Production of Antimicrobial Metabolites by Streptomyces lavendulocolor VHB-9 Isolated from Granite Mines

ABSTRACT The actinobacterial strain Streptomyces lavendulocolor VHB-9 was isolated from granite mine soil samples of Khammam district, Telangana state, India. The strain was identified based on detailed microorphological, cultural and phylogenetic analysis. Bioactive guided isolation of the secondary metabolites of the strain was carried out by growing the strain in optimized medium (0.5% lactose, 0.5% peptone, 0.05% K2HPO4, 0.2% CaCO3 with pH adjusted to 7.0). Separation and purification of the active fractions from the crude ethyl acetate extract was carried out by silica gel column chromatography and resulted in the isolation of two active fractions. Structural elucidation of the two (B2 and B3) active compounds was carried out by FT-IR, Mass and NMR spectroscopy and were identified as Bis (7-methyloctyl) phthalate and (Z)-3-aminoacrylic acid. The antimicrobial activity of the bioactive compounds produced by S. lavendulocolor VHB-9 was expressed in terms of minimum inhibitory concentration against opportunistic pathogenic bacteria and fungi. Both fractions exhibited good antimicrobial potential against the bacteria and fungi tested.

Antimicrobial profile of Arthrobacter kerguelensis VL-RK_09 isolated from Mango orchards

Abstract An actinobacterial strain VL-RK_09 having potential antimicrobial activities was isolated from a mango orchard in Krishna District, Andhra Pradesh (India) and was identified as Arthrobacter kerguelensis. The strain A. kerguelensis VL-RK_09 exhibited a broad spectrum of in vitro antimicrobial activity against bacteria and fungi. Production of bioactive metabolites by the strain was the highest in modified yeast extract malt extract dextrose broth, as compared to other media tested. Lactose (1%) and peptone (0.5%) were found to be the most suitable carbon and nitrogen sources, respectively, for the optimum production of the bioactive metabolites. The maximum production of the bioactive metabolites was detected in the culture medium with an initial pH of 7, in which the strain was incubated for five days at 30 °C under shaking conditions. Screening of secondary metabolites obtained from the culture broth led to the isolation of a compound active against a wide variety of Gram-positive and negative bacteria and fungi. The structure of the first active fraction was elucidated using Fourier transform infrared spectroscopy, electrospray ionization mass spectrometry, 1H and 13C nuclear magnetic resonance spectroscopy. The compound was identified as S,S-dipropyl carbonodithioate. This study is the first report of the occurrence of this compound in the genus Arthrobacter.

Production of Amylase by Arthrobacter kerguelensis VL-RK_09 Isolated from Mango Orchards.

Objectives: To optimize the cultural parameters for improved production of amylase by Arthrobacter kerguelensis VL-RK_09 isolated from Mango orchards of Vissannapet, Krishna District, A.P., India. Methods: The strain A. kerguelensis was screened initially for amylase production on Inorganic salts starch agar medium (ISP-4). The enzyme assay was performed as per the procedure described by Bernfield (1955). One amylase unit equals to that amount of enzyme needed to release 1 mg of reducing sugar (maltose as standard) for 15 min at 37°C. Attempts were also made to optimize cultural parameters such as pH, temperature, carbon and nitrogen sources affecting the production of amylase by the strain. Results: Maximal yields of amylase were recorded after 4 days of incubation in Inorganic salts starch medium with initial pH 7.0 and temperature 35°C. ISP-4 broth amended with sorghum flour (2%) and yeast extract (0.5%) with initial pH 7.0 inoculated with Arthrobacter kerguelensis VLRK_ 09 and incubated at 30°C for 96 h resulted in improved production of amylase from initial 4.0 U to 10.4 U/mL. Conclusion: This is the first report on the production and optimization of amylase by A. kerguelensis and further studies on purification and characterization of the enzyme are in progress.

Optimization of Culture Conditions for Enhanced Antimicrobial Activity of Rhodococcus erythropolis VLK-12 Isolated from South Coast of Andhra Pradesh, India.

Aims: To Isolate and characterize the antimicrobial actinomycetes from the marine habitats of south coast of Andhra Pradesh, India. Place and Duration of the Study: Marine habitats of south coast of Andhra Pradesh, India, between June 2011 and July 2012. Methodology: The soil samples were collected, pre-treated and plated on yeast extractmalt extract dextrose agar medium. Identification of the strain was carried out by employing the polyphasic taxonomical studies including the 16S rRNA sequence based analysis. Phylogenetic tree was constructed using the Molecular Evolutionary Genetic Analysis (MEGA) version 5. The influence of culture conditions and the effect of environmental factors on the biomass and antimicrobial activy\ity of the strain was the focus of this study. Results: A total of 20 actinobacteria were isolated from the marine habitats of south coast of Andhra Pradesh, India, and screened for antimicrobial activity against test bacteria and fungi. The potent bioactive metabolite producing strain was designated as VLK-12. Further polyphasic studies revealed that the Isolate VLK-12 belongs to the genera Rhodococcus. Phylogenetic analysis of 16S rRNA sequencing studies revealed that the strain is closely related to Rhodococcus erythropolis. The crude ethyl acetate extract obtained by culturing the strain on YMD inhibited Gram positive and Gram negative bacteria along with fungi. Conclusion: Rhodococcus erythropolis isolated from the marine habitats of south coast of Andhra Pradesh exhibited antimicrobial activity against pathogens.