Fatma Hadrich

A newly high alkaline lipase: an ideal choice for application in detergent formulations

BackgroundBacterial lipases received much attention for their substrate specificity and their ability to function in extreme environments (pH, temperature...). Many staphylococci produced lipases which were released into the culture medium. Reports of thermostable lipases from Staphylococcus sp. and active in alkaline conditions are not previously described.ResultsA newly soil-isolated Staphylococcus sp. strain ESW secretes an induced lipase in the culture medium. The effects of temperature, pH and various components in a detergent on the activity and stability of Staphylococcus sp. lipase (SL1) were studied in a preliminary evaluation for use in detergent formulation solutions. The enzyme was highly active over a wide range of pH from 9.0 to 13.0, with an optimum at pH 12.0. The relative activity at pH 13.0 was about 60% of that obtained at pH 12.0. It exhibited maximal activity at 60°C. This novel lipase, showed extreme stability towards non-ionic and anionic surfactants after pre-incubation for 1 h at 40°C, and relative stability towards oxidizing agents. Additionally, the crude enzyme showed excellent stability and compatibility with various commercial solid and liquid detergents.ConclusionsThese properties added to the high activity in high alkaline pH make this novel lipase an ideal choice for application in detergent formulations.

The α-Glucosidase and α-Amylase Enzyme Inhibitory of Hydroxytyrosol and Oleuropein

To date, numerous studies have reported on the antidiabetic properties of various plant extracts through inhibition of carbohydrate-hydrolysing enzymes. The objective of this research was to evaluate the inhibitory effect of the hydroxytyrosol and the oleuropein against α-amylase and α-glucosidase. The hydroxytyrosol was purified from olive leaves. The result shows that the hydroxytyrosol had the strongest α-glucosidase inhibitory effect with IC50 values of 150 μM with mild inhibition against α-amylase. The enzyme kinetic studies, using Lineweaver-Burk indicated that, in the presence of the hydroxytyrosol, the Michaelis-Menton constant (Km) remained constant but the maximal velocity (Vmax) decreased, revealing a non-competitive type of inhibition with inhibition constants; Ki for the formation of the inhibitor-enzyme complex and Kis for the formation of the inhibitor-enzyme-substrate complex of 104.3 and 150.1 μM, respectively. On the other hand, oleuropein showedan uncompetitive inhibition. The concentrations used in this work were below cytotoxic levels observed at 400 μM. However, at 600 μM, the hydroxytyrosol significantly decreased viability of the Caco-2 cells (p < 0.05) and in the case of the oleuropein, theres an increase in cell number compared to control (p < 0.05). These results suggest that the hydroxytyrosol and oleuropein are two potential effective α-glucosidase inhibitors for management of postprandial hyperglycemia.

Assessment of Olea europaea L. fruit extracts: Phytochemical characterization and anticancer pathway investigation

Olea europaea L. has been widely used as an advantageous rich source of bioactive compounds of high economic value leading to its use in pharmaceutical, cosmetic, and agriculture industries. Ethanolic extracts of olive fruits from three different cultivars (OFE) were studied for their phytochemical contents and were investigated for antioxidant activities and anticancer potential. Major polyphenols detected in these extracts were tyrosol, hydroxytyrosol, oleuropein, rutin, quercetin and glucoside forms of luteolin and apigenin. All these compounds have shown to significantly contribute to the antioxidant activity of OFE, which was evaluated by DPPH and ABTS assays. Proliferation of hepatic and colon cancer cells, HepG2 and Caco-2, were shown to be sensitive to OFE with IC50 less than 1.6mg/ml for all tested extracts. Moreover, flow cytometry analysis showed that OFE induced cell cycle arrest in the S-phase within both HepG2 and Caco-2 cells. This has triggered a cell death mechanism as shown by DNA fragmentation, expression of p53 and phosphorylation level of Akt and Erk proteins. Interestingly, these extracts could be further used as a potential source of natural compounds with both antioxidant and anticancer effects.

Oleuropein activated AMPK and induced insulin sensitivity in C2C12 muscle cells.

