Accurate characterization of melanin using analytical methodologies has proved to be difficult due to its heterogeneity, insolubility in wide pH and broad range of solvents. The present study was undertaken to characterize melanin extracted from an environmental Aspergillus fumigatus AFGRD105 by studying its genes, chemical properties and spectral data. A gene based approach to confirm the type of melanin carried out indicated the extracted melanin to be of the dihydroxynaphthalene type. On comparison with synthetic melanin, UV–Vis and IR spectra of the extracted melanin revealed characteristic peaks that can be further used for confirmation of DHN-melanin extracted from any source. Solid state 13C NMR spectroscopy established the presence of the hydroxyl-naphthalene moiety and validated the results obtained by genetic analysis. The correct assignment of the observed spectral frequency characteristic of functional groups can be further adapted in future works that deal with binding capacities and biomolecule systems involving melanin.

Melanins are indolic polymers produced by many genera included among plants, animals and microorganisms and targeted mainly for their wide range of applications in cosmetics, agriculture and medicine. An approach to analyse the cumulative effect of parameters for enhanced melanin production was carried out using response surface methodology. In this present study, optimization of media and process parameters for melanin production from Aspergillus fumigatus AFGRD105 (GenBank: JX041523; NFCCI accession number: 3826) was carried out by an initial univariate approach followed by statistical response surface methodology. The univariate approach was used to standardise the parameters that can be used for the 12-run Plackett–Burman design that is used for screening for critical parameters. Further optimization of parameters was analysed using Box–Behnken design. The optimum conditions observed were temperature, moisture and sodium dihydrogen phosphate concentration. The yield of every run of both designs were confirmed to be melanin by laboratory tests of analysis in the presence of acids, base and water. This is the first report confirming an increase in melanin production A. fumigatus AFGRD105 without the addition of costly additives.

Bioremediation of chromates using bacteria primarily involves the removal/reduction of heavy metals in effluent using indigenous micro-organisms such as chromium reducing bacteria as biosorbents for cleaner and healthier environment. In the present study, the removal of hexavalent chromium by micro-organisms isolated from acclimatized tannery effluent was investigated. Biochemical assays and molecular sequencing revealed strain SRS05 to be Stenotrophomonas maltophilia. Resistance to chromium was determined by agar and broth dilution assays followed by determination of minimal inhibitory concentration. Strain SRS05 was able to resist 400 mg/ml of chromium which reflects that the heavy metal could be utilized by the micro-organism for its growth. Results by atomic absorption spectroscopy, Fourier transform infrared spectroscopic analysis and scanning electron microscopy revealed effective biosorption of chromium by S. maltophilia SRS05 with no intracellular changes morphologically indicating the stability of the organism in the presence of chromium. It is therefore recommended that this bacterium can be used widely for remediation of hexavalent chromium although the genetic basis for observations concluded in this study is to be confirmed.

Fifteen flavobacterium strains were isolated from raw chicken meat, raw goat meat and poultry soil in Coimbatore, Tamil Nadu. Most of the isolates developed yellow pigmented colonies with mucoid-spreading edges on food flavobacterium medium. The flavobacteria were Gram-negative rods and failed to produce indole and were non-fermentative. Moreover, they produced a rich array of enzymes such as amylase, lipase, catalase, urease, gelatinase, DNase, and oxidase. Phylogenetic analyses of the strain SKS05-GRD based on 16S rRNA gene sequences revealed the bacterium as Myroides odoratimimus (nucleotide sequence accession number JQ178355). Antimicrobial susceptibility test for M. odoratimimus SKS05-GRD and other strains were assessed by disc diffusion method. M. odoratimimus SKS05-GRD showed wide resistance to the antibiotics such as amikacin, ampicillin, cefadroxil, cefoperazone, ceftazidine, ceftriaxone, netillin and gentamicin. M. odoratimimus was subjected to plasmid isolation and plasmid curing to seek the relationship between plasmid and antibiotic resistance. Plasmid curing was done by using ethidium bromide and was found to be effective at 300 and 500 μg/ml. Assessment of antibiotic sensitivity of M. odoratimimus SKS05-GRD showed sensitivity to amikacin, gentamicin and kanamycin confirming that resistance to these three antibiotics is plasmid mediated and other antibiotic resistance are chromosomal mediated.

Foodborne pathogens are the main threat and cause of food poisoning. The majority of food infections have been related to the biofilm formation of foodborne pathogens in the food industry. Shewanella putrefaciens (KX355803, GRD 03), a Gram-negative pathogen isolated from mackerel fish, was identified and recognized as a food spoilage bacterium and a strong biofilm producer. The adhesion or attachment ability of Shewanella putrefaciens was determined on steel, plastic, glass, PVC and wood. NB (Nutrient broth), LB (Luria-Bertani broth), TSB (Tryptic soy broth) and BHI (Brain heart infusion broth) were enriched with glucose and shows optimum for bacterial adhesion. In the microtiter plate method (MTP), the strong attachment was observed at 48 and 72 hours of incubation and significant differences were obtained at p < 0.05. As the incubation period increases, the OD value (Optical density) of samples also increase. Biofilm formation is the major cause cross-contamination, and shows resistance to certain disinfectants, which leads to environmental stress tolerance. This study suggested with optimum biofilm production of isolate from fish by using glucose enriched media on different substrates, also comparing different growth media provide a detailed idea about biofilm-forming ability at different incubation time intervals.