No abstract

The bacteria associated with contamination of ready-to-eat (RTE) cooked rice in Lagos, Nigeria were studied using standard microbiological methods. The objective of this study was to investigate the distribution of pathogenic bacteria recovered from RTE cooked rice in Lagos, assess bacteria load in the contaminated RTE cooked rice and evaluate their microbial quality. The microbial load of the RTE cooked rice ranged from 1.5 ± 0.29x 10 4 -4.8 ± 0.46x 10 6 cfu/g for three markets. A further test revealed that the average bacteria counts at Ketu was significantly different from those at Yaba and Odogunyan. However it was found that counts at Yaba and Odogunyan were not significantly different. Based on the specification by the International Microbiological Standard limits for Foods (IMSF), the levels of contamination of the total samples that were above and below microbiological acceptable limit were 91.7% and 8.3% respectively. The predominant pathogenic bacteria associated with contamination of the RTE cooked rice samples were identified as Staphylococcus aureus, Brahamella sp, Enterobacter aerogenes and Salmonella typhi. Out of a total of 36 RTE cooked rice samples analyzed, Enterobacter aerogenes 36 (100%) had the highest occurrence followed in descending order by Staphylococcus aureus 33 (91.7%), Brahamella sp. 29 (80.6%) and Salmonella sp. 25(69%). The results indicated that most of the RTE cooked rice samples examined in this study did not meet bacteriological quality standards. These findings suggest that the presence of food pathogens in RTE rice hawked in our local markets may pose serious potential health risks to the consumers in the public.

Mutagenic and genotoxic effects of cassava wastewater (CWW) were investigated by assay of Allium cepa root meristematic cells. The physicochemical parameters of the wastewater samples showing cyanide content were also determined. In Allium root growth inhibition test, experimental onion bulbs were cultivated in various concentrations of the CWW and distilled water was used as a negative control. After 72 h, the root tips from the treated bulb were processed for cytological studies by orcein squash technique. The mean lengths of root bundles were obtained and effective concentration (EC) values calculated. The cytotoxic effects on the onion root tips showed strong growth retardation at high concentrations of the effluent with EC value of 10%. The 50 mitotic index (MI) rapidly decreased with increasing effluent concentration compared to control. There was significant increase in frequency of chromosome aberrations (sticky chromosome, c-mitosis, vagrant chromosome, bridges fragment, binucleated cells, multipolar anaphase, attached chromosome and laggard chromosome) in root tip meristem cells of Allium cepa at all tested concentrations. Further analysis using oneway ANOVA revealed that there was a statistically significant difference (p<0.05) in concentration-dependent inhibition of onion root growth, mitotic index and induction of chromosomal aberration in the Allium cepa test. The results indicate that the effluent samples collected were highly mutagenic. The results of physicochemical analysis revealed that the concentrations of some parameters (conductivity, total suspended solid (TSS), total dissolved solid (TDS), biological oxygen demand (BOD), nitrate, cyanide, chloride and metals-magnesium, aluminum, chromium, cadmium, manganese and iron) were above the maximum permissible limit set by world health organization (WHO) and could partly be correlated with the toxicity of wastewater. The findings indicate that the substances contained in the cassava effluents may be toxic to living organisms and may pollute the environment if untreated.

