Antioxidant properties, antimicrobial and anti-adhesive activities of DCS1 lipopeptides from Bacillus methylotrophicus DCS1

BACKGROUND

The present work aims to investigate the antioxidant and antimicrobial activities as well as the potential of DCS1 lipopeptides produced by Bacillus methylotrophicus DCS1 strain at inhibition and disruption of biofilm formation.

RESULTS

The produced biosurfactants were characterized as lipopeptides molecules by using thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FT-IR). The DCS1 lipopeptides were assayed for their antioxidant activity through five different tests. The scavenging effect on DPPH radicals at a concentration of 1 mg mL^-1 was 80.6%. The reducing power reached a maximum value of 3.0 (OD_{700 nm}) at 2 mg mL^-1. Moreover, the DCS1 lipopeptides exhibited a strong inhibition of β-carotene bleaching by linoleic acid assay with 80.8% at 1 mg mL^-1 and showed good chelating ability and lipid peroxidation inhibition. The in vitro antimicrobial activity of DCS1 lipopeptides showed that they display significant antibacterial and antifungal activities. The anti-adhesive activity of DCS1 lipopeptides was evaluated against several pathogenic microorganisms. The lipopeptides showed excellent anti-adhesive activity, even at low concentrations, in a polystyrene surface pre-treatment against all the microorganisms tested. Further, they can disrupt performed biofilms.

CONCLUSION

This study shows the potentiality of DCS1 lipopeptides as natural antioxidants, antimicrobial and/or anti-adhesive agent for several biomedical and industrial applications.

Identification and natural functions of cyclic lipopeptides from Bacillus amyloliquefaciens An6

Lipopeptides constitute a structurally diverse group of metabolites produced by various bacterial and fungal genera. In the past decades, research on lipopeptides has been fueled by their surfactant activities. However, natural functions of lipopeptides compounds have received considerably less attention. The aim of this study was to isolate and identify the lipopeptides from Bacillus amyloliquefaciens An6, and further evaluate their biological activities. An6 lipopeptides were detected by PCR using degenerated primers and MALDI-TOF-MS. An6 strain was found to produce surfactin, fengycin, and bacillomycin. Following their purification, the in vitro antioxidant activity of An6 lipopeptides was studied through different assays. The scavenging effect on 1,1-diphenyl-2-picrylhydrazyl radicals at a dosage of 0.75 mg/mL was 81%. Its reducing power was concentration-dependant and reached a maximum of 1.07 at 2.5 mg/mL. Moreover, they showed a strong inhibition of β-carotene bleaching. An6 lipopeptides mixture was also found to display significant antimicrobial activity against several Gram-positive, Gram-negative bacteria, and fungal strains. An6 lipopeptides were insensitive to proteolytic enzymes, stable between pH 4.0 and 12.0, and resistant to high temperature. Our results provided enough evidence proving that An6 lipopeptides could be used as functional-food components.

Isolation and biochemical characterisation of a bacteriocin-like substance produced by Bacillus amyloliquefaciens An6

This study focuses on the isolation and characterisation of a peptide with bacteriocin-like properties from Bacillus amyloliquefaciens An6. Incubation conditions were optimised, and the effects of the incubation period and of carbon and nitrogen sources were investigated. The produced bacteriocin was partially purified with ammonium sulphate precipitation, dialysis and ultrafiltration and was then biochemically characterised. Maximum bacteriocin production was achieved after 48h of incubation in a culture medium containing 20g/L starch and 10g/L yeast extract, with an initial pH 8.0 at 30°C under continuous agitation at 200rpm. The bacteriocin was sequentially purified and its molecular weight was determined to be 11kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The bacteriocin was relatively heat-resistant and was not sensitive to acid and alkaline conditions (pH 4.0-10.0). Its inhibitory activity was sensitive to proteinase K but was resistant to the proteolytic action of alcalase, trypsin, chymotrypsin and pepsin. In conclusion, bacteriocin An6, owing its wide spectrum of activity as well as its high tolerance to acidic and alkaline pH values, temperature and proteases shows great potential for use as a food biopreservative.

Acute and sub-chronic oral toxicity profiles of lipopeptides from Bacillus mojavensis A21 and evaluation of their in vitro anticoagulant activity

The aim of the present study was to evaluate the acute and sub-chronic toxicity of lipopeptides mixture produced by Bacillus mojavensis A21 as well as their in vitro anticoagulant activity. A21 lipopeptides was given to mice at single dose from 75 mg to 1000 mg/kg body weight (bw). The median lethal dose (LD50) of A21 lipopeptides was about 550 mg/kg bw. Sub-chronic toxicity study for 28 days was done by daily oral administration of A21 lipopeptides at doses of 40 and 400 mg/kg bw in rats. Results showed that A21 lipopeptides did not cause any change in body weights and they did not produce any marked alterations in the hematological blood parameters including hematocrit concentration, hemoglobin level, white and red cells count. However, the platelets level decreased significantly compared to control value. Moreover, no significant differences in the serum biochemical characteristics were observed for rats treated by the lowest dose. In contrast, a little enhancement of alanine-aminotransferase (ALT) activity and decrease in total cholesterol were observed with the highest dose. A21 lipopeptides were also found to cause a prolongation of the thrombin time (TT), the prothrombin time (PT) and the activated partial thromboplastin time (APTT). Overall, A21 lipopeptides may be very promising compounds for therapeutic purposes.

