Florence Husson

Comparison of some new pretreatment methods for second generation bioethanol production from wheat straw and water hyacinth

Pretreatment of lignocellulosic residues like water hyacinth (WH) and wheat straw (WS) using crude glycerol (CG) and ionic liquids (IL) pretreatment was evaluated and compared with conventional dilute acid pretreatment (DAT) in terms of enzymatic hydrolysis yield and fermentation yield of pretreated samples. In the case of WS, 1-butyl-3-methylimidazolium acetate pretreatment was found to be the best method. The hydrolysis yields of glucose and total reducing sugars were 2.1 and 3.3 times respectively higher by IL pretreatment than DAT, while it was 1.4 and 1.9 times respectively higher with CG pretreatment. For WH sample, CG pretreatment was as effective as DAT and more effective than IL pretreatment regarding hydrolysis yield. The fermentation inhibition was not noticeable with both types of pretreatment methods and feedstocks. Besides, CG pretreatment was found as effective as pure glycerol pretreatment for both feedstocks. This opens up an attractive economic route for the utilization of CG.

Contribution of exofacial thiol groups in the reducing activity of Lactococcus lactis.

Lactococcus lactis can decrease the redox potential at pH 7 (Eh7) from 200 to −200 mV in oxygen free Man–Rogosa–Sharpe media. Neither the consumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease in Eh7 by the bacteria. Thiol groups located on the bacterial cell surface appear to be the main components that are able to establish a greater exchange current between the Pt electrode and the bacteria. After the final Eh7 (−200 mV) was reached, only thiol‐reactive reagents could restore the initial Eh7 value. Inhibition of the proton motive force showed no effect on maintaining the final Eh7 value. These results suggest that maintaining the exofacial thiol (–SH) groups in a reduced state does not depend on an active mechanism. Thiol groups appear to be displayed by membrane proteins or cell wall‐bound proteins and may participate in protecting cells against oxidative stress.

Biogeneration of 1-octen-3-ol by lipoxygenase and hydroperoxide lyase activities of Agaricus bisporus

Abstract The biogeneration of 1-octen-3-ol by lipoxygenase and associated hydroperoxide lyase activities of a homogenate of the cultivated mushroom Agaricus bisporus was investigated using linoleic acid as a substrate. The optimal substrate and protein concentrations were 1.5 mM and 1.5 mg ml −1 , respectively. The V max value for the enzymic coupled reaction lipoxygenase–hydroperoxide lyase was 6 μg of 1-octen-3-ol ml −1 min −1 , with a K m value of 0.3×10 −3 M. The highest enzymic activity was observed in the presence of pure oxygen (22.9 μg of 1-octen-3-ol ml −1 ), with a bioconversion yield of 36%. The production of 380 μg 1-octen-3-ol per g of mushroom homogenate was demonstrated using an oxygenated reaction medium of 1-l containing 0.5% polyvinylpyrrolidone.

Fusarium proliferatum : Induction and intracellular location of a lipoxygenase

The fungus Fusarium proliferatum was grown in a soya oil- and glucose-supplemented medium. Induction of lipoxygenase activity (13-fold) in an extract of Fusarium biomass has been observed at day four on soya oil culture medium. A band at 232 kDa was detected using a specific lipoxygenase stain combined with native PAGE. The method of fungal homogenate obtained has been checked via subcellular marker enzymes activities: succinate dehydrogenase (SDH) for mitochondrial fraction and NADH-cytochrome C reductase (NADH-cyt. C) for the microsomal fraction. Protoplasts production and disintegration followed by subcellular fractionation using differential centrifugation was the best method to recover pure fractions. The results of subcellular fractionation showed that lipoxygenase is mainly distributed among microsomal and mitochondrial fractions with a high enrichment of specific activity in the microsomal fraction.

Size measuring techniques as tool to monitor pea proteins intramolecular crosslinking by transglutaminase treatment

In this work, techniques for monitoring the intramolecular transglutaminase cross-links of pea proteins, based on protein size determination, were developed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles of transglutaminase-treated low concentration (0.01% w/w) pea albumin samples, compared to the untreated one (control), showed a higher electrophoretic migration of the major albumin fraction band (26 kDa), reflecting a decrease in protein size. This protein size decrease was confirmed, after DEAE column purification, by dynamic light scattering (DLS) where the hydrodynamic radius of treated samples appears to be reduced compared to the control one.

For me the taste of soy is not a barrier to its consumption. And how about you

This research investigates the cultural influence on beliefs about and attitudes towards soy foods (French from France vs. Vietnamese from Vietnam) and possible change of beliefs and attitudes and soy consumption habits with a change in cultural environment (French from France vs. French from Vietnam, Vietnamese from Vietnam vs. Vietnamese from France) of French and Vietnamese participants, two countries with very different soy food consumption. Expressed beliefs and attitudes of soy foods resulting from discussions in focus groups, conducted in both countries, were collected and used to derive a questionnaire. French participants differ mainly from Vietnamese participants in questions associated to taste and price of soy foods. Both groups reported positive attitudes towards health benefits of soy foods. With a change in cultural environment, French participants showed a notable change in attitudes related to taste and price of soy foods and in soy consumption habit whereas almost no change was observed in Vietnamese participants. The asymmetry in magnitude of change and cultural differences in components of beliefs and attitudes are discussed.

