Degradation of poly aromatic fractions of crude oil and detection of catabolic genes in hydrocarbon-degrading bacteria isolated from Agbabu bitumen sediments in Ondo State.

Pollution due to release of Poly aromatic hydrocarbons (PAHs) are a major environmental issue especially in oil producing communities. This study investigates the polyaromatic hydrocarbon degradation potentials of some bacteria: Campylobacter hominis, Bacillus cereus, Dyadobacter koreensis, Pseudomonas aeruginosa and Micrococcus luteus isolated from Agbabu bitumen sediments in Ondo State. The isolates were used singly and in consortium for the degradation of Bonny light crude oil. Concentrations of residual aromatic hydrocarbons in crude oil degraded by these isolates were determined by Gas chromatography/Mass Spectroscopy with flame ionization detector (FID). Detection of catabolic genes (nahH, CatA and AlkB) in the isolates was determined by PCR amplification of their specific primers. The GC-MS analyses showed degradation of poly aromatic hydrocarbons (PAHs) by these isolates. The consortium exhibited the highest PAH reduction (73%) while C. hominis had the least PAH reduction (56%). Dyadobacter koreensis, P. aeruginosa, Micrococcus luteus and B. cereus, displayed 66%, 60%, 59% and 58% PAH reduction respectively. The catabolic gene nahH gene was present in B. cereus, D. koreensis, P. aeruginosa and M. luteus, alkB gene was present in B. cereus, C. hominis, and D. koreensis while CatA was not detected in any of the isolates. The findings of this study affirmed the hydrocarbon-degrading abilities and presence of catabolic genes in these bacteria, these make them potential tools in oil prospecting and cleaning up of hydrocarbon contaminated sites.

Characterization and antimicrobial activity of 4-(ß-D-glucopyranosyl-1→4-α-L-rhamnopyranosyloxy)-benzyl thiocarboxamide; a novel bioactive compound from Moringa oleifera seed extract.

Antimicrobial activity of crude seed extract of Moringa oleifera was investigated by thin layer chromatography bioassay against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Cladosporium cladosporioides, and Penicillium sclerotigenum; most of them were prominently inhibited by an isolate with R(F) 0.92-0.96. Characterization and identification of the extract revealed the occurrence of three bioactive compounds: 4-(α-L-rhamnopyranosyloxy)benzyl isothiocyanate, methyl N-4-(α-L-rhamnopyranosyloxy) benzyl carbamate (both known compounds), and 4-(ß-D-glucopyranosyl-1→4-α-L-rhamnopyranosyloxy)-benzyl thiocarboxamide, existence of which in any Moringa spp. or plant is reported for the first time. The UV spectrum of the novel compound showed maximum absorption at 273 and 225 nm in MeOH while the IR spectrum revealed several characteristic bands at 3100, 2900, 1700, 1500, 1300, 1100 and 1000 cm(-1). The (1)H-NMR showed signals at 1.2 and 3.77 ppm and the (13)C-NMR presented signals at 155, 122, 91.7 and 98.4 ppm. All the compounds at 5 mg/L had very high bactericidal activity against some of test pathogens even at contact period 1-2 h. 4-(ß-D-Glucopyranosyl-1→4-α-L-rhamnopyranosyloxy)benzyl thiocarboxamide was the most potent, with 99.2 % inhibition toward Shigella dysenteriae and 100 % toward Bacillus cereus, E. coli and Salmonella typhi within 4 h of contact.

Fermentation of yam: microbiology and sensory evaluation of cooked fermented yam tissues.

The microflora of white yam (Dioscorea rotundata L.) slices fermented anaerobically in 1.5 percent brine for five days at room temperature were studied. The hydrolysis of the carbohydrate and the subsequent conversion of sugars and minerals by the fermenting microbes contributed much to the increased microbial load especially within the first 72 hours of fermentation. The organisms implicated in the fermentation include the species of Pediococcus, Lactobacillus and Pseudomonas, Bacillus subtilis and two other Gram negative coccal cells, yet to be identified. The decrease in microbial counts at the latter stage of fermentation was attributed to the high total acidity of the medium, which was about 2.67 times the initial value of 0.027% lactic acid. Meanwhile, the lactic acid bacteria increased continuously throughout the period of fermentation.

Toxicity of citric and succinic acids for the pycnidiospores ofBotryodiplodia theobromae.

