African journal of microbiology research (AFR J MICROBIOL RES )


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    ABSTRACT: In this study, we have isolated four different species from effluent contaminated soil using a mixture of aniline and 4-chloroaniline (4CA) as principal carbon sources. The four species were identified as Pseudomonas stutzeri A, Comamonas testosterone B, Pseudomonas putida C and Stenotrophomonas maltophilia D. Growth studies on aniline and 4CA as single and mixed substrates demonstrated that the bacteria preferred to grow on and utilize aniline rather than 4CA. However, despite 100% disappearance of the parent substrates, the degradation of 4CA was always characterized by incomplete dechlorination and 4-chlorocatechol accumulation. HPLC-UV analysis showed that 4-chlorocatechol was further degraded via an ortho-cleavage pathway by the bacterial consortium. This hypothesis was supported by the results from enzyme assays of the crude cell extract of the consortium revealing catechol 1,2-dioxygenase activity which converted catechol and 4-chlorocatechol to cis,cis-muconic acid and 3-chloro-cis,cis-muconic acid, respectively. However, the enzyme had a much higher conversion rate for catechol than for 4-chlorocatechol, indicating preference for non-chlorinated substrates. Members of the bacterial consortium were also characterized individually. All isolates were able to assimilate aniline. P. putida C was able to grow on 4CA solely, while S. maltophilia D was able to grow on 4-chlorocatechol. These results suggest that the degradation of 4CA in the presence of aniline by the bacterial consortium was a result of interspecies interactions.
    African journal of microbiology research 01/2015; 9(1):17-25.
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    ABSTRACT: Pre-dehulling treatments with some culture extracts of Aspergillus oryzae of various incubation periods played an important role in improving the dehulling properties of pigeon pea (Cajanus cajan L.). Yield percent of dehulling grains and dehulling efficiency increased concurrently with increase of incubation period of culture extracts. Maximum dehulled grains were achieved by 12-day old culture extract to the tune of 73% with lease amount of undehulled kernels and fines (6.6 and 6.5% respectively). Pre-dehulling trials conducted on pigeon pea grain employing wheat bran and pigeon pea based culture extracts of A. oryzae showed dehulling efficiency of 73% for wheat bran (12-day incubation period) and pigeon pea husk (9 day incubation period) in comparison with uninoculated extract (control) in the range of 62.2-64.4%. Based on the results obtained, dehulling properties affected by pigeon pea husk based culture extract proved better than wheat bran culture extract.
    African journal of microbiology research 11/2014; 8(51):3960-3968.
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    ABSTRACT: The growth rate of Isochrysis galbana was determined under flashing light conditions (104 μmol m-2s-1 light intensity, 10 kHz frequency, and 50% of the duty cycle) of several colors. The most suitable light for the growth of I. galbana was blue (dominant wavelength: 470 nm). After six days, the cell density under blue light was 34.0 × 105 cells mL-1, and was 1.4, 1.6, 1.8,and 2.2 times higher than those under white, red, white non-flashing, and green light, respectively. The peak wavelengths of white and blue lights are nearly consistent with the absorbance maxima of major pigments, which are chlorophylls and xanthophylls, in I. galbana. White and blue light were considered to be most effective for I. galbana growth.
    African journal of microbiology research 11/2014; 8(47):3815-3820.
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    ABSTRACT: This study aimed at evaluating the microbial quality of bottled water available in the Bulawayo market necessitated by the influx of local and imported bottled water brands into the market. The samples were analysed for Escherichia coli, heterotrophic plate count (HPC), total coliforms, feacal coliforms and for Pseudomonas aeruginosa. Total coliforms had a prevalence of 10% in local bottled water brands with bacterial counts not exceeding 30 cfu/250 ml. E. coli and feacal coliforms had prevalence of 2.5 and 5% respectively with maximum counts of 2 cfu/ml for E. coli and 5 cfu/250 ml for feacal coliform counts. P. aeruginosa was detected in 8.6% of local brand samples with counts not exceeding 10 cfu/250 ml. For heterotrophic plate count, 78% of the local brand samples had HPC ≤ 100 cfu/ml with counts as high as 2 x 103 cfu/ml recorded for the non-conforming samples. In the imported brands, 92% of the samples conformed to HPC ≤ 100 cfu/ml while counts for non-conforming samples ranged between 1.17 x 102 and 3.4 x 102 cfu/ml. The imported bottled water brands had significantly (p < 0.05) lower P. aeruginosa and total coliforms counts as compared to local bottled water brands, while there was no significant difference in E. coli, heterotrophic plate count and feacal coliform counts. However, based on International Bottled Water Association and WHO drinking water guidelines, P. aeruginosa, coliforms and E. coli counts in some local and imported bottled water samples exceeded the recommended maximum of no detection. This may have health implications to consumers. The quality of bottled water in the market maybe unsatisfactory for human consumption and warrants the need for strict monitoring and control in the production and trade in bottled water. Key words: Bottled water, microbial quality, bacteriology, Bulawayo market, Zimbabwe.
    African journal of microbiology research 10/2014; 8(42):3656-3661.