AIMS Oleuropein has been recognized as an important medicinal compound because of its various biological properties, including anti-cancer, antidiabetic and anti-atherosclerotic activities. Here, we evaluate the antioxidant activity as well as the mechanism of the hypoglycemic effects of oleuropein in C2C12 cells and we establish the mechanism underlying these effects. MAIN METHODS To perform this study, C2C12 cells viability was analyzed via MTT assay and the antioxidant activity was investigated by ROS and TBARS assays. Also, the effect of oleuropein on AMPK and PI3 kinase signaling pathways was evaluated. KEY FINDINGS Treatment with oleuropein was able to protect cells against H2O2 induced stress in cells. On the other hand, the molecular bases of its actions have been scarcely understood. Oleuropein significantly enhanced glucose consumption and the phosphorylation of AMPK (AMP-activated protein kinase/ACC (acetyl-CoA carboxylase)) and MAPKs (mitogen-activated protein kinases), but not PI3 kinase (Phosphatidylinositol 3-kinase)/Akt. However, the co-treatment of oleuropein and insulin improved the insulin sensitivity via insulin-dependent (PI3 kinase/Akt) and insulin independent (AMPK/ACC) pathways. These results could be confirmed from the findings of GLUT4 translocation which was strongly enhanced in the case of oleuropein. SIGNIFICANCE Our results provide important insights for the possible mechanism of action of oleuropein as a therapeutic agent in diabetic patients.

Strategy for improving extracellular lipolytic activities by a novel thermotolerant Staphylococcus sp. strain

BackgroundExtracellular bacterial lipases received much attention for their substrate specificity and their ability to function under extreme environments (pH, temperature...). Many staphylococci produced lipases which were released into the culture medium. Reports of extracellular thermostable lipases from Staphylococcus sp. and active in alkaline conditions are not previously described.ResultsThis study focused on novel strategies to increase extracellular lipolytic enzyme production by a novel Staphylococcus sp. strain ESW. The microorganism needed neutral or alkaline pH values between 7.0 and 12.0 for growth. For pH values outside this range, cell growth seemed to be significantly inhibited. Staphylococcus sp. culture was able to grow within a wide temperature range (from 30 to 55°C). The presence of oils in the culture medium leaded to improvements in cells growth and lipolytic enzyme activity. On the other hand, although chemical surfactants leaded to an almost complete inhibition of growth and lipolytic enzyme production, their addition along the culture could affect the location of the enzyme. In addition, our results showed that this novel Staphylococcus sp. strain produced biosurfactants simultaneously with lipolytic activity, when soapstock (The main co-product of the vegetable oil refining industry), was used as the sole carbon source.ConclusionA simultaneous biosurfactant and extracellular lipolytic enzymes produced bacterial strain with potential application in soap stock treatment

Production, characterization and biotechnological potential of lipopeptide biosurfactants from a novel marine Bacillus stratosphericus strain FLU5

This work aimed at studying the potential of a new hydrocarbonoclastic marine bacterium, Bacillus stratosphericus FLU5, to produce an efficient surface-active agent BS-FLU5. Biosurfactant production was examined on different carbon sources; using the surface tension measurement and the oil displacement test. Strain FLU5 showed its capacity to produce biosurfactants from all tested substrates, in particular the residual frying oil, which is a cheap renewable carbon source alternative, thus minimizing the high cost of producing those surfactants. MALDI-TOF MS/MS analysis confirmed the presence of lipopeptides, which are identified as members of surfactin and pumilacidin series. The critical micelle concentration (CMC) of the purified lipopeptides produced by strain FLU5 was 50 mg/l. At this concentration, the surface tension of the water was reduced from 72 to 28 mN/m. Furthermore, the crude lipopeptides showed an interesting stability against a broad range of pH, temperature and salinity. In addition, the application of BS-FLU5 in oil recovery from hydrocarbons-contaminated soil (used motor oil) showed that it was more effective on the hydrocarbon-remobilization than some tested synthetic surfactants. Interestingly, the biosurfactant BS-FLU5 showed a negligible cytotoxic effect against the mammalian cells HEK293. These results highlight the applicability of the lipopeptides BS-FLU5 in different fields, especially in environmental remediation processes.