Background The use of nitrile compounds is usually high, particularly in chemical industries, which calls for serious concern because of their relevance to the environment. The essential role of nitrilases in the bioremediation of harmful nitriles from environmental wastes cannot be overemphasized. The study aimed to unveil the biodegradative potentials of bacterial strains associated with the degradation of nitrile pollutants. Methods Bacterial strains capable of utilizing glutaronitrile as the sole source of carbon and nitrogen were isolated from solid waste leachates by a selective enrichment culture technique. The test organisms were grown in mineral salts medium (MSM), and the metabolic products were determined using gas chromatography-flame ionization detection (GC-FID). The nitrilase gene was amplified by polymerase chain reaction (PCR) and by using appropriate primers. Results The growth studies showed that the test organisms grew on the two nitriles. The doubling times of 12.16 d and 9.46 d (specific growth rate, µ=0.082 d−1, 0.106 d−1) were obtained for  each pure culture of Bacillus sp. srain WOD8 and Corynebacterium sp. srain WOIS2 on glutaronitrile (as single substrate), respectively. While the same strains  had doubling times of 11.11 d and 10.00 d (µ=0.090 d−1, 0.100 d−1) on benzonitrile (as single substrate). However, the mixed culture (comprising the two strains)  had doubling times of 7.40 d and 7.75 d (µ=0.135 d−1, 0.129 d−1) on glutaronitrile (as single  and mixed substrates), respectively.  While doubling times of 8.09 d and 8.71 d (µ=0.124 d−1, 0.115 d−1) were obtained  for the same mixed culture on  benzonitrile (as single and mixed substrates). Based on gas chromatographic analysis, the residual glutaronitrile concentrations at day 16 for strains WOD8 and WOIS2 were 35.77 g L−1 (72.2%) and 9.30  g L−1 (92.5%), respectively, whereas the residual benzonitrile concentrations for the same strains were 27.39 g L−1 (78.8%) and 13.79 g L−1 (89.2%), respectively. For the mixed culture, residual glutaronitrile and benzonitrile concentrations at day 16 were 13.40 g L−1 (88.5%) and 10.42 g L−1 (91.5%), respectively, whereas for the mixed substrates  (glutaronitrile and benzonitrile), 7.21 g L−1 (91.7%) and 4.80 g L−1 (94.2%) of residual glutaronitrile and benzonitrile concentrations were obtained by the same consortium. The gene for nitrilase involved in nitrile degradation was detected in the genome of the bacterial strains. The amplified nitrilase gene gave PCR products of sizes 1400 bp and 1000 bp, as expected for strains WOD8 and WOIS2, respectively. 4-Cyanobutyric acid (4CBA), glutaric acid (GA), and benzoic acid (BA) were obtained as metabolites following nitrile degradation in vitro. Conclusion These results revealed that strains WOD8, WOIS2 and the mixed culture (consisting of the two strains) have proven to have the capacity to metabolize nitriles (glutaronitrile and benzonitrile) as the carbon and nitrogen sources. However, the mixed culture had higher nitrile degradation rate as compared to each pure culture of the two test organisms. These results also provide insight into the evolutionary genetic origin of a nitrilase gene that encodes an enzyme that catalyzes nitrile degradation in these strains. Hence, the bacterial strains that harbor this kind of gene may be used as promising biological agents for the remediation of sites polluted with nitriles, thereby opening new perspectives for encouraging data for a bioremediation bioprocess.

Crude oil, though not manmade but largely manipulated by man to provide different oil-based products has become a major source of environmental pollution. This menace on land do contribute to the retardation of vegetation growth and human health hazards, while in water it may be toxic to aquatic animals. The search for the solution to ameliorate the seemingly unending pollution and its side effects necessitated the evaluation on the effect of bioaugmentation, biostimulation and natural attenuation of crude oil pollution in soil microcosms. The bacterial species selected for this study (Bacillus thuringensis strain LG32 and Burkolderia pseudomallei strain A81) were preliminarily identified using the conventional biochemical tests and further identification was carried out using the API kit. The results of the study carried out over a period of five weeks indicated that there was a marked reduction in the available phosphorous and potassium in the bioaugmented and biostimulated soils compared with that of the control. The mean values for total viable counts (TVC) of population of hydrocarbon -1 utilizing bacteria (HUB) was higher in the bioaugmented soil ranged (LG32=6.0-7.5log10cfu g ; A81=5.5-7.5log10cfug ; LG32+A81=6.0-7.5log10cfug ) compared with that of the control (6.0-6.2log10cfug ). When -1 bioaugmentation was combined with biostimulation, the soil had higher counts of HUB (6.0-9.0log10cfug ) and -1 HUF (3.5-6.5log10cfug ) compared to bioaugmentation without stimulation (HUB: 6.0-7.5; HUF: 3.5-5.5). The GC result indicated that by day 35, 96.92% of the aliphatic and aromatic components have been degraded in the augmented soil, higher than the natural attenuation control.