Structural, physicochemical and antioxidant properties of sodium alginate isolated from a Tunisian brown seaweed

An original sodium alginate from Tunisian seaweed (Cystoseira barbata) was purified and characterized by circular dichroism (CD) and ATR-FTIR spectroscopies. ATR-FTIR spectrum of C. barbata sodium alginate (CBSA) showed the characteristic bands of mannuronic (M) and guluronic acids (G). The M/G ratio was estimated by CD (M/G = 0.59) indicating that CBSA was composed of 37% mannuronic acid and 63% guluronic acid. The analysis of viscosity of CBSA showed evidence of pseudoplastic fluid behaviour. The emulsifying capacity of CBSA was evaluated at different concentrations (0.25-3%), temperatures (25-100 °C) and pH (3.0-11.0). Compared to most commercial emulsifiers, the emulsion formulated by CBSA was found to be less sensitive to temperature changes and more stable at acidic pH. CBSA was examined for antioxidant properties using various antioxidant assays. CBSA exhibited important DPPH radical-scavenging activity (74% inhibition at a concentration of 0.5 mg/ml) and considerable ferric reducing potential. Effective hydroxyl-radical scavenging activity (82% at a concentration of 5 mg/ml) and potent protection activity against DNA breakage were also recorded for CBSA. However, in the linoleate-β-carotene system, CBSA exerted moderate antioxidant activity (60% at a concentration of 1.5 mg/ml). Therefore, CBSA can be used as a natural ingredient in food industry or in the pharmaceutical field.

Rhelogical, dermal wound healing and in vitro antioxidant properties of exopolysaccharide hydrogel from Pseudomonas stutzeri AS22

The in vitro antioxidant activity and the in vivo wound healing performance of the exopolysaccharide EPS22, produced by Pseudomonas stutzeri AS22, were investigated. Antioxidant activity was evaluated by three different tests. The scavenging effect on DPPH radicals at a concentration of 1mg/ml was 80±1.41%. The reducing power reached a maximum of 1.26±0.02 at 2 mg/ml. Moreover, EPS22 showed good chelating ability and chelated almost 88.5±0.7% of ferrous ions at 0.75 mg/ml. The rheological characterization of EPS22 gel (0.5%) showed a pseudoplastic behavior, high elasticity, good mechanical strength and stability with high water-absorption ability. The application of the EPS22 gel on dermal full-thickness excision wounds in a rat model every two days, enhanced significantly wound healing activity and a total closure was achieved after 12 days of wound induction. Further, histological examination of biopsies showed advanced tissue regeneration, characterized by the presence of well-organized stratum of both derma and epidermis.

[Osteoarticular manifestations of sickle cell anemia. Update apropos of a series of 29 cases]

In a retrospective study, the authors report 14 cases of osteoarticular manifestations, among 29 patients affected with a sickle cell disease observed at adult age. They insist on their frequency and their interest for diagnosis and prognostic. Effectively, the diagnosis has been revealed on occasion of these manifestations in 9 cases/14. The articular signs are noted in 35%, and the osseous signs in 25% of cases.

[Phaeochromocytoma with psychiatric disturbances. One case (author's transl)]

A case of phaeochromocytoma which presented with hypertension and severe psychiatric disturbances including three attempts at suicide. These psychiatric problems regressed completely following removal of the tumour. Although inconstant, the combination of hypertension and psychiatric problems should always lead to studies for the possible presence of a phaeochromocytoma. The mechanism of these disturbances is not clearly understood but either a direct action of catecholamines on cerebral tissue or changes secondary to blood pressure variations are suggested.

Renovascular hypertension: the role of nonspecific factors in the antihypertensive effect of surgery

Effective surgical treatment was carried out in 67 patients who were selected from a population of 336 subjects with renovascular hypertension. Split renal function studies and estimation of plasma renin activity in both renal veins were made to demonstrate the functional significance of the stenosis. The degree of disturbance of these tests did not correlate with the preoperative blood pressure level. The percentage decrease in postoperative blood pressure was directly related to the preoperative blood pressure (P less than 0.01). In 23 postoperative patients followed yearly for 5 years, the blood pressure increased progressively and was positively correlated with the duration of follow up (P less than 0.02). Patients with renovascular hypertension had a lower frequency of blood group 0 and a higher frequency of blood group A than did normotensive controls. The results of the study suggest that, in renovascular hypertension, the antihypertensive effect of surgical treatment is not exclusively related to the physiological consequence of the stenosis and that nonspecific factors, possibly of genetic origin, may determine the blood pressure response after surgical treatment.