Advanced Journal of Microbiology Research

Advanced Journal of Microbiology Research Vol. 2012

Available online at http://internationalscholarsjournals.org/journal/ajmr

© 2012 International Scholars Journals

Full Length Research Paper

Statistical optimization of medium components for chromate reduction by halophilic Streptomyces sp. MS-2

Mona E. M. Mabrouk

Botany Department, Faculty of Science, Damanhour, Alexandria University, Egypt. E-mail: [email protected].

Accepted 18 March, 2012

Extensive use of hexavalent chromium Cr(VI) in various industrial applications has caused substantial environmental contamination. A marine bacterium, Streptomyces sp. MS-2 showed a high Cr(VI) reduction performance. Streptomyces sp. MS-2 completely reduced 75 mg/l Cr(VI) within 72 h of growth. The effectiveness of the bacterium for reducing Cr(VI) under different conditions was evaluated. Optimum pH and temperature were 7.0 and 37^oC, respectively. Statistical screening of medium components for Cr reduction by Streptomyces sp. MS-2 was carried out by Plackett–Burman design. Peptone, yeast extract, inoculum size, and volume of the medium were shown as significant components influencing Cr(VI) reduction. By applying a verification experiment, Streptomyces sp. MS-2 completely reduced 75 mg of Cr(VI) to Cr(III) within 12 h. This optimization strategy led to a 6-fold increase in the reduction rate. This holds great promise for detoxification of Cr(VI) under a wide range of environmental conditions.

Key words: Streptomyces MS-2; hexavalent chromium; Plackett–Burman design.

Advanced Journal of Microbiology Research Vol. 2012

Available online at http://internationalscholarsjournals.org/journal/ajmr

© 2012 International Scholars Journals

Full Length Research Paper

Microbiological quality of water, associated management practices and risks at source, transport and storage points in a rural community of Lungwena, Malawi

Taulo, S.^{1, 3*}, Wetlesen, A.¹, Abrahamsen, R.¹, Mkakosya, R.² and Kululanga, G.³

¹Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Science, P.O. Box 5003, N-1432 As, Norway.

²Department of Microbiology, College of Medicine, P/B 360, Blantyre, Malawi.

³Faculty of Engineering, University of Malawi, P/B 303, Blantyre, Malawi.

Accepted 8 May, 2012

Abstract

This study investigated and compared the microbiological quality of source, transported and stored water in Lungwena households. It also examined water management practices at all the investigated points. One hundred and eighty (180) water samples were collected from 6 villages and tested for Escherichia coli, Salmonella, E .coli 0157:H7 and Campylobacter jejuni using standard methods. Water contamination practices were observed in two hundred and eighty seven households. E. coli, Salmonella, E. coli 0157:H7 and C. jejuni were isolated in 54, 24, 6.7 and 2.2% of the samples, respectively. Sampling points revealed a significant difference (p = 0.001) in E. coli concentration. Salmonella concentration between sampling points was not significant (p > 0.05). E. coli concentration was significantly (p = 0.042) higher than that of Salmonella spp. The microbiological quality of water was found to be poor as a result of both poor water management practices and environmental sanitation. There were no significant differences (p > 0.05) in water management practices among the villages.

Key words: Pathogens, stored water, transport water, water contamination.

Advanced Journal of Microbiology Research Vol. 2012

Available online at http://internationalscholarsjournals.org/journal/ajmr

© 2012 International Scholars Journals

Full Length Research Paper

Drynaria quercifolia (L.) J.Sm: A potential resource for antibacterial activity

M. Kandhasamy¹, K. D. Arunachalam²* and A. J. Thatheyus³

¹Department of Microbiology, PGP College of Arts and Science, Namakkal

²Department of Bio-Technology, SRM University, Chennai.

³PG and Research Department of Zoology, The American College, Madurai.

Accepted 23 July 2012

Abstract

Six different organic solvents such as ethanol, methanol, petroleum ether, hexane, benzene and chloroform were used to extract the bioactive compounds from the rhizome of Drynaria quercifolia to screen the antibacterial activity against infectious disease causing bacterial pathogens such as Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Salmonella paratyphi A, Salmonella paratyphi B, Salmonella marscence, Staphylococcus aureus and Bacillus subtilis by agar diffusion method. The ethanolic extract of D. quercifolia was more active against 80% of the organisms tested. It was followed by methanolic extract (70%), benzene (50%) and chloroform extract (40%) in inhibiting the growth of the organisms tested. Petroleum ether and hexane extract of D. quercifolia did not show any antibacterial activity against any of the pathogenic bacteria tested. Among the bacteria tested, gram-negative bacteria were more susceptible to the crude extracts compared to gram-positive bacteria. Among gram-positive bacteria, S. aureus was susceptible to ethanolic, methanolic and chloroform extracts whereas B. subtilis was susceptible to methanolic extract of D. quercifolia alone. In the present study ethanolic and methanolic extracts of rhizome of D. quercifolia showed high efficiency of antibacterial activity and gram-negative bacteria were more susceptible to all the extracts tested.

Key words: Drynaria quercifolia, rhizome, crude extract, antibacterial activity.

