Extraction of lipids from Yarrowia Lipolytica

BACKGROUND: Microorganisms have often been considered for the production of oils and fats as an alternative to agricultural and animal resources. Extraction experiments were performed using a strain of the yeast Yarrowia lipolytica (Y. lipolytica), a high‐lipid‐content yeast. Three different methods were tested: Soxhlet extraction, accelerated solvent extraction (ASE) and supercritical carbon dioxide (SCCO₂) extraction using ethanol as a co‐solvent. Also, high pressure solubility measurements in the systems ‘CO₂ + yeast oil’ and ‘CO₂ + ethanol + yeast oil’ were carried out. RESULTS: The solubility experiments determined that, at the conditions of the supercritical extractor (40 °C and 20 MPa), a maximum concentration of 10 mg of yeast oil per g of solvent can be expected in pure CO₂. 10% w/w of ethanol in the solvent mixture increased this value to almost 15 mg of yeast oil per g of solvent. Different pretreatments were necessary to obtain satisfactory yields in the extraction experiments. The Soxhlet and the ASE method were not able to complete the lipid extraction. The ‘SCCO₂ + ethanol’ extraction curves revealed the influence of the different pretreatments on the extraction mechanism. CONCLUSION: Evaluating the effectiveness of a given pretreatment, ASE reduced the amount of material and solvent used compared with Soxhlet. In all three cases, the best total extraction performance was obtained for the ethanol‐macerated yeast (EtM). Addition of ethanol to the solvent mixture enhanced the oil solubility. Oil can be extracted from Y. lipolytica in two different steps: a non‐selective ethanol extraction followed by TAG‐selective SCCO₂ purification. © 2012 Society of Chemical Industry     

Effects of chemical and thermochemical pretreatments on sunflower oil cake in biochemical methane potential assays

BACKGROUND: The effects of chemical and thermochemical pretreatments on the composition and anaerobic biodegradability of sunflower oil cake were studied to compare these pretreatments and to assess their effectiveness. Four reagents (lime, sodium hydroxide, sulphuric acid, and sodium bicarbonate) at concentrations of 25% (w/w) of dry weight of substrate and 20 g L^?1 substrate concentration were used for the chemical pretreatment for 4 h. The same conditions were used for thermochemical pretreatment with heating at 75°C. After the pretreatments, the solid and liquid fractions were separated and subjected to biochemical methane potential tests. RESULTS: The methane yields of the solid fraction obtained with lime, sodium hydroxide, sulphuric acid and bicarbonate were 130±9, 54±4, 61±6 and 88±7 mL CH₄ g^‐1COD_added, respectively, and after thermochemical pretreatment were 26±2, 84±7, 74±7, and 77±6 mL CH₄ g^‐1COD_added, respectively. The methane yields for liquids were 152±13, 2±0, 0±0, 249±19 mL CH₄ g^‐1COD_added, for the chemical pre‐treatment, respectively, and after the thermochemical pretreatment were 273±13, 58±5, 0±0 and 145±12 mL CH₄ g^‐1COD_added, respectively. CONCLUSION: Only the solid fraction obtained after the chemical pretreatment with lime gave a methane yield higher (130 mL CH₄ g^‐1COD_added) than the obtained for the untreated solid material (114 mL CH₄ g^‐1COD_add). No thermochemical pretreatment enhanced the methane yield of the solid or liquid fractions of the untreated material. © 2012 Society of Chemical Industry     

Effect of Clay Modification on the Mechanism of Local Deformations in PA6 Nanocomposites

PA nanocomposites are prepared from clays organophilized with a phosphonium and an ammonium salt, and sodium montmorillonite is used as reference. The analysis of mechanical and micromechanical properties of the composites reveal that several micromechanical deformation processes occur in the PA/MMT composites. The matrix cavitates at relatively small stress. Processes related to non‐exfoliated clay structural units are initiated at larger stresses. Sound is emitted mainly by the fracture of particles, but debonding may also occur. The plastic deformation of the matrix dominates at larger stresses and deformations. The various local deformations are independent of each other and composite properties are not determined by silicate related processes but by the deformation of the matrix.

     

High polymer/surfactant ratio in the seeded semicontinuous heterogeneous polymerization of vinyl acetate

Vinyl acetate (VAc) was polymerized by a seeded semicontinuous heterogeneous process. Stable latexes with a polymer/surfactant weight ratio of 65 were obtained, which is comparable with the highest value reported in the literature for emulsion polymerization but with the advantage of obtaining smaller particles (average diameter, D_p = 53 nm) which are similar to those obtained by microemulsion polymerization. The surfactant (sodium dodecylsulfate, SDS) concentration used in the recipe (0.32 wt%) is much lower than those typically used in microemulsion polymerization. Although molar masses increased during the continuous monomer addition period, they were small at the end of the reaction (M_n = 69 × 10³ g·mol^–1) and this was attributed to bimolecular termination inside the particles. The values of polymerization rate (R_p) and monomer addition rate (F_m) were nearly the same, indicating that polymerization was performed under monomer starved conditions. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Properties of Polyurethane Elastomers with Different Hard/Soft Segment Ratio

Three polyurethane elastomers (PU) containing different hard/soft (h/s) segment ratios were prepared. The PUs were characterized using Gel Permeation Chromatography (GPC), DSC, Wide Angle X-ray Diffraction (WAXD). Dynamic Mechanical Thermal Analysis (DMTA), and Stress-controlled rheometry. The surface properties were evaluated from contact angle measurements. The PUs were used as raw materials for solvent-based adhesives, whose adhesion properties were measured from T-peel tests of solvent-wiped polyvinyl chloride (PVC)/polyurethane adhesive joints. The increase in the amount of h/s segment ratio affected the structure and morphology of the PUs, reducing the degree of phase separation and the extent of the secondary interactions between polymer chains. The h/s segment ratio determined the thermal, mechanical, rheological and adhesion properties of the PUs.     

Trickle Bed Wetting Factors From Pressure Drop And Liquid Holdup Measurements

In this work, solid-liquid wetting factors were determined from liquid holdup and pressure drop measurements according to the model proposed by Pironti et al. for different air-liquid systems: distilled water and CMC solutions at viscosity values of 3, 6, 9, and 12 mPa.s. The experiments were carried out at atmospheric conditions in a column of 10.2 cm internal diameter and 2 m high, packed with a cylindrical material. The superficial mass velocities varied from 0.67 to 18.6 kg/m 2 s for liquid flow and from 0.024 to 0.31 kg/m 2 s for gas flow. Under these operating conditions, regime of continuous gas flow was observed. The wetting factors obtained were in agreement with those reported by other methods, which allow us to confirm that the model used in this work is applicable to fluids of different properties at low gas velocities.