Assessment of four different methods for selecting biosurfactant producing extremely halophilic bacteria

Biosurfactants are surface active agents with broad range commercial applications in various industries and have considerable advantages over their chemical counterparts. In this study, drop collapse assay, oil spreading assay, emulsification assay and surface tension measurement were compared for their reliability and ease of use to screen biosurfactant producing six extremely halophilic bacteria isolated from saline soil of Chott El Hodna-M’sila (Algeria), which is considered as a thalassohaline environment. Results from screening methods revealed that, CH2 and CH5 strains are potential candidates for biosurfactant production. Among these, there was a very strong negative linear correlation between the emulsification index and surface tension (rs= - 0.987) and a strong negative linear correlation between the oil spreading technique and surface tension (rs= - 0.971) and a weaker negative correlation between the drop collapse method and surface tension (rs= - 0.807), suggesting that strains highly active in any one of these methods were active in other three methods. As every method has its advantages and disadvantages, a combination of different methods is appropriate for a successful screening.Key words: Biosurfactant, drop collapse, emulsification stability, extremely halophilic bacteria, oil spreading, surface tension

Susceptibility of twelve soft wheat varieties (Triticum aestivum) to Sitophilus granarius (L.) (Coleoptera: Curculionidae)

International audienceThe aim of study is the effect of trophic medium of twelve soft wheat varieties on the biotic potential of S.granarius L. After 3 months of storage under laboratory conditions at 27 ± 2 ° C and 70 ± 5% rh, have reveals that the preferred varieties for development of this species are Hidhab, Mahon Demias, Arfort and Siete Ceros. This latest was found to be the most susceptible. Growth index and loss were highest with 2.08 and 3.27% respectively. Laboratory analysis of the main grain components of the different varieties suggested that the susceptibility of these varieties to S. granarius infestation may be attributed to the high content of protein and low content of carbohydrate compared to resistance varieties

COMPARATIVE STUDY: THE ANTIBACTERIAL ACTIVITY OF MELISSA IN RELATIONS TO OTHER PLANTS IN THE REGION OF SETIF, ALGERIA

Antibacterial properties of essential oils, hydro ethanoicextracts, and aqueous bactericidal extracts of four medical plants, known for their therapeutic effects: Melissa officinalis , Origanum vulgare , Lavandula angustifolia and Mentha piperita. The last three are largely used in Algeria; however, Melissa appears to be less famous. The following work has been executed in a laboratory for the purpose of, yet again, revealing and confirming the benefits of Melissa, and comparing it to other plants. Two microorganisms have been used: Escherichia coli and Staphylococcus aureus. Using the method of Aromatogram with essential oils, Melissa was active the most with zones of inhibition of 8 mm for Escherichia coli and 7 mm for Staphylococcus aureus. Applying the same method for hydro ethanoicextracts, Melissa was effective the most with a 50 mm zone of inhibition for Escherichia coli, followed by mint (40 mm zone of inhibition). As for Staphylococcus aureus, Melissa presented a 14 mm zone of inhibition, while mint displayed a zone of inhibition of 13 mm. Using the bioassay method with essential oils, Melissa has the best effect with a 40 mm zone of inhibition for Escherichia coli and 35mm for Staphylococcus aureus. Always with the same technique but with hydro ethanoicextracts, both Melissa and Mint presented the best inhibition value of 50 mm for Escherichia coli. As for Staphylococcus aureus, Melissa presented a 26 mm zone of inhibition, followed by mint with 24 mm. For the spectrophotometry technique, almost all four plants, witht heir aqueous extracts, presented a antibacterial activity for both bacteria. These results confirm the strong anti- bacterial and bactericidal activity of the four plants, especially Melissa, and their diverse traditional use