returning to the pre-antibiotic era, new alternative approaches are required such as quorum-sensing (QS) disruption and virulence inhibition, both of which apply no discernible selective pressure on bacteria, therefore mitigating the potential for the development of resistant strains. Bearing in mind the significant role of QS in orchestrating bacterial virulence, disrupting QS becomes essential for effectively diminishing bacterial virulence. This study aimed to assess the potential use of sub-inhibitory concentration (0.25 mg/mL) of glyceryl trinitrate (GTN) to inhibit virulence in Serratia marcescens and Pseudomonas aeruginosa. GTN could decrease the expression of virulence genes in both tested bacteria in a significant manner. Histopathological study revealed the ability of GTN to alleviate the congestion in hepatic and renal tissues of infected mice and to reduce bacterial and leukocyte infiltration. This study recommends the use of topical GTN to treat topical infection caused by P. aeruginosa and S. marcescens in combination with antibiotics.

PtrA regulates prodigiosin synthesis and biological functions in Serratia marcescens FZSF02

Serratia marcescens is a gram-negative bacterium that is able to produce many secondary metabolites, such as the prominent red pigment prodigiosin (PG). In this work, a ptrA-disrupted mutant strain with reduced PG production was selected from Tn5 transposon mutants. RT-qPCR results indicated that ptrA promoted elevated transcription of the pig gene cluster in S. marcescens FZSF02. Furthermore, we found that ptrA also controls several other important biological functions of S. marcescens, including swimming and swarming motilities, biofilm formation, hemolytic activity, and stress tolerance. In conclusion, this study demonstrates that ptrA is a PG synthesis-promoting factor in S. marcescens and provides a brief understanding of the regulatory mechanism of ptrA in S. marcescens cell motility and hemolytic activity.

Diminishing the Pathogenesis of the Food-Borne Pathogen Serratia marcescens by Low Doses of Sodium Citrate

Protecting food from bacterial contamination is crucial for ensuring its safety and avoiding foodborne illness. Serratia marcescens is one of the food bacterial contaminants that can form biofilms and pigments that spoil the food product and could cause infections and illness to the consumer. Food preservation is essential to diminish such bacterial contaminants or at least reduce their pathogenesis; however, it should not affect food odor, taste, and consistency and must be safe. Sodium citrate is a well-known safe food additive and the current study aims to evaluate its anti-virulence and anti-biofilm activity at low concentrations against S. marcescens. The anti-virulence and antibiofilm activities of sodium citrate were evaluated phenotypically and genotypically. The results showed the significant effect of sodium citrate on decreasing the biofilm formation and other virulence factors, such as motility and the production of prodigiosin, protease, and hemolysins. This could be owed to its downregulating effect on the virulence-encoding genes. An in vivo investigation was conducted on mice and the histopathological examination of isolated tissues from the liver and kidney of mice confirmed the anti-virulence activity of sodium citrate. In addition, an in silico docking study was conducted to evaluate the sodium citrate binding ability to S. marcescens quorum sensing (QS) receptors that regulates its virulence. Sodium citrate showed a marked virtual ability to compete on QS proteins, which could explain sodium citrate’s anti-virulence effect. In conclusion, sodium citrate is a safe food additive and can be used at low concentrations to prevent contamination and biofilm formation by S. marcescens and other bacteria.

Advancing PHBV Biomedical Potential with the Incorporation of Bacterial Biopigment Prodigiosin

The quest for sustainable biomaterials with excellent biocompatibility and tailorable properties has put polyhydroxyalkanoates (PHAs) into the research spotlight. However, high production costs and the lack of bioactivity limit their market penetration. To address this, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was combined with a bacterial pigment with strong anticancer activity, prodigiosin (PG), to obtain functionally enhanced PHBV-based biomaterials. The samples were produced in the form of films 115.6-118.8 µm in thickness using the solvent casting method. The effects of PG incorporation on the physical properties (morphology, biopolymer crystallinity and thermal stability) and functionality of the obtained biomaterials were investigated. PG has acted as a nucleating agent, in turn affecting the degree of crystallinity, thermal stability and morphology of the films. All samples with PG had a more organized internal structure and higher melting and degradation temperatures. The calculated degree of crystallinity of the PHBV copolymer was 53%, while the PG1, PG3 and PG3 films had values of 64.0%, 63.9% and 69.2%, respectively. Cytotoxicity studies have shown the excellent anticancer activity of films against HCT116 (colon cancer) cells, thus advancing PHBV biomedical application potential.

