Melanin biopolymers from newly isolated Pseudomonas koreensis strain UIS 19 with potential for cosmetics application, and optimization on molasses waste medium.

AIMS: Bacterial melanins are UV-absorber biopolymers with potential applications in cosmetics and pharmaceutical industries. However, the cost concern of these pigments remains a limiting factor for their commercial production. Hence, the present study was aimed to isolate a bacterium with high yield of melanin by optimization of an inexpensive waste sources. METHODS AND RESULTS: Pseudomonas koreensis UIS 19 (accession number: MG548583), which displayed significant bioproduction of melanin along with high tyrosinase enzyme activity was isolated from soil and introduced as a melanin-producing bacterium. Scanning and transmission electron microscope studies revealed that melanin pigments accumulated inside as well as the extracellular space of the cells. Melanin was extracted from the isolated strain and its detection was investigated using NMR and HPLC analyses. Here, we showed that the DPPH radical scavenging activity of 20 mg ml-1 melanin extracted from the isolated strain was >92·42% and its sun protection factor (SPF) value was 61·55. Melanin production by the UIS 19 in molasses medium showed sugar consumption (32 g l-1 ) for biomass production (5·4 g dry wt) and melanin yield of 0·44 g dry wt g-1 biomass from l-tyrosine. Some critical intermediated such tyramine, l-dopa, dopamine and dopaquinone related to the melanin Raper Mason pathway were detected by H-NMR. Furthermore, to achieve high bioproduction of melanin in inexpensive media include 5% molasses 5 Brix as an industrial waste, nutritional and environmental parameters were screened using response surface methodology by Box-Behnken design in which, maximum melanin yield of 5·5 g dry wt l-1 was obtained. CONCLUSIONS: The bioproduction of melanin as valuable compound from P. koreensis was performed using an optimized waste medium. The purified melanin showed high radical scavenging activity and high SPF value. SIGNIFICANCE AND IMPACT OF THE STUDY: Pseudomonas koreensis UIS 19 is a promising candidate for industrial production of melanin as cosmetic skin-care product.

Antimicrobial Effect of Copper Oxide Nanoparticles on Some Oral Bacteria and Candida Species.

STATEMENT OF PROBLEM: Acid producing bacteria including Streptococcus mutans and lactobacilli cause tooth demineralization and lead to tooth decay. Also, oral colonization of the species of Candida has been reported in many studies that are resistant to antifungal agents. OBJECTIVES: In this study, antibacterial and antifungal effects of nano-CuO were studied against some oral bacteria and yeast fungi. MATERIALS AND METHODS: The minimum inhibitory concentrations (MICs) of copper oxide nanoparticles (CuO NPs) for oral bacterial and fungal test strains were determined in 96-well microtiter plate technique. The agar diffusion test (ADT) was employed to assess the antifungal properties of nystatin. RESULTS: The MIC50 value of CuO NPs was determined at the range of 1-10 µg/ml for S. mutans, < 1 µg/ml for L. acidophilus, and 10 µg/ml for L. casei. Higher concentrations of CuO NPs (100-1000 µg/ml) were effective on the bacterial cell growth, resulting in 100% reduction in the optical density in TSB medium. The cells of Candida albicans, C. krusei and C. glabrata were treated with CuO NPs and the results showed a decrease in fungal growth at a concentration of 1-1000 µg/ml in TSB medium. The MIC50 value of CuO NPs was determined 1000 µg/ml for three species of Candida. The diameter of growth inhibition zones of 1100 µg/ml nystatin was obtained 15-21 mm for clinical isolates of three species of Candida. CONCLUSIONS: With respect to the potential bactericidal activity of CuO NPs on various cariogenic bacteria examined in this study, these NPs could be introduce as a candidate control agent for preventing dental caries or dental infections. In our study, on the other hand, Nano copper oxide had a weak effect on the candida species.

Isolation a new strain of Kocuria rosea capable of tolerating extreme conditions.

A new actinobacterial strain was isolated from Ab-e-Siah spring (dark water) taken from the Ramsar city in Iran, and subjected to several stress conditions investigation. The isolate, named MG2 strain, was Gram-positive, aerobic, diplococci or tetrad shaped, non-spore forming and non-motile. Phylogenetic analysis of the isolate using 16S rDNA sequence indicated that the organism matched best with the genus Kocuria and the highest sequence similarities (98.55%) being found with Kocuria rosea. The 16S rDNA sequence determined in this study has been deposited in the NCBI database with the accession no. JX534199, K. rosea strain MG2. The isolated strain was an alkaliphilic-mesophilic bacterium because the optimal growth was observed at pH 9.2 and temperature of 28 °C under aerobic condition. MG2 was a halotolerant strain and tolerated maximally to 15% NaCl concentraion. Viability analysis by flow cytometry indicated that this strain had highly resistance to UV-C radiation and moderately resistance to desiccation after 28 days. The viability of K. rosea strains MG2 and Deinococcus radiodurans R1 were determined D87 and D98 according to D index, respectively, by a dose radiation 25 J/cm (Appukuttan et al., 2006). Thus the UV resistance of strain MG2 was comparable with representative radiation resistant Deinococcus. Also MG2 was grown at 1-4% of H2O2 as an oxidant agent. This research is the first study on multiple extreme resistance of Kocuria rosea new strain (MG2) isolated in Iran.

Identification of thermophilic and mesophilic bacteria and fungi in Esfahan (Iran) municipal solid waste compost.

The thermophilic and mesophilic microbiota in compost produced from Esfahan municipal solid waste were examined at different stages of composting process from day zero to 28 days and was conducted in four different seasons. Some of the mesophilic bacteria observed in initial stages of composting process were gram negative Escherichia, Klebsiella, Aeromonas and Alcaligenes, and gram positive Enterococcus and Bacillus species. After 20 days of the composting process lower species diversity of mesophiles (only Bacillus species) were isolated, which was most likely due to the high temperature (60-68 degrees C) condition. Some of the observed thermophilic bacteria at later stages of the process are: Bacillus subtilis, B. polymyxa, B. pumilus, B. sphaericus, and B. licheniformis from thermotolerants, and B. stearothermophilus, B. acidocaldarius, and B. schleglii from thermophiles. Among the mesophilic fungi, at the initial stages of composting process some types of yeasts and molds were isolated, but after day 20 due to high temperature condition (60-68 degrees C), no mesophilic fungi were obtained. On the 15th day of composting the highest diversity of thermotolerant fungi such as Cladosporium, Aspergillus, Mucor, Rhizopus, and Absidiae spp. were observed. The results indicated that, in order to obtain a sanitary product in cold seasons, the composting process needs a longer duration and fewer turnings.