Bacteriological and chemical studies of on roof reservoirs in Cairo

240 water samples were collected from water-supply treatment stations and on-roof reservoir houses near and far from these stations belonging to four sectors of Cairo [East, West, South and North] during four seasons of the years 1989-1990. These samples were tested for four indicators of fecal pollution, Escherichia coli, Streptococcus faecalis, Pseudomonas aeruginosa and Clostridium perfringens. Bacteriological analysis revealed that total bacterial count at 22C exceeds that was counted at 37C in the examined water samples. Total count of samples withdrawn from houses faraway from stations was higher than samples taken from the nearer ones. A marked seasonal variation in the bacterial counts was observed where count increased in warm summer and decreased in cold winter months. Around 90% of the samples taken from reservoirs showed coliform densities more than 10 cells/100 ml. Different strains of enteropathogenic E. coli responsible for infantile diarrhea were isolated having the serotyping 0142K86, 0124K72 and 0114K90. Chemical analysis of water samples for Na+, K+, Ca++, Mg++, Mn+2, Fe+2, Cu+2, Zn+2, Cl-2, SO4-2, and Cd+ showed that their levels didn't exceed the permissible levels of the Egyptian Standards for drinking water. However, Pb+ is beyond the permissible level. The use of household water filters are not efficient for preventing the passage of bacteria through it

Reduction in aflatoxins during the process of making balady and white bread from contaminated wheat

Reduction in levels of aflatoxins during the process of making balady and white bread from contaminated wheat flour has been investigated. The amounts of aflatoxins was reduced significantly during fermentation and baking [the process] when wheat flour of 82% and 72% extraction were used. Fermentation time of 30 min intervals from 30 to 180 min, followed by baking produced a reduction in AFB1 of 71.5 to 93.3%, in AFB2 of 74.4 to 98.4% in AFG1 of 23 to 63.2% and in AFG2 of 21 to 99% [pH values during fermentation time ranged from 5.98 to 5.46] in active dry yeast bread 82% extraction. However, in the baker's yeast bread [82% extraction] the corresponding reductions were 89.4 to 94% for AFB1, 80.4 to 98.8% for AFB2, 56 to 92.2% for AFG1 and 57 to 92% for AFG2 in the presence of adequate moisture [65%], values of pH ranged from 5.67 to 5.30 during fermentation time. However, the results from active dry yeast bread [72% extraction] gave reductions of 89.5 to 97.1%, 69.8 to C. 100%, 46.2 to C. 100% and 87 to 97% of AFB1, AFB2, AFG1 and AFG2, respectively, where pH values during fermentation time ranged from 5.48 to 5.12. When baker's yeast was used in the preparation of bread [72% extraction], the percentage reduction of toxin after baking ranged from 80.8 to 92% for AFB1, 61.4 to 82.8% for AFB2, 33.8 to 67.4% for AFG1 and 85 to 98% for AFG2, where moisture content was 75%, pH values ranged from 5.59 to 5.20 during fermentation time. Because wheat consumption in Egypt is largely in the form of bread these findings are of importance to public health authorities

Mycotoxins of corn grains

The mycoflora and aflatoxins of corn grains were detected and identified. Six genera and eleven species represented by 90 strains were isolated from non-disinfected grains and 21 strains representing three genera and seven species were recorded from disinfected corn grains. Species of Aspergillus and Rhizopus were the predominant fungi isolated from non-disinfected grains, whereas species of Mucor, Penicillium, Fusarium and Alternaria occurred in low counts. In case of disinfected grains, Rhizopus spp. And Penicillium spp. Were the predominant [23.81%] of the total count, A. niger and A. flavus were 14.28%, while A. oryzea, A. parasiticus and A. ochraceus were 4.76%. Screening the isolate fungal species and strains by the fluorescence technique revealed that three strains of A. flavus and one strain of A. Parasiticus were produced blue fluorescent zones. Bacillus megaterium was used for detecting the aflatoxins produced by the tested microorganisms. A. Parasiticus produced the strongest inhibition effect on B. megaterium than the other fungi screened. Aflatoxins produced by the isolated fungi were confirmed by TLC. Three isolates were identified as A. flavus produced aflatoxin B1 and B2 and one isolated as A. parasiticus produced B1, B2, G1 and G2

Studies on beta-galactosidase from Candida pseudotropicalis II- Production and some properties of the crude enzyme

Production of beta-galactosidase by Candida pseudotropicalis was found to be affected with some growth conditions and nutritional factors. The highest enzyme production was after 48 hours of incubation at pH 7.0 and an incubation temperature of 30 degrees. The carbon source influenced beta-galactosidase production. Higher enzyme yields were obtained when either galactose or lactose was used as the sole carbon source at 6% w/v level. Dibasic ammonium hydrogen phosphate at 4.58 g/l level was the best nitrogen source for enzyme production. The properties of the enzyme have been studied. The maximum activity could be obtained when the crude enzyme was incubated in 0.2 M potassium phosphate buffer at pH 7.0 with ONPG at 30 degrees for 25 minutes. The thermostability and pH stability of the crude enzyme were also studied

Effect of growth conditions on the activity of Kluyveromyces lactis killer toxin

A study has been made of the relationship between incubation temperatures [[20 and 30'C] at different pH values [4,6and 8] and different carbon sources [maltose, mannitol and glycerol] on the growth and toxin production by Kluyveromyces lactis [y-1140]. The highest level of toxin production was observed nearly at a temperature of 30°, when maltose was used as the carbon source rather than mannitol and glycerol. Also the inhibitory effects of K.lactis Killer toxin against sensitive yeasts cells was significantly enhanced when plate assays were performed in media at pH 6 rather than at both pH 4 and pH Sand at an incubation temperature of 30° rather than at 20°. However the interference of K.lactis killer toxin with some test yeasts toxin could not be ignored

Effect of gamma radiation on growth and chemical composition of Azotobacter chroococcum

The total lipids, nucleic acids nitrogen and sugars content of irradiated and non-irradiated Azotobacter chroococcum cells, were compared. Irradiated cells were less efficient in nitrogen fixation and sugar consumption than non-irradiated cells. Nucleic acids and sugars were higher in the control than in irradiated cells but the reverse was true for total lipids at irradiation doses above 2 KGy. Qualitative as well as quantitative differences were reported for phospholipids. Thus each of phosphatidyl glycerol, phosphatidyl ethanolamine, phosphatidic acid, phosphatidyl N-methyl ethanolamine and esterified sterolglycoside was significantly decreased in its relative proportion as the irradiation dose increased. Glucose in a free or bound form was always at a higher levels in control cells as compared to irradiated cells. Rhamnose disappeared from sugar extracts after cell exposure to irradiation doses of more than 1 KGy