Characterization of lactic acid bacteria isolated from Algerian arid zone raw goats\' milk

Diversity and density of lactic acid bacteria isolated from Algerian raw goats\' milk in arid zones were studied by determination of morphological, cultural, physiological and biochemical characteristics. 206 lactic acid bacterial strains were isolated, with 115 of them belonging to lactic acid cocci and others to the genus, Lactobacillus. The representative species of the total cocci were Lactococcus sp. (76.16%), Streptococcus thermophilus (14.78%) and Leuconostoc sp. (8.6%). The dominating species is Lactococcus lactis subsp. Lactis. Lactobacilli species found in local raw goats\' milk and their proportion were: Lb. curvatus (25.25%), Lb. helviticus (10.98%), Lb. plantarum (9.89%), Lb. reuteri (9.89%), Lb. casei (7.69%), Lb. brevis (5.49%), Lb. bulgaricus (5.49%) Lb. paracasei (4.39%) and Lb. acidophilus (2.19%). Key Words: Lactic acid bacteria, raw milk, goat, arid zones, identification. African Journal of Biotechnology Vol.3(6) 2004: 339-34

Boundedness and Square Integrability in Neutral Differential Systems of Fourth Order

The aim of this paper is to study the asymptotic behavior of solutions to a class of fourth-order neutral differential equations. We discuss the stability, boundedness and square integrability of solutions for the considered system. The technique of proofs involves defining an appropriate Lyapunov functional. Our results obtained in this work improve and extend some existing well-known related results in the relevant literature which were obtained for nonlinear differential equations of fourth order with a constant delay. The obtained results here are new even when our equation is specialized to the forms previously studied and include many recent results in the literature. Finally, an example is given to show the feasibility of our results

A physical model of the photo- and radiation-induced degradation of ytterbium-doped silica optical fibres

International audienceWe propose a model to describe the photo-or/and the radiation-induced darkening of ytterbium-doped silica optical fibers. This model accounts for the well-established experimental features of photo-darkening. Degradation behaviors predicted for fibers pumped in harsh environments are also fully confirmed by experimental data reported in the work by Duchez et al. (this proceeding), which gives a detailed characterization of the interplay between the effects of the pump and those of a superimposed ionizing irradiation (actual operation conditions in space-based applications for instance). In particular, dependences of the darkening build-up on the pump power, the total ionizing dose and the dose rate are all correctly reproduced. The presented model is a 'sufficient' one, including the minimal physical ingredients required to reproduce experimental features. Refinements could be proposed to improve, e.g., quantitative kinetics

The reproducibility of random amplified polymorphic DNA (RAPD) profiles of Streptococcus thermophilus strains with XD9, M13 and OPI-02 MOD primers

We optimized the conditions for generating random amplified polymorphic DNA (RAPD) profiles of Streptococcus thermophilus strains by using the polymerase chain reaction (PCR). Several factors can cause the amplification of false and non reproducible bands in the RAPD profiles. We tested three primers, OPI-02 MOD, M13 and XD9 throughout this study. In addition, we tested different concentrations of primer, DNA template and Taq DNA polymerase. We adjusted the ratio of the primer to DNA template. All the three primers yielded reproducible profiles on several days, under optimized concentrations of components and cycling parameters used. The bands of such profiles probably corresponded to perfect annealing sites amplified with good efficacy or present in multiple copies in the genome. Five months later, repeated experiment generated identical bands. However, extra faint bands were detected with M13 and XD9 primers, possibly, corresponding to nonspecific binding resulting from slight variation in temperature or calibration of the thermocycler. Therefore, OPI-02 MOD was determined as the most reliable primer for reproducible profiles of S. thermophilus strains.Key words: Streptococcus thermophilus, random amplified polymorphic DNA (RAPD), DNA template, Taq DNA polymerase, OPI-02MOD, XD9, M13, optimization, reproducibility

A new manometric method for measuring carbon dioxide production by dairy starter culture: a case of Leuconostoc mesenteroides

