Screening of potential biosurfactant-producing bacteria isolated from seawater biofilm

Seawater represents a specific environment harboring complex bacterial community which is adapted to harsh conditions. Hence, biosurfactant produced by these bacteria under these conditions have interesting proprieties. The screening of biosurfactant producing strains isolated from seawater biofilm was investigated. Specific media, which have been reported to induce biosurfactant production, were used to prepare bacterial cultures and four methods; drop collapse, blue agar, blood-agar lysis and emulsification index, were applied to screen for biosurfactant production. 16 culturable, aerobic bacterial strains were isolated from biofilm in this study. Among these isolates, nine strains were Gram-positive and seven were Gram-negative. However the majority of the biosurfactant producer strains were Gram-negative belonging to different genera according to " a multitube micromethod for identification of bacteria (API system gallery)". Some of the isolated genera such as: Bacillus, Pseudomonas, Micrococcus, Neisseria, and Aeromonas are well known as biosurfactant producers, while other genera, mainly Staphylococcus, Chrysomonas and Photobacterium, were described for the first time as biosurfactant producers in this work.Keywords: Biosurfactant, seawater biofilm, bacteri

Use of gas chromatography-mass spectrometry techniques (GC-MS, GC-MS/MS and GC-QTOF) for the characterization of lipid photooxidation and autoxidation products in senescent autotrophic organisms

International audienceThis paper reviews applications of gas chromatography-mass spectrometry techniques for the characterization of lipid photooxidation and autoxidation products in senescent phototrophic organisms. Particular attention is given to: (i) the selection of oxidation products that are sufficiently stable and specific to each lipid class and degradation route, (ii) the description of electron ionization mass fragmentation of trimethylsilyl derivatives of these compounds and (iii) the use of specific fragment ions for monitoring the oxidation of the main unsaturated lipid components of phototrophs. The techniques best geared for this task were gas chromatography-quadrupole-time of flight to monitor fragment ions with very high resolution and accuracy, and gas chromatography-tandem mass spectrometry to monitor very selective transitions in multiple reaction monitoring mode. The extent of the degradation processes can only be estimated if the oxidation products are unaffected by fast secondary oxidation reactions, as it is notably the case of 5-sterols, monounsaturated fatty acids, chlorophyll phytyl side-chain, and di-and triterpenoids. In contrast, the primary degradation products of highly branched isoprenoid alkenes possessing more than one trisubstituted double bond, alkenones, carotenoids and polyunsaturated fatty acids, appear to be too unstable with respect to secondary oxidation or other reactions to serve for quantification in senescent phototrophs

The effect of chemical dispersant of the third generation (Finasol OSR 62) on the microbial biodegradation process of Zarzaitine oil in water treatment

International audienceThe application of chemical dispersants aims to stimulate microbial oil degradation by increasing the bioavailability of oil compounds. Overall, nine microcosms were prepared (three for each treatment) using treated sediment with (i) dispersant (d: 25 ppm), (ii) oil (500 ppm), and (iii) with oil + dispersant (500: 25 ppm), respectively. There are also three control microcosms containing only water and sediment without petroleum. Then, we analyzed bacterial abundance, total hydrocarbon, biological oxygen demand (BOD5), and chemical oxygen demand (COD) in each microcosm. Bacterial response density was significantly affected after 40 days of exposure; it was higher in the control microcosm and d (> 24.103 cell/l) than in the other treatments. The index of total hydrocarbons was equal to 53 mg/kg dw in oil and 56 mg/kg dw in oil + dispersant. The higher BOD5 found in oil and in oil + d shows the increased amount of oxygen consumed, which indicates enhanced bacterial activity. Microcosms treated with dispersant had higher COD than the others, but the dispersant did not stimulate microbial hydrocarbon degradation