Optimization of the Hydrolysis of Safflower Oil for the Production of Linoleic Acid, Used as Flavor Precursor.

Commercial lipases, from porcine pancreas (PPL), Candida rugosa (CRL), and Thermomyces lanuginosus (Lipozyme TL IM), were investigated in terms of their efficiency for the hydrolysis of safflower oil (SO) for the liberation of free linoleic acid (LA), used as a flavor precursor. Although PPL, under the optimized conditions, showed a high degree of hydrolysis (91.6%), its low tolerance towards higher substrate concentrations could limit its use for SO hydrolysis. In comparison to the other investigated lipases, Lipozyme TL IM required higher amount of enzyme and an additional 3 h of reaction time to achieve its maximum degree of SO hydrolysis (90.2%). On the basis of the experimental findings, CRL was selected as the most appropriate biocatalyst, with 84.1% degree of hydrolysis. The chromatographic analyses showed that the CRL-hydrolyzed SO is composed mainly of free LA.

A New Alternative In Vitro Method for Quantification of Toxoplasma gondii Infectivity

Abstract: An in vitro method to determine the infectious potency of an unknown suspension of the protozoan parasite Toxoplasma gondii based on kinetics of host cells lysis was developed. Mic1-3KO a mutant strain of T. gondii RH tachyzoites was inoculated in 25-cm2 flasks containing a 90% confluent monolayer of human foreskin fibroblasts. Lysis kinetics was monitored for infection ratios ranging from 1∶106 to 1∶10; we defined 106 tachyzoites/ml−1 as the threshold value for parasite egress. Results allowed us to build a calibration curve relating the initial infection ratios to the time needed to reach 106 tachyzoites/ml−1. Finally, we validated the method using a known mixture of dead and live parasites. This method was found to estimate with accuracy the initial ratio of infection of the unknown parasite suspension. This easy-to-use method is reproducible and can be applied to any T. gondii tachyzoite RH strain, genetically modified or not. This method is also suitable for testing promising candidates for an effective live vaccine.

Biocatalysis with hydroperoxide lyase in extracts from Penicillium camemberti in neat organic solvent media

Abstract Biocatalysis with hydroperoxide lyase (HPL) in extracts from Penicillium camemberti, in neat organic solvent media has been investigated. The effects of reaction conditions including organic solvent mixtures, initial water activity (aw) and reaction temperature as well as the effect of the lyoprotectants, KCl and dextran 1 kDa, on HPL activity were studied. The addition of KCl to the enzymatic extract (70:1 protein, w/w) prior to lyophilization, enhanced HPL activity 6.53-fold. In contrast, the presence of dextran at a ratio of 8:1 decreased the enzymatic activity. Using hexane as the reaction medium, with an initial aw of 0.1 and 0.5, the HPL specific activity was determined to be as 6.3 and 65.9 nmol converted 10-HPOD/mg protein/min, for the enzymatic extract without and with KCl present, respectively. Although HPL enzymatic extract with KCl showed a relatively low optimum reaction temperature (45°C) compared to 55°C without KCl, it exhibited a 2.51- and 2.78-fold higher thermal stability at 60 and 80°C, respectively. The kinetic results indicated that the highest HPL catalytic efficiency, Vmax/Km, of 6.58 × 10−2 mL/mg protein/min, was obtained in the presence of KCl.

Selected dehydrogenases in Yarrowia lipolytica JMY 861: their role in the synthesis of flavor compounds.

The presence of selected dehydrogenases, including alcohol dehydrogenase (ADH-YL) and aldehyde dehydrogenase (ALDH-YL), in Yarrowia lipolytica JMY 861, and their potential role in flavor synthesis were investigated. The experimental findings showed that using reduced form of nicotinamide adenine dinucleotide (NADH) as cofactor, the ADH-YL activity in vitro was 6-fold higher than that with reduced form of nicotinamide adenine dinucleotide phosphate (NADPH); however, under the experimental conditions used in this study, an ALDH-YL activity was not detected. The in situ hexanal reduction reaction was found to be instantaneous; however, when the yeast cells suspension was diluted 150 times, the initial relative hexanal concentration was increased by 84.1%. The chromatographic analyses indicated the conversion, in situ, of linoleic acid hydroperoxides (HPODs) into volatile C6-compounds after 60 min of HPODs addition to the yeast cells suspension. Graphical abstract An endogenous alcohol dehydrogenase in Yarrowia lipolytica JMY 861 along with the genetically cloned hydroperoxide lyase from green bell pepper.