Biopreservation of Fresh Sardines (Sardina pilchardus) Using Lactiplantibacillus plantarum OV50 Isolated from Traditional Algerian Green Olives Preparations.

Lactiplantibacillus plantarum OV50 is a novel strain that was isolated from Algerian olives. Prior to its use as a natural biopreservative, OV50 underwent characterization for various functions. OV50 shows no proteolytic, lipolytic, or hemolytic activity. In addition, it is non-cytotoxic to eukaryotic cells and does not exhibit acquired antibiotic resistance. OV50 was tested with Pseudomonas aeruginosa ATCC 27835, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 8739, and Vibrio cholerae ATCC 14035 in a sardine based-medium at 37 °C and 7 °C. At 37 °C, OV50 completely inhibited the growth of these foodborne pathogens for a maximum of 6 h. At 7 °C, it suppressed their growth for a maximum of 8 days, except for S. aureus ATCC 6538, whose growth was reduced from 4 to 2 log CFU/mL. Microbiological counts, total volatile basic nitrogen (TVB-N), and peroxide values (PV) concentrations were determined in fresh sardines inoculated with OV50 and kept at 7 °C for 12 days. The inoculated sardines showed a significant reduction in TVB-N levels at D8 (34.9 mg/100 g) compared to the control (59.73 mg/100 g) and in PV concentrations at D4 (6.67 meq/kg) compared to the control (11.44 meq/kg), as well as a significant reduction in the numbers of Enterobacterales, Coliforms, Pseudomonas spp., Vibrio spp., and S. aureus At D8 and D12 compared to the control. Taken together, these results indicate that OV50 can improve the microbiological safety, freshness, and quality of sardines.

Peroxidase-producing actinobacteria from Algerian environments and insights from the genome sequence of peroxidase-producing Streptomyces sp. S19 / Actinobacteria productora de peroxidasa de ambientes argelinos y perspectivas de la secuencia genómica de Streptomyces sp. S19

Unique environments often serve as a source of novel microorganisms with novel chemistries. In this study, telluric samples collected from different regions of Algeria were processed for the isolation of novel peroxidase-producing actinobacterial strains. An agar-based screening identified 45 isolates with the ability to produce peroxidase. The 16S rRNA gene sequencing showed that most of the strains belong to the genus Streptomyces. Optimization of cultivation conditions was performed for the top five peroxidase-producing strains. Apart from strain 36 (optimal growth temperature of 30 °C) and strain 45 (optimal medium pH of 6.0), the strains exhibited optimal peroxidase production when cultivated for 5 days at 37 °C and in a medium at pH 7.0. Extracellular peroxidase production was induced by ferulic acid in three of the five strains, while the presence of canola lignocellulosic waste (CLW) induced peroxidase production in all strains. Strain 19 (S19) was selected for further optimization and the extracellular peroxidase purified using acid and acetone precipitation, followed by size exclusion chromatography. The purified fraction showed a single band on the polyacrylamide gel with an estimated molecular weight of 21.45 kDa. Genome analysis confirmed the assignment of S19 to the genus Streptomyces, the presence of genes encoding for peroxidases, and the presence of genes encoding for carbohydrate-active enzymes. The presence of biosynthetic gene clusters potentially encoding for biosurfactants further highlighted the great biotechnological potential of the strain.(AU)

Peroxidase-producing actinobacteria from Algerian environments and insights from the genome sequence of peroxidase-producing Streptomyces sp. S19.

Unique environments often serve as a source of novel microorganisms with novel chemistries. In this study, telluric samples collected from different regions of Algeria were processed for the isolation of novel peroxidase-producing actinobacterial strains. An agar-based screening identified 45 isolates with the ability to produce peroxidase. The 16S rRNA gene sequencing showed that most of the strains belong to the genus Streptomyces. Optimization of cultivation conditions was performed for the top five peroxidase-producing strains. Apart from strain 36 (optimal growth temperature of 30 °C) and strain 45 (optimal medium pH of 6.0), the strains exhibited optimal peroxidase production when cultivated for 5 days at 37 °C and in a medium at pH 7.0. Extracellular peroxidase production was induced by ferulic acid in three of the five strains, while the presence of canola lignocellulosic waste (CLW) induced peroxidase production in all strains. Strain 19 (S19) was selected for further optimization and the extracellular peroxidase purified using acid and acetone precipitation, followed by size exclusion chromatography. The purified fraction showed a single band on the polyacrylamide gel with an estimated molecular weight of 21.45 kDa. Genome analysis confirmed the assignment of S19 to the genus Streptomyces, the presence of genes encoding for peroxidases, and the presence of genes encoding for carbohydrate-active enzymes. The presence of biosynthetic gene clusters potentially encoding for biosurfactants further highlighted the great biotechnological potential of the strain.

Heterologous Biosynthesis of Five New Class II Bacteriocins From Lactobacillus paracasei CNCM I-5369 With Antagonistic Activity Against Pathogenic Escherichia coli Strains.

Lactobacillus paracasei CNCM I-5369 isolated from a traditional Algerian dairy product produces extracellular inhibitory substances, namely, bacteriocins, which are active against a panel of pathogenic Escherichia coli strains. This activity was observed only at a narrow pH 4.5-5, and resulted to be heat stable and sensitive to the action of proteolytic enzymes, which indicate a proteinaceous nature. This new strain has a genome of 2,752,975 bp, with a 46.6% G + C ratio and contains at least 2664 coding sequences. The Bagel software analysis identified five open reading frames (ORFs) that are translated to new class II bacteriocin. Each ORF was cloned in frame with a His-tag tail and expressed in E. coli BL21 (DE3) (pLysS) strain. Of note, each fusion protein carrying any of these ORFs at the C- or N-terminal position resulted to be active against E. coli 184 strain used as target organism. This manuscript reports the first multi-bacteriocinogenic strain producing five new class II bacteriocins with activity against Gram-negative bacilli (GNB), namely, E. coli. Heterologous expression and activity of each new class II bacteriocin were demonstrated.

Characterization and purification of a bacteriocin from Lactobacillus paracasei subsp. paracasei BMK2005, an intestinal isolate active against multidrug-resistant pathogens.

A strain of Lactobacillus paracasei subsp. paracasei BMK2005 isolated from healthy infant faeces has shown a remarkable antibacterial activity against 32 bacterial pathogenic strains of human clinical isolates. Among them, 13 strains belonging to species of Escherichia coli, Citrobacter freundii, Citrobacter diversus, Klebsiella oxytoca, Enterobacter cloacae and Pseudomonas aeruginosa were resistant to Cefotaxime (CTX) and Ceftazidime (CAZ), and 4 strains of Staphylococcus aureus were resistant to Methicillin (MRSA). This antibacterial activity was attributed to a bacteriocin designated as Paracaseicin A. It was heat-stable up to 120°C for 5 min and active within the pH range of 2-5. Its activity was lost when treated with proteases, which reveals its proteinaceous nature. This bacteriocin was successfully purified only by two steps of reversed phase chromatography. Its molecular mass, determined by mass spectrometry analysis, was 2,462.5 Da. To our knowledge, the present study is the first report on characterization and purification of a bacteriocin, produced by a L. paracasei subsp. paracasei strain exhibiting an antibacterial activity against various multidrug-resistant species of Gram-positive and Gram-negative bacteria, which reveals its potential for use in prevention or treatment of infections caused by multidrug-resistant species especially in cases of antibiotics-associated diarrhea (AAD).