RESUMENAislamiento de bacterias del ácido láctico para su posible uso en la fermentación de aceitunas verdes argelinas.Este estudio se emprendió con el objetivo de obtener bacterias del ácido láctico con capacidad para utilizarse como cultivo iniciador en la fermentación de aceitunas. Por esta razón, 32 cepas de bacterias del ácido láctico procedentes de fermentaciones espontáneas de aceitunas verdes se caracterizaron e identificaron en función de criterios morfológicos y bioquímicos. Catorce cepas se identificaron como Lactococcus lactis, 11 cepas como Lactobacillus plantarum y 7 cepas como Enterococcus sp. De las 18 cepas que se examinaron para detectar actividades antagóni-cas, se encontró que 3 cepas de Lactobacillus plantarum y una de Enterococcus sp. mostraban zonas de inhibición contra 5 cepas indicadoras de bacterias del ácido láctico aisladas en este estudio. El sobrenadante libre de células Lactobacillus plantarum OL9 fue activo contra diversas bacterias Gram-positivas (Lactobacillus, Enterococcus y Propionibacterium) y contra una cepa de bacteria Gram-negativa relacionada con alteraciones (Erwinia). PALABRAS-CLAVE: Aceitunas -Antagonismo -Bacterias del ácido láctico -Identificación. SUMMARY Isolation of lactic acid bacteria for its possible use in the fermentation of green algerian olives.This study was undertaken with the aim of obtaining lactic acid bacteria with the ability to ferment olives for possible use as starter cultures. For this reason, 32 isolates of lactic acid bacteria isolated from the spontaneous fermentation of green olives were characterized and identified on the basis of morphological and biochemical criteria. 14 of them were identified as Lactococcus lactis, 11 isolates as Lactobacillus plantarum and 7 isolates as Enterococcus sp. Of the 18 isolates examined for antagonistic activity, 3 isolates of Lactobacillus plantarum and one isolate of Enterococcus sp. were able to give distinct zones of inhibition against 5 indicator strains of lactic acid bacteria isolated in this study. Cell free supernatant of Lactobacillus plantarum OL9 was active against Gram-positive bacteria (Lactobacillus, Enterococcus and Propionibacterium) and also against one Gram-negative bacteria strain of spoilage significance (Erwinia).

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Twenty-three strains of lactic acid enterococci isolated from dromedary raw milks in Southern Algeria were investigated for their proteolytic activity and ability to produce biogenic amines by decarboxylating amino acids: histidine, tyrosine and ornithine. All strains tested displayed proteolytic activities, but none of them were able to produce detectable biogenic amines in the usual adequate laboratory media, namely, Joosten and Northolt medium and Leuschner medium. Polymerase chain reaction experiments indicate a positive correlation between the absence of the hdc and odc genes and the lack of histamine and putrescine production for all tested strains. By contrast, all strains appeared to possess tdc gene, but no correlation was found with a negative expression of tyrosine decarboxylase. PRACTICAL APPLICATIONSIn foods, biogenic amines are mainly generated by decarboxylation of the corresponding amino acids through substrate-specific enzymes of the microorganisms present in this environment, particularly histidine, tyrosine, lysine, ornithine and arginine, and the capability of enterococci and some other lactic acid bacteria to produce biogenic amines has been described. For this purpose, several qualitative and quantitative methods to determine biogenic amines production by these microorganisms have been developed. There is great interest to identify and to characterize the bacteria strains intended for an industrial use and to verify if they are potentially able to produce biogenic amines in order to prevent it's synthesis and limit the poisoning risk.

The analysis of coccal lactic acid bacteria (CLAB) strains for their competence in polysaccharide production has been given proper attention as texturing and thickening agents. The characterization of these strains has been performed from two natural environments (camel milk and red meat). All the isolates were evaluated for exopolysaccharides (EPS) production on certain solid medium and ruthenium red milk agar plate. Based on their EPS-producing colony phenotype, five strains were chosen giving an important white-color and mucoid aspect on sucrose-based media which being the best for detecting the EPS. Quantitative estimation of EPS indicated that amount of this polymer rendered more than 400 mg/L and the apparent viscosity ranged from 2.1 to 2.9 milli Pascals per second (mPa.s). Therefore, there was not found a close relationship between the amount of EPS and the apparent viscosity. Three strains were selected for their significant production of EPS. For protein assay, a low content of protein was obtained on crude polymer revealing the quality of EPS extracts.

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RESUMENDetección y actividad de plantaricina OL15, una bacteriocina producida por Lactobacillus plantarum OL15 aislado de aceitunas fermentadas de Argelia.Lactobacillus plantarum OL15, aislado de aceitunas verdes argelinas, produce un compuesto antimicrobiano en el medio de cultivo, observándose un efecto inhibidor frente a otras cepas de Lactobacillus, Lactococcus y Propionibacterium. Dicha actividad desaparece completa o parcialmente después del tratamiento con enzimas proteolíticas, es estable al pH en el rango de 3,0 a 8,0 y es, asimismo estable al calor incluso después de someterla a un proceso térmico de 121 o C durante 15 minutos. La bacteriocina pasa a través de membranas de celulosa de corte molecular de 1000.000 pero no a través de las de 10.000. PALABRAS-CLAVE: Aceitunas de mesa -Bacterias del ácido láctico -Bacteriocina -Inhibición -Lactobacillus plantarum. SUMMARY Detection and activity of plantaricin OL15 a bacteriocin produced by Lactobacillus plantarum OL15 isolated from Algerian fermented olives.Lactobacillus plantarum OL15 previously isolated from Algerian fer mented green olives produces antimicrobial conpounds in its culture medium. Inhibitory action against other strains of Lactobacillus, Lactococcus, and Propionibacterium was observed. Activity was completely or partially inactivated by proteolytic enzymes, stable at pH values ranging from 3.0 to 8.0, and heat stable even after autoclaving at 121 o C for 15 min. The bacteriocin activity was able to pass through cellulose membranes with 100,000 but not through 10,000 molecular weight cut-off.