Optimization of dextran production from Leuconostoc strains isolated from different dairy products from Ouargla region Algeria

2022 ◽  
Vol 11 (6) ◽  
pp. 690-699
Author(s):  
M'hamed Bouricha ◽  
Roukia Hammoudi ◽  
Soumia Djelloul Daouadji ◽  
Samia Bissati Bouafia ◽  
Mahfoud Hadj Mahammed ◽  
...  
Keyword(s):  
Yeast Extract ◽  
Dairy Products ◽  
Assay Method ◽  
Total Sugars ◽  
Commercial Use ◽  
Physiological And Biochemical Characteristics ◽  
Good Production ◽  
Sucrose Medium ◽  
Physiological And Biochemical ◽  
Better Than

Leuconostoc (Ln) sp. belongs to a group of lactic acid bacteria, which has the capacity to produce dextran (an exopolysaccharides) in the presence of su-crose. dextran is industrially important, it was the first microbial exopolysac-charide affirmed for commercial use. This study aimed to optimize the pro-duction of the synthesized dextran by Ln strains species isolated from differ-ent dairy products. Morphological, cultural, physiological and biochemical characteristics were employed to identify 23 isolated strains. We have identi-fied the species: Ln. gelidum, Ln. carnosum, Ln. citreum, Ln. fallax, Ln. mesen-teroides subsp mesenteroides, Ln. mesenteroides subsp dextranicum, Ln. mesenteroides subsp cremoris. 20 strains had the capacity to produce dex-tran from sucrose. The precipitation and quantification of EPS on MRSs (Mark rogosa et sharpe sucrose) medium revealed a difference between the strains, by the total sugars assay method, the amount of EPS varied between 0.63 ± 0.19 and 2.41 ± 0.17 g / L of strains LnF70 and LnC1 (isolated from goat's milk), respectively. The dextran production from MRSs medium was better than from liquid MSE. The optimization of production on MRSs medi-um with different concentration of glucose, yeast extract and sucrose showed that the strains had good production with a concentration of 2% glucose, 0.3% yeast extract and 10% sucrose.

Assessment of different selective agar media for enumeration and isolation ofListeriafrom dairy products

1988 ◽  
Vol 55 (4) ◽  
pp. 579-583 ◽  
Author(s):  
Lucas Dominguez ◽  
José Francisco Fernández ◽  
Victor Briones ◽  
José Luis Blanco ◽  
Guillermo Suárez
Keyword(s):  
Dairy Products ◽  
Agar Medium ◽  
Raw Milk ◽  
Superior Performance ◽  
Direct Plating ◽  
Selective Agar ◽  
Natural Microflora ◽  
Agar Media ◽  
The Difference ◽  
Better Than

SummaryDifferent selective agar media were compared for the recovery and isolation of five species ofListeriafrom raw milk and cheese. The selective media examined were Beerens medium, MacBride medium and that described by Dominguezet al.(1984) with 6 mg/1 acriflavine, listeria selective agar medium (LSAM), and LSAM with 12 mg/1 acriflavine (LSAM × 2A); a non-selective yeast glucose Lemco agar was included for comparison. When the difference between listeria and the natural microflora of raw milk and cheese was 102cfu/ml, listeria could be isolated by direct plating on all media tested. When it was lower than 103–104cfu/ml, listeria were isolated by direct plating only on LSAM and LSAM × 2A. When the difference was greater than 104cfu/ml, a previous enrichment was necessary to isolate them. LSAM and LSAM × 2A media performed better than the other media tested for isolating listeria by direct plating and improved their isolation from dairy products. This superior performance was evaluated by the ability of these media to support colony formation of different species ofListeriatested, the easy recognition of these colonies from those formed by other microorganisms and by their capacity to inhibit the natural microflora of these foods.

Roquefortine C Occurrence in Blue Cheese

2001 ◽  
Vol 64 (2) ◽  
pp. 246-251 ◽  
Author(s):  
CARLO FINOLI ◽  
ANGELA VECCHIO ◽  
ANTONIETTA GALLI ◽  
IVAN DRAGONI
Keyword(s):  
Yeast Extract ◽  
Culture Media ◽  
Penicillium Roqueforti ◽  
Blue Cheese ◽  
Penicillium Crustosum ◽  
Sucrose Medium ◽  
Low Toxicity ◽  
Yeast Extract Sucrose ◽  
Roquefortine C

Several strains of Penicillium are used for the production of mold-ripened cheeses, and some of them are able to produce mycotoxins. The aims of the research were the determination of roquefortine C and PR toxin in domestic and imported blue cheeses, the identification of the penicillia used as starter, and the investigation of their capacity for producing toxins in culture media. Roquefortine C was always found in the cheeses at levels ranging from 0.05 to 1.47 mg/kg, whereas the PR toxin was never found. The identification of the fungal strains present in the domestic cheeses included Penicillium glabrum, Penicillium roqueforti, and Penicillium cyclopium in the Gorgonzola “dolce” and Penicillium roqueforti in the Gorgonzola “naturale”; in one case, the presence of Penicillium crustosum was observed. The strains isolated from the foreign cheeses belonged to P. roqueforti. The strains were able to produce between 0.18 and 8.44 mg/liter of roquefortine in yeast extract sucrose medium and between 0.06 and 3.08 mg/liter and less than 0.05 mg/liter when inoculated in milk at 20°C for 14 days and 4°C for 24 days, respectively. Linear relations between production of roquefortine in culture media and cheeses did not emerge. PR toxin ranged from less than 0.05 to 60.30 mg/liter in yeast extract sucrose medium and was produced in milk at 20°C from only one strain. The low levels and the relatively low toxicity of roquefortine make the consumption of blue cheese safe for the consumer.

Comparative Characteristics and Desilicon Ability of 10 Strains of Silicate Bacteria Screened from Different Bauxite Ores

2012 ◽  
Vol 524-527 ◽  
pp. 953-956
Author(s):  
Chan Juan Zhong ◽  
De Si Sun ◽  
Hong Bao ◽  
Hao Chen
Keyword(s):  
Henan Province ◽  
Jiangxi Province ◽  
Biochemical Characteristics ◽  
Physiological And Biochemical Characteristics ◽  
Silicate Bacteria ◽  
Bauxite Ore ◽  
Physiological And Biochemical

Ten strains of silicate bacteria were screened from three bauxite samples in Jiangxi Province and Henan Province in China. The ten strains were determined as B. mucilaginosus according to the results of physiological and biochemical characteristics and desilicon ability. Bioleaching tests showed that the ten strains all can decompose bauxite ore and release silicon from bauxite, but had a large difference of desilicon ability among them.

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