Influence of Homogenization Treatment on Physicochemical 4 Properties and Enzymatic Hydrolysis Rate of Pure 5 Cellulose Fibers

in Applied Biochemistry and Biotechnology (in press)

The aim of this study is to compare the effect of different homogenization treat- 12 ments on the physicochemical properties and the hydrolysis rate of a pure bleached 13 cellulose. Results obtained show ... [more ▼]

The aim of this study is to compare the effect of different homogenization treat- 12 ments on the physicochemical properties and the hydrolysis rate of a pure bleached 13 cellulose. Results obtained show that homogenization treatments improve the enzymatic 14 hydrolysis rate of the cellulose fibers by 25 to 100 %, depending of the homogenization 15 treatment applied. Characterization of the samples showed also that homogenization had an 16 impact on some physicochemical properties of the cellulose. For moderate treatment inten- 17 sities (pressure below 500 b and degree of homogenization below 25), an increase of water 18 retention values (WRV) that correlated to the increase of the hydrolysis rate was highlighted. 19 Result also showed that the overall crystallinity of the cellulose properties appeared not to be 20 impacted by the homogenization treatment. For higher treatment intensities, homogenized 21 cellulose samples developed a stable tridimentional network that contributes to decrease 22 cellulase mobility and slowdown the hydrolysis process. [less ▲]

Surface activity of a fluorinated carbohydrate ester in water/carbon dioxide emulsions

in Journal of Colloid & Interface Science (2013), 398

The water/carbon dioxide (W/CO2) interfacial activity and emulsifying capacity of hydrocarbon and fluorinated carbohydrate esters are investigated of the first time and compared to the performance of ... [more ▼]

The water/carbon dioxide (W/CO2) interfacial activity and emulsifying capacity of hydrocarbon and fluorinated carbohydrate esters are investigated of the first time and compared to the performance of sodium-bis(2-ethylhexyl)sulfosuccinate (AOT). The reduction of the W/CO2 interfacial tension was measured using a pendant drop tensiometer equipped with a cell view pressurized with CO2 at 80 bar and 45 °C. It was found that the interface stabilization improved in the order AOT < 6-O-myristoyl mannose < 6-O-(2H,2H,3H,3H-perfluoroundecanoyl)-D-mannose. In the latter case, a drastic reduction of the W/CO2 interfacial tension was observed (85% reduction, interfacial tension at the equilibrium = 3.6 mN/m), which emphasizes the advantage of using a fluorinated CO2-philic tail and the potential of sugars as hydrophilic head. The formulation of stable W/CO2 emulsions was also achieved using the fluorinated mannose derivative. This study paves the way to the design of a novel class of competitive surface active agents for W/CO2 emulsions. [less ▲]

Enzymatic synthesis and surface properties of novel rhamnolipids

in Process Biochemistry (2013), 48

New rhamnolipids were obtained via the development of a synthesis procedure consisting of two biocatalyzed steps. In the first step, naringinase was used to introduce a primary alcohol function onto ... [more ▼]

New rhamnolipids were obtained via the development of a synthesis procedure consisting of two biocatalyzed steps. In the first step, naringinase was used to introduce a primary alcohol function onto rhamnose by glycosylation of 1,3-propanediol. In the second step, immobilized lipase B from Candida antarctica catalyzed the esterification of the primary hydroxyl group with mono- and di-carboxylic fatty acids of increasing chain length (from C8 to C14). For the monoic acids, the initial rate and 24 h yield decreased with increasing chain length. For the dioic acid, the number of carbon atoms of the acid did not influence these parameters. The new rhamnolipid obtained with tetradecanoic acid showed very good surface properties. At pH 5, it had a very low critical aggregation concentration of 1.70 M and it diminished water’s surface tension to 27.6 mN/m. It was also able to form stable insoluble monolayers. On the other hand, the rhamnolipid formed with tetradecanedioic acid showed far less interesting surface properties. [less ▲]

Fast and high yield recovery of arabinose from destarched wheat bran

in Industrial Crops & Products (2013), 43

Enzymatically destarched wheat bran (DWB) contained 13.8% of arabinose and 23.1% xylose. Up to a maximum of 70% of the arabinose was progressively released from DWB when heated at 80 or 100°C in media ... [more ▼]

Enzymatically destarched wheat bran (DWB) contained 13.8% of arabinose and 23.1% xylose. Up to a maximum of 70% of the arabinose was progressively released from DWB when heated at 80 or 100°C in media acidified with HCl. Whereas microwave irradiation at higher temperatures in pressure vessels could lead to higher yields of extraction. A Box-Behnken experimental design established an efficient model describing the effects of temperature, irradiation duration and pH on arabinose extraction. The pH appeared as the most important factor of the process. 4-5 min of microwave heating at 150ºC and pH 1 appeared as a fast and highly efficient method to recover more than 90% of the arabinose of DWB. When plotting the percentages of arabinose against the combined severity factors LogR’0 (calculated from the temperature/duration/pH conditions applied), two different fitting profiles were obtained for both the heating techniques. Under microwave heating, high free xylose’s release could also occur. The experimental design led to a quadratic model predicting the release of xylose from DWB. A range of conditions enabled to minimize xylose and hydrolyze around 50% of the total arabinose, yielding a high purity fraction. An alternative would be to release more than 90% of both arabinose and xylose, for further arabinose purification or for a common valorization of both pentoses. [less ▲]

Optimization of Production and Preliminary Characterization of New Exopolysaccharides from Gluconacetobacter hansenii LMG1524

in Advances in Microbiology (2012), 2(4), 488-496

The influence of different carbon and nitrogen sources, of ethanol concentration, the optimal pH, temperature and me-dium composition were evaluated on extracellular polysaccharides (EPS) synthesis and ... [more ▼]