Crystal structure of prodigiosin binding protein PgbP, a GNAT family protein, in Serratia marcescens FS14

Acetylation is a conserved modification catalyzed by acetyltransferases that play prominent roles in a large number of biological processes. Members of the general control non-repressible 5 (GCN5)-N-acetyltransferase (GNAT) protein superfamily are widespread in all kingdoms of life and are characterized by highly conserved catalytic fold, and can acetylate a wide range of substrates. Although the structures and functions of numerous eukaryotic GNATs have been identified thus far, many GNATs in microorganisms remain structurally and functionally undescribed. Here, we determined the crystal structure of the putative GCN5-N-acetyltransferase PgbP in complex with CoA in Serratia marcescens FS14. Structural analysis revealed that the PgbP dimer has two cavities, each of which binds a CoA molecule via conserved motifs of the GNAT family. In addition, the biochemical studies showed that PgbP is a prodigiosin-binding protein with high thermal stability. To our knowledge, this is the first view of GNAT binding to secondary metabolites and it is also the first report of prodigiosin binding protein. Molecular docking and mutation experiments indicated that prodigiosin binds to the substrate binding site of PgbP. The structure-function analyses presented here broaden our understanding of the multifunctionality of GNAT family members and may infer the mechanism of the multiple biological activities of prodigiosin.

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.

Recent Advances in Prodigiosin as a Bioactive Compound in Nanocomposite Applications

Bionanocomposites based on natural bioactive entities have gained importance due to their abundance; renewable and environmentally benign nature; and outstanding properties with applied perspective. Additionally, their formulation with biological molecules with antimicrobial, antioxidant, and anticancer activities has been produced nowadays. The present review details the state of the art and the importance of this pyrrolic compound produced by microorganisms, with interest towards Serratia marcescens, including production strategies at a laboratory level and scale-up to bioreactors. Promising results of its biological activity have been reported to date, and the advances and applications in bionanocomposites are the most recent strategy to potentiate and to obtain new carriers for the transport and controlled release of prodigiosin. Prodigiosin, a bioactive secondary metabolite, produced by Serratia marcescens, is an effective proapoptotic agent against bacterial and fungal strains as well as cancer cell lines. Furthermore, this molecule presents antioxidant activity, which makes it ideal for treating wounds and promoting the general improvement of the immune system. Likewise, some of the characteristics of prodigiosin, such as hydrophobicity, limit its use for medical and biotechnological applications; however, this can be overcome by using it as a component of a bionanocomposite. This review focuses on the chemistry and the structure of the bionanocomposites currently developed using biorenewable resources. Moreover, the work illuminates recent developments in pyrrole-based bionanocomposites, with special insight to its application in the medical area.

Synthesis, Anticancer Potential and Comprehensive Toxicity Studies of Novel Brominated Derivatives of Bacterial Biopigment Prodigiosin from Serratia marcescens ATCC 27117

Prodigiosins (prodiginines) are a class of bacterial secondary metabolites with remarkable biological activities and color. In this study, optimized production, purification, and characterization of prodigiosin (PG) from easily accessible Serratia marcescens ATCC 27117 strain has been achieved to levels of 14 mg/L of culture within 24 h. Furthermore, environmentally friendly bromination of produced PG was used to afford both novel mono- and dibrominated derivatives of PG. PG and its Br derivatives showed anticancer potential with IC₅₀ values range 0.62–17.00 µg/mL for all tested cancer cell lines and induction of apoptosis but low selectivity against healthy cell lines. All compounds did not affect Caenorhabditiselegans at concentrations up to 50 µg/mL. However, an improved toxicity profile of Br derivatives in comparison to parent PG was observed in vivo using zebrafish (Danio rerio) model system, when 10 µg/mL applied at 6 h post fertilization caused death rate of 100%, 30% and 0% by PG, PG-Br, and PG-Br_2, respectively, which is a significant finding for further structural optimizations of bacterial prodigiosins. The drug-likeness of PG and its Br derivatives was examined, and the novel Br derivatives obey the Lipinski’s “rule of five”, with an exemption of being more lipophilic than PG, which still makes them good targets for further structural optimization.

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.