The toxic effect of citric and succinic acids on the germination of the pycnidiospores ofBotryodiplodia theobromae, mycelial growth and the killing rate of theB. theobromae spores was investigated. The percentage inhibition of germination of viable fungal spores by 0.01% succinic or citric acid ranged between 51.6 and 58.1%, respectively.B. theobromae was found to grow in 2% malt extract broth at 28 degrees C at the rate of 0.13 CFU/h. Citric acid exhibited a higher killing rate of 0.26 CFU/h and was more effective against the germination of the fungal spores. At concentrations of 0.3% and above, citric acid could be used as pre- and post-infectional fungicide.

Monitoring microbiological and biochemical changes in fermented yam.

The microbiological and biochemical changes occurring in yam (Dioscorea rotundata L.) tissues fermented in 2% brine under anaerobic conditions at ambient temperature were studied. The ash. fibre and fat contents of the yam tissues were reduced at an average rate of 1.98, 1.72 and 0.42 mg g(-1) d(-1), respectively.Lactobacillus andLeuconostoc spp., as well as other fermentative microorganisms, showed a tendency to increased growth. The decrease in the total aerobic count after a 4-d fermentation was due to depletion of available nutrients, increased acidity of the medium and complete anaerobiosis of the environment. The fermenting microbes showed a higher amylolytic activity, releasing between 52 and 73 mg glucose per mL, than proteolytic activity, where between 120 and 250 microg amino acids per mL was released.

Antifungal properties of yam (Dioscorea alata) peel extract.

The extraction of natural antifungal compounds from the peels of yam (Dioscorea alata) and the effect of these compounds on both the vegetative and reproductive structures of some yam not pathogens were studied. Four prominent antifungal components were obtained; one of the components was fully characterized and identified as beta-sitosterol. The antifungal activity of the compounds toward the germination of spores of two yam pathogens showed an inhibition of less than 57% at a concentration of 50 mg/L while inhibition on the elongation of germ-tubes of Fusarium moniliforme was as high as 82% at the same concentration. However, the ED50 for inhibition of germ-tube elongation in the yam compounds for the same organism was below 32 mg/L. The role of the yam compounds at high concentrations in disease resistance is discussed.

Alcohol production in submerged cashew pomace.

The variations in the total titratable acidity, hydrogen ion concentration, reducing sugar, soluble solids and alcohol contents of the supernatant of the submerged cashew pomace in a non-aseptic condition were investigated. The crude fibre content of the pomace was also determined during fermentation. At intervals, the changes in microbial load in both the pomace and its supernatant were examined during the 14-day study. Fifty four percent of the total soluble solids (TSS) was utilised within 7 days of degradation while an increase of about 91% in the total titratable acidity occurred in the cashew pomace within the same period bringing its pH to 3.24. Acid hydrolysis of the pomace accounted for the relative high value of 2.15% TSS on the 8th day. Isolates of the genera Leuconostoc, Lactobacillus, Pediococcus, Aspergillus, Rhizopus and some yeast strains were obtained from the fresh pomace. The fungal colonies constituted about 76% of the population in the cashew pomace. The 86% drop in microbial population of the 8th day biodegraded pomace could be attributed to a decrease in nutrients of the substrate and the inhibitory effect of the organic acids produced during fermentation.

Potentials of biodegraded cashew pomace for cake baking.

The use of biodegraded cashew pomace processed into flour for cake baking was investigated. The physico-chemical changes during the submerged fermentation of the pomace and the organoleptic qualities of the composite cake were also monitored. There was an increase of about 50% in protein content of the pomace after 96 h of fermentation. However, a reduction of about 61% in the total microbial count after 24 h was due to the toxic effect of the organic acids on the microbial cells during fermentation. The cashew flour had high crude fibre (ca. 20-33%) and carbohydrate (ca. 16-47%) values. The composite cake made from a 10:90 combination of 96 h-degraded cashew flour/wheat flour respectively was the most accepted. The cake which had a specific volume of 0.53 ml/g lost 11.1% moisture when 38 g of its batter was exposed to 190 degrees C for 10 minutes. This cake had a calorie value of 293.8/100 g and may be useful in feeding diabetic patients who require low carbohydrate foods.

The effect of beta-sitosterol on spore germination and germ-tube elongation of Aspergillus niger and Botryodiplodia theobromae.

The effect of beta-sitosterol on spore germination and prevention of elongation of germ-tube of Aspergillus niger and Botryodiplodia theobromae was studied. The antifungal activity of the compound showed a percentage inhibition, of the fungal spore germination, of about 40% at a concentration of 50 micrograms/ml while inhibition on the elongation of germ-tubes was as high as 65% at the same concentration. The ED50 for inhibition of germ-tube elongation in A. niger was about 31 micrograms/ml. The role of the compound in disease resistance is discussed.