Saad Ibnsouda Koraichi

Cellulolytic potential of fungi in wood degradation from an old house at the Medina of Fez

During the history of civilizations, advanced wood decay results from exposure to various agents for long periods of time. Bio-deterioration, under the influence of living organisms like fungi, can cause massive damage to historical monuments. In this work, we found that fungi participating in wood degradation share a single strategy for degrading wood polymers by secreting enzymes that break down the main constituents of wood such as cellulose, hemicellulose and lignin. WhilePenicillium commune, Penicillium granulatum andPenicillium chrysogenum showed the highest cellulase productivity and are therefore the most destructive for timber, other fungal species participate also in this biodegradation includingPenicillium crustosum, Penicillium expansum Cladosporium cladosporioides and a cellulotic specieThielavia hyalocarpa that we describe here for the first time.

The effect of the Thymus vulgaris extracts on the physicochemical characteristics of cedar wood using angle contact measurement

The aim of the study was to investigate the effect of crude extracts of Thymus vulgaris on wood surface physicochemical characteristics. Thus, the Lifshitz-van der Waals (), acid–base (surface tension components ΔGiwi, electron donor () and electron acceptor () parameters of untreated and treated wood were assessed using contact angle measurement. The main results showed that all T. vulgaris extracts are able to change wood surface properties. Indeed, the samples treated with the product obtained by maceration and ultrasound indicated the hydrophilic character (θw = 29.7 ± 0.3°, ΔGiwi = 17. 78 ± 0.48 mJ/m2 and θw = 18.2 ± 0.2°, ΔGiwi = 30.62 ± 0.31 mJ/m2) respectively, and had less contact angle values than that of untreated wood (θw = 86.0 ± 0.2°). In addition, this treatment has made the wood more donor ( = 44.76 ± 0.3 mJ/m2 and  = 53.80 ± 0.3 mJ/m2) than the electron acceptor compared to sample control ( = 2.03 ± 0.04 mJ/m2). Finally, the effect of the extract obtained by ultrasound was found to be more important and significant than those recovered by classical extraction.

Yeast strains from the endogenous microflora of the olive fliesBactrocera oleae larvae which could degrade the olive oil mill wastewaters polyphenols

Worldwide, wastewaters constitute a major environmental pollutant. They are very toxic against a wide range of plants and soil microorganisms. Their toxicity is due to the presence of compounds such as polyphenols. In this study, we have isolated yeast strains from the endogenous microflora of the olive fliesBactrocera oleae larvae that were capable of degrading the olive oil mill wastewater polyphenols. The results obtained showed the presence, in the digestive tract of the larvae, of yeast strains resisting to polyphenols. Two resistant strains were isolated and have shown variable capacity of polyphenols degradation that could reach up to 72%. The two isolated strains were identified by two methods: conventional technique and molecular method associating PCR amplification and DNA sequencing of the 5.8S ribosomal RNA gene. Both techniques showed that the two isolated strains corresponded to theCandida diddensiae specie. Related to its capacity to degrade polyphenols, this specie would be a potential candidate for wastewater treatment and environmental protection.

Dairy biofilm: an investigation of the impact on the surface chemistry of two materials: silicone and stainless steel

Biofilms are the most common mode of bacterial growth in nature and the formation will occur on organic or inorganic solid surfaces in contact with a liquid. The aims of this study were, by combining numeration and sessile drop technique, (i) to characterize the structural dynamics of dairy biofilm growth and the physico chemical properties on silicone and stainless steel and (ii) to evaluate the impact of bio-adhesion on chemistry of surfaces at different times of contact (2, 7, 9 and 24 h). Significantly, greater biofilm volumes were observed after 48 h on two materials. Gram-positive bacteria and fungal population exhibited a significantly higher biofilm organization than gram-negative (43–64%). Elsewhere, after 48 h, results showed a slight difference on gram-negative adhered cells on stainless steel than silicone (2.6 × 107 cfu/cm2 and 4.7 × 105 cfu/cm2, respectively). Moreover, the physico chemical properties of the surfaces showed that the silicone and stainless steel have a hydrophobic character (Giwi = −68.28 mJ/m2 and −57.6 mJ/m2, respectively). Also, both the surfaces present a weak electron donor character (γ − = 2.2 mJ/m2 and 4.1 mJ/m2, respectively). The real-time investigation of the impact of dairy biofilm on the physico chemical properties of the materials has shown a decrease of hydrophobicity degree of the silicone surface that becomes hydrophilic (ΔGiwi = 11.47 mJ/m2) after 7 h and the increase of electron donor character (γ − = 75.8 mJ/m2). Elsewhere, bio-adhesion on stainless steel was accompanied with a decrease of hydrophobicity degree of the surface, which becomes hydrophilic after 7 h of contact (ΔGiwi = 6.62 mJ/m2) and the increase of the electron donor character (γ − = 44.8 mJ/m2). While, after 24 h of contact, results showed a decrease of the hydrophilicity degree and surface energy components of silicone and stainless steel that become hydrophobic (ΔGiwi = −21.2 mJ/m2 and ΔGiwi = −56.51 mJ/m2, respectively) and weak electron donor (γ − = 14.0 and 2.3 mJ/m2, respectively).

Wicherhamomyces anomalus biofilm supported on wood husk for chromium wastewater treatment

A Wickeramomyces anomalus biofilm supported on wood husk was used to remediate water bodies contaminated with chromium (Cr), in batch and open systems. The favorable adhesion ability of the chromium-resistant yeast strain on the wood husk was predicted by XDLVO theory and confirmed by environmental scanning electronic microscopy. The chromium decontamination was then optimized in a batch mode using a central composite design (CCD). Analysis of variance (ANOVA) showed a high coefficient of determination (R2) value of 0.93-0.91 for Cr(VI) and total Cr removal, respectively, ensuring a satisfactory fitting of the second-order regression model to the experimental data. In batch system, the concentration of biomass exhibited the minimal effect on the process. An acidic pH of 3.72 and 5.48, an initial chromium concentration of 10 and 16.91 mg/L and a support dose of 6.95 and 8.20 g/L were optimal for Cr(VI) and total Cr removal, respectively. The breakthrough curves were determined in open system for different initial chromium concentrations. The study of glucose concentration effect on the yeast extracellular polymeric substances (EPS) production showed that a medium exempt of glucose allowed maximal EPS production and minimal chromium removal efficiency, while 20 g/L glucose concentration of presented the optimal condition for chromium removal.

Correlation between cell surface physicochemical properties of bacterial strains and their chromium removal potential

Abstract Physicochemical characterization of microbes has gained recently a great interest by scientific community. It is proved of extreme importance in several fields of science and technology applications such as bioremediation. In this work, we investigated the establishment of a possible correlation between chromium removal capacity of seven bacterial strains isolated from contaminated sites with industrial wastes including tanning processing and their cell surface physicochemical properties. Thus, hydrophobicity and donor/acceptor electrons character were obtained using contact angle measurements. Statistical analysis showed a high significant positive correlation between hexavalent chromium (Cr(VI)) removal by the strains and their acceptor electron character γ+(r = 0.90). While significant negative correlation between the Cr(VI) removal potential and the ΔGiwi value (r = −0.844) and also with their donor electron character γ− (r = −0.746) were observed. These results may contribute to determine a selectrion criteria of bacteria that can be operated in bioremediation applications.