The influence of different carbon and nitrogen sources, of ethanol concentration, the optimal pH, temperature and me-dium composition were evaluated on extracellular polysaccharides (EPS) synthesis and bacterial growth of Gluconace-tobacter hansenii LMG1524, and preliminary characterization of EPS was investigated. The highest EPS yields were obtained using glycerol and ammonium sulphate as carbon and nitrogen sources, respectively. The increase of ethanol concentration in the medium did not influence the EPS synthesis but reduced the bacterial growth. The optimum tem-perature and pH for polysaccharides production were respectively 25 °C and 5; whereas for cell growth were respec-tively 30 °C and 4. The optimal culture medium composition was determined as follows : 10 g/L sucrose, 0.892 g/L (NH4)2SO4, 0.34 g/L NaNO3, 3 mL acetic acid, 1.5 g/L KH2PO4, 1.5 g/L K2HPO4 and 0.6 g/L MgSO4. The polysaccha-rides produced were of 14 and 10 polymerization degrees (DP) and constituted mainly of glucose, galactose and man-nose, in relative percent of 36.36, 33.94 and 22.42, respectively. [less ▲]

Influence of steam explosion on physico-chemical properties and hydrolysis rate of pure cellulose fibers

in Bioresource Technology (2012), 121(221-227),

The aim of the present study is to compare the effect of different steam explosion treatments on physicochemical properties and hydrolysis rate of a pure bleached cellulose. The results showed that ... [more ▼]

The aim of the present study is to compare the effect of different steam explosion treatments on physicochemical properties and hydrolysis rate of a pure bleached cellulose. The results showed that moderate steam explosion treatments (severity factor below 5.2) did not improve the enzymatic hydrolysis rate of the cellulose fibers. The characterization of the obtained samples showed an increase of the cellulose accessibility coupled with an increase of the overall crystallinity of the substrate. In these conditions, the higher accessibility is counterbalanced by the increased crystallinity. Indeed, a greater proportion of the substrat is accessible by only a fraction of the enzymatic complex (exo-glucanases) activities. When the severity factor reached 5.2, a decrease of the cellulose enzymatic hydrolysis rate was observed. In this case, TGA analysis showed an increase of the char level at the end of the pyrolysis which traduced an important thermal degradation of the samples. The thermal degradation of cellulose lead to an important change in substrate composition, which induced a decrease of the cellulose ratio available for hydrolysis and caused a decrease of the hydrolysis yields. [less ▲]

Improvement of the cellulose hydrolysis yields and hydrolysate concentration by management of enzymes and substrate input

in Cerevisia : Belgian Journal of Brewing and Biotechnology (2012), 37

In order to improve the hydrolysis of cellulose fiber and to obtain highly concentrated hydrolysate, two methods based on successive addition of enzyme and substrate were assessed. The first method, which ... [more ▼]

In order to improve the hydrolysis of cellulose fiber and to obtain highly concentrated hydrolysate, two methods based on successive addition of enzyme and substrate were assessed. The first method, which required only substrate addition, allowed to increase by 50% the hydrolysate concentration and to decrease by 30% enzyme units needed. The second method highlighted the ability to reach very high concentrated hydrolysate (up to 170 g/l) by simultaneous addition of enzyme and substrate. In parallel, relationships between some limiting factors and the yields of hydrolysis were investigated. In conclusion, viscosity evolution of cellulose suspension during hydrolysis step was investigated with an aim to improve the management of enzyme and substrate addition. [less ▲]

Optimization of a formic/acetic acid treatment of beech wood for lignin extraction

Conference (2012, August)

Lignocellulosic substrates are a promising alternative resource for the sustainable production of energy (biofuels), bio-based products and organic compounds. In the past, the extraction and recycling of ... [more ▼]

Lignocellulosic substrates are a promising alternative resource for the sustainable production of energy (biofuels), bio-based products and organic compounds. In the past, the extraction and recycling of cellulose (into fermentable glucose) constituted the central axis of lignocellulosic biorefinery processes. Degraded hemicelluloses and lignins were recovered as side-products with no possibilities of high-added value applications. Within the context of an integrated biorefinery, and for economic reasons, the recovery and the non-energetic valorization of lignins have opened recently new horizons. Lignin is a cross-linked phenolic polymer and is considered as potential alternative to petrochemical polymers or as a source of antioxidants for cosmetics and food industry, resins, chelating agent... As the final application of lignin depends on both extraction process and type of lignocellulosic sources, the development of fast and efficient physicochemical characterization methods is thus a prerequisite to optimize extraction processing conditions. In this study, beech wood particles (Fagus sylvatica L.) are delignified at atmospheric pressure by a formic acid/acetic acid/water mixture. Firstly, response surface methodology is used to optimize cooking time and temperature for delignification, pulp yield and concentration of degradation products (2-furfural and 5-hydroxymethylfurfural). The results highlight that best delignification is obtained in the highest cooking times and temperatures and that 5-hydroxymethylfurfural is produced during the formic/acetic acid treatment but is also degraded into 2-furfural. With the aim to develop an integrated biorefinery approach, multi-criteria optimization is used to find ideal cooking time and temperature (5h07, 104.2°C) leading to the maximization of delignification and pulp yield and to the minimization of 2-furfural production Finally, physicochemical and chemical structures of extracted lignins are found dependent on treatment conditions harshness. [less ▲]

Use of glycosurfactants for the synthesis of polyHIPES in supercritical carbon dioxide

Poster (2012, June 04)

The abstract is available as a pdf file.

Bioraffinerie végétale : chimie et technologie des structures osidiques (TECHNOSE)

Report (2012)