Biosurfactant production from newly isolated Rhodotorula sp.YBR and its great potential in enhanced removal of hydrocarbons from contaminated soils.

One of the very promising methods in the field of bioremediation of hydrocarbons is the application of biosurfactant- producing microorganisms based on the use of wastewater as renewable substrates of culture media, contributing to the reduction of costs. With this aim, the production, characterization and properties of the yeast strain YBR producing a biosurfactant newly isolated from an oilfield in Algeria, using wastewater from olive oil mills (OOMW) as a substrate for a low-cost and effective production, have been investigated. Screening of biosurfactant production was carried out with different tests, including emulsification index test (E24), drop collapse test, oil spreading technique and measurement of surface tension (ST). The isolated yeast strain was found to be a potent biosurfactant producer with E24 = 69% and a significant reduction in ST from 72 to 35 mN m-1. The study of the cultural, biochemical, physiological and genetic characteristics of the isolate allowed us to identify it as Rhodotorula sp. strain YBR. Fermentation was carried out in a 2.5 L Minifors Bioreactor using crude OOMW as culture medium, the E24 value reached 90% and a reduction of 72 to 35 mN m-1 in ST. A biosurfactant yield = 10.08 ± 0.38 g L-1 was recorded. The characterization by semi-purification and thin layer chromatography (TLC) of the crude extract of biosurfactant showed the presence of peptides, carbohydrates and lipids in its structure. The crude biosurfactant exhibited interesting properties such as: low critical micellar concentration (CMC), significant reduction in ST and strong emulsifying activity. In addition, it has shown stability over a wide range of pH (2-12), temperature (4-100 °C) and salinity (1-10%). More interestingly, the produced biosurfactant has proven to be of great potential application in the remobilization of hydrocarbons from polluted soil with a removal rate of greater than 95%.

Evaluation of Protective Impact of Algerian Cuminum cyminum L. and Coriandrum sativum L. Essential Oils on Aspergillus flavus Growth and Aflatoxin B1 Production.

BACKGROUND AND OBJECTIVE: Aflatoxin B1 (AFB1) is a highly toxic and carcinogenic metabolite produced by Aspergillus species on food and agricultural commodities. The aim of this investigation was to evaluate the inhibition of growth Aspergillus flavus E73 (A. flavus E73) and AFB1 production by Cuminum cyminum L. (C. cyminum L.) and Coriandrum sativum L. (C. sativum L.) essential oils (EOs) as well their antioxidant and phytotoxicity activities. METHODOLOGY: The C. cyminum L. and C. sativum L. EOs were extracted by hydrodistillation. The chemical profile of EOs was identified by GC-MS, antifungal activity was assessed by poisoned food technique and in term Minimal Inhibitory Concentration (MIC) and minimal fungicidal concentration (MFC) and antiaflatoxin effect by broth medium. The antioxidant activity of EOs was determined by DPPH free radical scavenging assay, ß-carotene bleaching test and total phenolic content by Folin-Ciocalteu. Phytotoxicity of C. cyminum L. and C. sativum L. EOs were determined for varieties of wheat. The results were analyzed by analysis of variance (one way ANOVA). RESULTS: The GS/MS analysis showed that the major components of C. cyminum L. EO were cuminaldehyde (65.98%), o-cymene (18.40%) and C. sativum L. EO was mainly consisted of linalool (78.86%). The results showed that both the EOs could inhibit the growth of A. flavus E73 in the range of 24.27-84.90% for C. cyminum and 15.09-65.00% for C. sativum. During antiaflatoxin investigation, the oils exhibited noticeable inhibition on dry mycelium weight and synthesis of AFB1 by A. flavus E73. EOs of C. cyminum L. and C. sativum L. revealed complete inhibition of AFB1 at 1.25 and 1.5 mg mL-1, respectively. EOs exhibited inhibitory influence against some fungi. The IC50 values of C. cyminum L. and C. sativum L. EOs were 494.93 and 756.43 µg mL-1, respectively, while, ß-carotene/linoleic acid bleaching was 47.68 and 29.29% , respectively. Total phenolic content of C. cyminum L. and C. sativum L. were 10.66 and 6.2 µg mg-1. Additionally, the EOs were non-phytotoxic on the two verities of wheat seeds. CONCLUSION: The C. cyminum L. and C. sativum L EOs could be good alternative to protect foods.

Display life of beef packaged with an antioxidant active film as a function of the concentration of oregano extract.

Fresh beef steaks were packaged with a new antioxidant active system containing increasing concentrations (0.5, 1, 2 and 4%) of an oregano extract. Control samples were packaged without the active film. Additional samples were sprayed with the extract and packaged as the control samples. Packages were filled with a 80%O(2)/20%CO(2) atmosphere and displayed under illumination (14 h) at 1 ± 1 °C for 28 days. Metmyoglobin formation, lipid oxidation (TBARS), instrumental colour (CIE a*) and sensory colour, discoloration, off-odour and oregano smell were determined. Active packaging significantly (P < 0.05) enhanced oxidative stability of beef steaks, depending on the oregano concentration of the active film. The display life of beef samples demonstrated that at least 1% oregano was needed for obtaining a significant increase of display life from 14 to 23 days. A concentration of 4% gave rise to unacceptable oregano smell. As a consequence, most suitable oregano extract concentrations for optimum active packaging in this system should be within the range 1-2%.