Chemical composition and antioxidant and antibacterial properties of the essential oils extracted from Citrus sinensis peels by hydrodistillation and microwave methods.

The present study is devoted to evaluate in vitro the chemical composition and the antioxidant and antibacterial properties of essential oils (Eo) extracted by hydrodistillation (HD) and microwave (MW) from the plant peels of Citrus sinensis. The extraction provided yields of 0.26% and 0.02%, respectively. The essential oils were analyzed by GC-MS whose major component is limonene that has a remarkable percentage (78.192% and 58.6%, respectively) for the essential oil extracted by HD and MW. The results of the antioxidant potential were noticeable in each of the essential oils with a higher priority to that extracted by hydrodistillation. The evaluation of the antioxidant power by the free radical scavenging method (DPPH) showed that the essential oils studied have good antioxidant activity, especially for the oil extracted by HD having presented an IC50 of (13.07 ± 0.169) mg/ml, while BHT and ascorbic acid showed very potent and effective anti-free radical activity with IC50 of the order of (19.54 ± 0.32) µg/ml and (1.17 ± 0.05) µg/ml respectively. According to the ß-carotene/linoleic acid test, the oxidation of ß-carotene was effectively inhibited by the two essential oils of Citrus sinensis peels with a percentage of inhibition of (56.46 ± 0.76) % and (31.39 ± 1.49) % respectively for HD and MW. Eo extracted by HD is more active than ascorbic acid (15.43%). In the antibacterial test, the activity was evaluated by the disc-diffusion method, the two types of sweet orange essential oils inhibited the growth of five bacterial strains out of six: The best activity was obtained against E. coli, Listeria monocytogenes, and Agrobacterium with a diameter of the zone of inhibition between 70 and 84 mm, with the exception of the strain of Bacillus subtilis, there is no zone of inhibition has been observed.

Antifungal effects of selected menthol and eugenol in vapors on green coffee beans during long-term storage.

Nowadays, coffee (Coffea Arabica L.) is among the most significant agricultural products of the world and drinking coffee has become one of the most popular habits in the world. The main contamination of stored coffee beans is related with the mycotoxin produced by the toxigenic fungi belonging the genus Aspergillus. Fungal infection followed by mycotoxin biosynthesis in coffee results in notable financial losses. subsequent mycotoxin biosynthesis in coffee leads to major economic losses. Complications ranging from mild to severe can be caused by the mycotoxins produced by this genus. The aim of this investigation was to determine the effect of menthol and eugenol on Aspergillus parasiticus (CBS 100926T) growth, spore germination, and their potential use as green coffee beans preservative during long-term storage (12 months). The minimum inhibitory concentrations (MICs) values of the menthol and eugenol were recorded to completely inhibit the growth of A. parasiticus in 400 µg/ml and 300 µg/ml, respectively. Both reduced spore germination by 9.33% and 5.66% at 300 µg/ml and 200 µg/ml, respectively. They showed efficacy in fumigated green coffee beans sample during the storage for up to 12 months providing an increase in the protection level of 62.5% for menthol and 73.21% for eugenol against the A. parasiticus contamination. This suggests that menthol and eugenol could be used as good alternatives for decreasing the deteriorations due to the fungal infections in green coffee beans during long-term storage.

Characterization by polyphasic approach of some indigenous halophilic archaea of Djelfa's rock salt "Hadjr el Meelh", Algeria.

Background and Objectives: Hadjr El Melh of Djelfa is an example of hypersaline ecosystems, which can harbor a wide variety of microorganisms under hostile physicochemical conditions. Given the importance of the study of halophilic microorganisms present there in terms of fundamental and applied microbiology, the purpose of this study was to characterize some halophilic archaea isolated from the brines of this environment. Materials and Methods: Eight water samples were chosen randomly and collected for physicochemical and microbiological analyses. Isolation of halophilic archaea was carried out by membrane filter technique. Ten strains were identified by polyphasic approach and tested for enzymes production. Results: Water samples of Djelfa's rock salt were slightly acidic to neutral in pH (6.55-7.36) with salinity ranging from 258.68 g/l to 493.91 g/l. Phenotypic, biochemical, taxonomic and phylogenetic characteristics indicated that all strains were classified within the family of Halobacteiaceae. Based on the comparison of DNA sequences encoded 16S rRNA, it was determined that seven strains were affiliated to the genus Haloarcula, two strains were related to the genus Halobacterium and one strain within the genus Haloferax. Production of different enzymes such as protease, amylase, esterase, lipase, lecithinase, gelatinase and cellulase on solid medium indicated that one strain (S2-2) produced amylase, esterase, lecithinase and protease. However, no strains showed cellulolytic or lipolytic activity. Gelatinase was found in all tested strains. Conclusion: This report constitutes the first preliminary study of culturable halophilic archaea recovered from the brines of Djelfa's rock salt with a promising enzymatic potential in various fields of biotechnology.

Actinobacteria Associated with Vineyard Soils of Algeria: Classification, Antifungal Potential Against Grapevine Trunk Pathogens and Plant Growth-Promoting Features.

Grapevine trunk diseases (GTDs) are among the most destructive diseases of vineyards worldwide, including Algeria. In the fungal complex involved in GTD symptoms, referred as grapevine trunk-pathogens, Paeomoniella chlamydospora and Phaeoacremonium minimum have a determining infecting role as pioneer fungi. Due to the lack of efficiency of conventional disease management practices, a search for alternative strategies, such as biocontrol, is needed. Taking the approach of looking for biocontrol candidates in the environment surrounding the plant, the present study explored actinobacteria diversity within vineyard soils of six grape-producing regions in Algeria. Based on their 16S rRNA gene sequence, identification and phylogenic analysis were performed on the 40 isolates of actinobacteria obtained. Forty percent of strains were attached to Streptomyces, including two evidenced new species, and 32.5% were affiliated to Saccharothrix. The other less represented genera were Actinoplanes, Nocardia, Nocardiopsis, Lentzea, Nonomuraea, Promicromonospora, Saccharopolyspora and Streptosporangium. Screening based on antagonistic and plant growth promotion (PGP) abilities of the strains showed that 47.5% of the isolates exhibited appreciable antagonistic activities against both Pa. chlamydospora and Pm. minimum, with the two best strains being Streptomyces sp. Ms18 and Streptomyces sp. Sb11. Screening for plant growth promoting properties demonstrated that majority of the strains were able to produce indole acetic acid, siderophores, ammonia, ACC deaminase, cellulase and amylase, and fix N2. Through a PGP-traits-based cluster analysis, the most interesting strains were highlighted. Taking into account both antagonistic and PGP properties, Streptomyces sp Sb11 was selected as the most promising candidate for further evaluations of its efficiency in a GTDs context.