Comparative biochemical analysis after steam pretreatment of lignocellulosic agricultural waste biomass from Williams Cavendish banana plant (Triploid Musa AAA group).

The accessibility of fermentable substrates to enzymes is a limiting factor for the efficient bioconversion of agricultural wastes in the context of sustainable development. This paper presents the results of a biochemical analysis performed on six combined morphological parts of Williams Cavendish Lignocellulosic Biomass (WCLB) after steam cracking (SC) and steam explosion (SE) pretreatments. Solid (S) and liquid (L) fractions (Fs) obtained from SC pretreatment performed at 180°C (SLFSC180) and 210°C (SLFSC210) generated, after diluted acid hydrolysis, the highest proportions of neutral sugar (NS) contents, specifically 52.82 ± 3.51 and 49.78 ± 1.39%w/w WCLB dry matter (DM), respectively. The highest proportions of glucose were found in SFSC210 (53.56 ± 1.33%w/w DM) and SFSC180 (44.47 ± 0.00%w/w DM), while the lowest was found in unpretreated WCLB (22.70 ± 0.71%w/w DM). Total NS content assessed in each LF immediately after SC and SE pretreatments was less than 2%w/w of the LF DM, thus revealing minor acid autohydrolysis consequently leading to minor NS production during the steam pretreatment. WCLB subjected to SC at 210 °C (SC210) generated up to 2.7-fold bioaccessible glucan and xylan. SC and SE pretreatments showed potential for the deconstruction of WCLB (delignification, depolymerization, decrystallization and deacetylation), enhancing its enzymatic hydrolysis. The concentrations of enzymatic inhibitors, such as 2-furfuraldehyde and 5-(hydroxymethyl)furfural from LFSC210, were the highest (41 and 21 µg ml(-1), respectively). This study shows that steam pretreatments in general and SC210 in particular are required for efficient bioconversion of WCLB. Yet, biotransformation through biochemical processes (e.g., anaerobic digestion) must be performed to assess the efficiency of these pretreatments.

Effect of different Bacillus subtilis lipopeptides on surface hydrophobicity and adhesion of Bacillus cereus 98/4 spores to stainless steel and Teflon.

Various lipopeptides produced by Bacillus subtilis were examined for their ability to modify the surface hydrophobicity of two substrata, stainless steel (SS) and Teflon. These modifications were evaluated by water contact angle measurements. The effects depended on the lipopeptide, its concentration, and the tested substratum. Treatment of SS with different concentrations of surfactin S1 showed an increase of the hydrophobicity between 1 and 100 mg l(-1). On the same substratum, fengycin increased hydrophobicity up to its critical micelle concentration (6.25 mg l(-1)). With higher concentrations of fengycin, hydrophobicity decreased. Surfactin, mycosubtilin, and iturin A decreased hydrophobicity on Teflon. The different effects of these three families of lipopeptides were related to their structural differences. A good correlation was shown between hydrophobicity modifications of surfaces and the attachment of B. cereus 98/4 spores. Enhancement in the hydrophobicity of the surfaces increased the number of adhering spores.

Astin C Production by the Endophytic Fungus Cyanodermella asteris in Planktonic and Immobilized Culture Conditions.

The fungal endophyte Cyanodermella asteris (C. asteris) has been recently isolated from the medicinal plant Aster tataricus (A. tataricus). This fungus produces astin C, a cyclic pentapeptide with anticancer and anti-inflammatory properties. The production of this secondary metabolite is compared in immobilized and planktonic conditions. For immobilized cultures, a stainless steel packing immersed in the culture broth is used as a support. In these conditions, the fungus exclusively grows on the packing, which provides a considerable advantage for astin C recovery and purification. C. asteris metabolism is different according to the culture conditions in terms of substrate consumption rate, cell growth, and astin C production. Immobilized-cell cultures yield a 30% increase of astin C production, associated with a 39% increase in biomass. The inoculum type as spores rather than hyphae, and a pre-inoculation washing procedure with sodium hydroxide, turns out to be beneficial both for astin C production and fungus development onto the support. Finally, the influence of culture parameters such as pH and medium composition on astin C production is evaluated. With optimized culture conditions, astin C yield is further improved reaching a five times higher final specific yield compared to the value reported with astin C extraction from A. tataricus (0.89 mg g-1 and 0.16 mg g-1 respectively).

