Ginette Turcotte

Ethanol Production from AFEX -Treated Forages and Agricultural Residues

Lignocellulosic materials derived from forages, namely timothy grass, alfalfa, reed canary grass, and agricultural residues, such as corn stalks and barley straw, were pretreated using ammonia fiber explosion (AFEX) process. The pretreated materials were directly saccharified by cellulolytic enzymes. Sixty to 80% of theoretical yield of sugars were obtained from the pretreated biomasses. Subsequent ethanolic fermentation of the hydrolysates byPachysolen tannophilus ATCC 32691 resulted in 40-60% of theoretical yield after 24 h, based on the sugars present in the hydrolysates. The uptake of sugars was not complete, indicating a possible inhibitory effect onP. tannophilus during the fermentation of these substrates.

CFD modeling of the mixing of water in oil emulsions

Abstract A computational fluid dynamics (CFD) model was developed for the mixing of water in oil emulsion in a lab-scale mixing tank equipped with a Rushton turbine impeller. Multiple reference frames (MRF) technique, k – ɛ model, and Eulerian–Eulerian approach were employed to model the impeller rotation, turbulence, and multiphase flow, respectively. The droplet size distribution within the mixing tank was estimated by means of the population balance approach, which employs the discrete method to describe coalescence and breakage of water droplets. To validate the CFD model, the cumulative probability size distribution computed using the model was compared with the experimentally determined values reported in the literature. This validated CFD model was then utilized to explore the effects of the impeller speed, oil type, and volume fraction of water on the cumulative probability droplet size distribution, number density, and distribution of local volume fraction of the dispersed phase.

Fabrication and characterization of novel biomimetic PLLA/cellulose/hydroxyapatite nanocomposite for bone repair applications

The purpose of this research is to develop and characterize a novel biomimetic nanocomposite that closely mimics the properties of real bone such as morphology, composition and mechanical characteristics. This novel porous nanocomposite is composed of cotton-sourced cellulose microcrystals, hydroxyapatite nanoparticles and poly l-lactide acid. A unique combination of commonly used fabrication procedures has been developed including pre-treatment of particles using a coupling agent. The effect of various weight ratios of the reinforcing agents was evaluated to assess their influence on the chemical, thermal, and mechanical properties of the nanocomposites. The prepared nanocomposites were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and compression testing. Our results indicated the presence of molecular interactions between all components leading to an increase of the crystallinity of the polymer from 50% to 80%. Compression test results revealed that increasing the weight ratio of microcrystalline cellulose/poly l-lactide acid and hydroxyapatite/poly l-lactide acid from 0.1 to 0.5 enhanced the compressive yield stress from 0.127 to 2.2MPa and The Youngs modulus from 6.6 to 38MPa, respectively. It was found that the fabricated nanocomposites are comparable with the trabecular bone from compositional, structural, and mechanical point of view.

Effect of Protein on Flux and Selectivity in Pervaporation of Ethanol from a Dilute Solution

The separation of ethanol from a 2% w/w ethanol–water mixture by pervaporation through a thin polydimethyl-siloxane (PDMS) membrane sheet was studied with and without a dissolved vegetable protein in the feed solution. Total flux and ethanol selectivity were measured at different feed temperatures (40, 50, and 60°C) and permeate-side pressures (1, 10, 20, and 40 mm Hg). An analysis of variance was done to detect effects and interactions. Protein at 10 g/L did not foul the membrane under the conditions used and had no significant effect on flux or selectivity. The effects of protein and temperature on ethanol selectivity interacted slightly.

A comparative study between an endoglucanase IV and its fused protein complex Cel5-CBM6

The recombinant endoglucanase IV (Cel5; encoded by egIV) of Ruminococcus albus was compared with protein Cel5-CBM6 comprised of Cel5 fused at the C-terminus with the single-cellulose binding domain II (CBM6) of Clostridium stercorarium xylanase A, in order to improve its binding ability. Previous analyses using ball-milled cellulose had suggested that a cellulose binding domain of xylanase A could enhance cellulase activity, especially with insoluble substrates. Comparison of the catalytic activities of Cel5 and Cel5-CBM6 were determined using carboxymethylcellulose, Avicel, and filter paper as substrates. This study confirmed previous findings, and provided further evidence suggesting that Cel5-CBM6 exhibits enhanced activity with insoluble cellulose compared to native Cel5. However, its hydrolytic activity with soluble substrates such as carboxymethylcellulose was comparable to Cel5. For both cellulases, central linkages of cellulooligosaccharides (up to six glucose residues) were found to be the preferred points of cleavage. The rates of hydrolysis with both cellulases increased with cellulooligosaccharide chain length, and at least three consecutive glycosyl residues seemed to be necessary for hydrolysis to occur. Cel5-CBM6 showed a higher affinity for cellulose substrates than did Cel5, as demonstrated by transmission electron microscopy. Taken together, these results suggest that CBM6 increases the affinity of Cel5 for insoluble substrates, and this increased binding capacity seems to result in increased catalytic activity.

Using tomography images to study the mixing of wheat straw slurries

ABSTRACT Wheat straw is a good renewable source for the production of bioethanol. However, the mixing of wheat straw slurry is a challenging task due to its complex rheology. This type of slurry behaves as a non-Newtonian fluid possessing a yield stress. In mixing operations, the presence of a yield stress creates a region of active motion (cavern) around the impeller and stagnant zones in the remainder of the vessel. In this paper, electrical resistance tomography (ERT) was employed to measure the dimensions of the cavern around the impeller as a function of the wheat straw concentration, fiber size, impeller speed, and impeller type. These data were then utilized to estimate the yield stress of wheat straw slurries. To test the accuracy of this technique, the yield stress of a xanthan gum solution calculated from the tomography method was compared to that achieved using a rheometer. This study is the first novel application of ERT to estimate the yield stress of wheat straw slurries, as opposed to directly measuring it using rheometry. Average yield stresses of 5, 7, and 10 wt% slurries were found to be 1.31 Pa, 4.2 Pa, and 14.8 Pa, respectively, for fiber size of ≤ 2 mm, and 3.4 Pa, 6.8 Pa, and 16.7 Pa, respectively, when fiber size was 8 mm.