The intensive use of nitrogen fertilizers in Algeria caused a pollution of the waters by nitrates. This concentration reached in the region of Collo （Wilaya of Skikda, Algeria） 570 mg/L, which is beyond the WHO stan...The intensive use of nitrogen fertilizers in Algeria caused a pollution of the waters by nitrates. This concentration reached in the region of Collo （Wilaya of Skikda, Algeria） 570 mg/L, which is beyond the WHO standard （50 mg/L）. This has negative consequences on human health （Methemoglobinemia） and on the environment （eutrophication）. In our works, we studied the elimination of this pollution with the use of a mixed culture of microorganisms. We replaced the standard synthetic carbon source and the nutritious medium by date powder. This contains minerals and sugars that can enhance bacterial growth. Our study showed that the effectiveness of denitrification is proportional to bacterial growth. It rises exponentially after a latency period of 8 hours. During the reaction of degradation we noticed a rise in pH in our engine, it moved from 7.00 to 8.38. In studying the influence of initial pH on the denitrification of the microorganisms, we observed that the ion hydrogen concentration modified the growth rate of bacteria and degradation of nitrates. An acid pH, the reduction of nitrates is incomplete; this is accounted for the accumulation of nitrous and nitric oxide that interferes in the reaction of denitrification. The velocity of the nitrate reduction is less important in an acid pH （0.0096 g.L^-l.h^-1） than in a basic pH （0.013 g.L^-1.h^-1）. The denitrification is optimal at temperature 35 ℃ for a ratio C/N = 2.5. In these conditions 95% of the nitrate initial quantity is eliminated after approximately 100 hour treatment.展开更多
The presence of Geotrichum candidum in fresh cheese is considered to be a contaminant and may lead to the product spoilage. The oxidative yeast Candida maltosa firstly isolated from the spoiled fruit yoghurt surface i...The presence of Geotrichum candidum in fresh cheese is considered to be a contaminant and may lead to the product spoilage. The oxidative yeast Candida maltosa firstly isolated from the spoiled fruit yoghurt surface in Slovakia belongs to the yeast contaminants of fermented dairy products. The effect of the cultivation temperature and the presence of Lactobacillus rhamnosus GG on the growth of dairy spoilage yeasts in ultrapasteurized milk was studied. Addition of Lb. rhamnosus GG in milk caused partial inhibition of the yeast growth dynamics in milk. The water activity transformation of Gibson model after the temperature modification （Tw） was applied to model growth dynamics of G. candidum in pure and mixed culture, respectively： In μ_Gc=-5.0376＋2.7281 Tw-0.4217Tw^2, lnμ_CC_LGG=-6.0033＋3.2996Tw-0.5553Tw^2. The effect of different Lb. rhamnosus GG addition and the incubation temperature on the C. maltosa growth dynamics was analyzed by linear regression methodology and described by using following equations： lnGr1=-5.3674＋0.2341T＋0.2599N0-0.0032T^2-0.0492N0^2-0.0068TN0 and lnGr11=-9.5457-0.249T＋2.3823N0 ＋0.0099T^2-0.2324N0^2＋0.0098TN0 Based on the principles of predictive microbiology, the mutual microbial interactions and potential application of the lactobacillus strains in food protection are discussed.展开更多
文摘The intensive use of nitrogen fertilizers in Algeria caused a pollution of the waters by nitrates. This concentration reached in the region of Collo （Wilaya of Skikda, Algeria） 570 mg/L, which is beyond the WHO standard （50 mg/L）. This has negative consequences on human health （Methemoglobinemia） and on the environment （eutrophication）. In our works, we studied the elimination of this pollution with the use of a mixed culture of microorganisms. We replaced the standard synthetic carbon source and the nutritious medium by date powder. This contains minerals and sugars that can enhance bacterial growth. Our study showed that the effectiveness of denitrification is proportional to bacterial growth. It rises exponentially after a latency period of 8 hours. During the reaction of degradation we noticed a rise in pH in our engine, it moved from 7.00 to 8.38. In studying the influence of initial pH on the denitrification of the microorganisms, we observed that the ion hydrogen concentration modified the growth rate of bacteria and degradation of nitrates. An acid pH, the reduction of nitrates is incomplete; this is accounted for the accumulation of nitrous and nitric oxide that interferes in the reaction of denitrification. The velocity of the nitrate reduction is less important in an acid pH （0.0096 g.L^-l.h^-1） than in a basic pH （0.013 g.L^-1.h^-1）. The denitrification is optimal at temperature 35 ℃ for a ratio C/N = 2.5. In these conditions 95% of the nitrate initial quantity is eliminated after approximately 100 hour treatment.
文摘The presence of Geotrichum candidum in fresh cheese is considered to be a contaminant and may lead to the product spoilage. The oxidative yeast Candida maltosa firstly isolated from the spoiled fruit yoghurt surface in Slovakia belongs to the yeast contaminants of fermented dairy products. The effect of the cultivation temperature and the presence of Lactobacillus rhamnosus GG on the growth of dairy spoilage yeasts in ultrapasteurized milk was studied. Addition of Lb. rhamnosus GG in milk caused partial inhibition of the yeast growth dynamics in milk. The water activity transformation of Gibson model after the temperature modification （Tw） was applied to model growth dynamics of G. candidum in pure and mixed culture, respectively： In μ_Gc=-5.0376＋2.7281 Tw-0.4217Tw^2, lnμ_CC_LGG=-6.0033＋3.2996Tw-0.5553Tw^2. The effect of different Lb. rhamnosus GG addition and the incubation temperature on the C. maltosa growth dynamics was analyzed by linear regression methodology and described by using following equations： lnGr1=-5.3674＋0.2341T＋0.2599N0-0.0032T^2-0.0492N0^2-0.0068TN0 and lnGr11=-9.5457-0.249T＋2.3823N0 ＋0.0099T^2-0.2324N0^2＋0.0098TN0 Based on the principles of predictive microbiology, the mutual microbial interactions and potential application of the lactobacillus strains in food protection are discussed.