Optimized prodigiosin production with Pseudomonas putida KT2440 using parallelized non-invasive online monitoring

The red pigment prodigiosin is of high pharmaceutical interest, due to its potential applications as an antitumor drug and antibiotic agent. As previously demonstrated, Pseudomonas putida KT2440 is a suitable host for prodigiosin production, as it exhibits high tolerance towards the antimicrobial properties of prodigiosin. So far, prodigiosin concentrations of up to 94 mg/L have been achieved in shake flask cultivations. For the characterization and optimization of the prodigiosin production process, the scattered light of P. putida and fluorescence of prodigiosin was measured. The excitation and emission wavelengths for prodigiosin measurement were analyzed by recording 2D fluorescence spectra. The strongest prodigiosin fluorescence was obtained at a wavelength combination of 535/560 nm. By reducing the temperature to 18 °C and using 16 g/L glucose, the prodigiosin concentration was more than doubled compared to the initial cultivation conditions. The obtained results demonstrate the capabilities of parallelized microscale cultivations combined with non-invasive online monitoring of fluorescence for rapid bioprocess development, using prodigiosin as a molecule of current biotechnological interest.

Farnesol and tyrosol: novel inducers for microbial production of carotenoids and prodigiosin

This study was performed to elucidate the effects of two fungal quorum sensing molecules (tyrosol and farnesol) on carotenoid synthesis in the yeast Rhodotorula glutinis and prodigioin synthesis in the bacterium Serratia marcencens. Farnesol or tyrosol was directly added to the flask cultures at the beginning (immediately after inoculation with the preculture) of day 1 or the beginning (49th h) of day 3. The results demonstrated that tyrosol supplementation increased the synthesis of carotenoids but farnesol supplementation increased the synthesis of prodigiosin. It was found that adding farnesol or tyrosol into the culture on day 3 compared to day 1 caused more increments in pigment synthesis. The maximum increase (fivefold) in the synthesis of prodigiosin was achieved with 200 μL/L farnesol supplementation, whereas the maximum increase (2.13 fold) in the synthesis of carotenoids was achieved with 4 mg/L tyrosol supplementation. This is the first report about the effects of fungal quorum sensing molecules (farnesol and tyrosol) on the synthesis of carotenoids and prodigiosin in microorganisms. Due to non-human toxicity and low price and of farnesol and tyrosol, these molecules can be used as novel inducers for large-scale production of microbial pigments.

Enhanced Large-Scale Production of Hahella chejuensis-Derived Prodigiosin and Evaluation of Its Bioactivity

Prodigiosin as a high-valued compound, which is a microbial secondary metabolite, has the potential for antioxidant and anticancer effects. However, the large-scale production of functionally active Hahella chejuensis-derived prodigiosin by fermentation in a cost-effective manner has yet to be achieved. In the present study, we established carbon source-optimized medium conditions, as well as a procedure for producing prodigiosin by fermentation by culturing H. chejuensis using 10 L and 200 L bioreactors. Our results showed that prodigiosin productivity using 250 ml flasks was higher in the presence of glucose than other carbon sources, including mannose, sucrose, galactose, and fructose, and could be scaled up to 10 L and 200 L batches. Productivity in the glucose (2.5 g/l) culture while maintaining the medium at pH 6.89 during 10 days of cultivation in the 200 L bioreactor was measured and increased more than productivity in the basal culture medium in the absence of glucose. Prodigiosin production from 10 L and 200 L fermentation cultures of H. chejuensis was confirmed by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) analyses for more accurate identification. Finally, the anticancer activity of crude extracted prodigiosin against human cancerous leukemia THP-1 cells was evaluated and confirmed at various concentrations. Conclusively, we demonstrate that culture conditions for H. chejuensis using a bioreactor with various parameters and ethanol-based extraction procedures were optimized to mass-produce the marine bacterium-derived high purity prodigiosin associated with anti-cancer activity.

RpoS Activates the Prodigionsin Production by Activating the Transcription of the RpoS-Dependent Pig Gene Cluster in Serratia marcescens FS14

RpoS, an alternative sigma factor of RNA polymerase, regulates the expression of a great deal of genes involved in stationary-phase survival and stress response. To identify the function of RpoS homologue in Serratia marcescens FS14, in-frame deletion mutant of rpoS was constructed. It was found that RpoS activates the biosynthesis of prodigiosin in FS14 which is just opposite to what was observed in Serratia sp. ATCC 39006. We also demonstrated that RpoS positively regulates the prodigiosin production by activating the transcription of pig cluster in FS14, and the transcription of pig cluster is RpoS-dependent. Further study showed that the differences in the promoters of pig clusters in FS14 and 39006 lead to the different selection of the sigma factors and result in the different regulation mechanisms. The -10 element and the spacer region between -10 and -35 elements of the pig cluster in FS14 are vital for the RpoS recognition in FS14.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-021-00952-4.