Anti-Salmonella activity and probiotic trends of Kluyveromyces marxianus S-2-05 and Kluyveromyces lactis S-3-05 isolated from a French cheese, Tomme d'Orchies.

Kluyveromyces marxianus S-2-05 and Kluyveromyces lactis S-3-05 were recently isolated from a traditional French cheese, Tomme d'Orchies, and characterized here for their advantages using a different application perspective. First, we established their anti-Salmonella activity and downregulation of the virulence sopD gene of Salmonella enterica subsp. enterica serovar Typhimurium, mainly in the presence of K. marxianus S-2-05. In addition to their antagonism, these non-Saccharomyces yeasts were able to survive under conditions mimicking the gastrointestinal environment and to form biofilms on an abiotic device such as polystyrene. These strains also displayed highly hydrophilic cell wall surfaces properties and capacity for adhesion to intestinal Caco-2 cells, thus enhancing their potential as probiotic strains.

Observing the overall rocking motion of a protein in a crystal.

The large majority of three-dimensional structures of biological macromolecules have been determined by X-ray diffraction of crystalline samples. High-resolution structure determination crucially depends on the homogeneity of the protein crystal. Overall 'rocking' motion of molecules in the crystal is expected to influence diffraction quality, and such motion may therefore affect the process of solving crystal structures. Yet, so far overall molecular motion has not directly been observed in protein crystals, and the timescale of such dynamics remains unclear. Here we use solid-state NMR, X-ray diffraction methods and µs-long molecular dynamics simulations to directly characterize the rigid-body motion of a protein in different crystal forms. For ubiquitin crystals investigated in this study we determine the range of possible correlation times of rocking motion, 0.1-100 µs. The amplitude of rocking varies from one crystal form to another and is correlated with the resolution obtainable in X-ray diffraction experiments.

Protein encapsulation in liposomes: efficiency depends on interactions between protein and phospholipid bilayer.

BACKGROUND: We investigated the encapsulation mechanism of enzymes into liposomes. The existing protocols to achieve high encapsulation efficiencies are basically optimized for chemically stable molecules. Enzymes, however, are fragile and encapsulation requires in addition the preservation of their functionality. Using acetylcholinesterase as a model, we found that most protocols lead to a rapid denaturation of the enzyme with loss in the functionality and therefore inappropriate for such an application. The most appropriate method is based on lipid film hydration but had a very low efficiency. RESULTS: To improve it and to propose a standard procedure for enzyme encapsulation, we separate each step and we studied the effect of each parameter on encapsulation: lipid and buffer composition and effect of the different physical treatment as freeze-thaw cycle or liposomes extrusion. We found that by increasing the lipid concentration, increasing the number of freeze-thaw cycles and enhancing the interactions of the enzyme with the liposome lipid surface more than 40% of the initial total activity can be encapsulated. CONCLUSION: We propose here an optimized procedure to encapsulate fragile enzymes into liposomes. Optimal encapsulation is achieved by induction of a specific interaction between the enzyme and the lipid surface.

Encapsulation of enzymes in liposomes: high encapsulation efficiency and control of substrate permeability.

Enzyme encapsulation into liposomes is a promising technique to stabilize and prevent them from denaturation and proteolysis. We demonstrate this using acetylcholinesterase which is the main target for pesticides. In order to achieve a reasonable encapsulation yield, we analyzed the parameters involved in each step of various encapsulation procedures. The only encapsulation method which did not denature the protein was the lipid film hydration technique, however the encapsulation efficiency was usually low. The efficiency could be increased up to more than 40% by induction of a specific interaction between the enzyme and the lipid surface. Once encapsulated, the enzyme encountered another problem: the permeability barrier of the lipid membrane drastically diminished the activity of the enzyme entrapped in the liposome by reducing the entrance rate of the substrate molecules and then reducing the substrate concentration inside the liposome. To solve this problem, we controlled the permeability of the liposome wall by reconstituting a porin from Escherichia coli. We succeeded to recover the full functionality of the enzyme, while retaining the protection against denaturation and proteolytic enzymes.