Advanced Journal of Microbiology Research Vol. 2012

Available online at http://internationalscholarsjournals.org/journal/ajmr

© 2012 International Scholars Journals

Full Length Research Paper

In vitro detection and characterization of bacteriocin-like inhibitory activity of lactic acid bacteria (LAB) isolated from Senegalese local food products

Michel Bakar DIOP¹, Robin DUBOIS-DAUPHIN¹, Carine DORTU¹, Jacqueline DESTAIN¹, Emmanuel TINE², and Philippe THONART¹,

¹Centre Wallon de Biologie Industrielle (CWBI), 2 passage des Déportés, B 5030 Gembloux, Belgium,

²Laboratoire de Microbiologie et Génie industrielle, Université Cheikh Anta DIOP, Ecole Supérieure Polytechnique, BP 5085 Dakar, Sénégal

Accepted 9 April, 2012

Abstract

The prevalence of lactic acid bacteria (LAB) in Senegalese local food products was determined to be 10⁹ CFU/g in millet flour and milk products, and 10³ CFU/g in seafood products. These food products are generally preserved by spontaneous fermentation (without addition of starters). Of 220 lactic acid bacteria strains randomly selected from such products, 12 isolates capable of producing bacteriocin-like substances (bac+) were detected. Based on the use of API 50 CH test kits and 16S rDNA sequencing, 11 isolates were characterized as Lactococcus lactis subsp. lactis strains and one as an Enterococcus faecium strain. Nisin- and enterocin B-encoding genes were respectively identified in the bac+ lactococcal strains and the E. faecium strain. Since the bac+ Lc. lactis strains were isolated from different products, it suggests a high potential of growth by these strains in variable ecological environments. Expression of the nisin gene was indicated for one of the lactococcal strains, designated Lc. lactis subsp. lactis CWBI-B1410, which showed the highest in vitro antibacterial activity. An antibacterial preparation prepared from the CWBI-B1410 strain showed many similarities with nisin with regards to its inhibitory effects, heat resistance, protease sensitivity profile, as well as retention time of the antibacterial substances on a C₁₈ column. These results suggest that a nisin-like substance is produced by the CWBI-B1410 strain. This strain has been selected for application as an additional barrier to supplementation with sodium chloride as a means to improve the bacterial quality of fish commodities in Senegal.

Key words: Lactococcus lactis, antimicrobial, bacteriocins, Nisin-like substance.

Advanced Journal of Microbiology Research Vol. 2012

Available online at http://internationalscholarsjournals.org/journal/ajmr

© 2012 International Scholars Journals

Full Length Research Paper

Chemical composition, antioxidant and antimicrobial properties of the essential oil of Dacryodes edulis (G. Don) H. J. Lam from Gabon

L. C. Obame^{1, 2}, P. Edou², I. H. N. Bassolé¹*, J. Koudou³, H. Agnaniet⁴, F. Eba² and A. S. Traore¹

Accepted 14 March, 2012

Abstract

The essential oil obtained by hydrodistillation from the resin of Dacryodes edulis (G. Don) H. J. Lam was simultaneously analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC -MS). Twenty four components were identified in the essential oil and the main components were sabinene (21.8%), terpinene-4-ol (19.8%), -pinene (17.5%) and p-cymene (11.3%), respectively. The antioxidant capacity of the essential oil was examined using an in vitro radical scavenging activity test and -carotene-linoleic acid assays. In the 2.2-Diphenylpicrylhydrazyl (DPPH) test system, the IC50 value of D. edulis oil was 68.5 ± 2.29 µg/ml. In the -carotene-linoleic acid test system, oxidation of linoleic acid was effectively inhibited by D. edulis (70.0%). The oil was less effective than butylated hydroxytoluene (BHT). Furthermore, the essential oil was evaluated for its antimicrobial activity using disc diffusion and microdilution methods. The essential oil showed better activity against bacterial species than against yeast.

Key words: Dacryodes edulis, Burseraceae, essential oil, antimicrobial activity; antioxidant activity; gas chromatography-mass spectrometry.

Advanced Journal of Microbiology Research Vol. 2012

Available online at http://internationalscholarsjournals.org/journal/ajmr

© 2012 International Scholars Journals

Full Length Research Paper

Purification and properties of a non-stereospecific dehalogenase enzyme E (DehE) from Methylobacterium sp. HJ1

Ng Hong Jing¹, Fatin Hanani Sulaiman¹, Roswanira Ab. Wahab², Rolando V. Pakinging Jr. ³, Noor Aini Abdul Rashid¹ and Fahrul Huyop¹*

¹Industrial Biotechnology Department, Faculty of Biosciences and Bioengineering, University Technology Malaysia, 81310 Skudai, Johor, Malaysia.

²Chemistry Department, Faculty of Science, University Technology Malaysia, 81310 Skudai, Johor, Malaysia.

³SouthEast Asian Fisheries Development Center Aquaculture Department, Tigbauan, Iloilo, 5021 Philippines.

Accepted 12 June, 2011

Abstract

The bacterial isolate HJ1, which was identified as a Methylobacterium sp., grew on 2, 2-dichloropropionic acid as the sole carbon source and produced a 2-haloalkanoic acid hydrolytic dehalogenase. This non-stereospecific dehalogenase E (DehE) catalysed the hydrolytic dechlorination of 2, 2-dichloropropionic acid and D, L-2-chloropropionic acid to produce pyruvate and lactate, respectively. The enzyme was purified to homogeneity and characterized. The molecular weight was 36 kDa by SDS-polyacrylamide gel electrophoresis and 72 kDa by gel filtration, suggesting that the enzyme is a protein dimer. The purified enzyme was only inhibited by HgSO4 and was non-stereospecific to haloalkanoic acids. The Km value for the hydrolysis of 2, 2- dichloropropionic acid was 0.25 mM. The enzyme removes chloride present on the -position, but not on the -position, of a number 2–carbon alkanoic acids.

Key words: haloalkanoic acid, dichloropropionate, 2, 2-dichloropropionic acid.