Usha Kiranmayi Mangamuri

Glucoamylase from a newly isolated Aspergillus niger FME: Detergent-Mediated production, purification, and characterization

Glucoamylase (EC 3.2.1.3) is an important group of enzymes in starch processing, also referred to as amyloglucosidases, which are exo-acting amylases that release glucose from the nonreducing end of starch and related oligosaccharides. The glucoamylase newly isolated from the Aspergillus niger FME) was reported for the first time. This enzyme was produced by detergent-mediated release and purified to ∼9.11 fold using Sephadex-G 100 and ion-exchange chromatography. Molecular mass of the glucoamylase was ∼36 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The product of starch hydrolysis, analysed by thin-layer chromatography, showed the presence of glucose. The optimum pH and temperature for glucoamylase activity was 5.0 and 45°C, respectively. The Km and Vmax values of the enzyme were also determined using soluble starch as substrate as 94 μg/mL and 39.02 U/mg, respectively. Moreover, glucoamylase was slightly activated by presence of Na and K ions and 10–20% inhibition was observed in presence of Zn2+, Sn2+, Mg2+, Ni2+, Mn2+, and almost 80% with Cu2+ ions, whereas the presence of ethylene diamine tetra acetic acid (EDTA) did not show significant inhibition. Glucoamylase, also assayed for surfactant property, shows significant surfactant tolerance at high concentrations of detergent and can retain 90% of its activity. Finally, secondary structure analysis of glucoamylase by circular dichroism spectroscopy showed the presence of 48% α-helix, 11% β-sheet, and 41% random structure.

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. Research Article British Microbiology Research Journal, 4(1): 63-79, 2014 64 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.

Optimization of process parameters for improved production of bioactive metabolites by Streptomyces tritolerans DAS 165T.

Aims: To optimize the process parameters for enhanced production of bioactive metabolites by Streptomyces tritolerans DAS 165. Place and Duration of Study: Department of Botany and Microbiology, April 2012 to August 2012. Methodology: Agar well diffusion assay was employed to study the effect of environmental parameters such as incubation period, pH, temperature and salt concentration and influence of various nutrients such as carbon and nitrogen sources and minerals on the bioactive metabolite production by Streptomyces tritolerans DAS 165.  Results: The production of antimicrobial metabolite was high when the strain was cultured for six days at 35oC in medium (pH 7.5) with sucrose at the concentration of 2% (carbon source), soya peptone at the concentration of 1% (nitrogen source) and sodium chloride at the concentration of 5%.  Conclusion: This is the first report on the optimization of bioactive metabolite production Original Research Article British Microbiology Research Journal, 4(4): 428-442, 2014 429 by Streptomyces tritolerans DAS 165. As the strain exhibited potent antimicrobial activity, it may be explored for biotechnological purposes. 

Bioactive natural products from Pseudonocardia endophytica VUK-10

Two proline containing cyclic dipeptides (CDPs), cyclo (L-Pro-L-Tyr) (1) and cyclo (L-Pro-L-Phe) (2) were isolated from the fermentation broth of Pseudonocardia endophytica VUK-10 originating from the Nizampatnam mangrove ecosystem on the south coast of Andhra Pradesh, India. The structures of the compounds were established by 1H NMR and 13C NMR spectroscopy, FTIR and EIMS. The antimicrobial and cytotoxic activities of the compounds were tested against a variety of medicinally and agriculturally important bacteria and fungi as well as on the MDA-MB-231, OAW-42, HeLa and MCF-7 human cell lines. Xanthomonas malvacearum was most sensitive toward 1 (MIC 4 μg/ml), whereas compound 2 had good antibacterial activity against Xanthomonas campestris (MIC 8 μg/ml). Fusarium solani was highly sensitive toward 1 (MIC 16 μg/ml). The compounds were cytotoxic against the human cell lines at micro molar concentrations; the highest activity (IC50 < 10 μM) of 1 was recorded against the MDA-MB-231 cancer cell line.

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

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.

Optimization of the Cultural Parameters for Improved Production of Antimicrobial Metabolites by Streptomyces gulbargensis DAS 131

Aims: To investigate the influence of appropriate culture medium by optimizing the cultural conditions affecting the growth and bioactive metabolite production by Streptomyces gulbargensisDAS 131 under submerged culture conditions in order to reduce the cost of fermentation process to improve the formation of antimicrobial compounds.