This paper describe a technique for carbon dioxide (CO2) measurement based on the displacement of acidifying liquid in burette at constant pressure. It was adapted to allow the growth of Leuconostoc sp. on semi-synthetic media and milk. A highly precise measurement was obtained using the chemical reaction of sodium carbonate with hydrochloric acid. This method has been proven to present an excellent linear response from 0 to 0.895 mM of CO2 with a high sensitivity. With cultures in milk medium, kinetics of CO2 evolved by Leuconostoc mesenteroides subsp. dextranicum L4 were higher than L. mesenteroides subsp. mesenteroides 19D and L. mesenteroides subsp. cremoris Ec195 grown on milk.. The use of L. mesenteroides subsp. dextranicum L4 and their variants Lac(-)Cit(+), Lac(+)Cit(-) and Lac(-)Cit(-) showed that the CO2 production correlated to the substrate utilization. The curve of CO2 measured was close to the amount of CO2 calculated from lactose and citrate used. The CO2 production rate was higher with the parental strain (6.5 mM/ h) than with the variants. The amount of CO2 produced was always close to the theoritical value, and was also correlated to the growth rate and substrates utilization by L. mesenteroides. The volume of CO2 produced by Leuconostoc in milk was highly correlated with the D-lactate production (r = 0.995). This method could be used routinely for the evaluation and the selection of bacteria having potential ability for CO2 production.Keywords: Leuconostoc sp., CO2 production, lactic acid, mil

The interplay between photo-and radiation-induced darkening in ytterbium-doped fibres

International audienceThis letter demonstrates a remarkable interplay between photo-and radiation-induced darkening of ytterbium-doped alumino-silica optical fibres operated in amplifying conditions and harsh environments (as e.g. in space-based applications). Influences of the pump power, ionizing dose and dose rate on this interaction are characterized. The pump is capable of accelerating or slowing-down the radiation-induced darkening build-up depending on the ionizing dose. The steady state photo-radio-darkening level is independent of the dose and at least equal to the equilibrium level of pure photo-darkening. This lower limit is notably reached at low dose rates, including those encountered in space. We therefore argue that photo-resistant ytterbium-doped fibres will resist against a space mission, whatever the dose

Identification of cultivable bifidobacterium species isolated from breast-fed infants feces in West-Algeria

Gastrointestinal microflora exerts a high impact on its host mainly by performing a great variety of metabolic activities, protecting the host against colonization by pathogen and stimulating the gut immune system. The integration of bifidobacteria in dairy products is of interest for reinstalling the intestinal microflora. The mother\'s milk is a prebiotic factor which stimulate the bifidobacteria growth in vivo. Results obtained in west Algeria area show that the number of bifidobacteria reach 26 109 cfu/g in breast-fed infant feces. The microbiological, fructose–6-phospho-ketolase and the biochemical tests have revealed Bifidobacterium strains. The most prevalent isolates belong to the species Bifidobacterium longum (75%) and Bifidobacterium breve (25%). In order to evaluate the potential use as a starter culture, the occurrence of some selected properties such as growth and survival in fermented milk were investigated. These strains have a fast growth in glucose, galactose and lactose media compared to reference species. All isolates studied are sensitive to the pH 8. the B. breve strain support the conservation conditions in pure culture better than in mixed culture with Streptococcus thermophilus or Lactobacillus acidophilus.African Journal of Biotechnology Vol. 4 (5), pp. 422-430, 200

EFFECT OF WATER STRESS ON YIELD AND ITS COMPOSANTSOF SOME CEREALS IN ALGERIA

In this study an attempt is made to study agronomic characters of adaptation to drought in yield and its composants under dry land and in irrigated conditions:25 barley varieties ( 16 of French origin, 7 of Syrian origin and 2 of Algerian origin ), 1 variety of durum wheat ( DURELLE, Fance) and 1 variety of triticale (CLERCAL, France)were compared during two successive years 2003/2004. A net effect on most agronomic characters was noticed, with the exception of the thousand –kernel weight in the second year trial. The moderate water defi cit ( conditions in the Ouest Algerian zone) allowed French varieties to perform better in both conditions than Algerian and Syrian varieties because they are considered to be tolerante to drought

Study of the Antimicrobial and Probiotic Effect of Lactobacillus Plantarum Isolated from Raw Goat's Milk from the Region of Western Algeria

The evolution from a spontaneous fermentation to a directed one is realised with selected lactic starters which give many dairy products processing various organoleptic characters. The integration of new lactic acid bacteria strains isolated from diverse ecosystems is now used to increase the duration of bio-preservation of dairy products. Moreover, some lactic acid bacteria probiotic activity is exploited to produce functional food. The aim of this study is the research of the possible probiotic and technological potential with some preventive and therapeutic characteristics of some Lactobacillus species isolated from Algeria