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Nowadays, demand for natural pigments has increased dramatically due to the awareness of the toxicity of some synthetic pigments. Because of the high cost of growth medium for natural pigment production, various studies have been carried out to explore medium which are less costly, such as agricultural waste. This study highlight on the application of firefly algorithm (FA) and bat algorithm (BA) in optimizing yellowish-orange pigment production (flexirubin) from the agricultural waste material. At present, response surface methodology (RSM) is the most preferred statistical method in optimizing pigment production. However, in the last two decades, nature-inspired metaheuristics approach has been used extensively in the fermentation process and have continually improve the efficiency in the optimization problem especially in pigment production. This study compared the analytics studies of RSM, FA and BA in the estimation of fermentation parameters (Lactose, Ltryptophan, and KH2PO4) in flexirubin production from Chryseobacterium artocarpi CECT8497T. All models provided similar quality predictions for the above three independent variables in term of flexirubin production with bat algorithm showing more accurate in estimation, with the coefficient value of 98.87% compare to RSM 98.20% and FA 98.38%. [ABSTRACT FROM AUTHOR]

Violacein, violet pigment produced by Chromobacterium violaceum, has attracted much attention recently due to its pharmacological properties including antibacterial activity. The present study investigated possible antibacterial mode of action of violacein from C. violaceum UTM5 against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) strains. Violet fraction was obtained by cultivating C. violaceum UTM5 in liquid pineapple waste medium, extracted, and fractionated using ethyl acetate and vacuum liquid chromatography technique. Violacein was quantified as major compound in violet fraction using HPLC analysis. Violet fraction displayed bacteriostatic activity against S. aureus ATCC 29213 and methicillin-resistant S. aureus ATCC 43300 with minimum inhibitory concentration (MIC) of 3.9 μg/mL. Fluorescence dyes for membrane damage and scanning electron microscopic analysis confirmed the inhibitory effect by disruption on membrane integrity, morphological alternations, and rupture of the cell membranes of both strains. Transmission electron microscopic analysis showed membrane damage, mesosome formation, and leakage of intracellular constituents of both bacterial strains. Mode of action of violet fraction on the cell membrane integrity of both strains was shown by release of protein, K+, and extracellular adenosine 5′-triphosphate (ATP) with 110.5 μg/mL, 2.34 μg/mL, and 87.24 ng/μL, respectively, at 48 h of incubation. Violet fraction was toxic to human embryonic kidney (HEK293) and human fetal lung fibroblast (IMR90) cell lines with LC50 value of 0.998 ± 0.058 and 0.387 ± 0.002 μg/mL, respectively. Thus, violet fraction showed a strong antibacterial property by disrupting the membrane integrity of S. aureus and MRSA strains. This is the first report on the possible mode of antibacterial action of violet fraction from C. violaceum UTM5 on S. aureus and MRSA strains. [ABSTRACT FROM AUTHOR]

The application of natural pigments from bacteria as the colorant in ballpoint and highlighter pen ink has been studied. The scope of this study includes the extraction of violacein and prodigiosin from Chromobacterium violaceum and Serratia marcescens cultures, antimicrobial test for violacein and prodigiosin through disk diffusion and spread plate method, and the application of violacein and prodigiosin in ballpoint and highlighter pen ink formulation. From this study, the extracted violacein and prodigiosin showed antimicrobial activity against Grampositive (S. aureus and B. cereus) and Gram-negative (P. aeruginosa and E. coli) bacteria. Ballpoint pen ink formulation consists of gum arabic, carrageenan, ethanol, water and pigment. Highlighter pen ink was formulated using pigment, glycerol and citric acid. Application of violacein produced blue coloured highlighter pen ink while prodigiosin gave pink coloured highlighter pen ink. Violacein and prodigiosin pigments were successfully applied as an alternative to hazardous synthetic pigments in ballpoint and highlighter pen ink formulations. [ABSTRACT FROM AUTHOR]

The aim of this work was to evaluate the effects of hexavalent chromium [Cr(VI)] addition at different growth phases on the Cr(VI) reducing capacity of the aerobic Gram-negative bacterium, Acinetobacter haemolyticus. The addition of 10–100 mg Cr(VI) L−1 as potassium dichromate at the time of inoculation (T0) resulted in the extension of time needed to reach the stationary phase, with a total growth inhibition at 70 mg Cr(VI) L−1, a decrease in bacterial count from 108 to 102 CFU mL−1, and a Cr(VI) reduction drop to 35% at 100 mg Cr(VI) L−1. However, bacterial growth was uninterrupted when 10–100 mg Cr(VI) L−1 were added at the early stationary phase (after 12 h of bacterial growth) indicated by a high bacterial count of 108 CFU mL−1. More than 95% of Cr(VI) was reduced at an initial Cr(VI) of 50 mg L−1. However, the Cr(VI) reduction capacity dropped to 50% at 100 mg Cr(VI) L−1. This study showed that the ability of Acinetobacter haemolyticus to reduce Cr(VI) depends strongly on the number of surviving cells present in the solution. Higher Cr(VI) reduction can be achieved when a high number of bacterial cells are present. To achieve this condition, it is suggested to introduce the Cr(VI) into cells suspension at the stationary phase rather than introducing the Cr(VI) at the time of inoculation. [ABSTRACT FROM AUTHOR]

The current research is focused on studying the biological efficacy of flexirubin, a pigment extracted from Chryseobacterium artocarpi CECT 8497.Different methods such as DPPH, H2O2, NO•, O2•−, •OH, lipid peroxidation inhibition by FTC and TBA, ferric reducing and ferrous chelating activity were carried out to evaluate the antioxidant activity of flexirubin. Molecular docking was also carried out, seeking the molecular interactions of flexirubin and a standard antioxidant compound with SOD enzyme to figure out the possible flexirubin activity mechanism. The new findings revealed that the highest level of flexirubin exhibited similar antioxidant activity as that of the standard compound according to the H2O2, •OH, O2•−, FTC and TBA methods. On the other hand, flexirubin at the highest level has shown lower antioxidant activity than the positive control according to the DPPH and NO• and even much lower when measured by the FRAP method. Molecular docking showed that the interaction of flexirubin was in the binding cavity of the SOD enzyme and did not affect its metal-binding site. These results revealed that flexirubin has antioxidant properties and can be a useful therapeutic compound in preventing or treating free radical-related diseases. [ABSTRACT FROM AUTHOR]

Fingerprint has been one of the powerful evidence in forensic investigation as it is useful for human identification, associating an individual to an item and/or location of interest, as well as reconstructing the crime scenes. Considering that latent fingerprints are commonly found at crime scenes and that it requires the use of fingerprint visualization methods due to its hidden nature, continuous research in developing suitable methods has been reported. However, the underlying physical and/or chemical interactions for certain visualization methods that have successfully visualized wet fingerprints remains unreported. This is probably because previous studies were primarily focused on establishing the fingerprint contrast rather than the comprehension of the physical and chemical aspects behind it. A good understanding on such aspects may prove useful in guiding future improvements, or modifications of existing fingerprint visualization methods. Hence, this review paper focuses on wet latent fingerprints, difficulties in the available wet fingerprint visualization methods, as well as its overview of the challenges and future insights. [ABSTRACT FROM AUTHOR]