Enzymatic biodiesel production: Technical and economical considerations

It is well documented in the literature that enzymatic processing of oils and fats for biodiesel is technically feasible. However, with very few exceptions, enzyme technology is not currently used in commercial‐scale biodiesel production. This is mainly due to non‐optimized process design and a lack of available cost‐effective enzymes. The technology to re‐use enzymes has typically proven insufficient for the processes to be competitive. However, literature data documenting the productivity of enzymatic biodiesel together with the development of new immobilization technology indicates that enzyme catalysts can become cost effective compared to chemical processing. This work reviews the enzymatic processing of oils and fats into biodiesel with focus on process design and economy.     

Hot-nanoparticle-mediated fusion of selected cells

Complete fusion of two selected cells allows for the creation of novel hybrid cells with inherited genetic properties from both original cells.Alternatively,via fusion of a selected cell with a selected vesicle,chemicals or genes can be directly delivered into the cell of interest,to control cellular reactions or gene expression.Here,we demonstrate how to perform an optically controlled fusion of two selected cells or of one cell and one vesicle.Fusion is mediated by laser irradiating plasmonic gold nanoparticles optically trapped between two cells (or a vesicle and a cell) of interest.This hot-particle-mediated fusion causes total mixing of the two cytoplasms and the two cell membranes resulting in formation of a new hybrid cell with an intact cell membrane and enzymatic activity following fusion.Similarly,fusion between a vesicle and a cell results in delivery of the vesicle cargo to the cytoplasm,and after fusion,the cell shows signs of viability.The method is an implementation of targeted drug delivery at the single-cell level and has a great potential for cellular control and design.     

Study of taste-active compounds in the water-soluble extract of mature Cheddar cheese

The chemical composition of the water-soluble extracts of mature Cheddar cheese were identified, with the emphasis on understanding the interplay of compounds contributing to the savoury taste in Cheddar. The ultra-filtered water-soluble extracts of two mature Cheddar cheeses were fractionated by gel permeation chromatography (GPC). By sensory evaluation, two taste-active GPC fractions were identified from each cheese. On the basis of chemical profiling of these fractions, aqueous model tastant mixtures were prepared and sensory omission tests carried out. Glutamic acid, organic acids and mineral salts were the main tastants, whereas the other amino acids had a limited impact on taste. The characteristic umami taste was explained by a synergistic effect of glutamic acid and salts. Matching umami taste intensities were obtained from different concentrations of glutamic acid and salts. Unmasking of a bitter or sweet taste from mixtures of sub-threshold concentrations of amino acids without glutamic acids was also observed.     

Physico-chemical characteristics of full scale sewage sludges with implications to dewatering

An investigation was carried out for a variety of different sewage sludges in order to establish correlations between sludge composition, structure and dewatering properties. Results indicated that the fraction of extracellular polymeric substances (EPS) in sludges was the most important parameter with respect to sludge structure. With high EPS contents, sludges had a lower shear sensitivity and lower degree of dispersion. This in turn lead to better filterability in terms of low resistance to filtration (SRF). The floc stabilising role of EPS components was not consistent with DLVO-theory, as the zeta-potential increased with increased EPS content due to increased EPS charge content. This indicates that polymer entanglement is a key factor to stable floc structure. This does not rule out the possible change in dispersion due to changed electrostatic repulsion for a given EPS content. While EPS had a good effect on floc stability and filterability, the cake dry matter content decreased with large EPS contents. This could be due to an osmotic pressure related to the polymer charge quantity, or it could be caused by water entrapment in the floc structures. A high degree of sludge dispersion increased the cake dry matter content in filtration. This mechanism is, however, impractical due to high SRF and not important to conditioned sludge. In practice, dewatering also includes sludge expression. Taking this into account, osmosis related to EPS charges is likely to be increasingly important (increasing the negative effect of EPS content on cake dry matter).     

Distribution of bacteria in a domestic hot water system in a Danish apartment building

Bacterial growth in hot water systems seems to cause problems such as bad odor of the water, skin allergies and increased heat transfer resistance in heating coils. In order to establish a basis for long-term suppression of bacterial growth, we studied the distribution of bacteria in a Danish domestic hot water system. Heterotrophic plate counts (HPC) were measured in both water and biofilm samples from various sampling sites in the system. In hot water samples, where the temperature was 55-60 degrees C, the HPC were 10(3)-10(4)CFU/mL at incubation temperatures of 25 degrees C or 37 degrees C and 10(5)CFU/mL at 55 degrees C or 65 degrees C. In the cold water (10 degrees C) supplying the hot water system, the HPC at 25 degrees C or 37 degrees C was lower than in the hot water, and no bacteria were found after incubation at 55 degrees C or 65 degrees C. HPC constituted from 38% to 84% of the AODC results in hot water but only 2% in cold water, which showed a high ratio of culturable bacteria in hot water. Biofilm samples from the hot water tank and the inner surface of the pipes in the cold and hot water distribution system were collected by specially designed sampling devices, which were exposed in the system for 42 days. The quasi-steady-state number of bacteria in the biofilm, measured as the geometric mean of the HPC obtained between 21 and 42 days, was five-fold higher in the hot water pipe (13x10(5)CFU/cm(2) at 55 degrees C) than in the cold water pipe (2.8x10(5)CFU/cm(2) at 25 degrees C). There was no significant difference between the number of bacteria in the biofilm samples from the top, middle and bottom of the hot water tank, and the number of bacteria in the biofilm counted at 55 degrees C ranged from 0.6x10(4) to 1.7x10(4)CFU/cm(2). The surfaces of the sacrificial aluminum anodes and the heating coils in the hot water tank also contained high bacterial numbers. The measured number of bacteria in water and biofilm samples was related to the dimensions of the hot water system, and calculations showed that the majority of bacteria (72%) were located in the biofilm especially in the distribution system, which accounts for the greatest surface area. Free-living bacteria accounted for 26% and only a minor part of the bacteria were in the sludge in the hot water tank (2%).     

Online multi-coloring on the path revisited

Multi-coloring on the path is a model for frequency assignment in linear cellular networks. Two models have been studied in previous papers: calls may either have finite or infinite duration. For hexagonal networks, a variation of the models where limited frequency reassignment is allowed has also been studied. We add the concept of frequency reassignment to the models of linear cellular networks and close these problems by giving matching upper and lower bounds in all cases. We prove that no randomized algorithm can have a better competitive ratio than the best deterministic algorithms. In addition, we give an exact characterization of the natural greedy algorithms for these problems. All of the above results are with regard to competitive analysis. Taking steps towards a more fine-grained analysis, we consider the case of finite calls and no frequency reassignment and prove that, even though randomization cannot bring the competitive ratio down to one, it seems that the greedy algorithm is expected optimal on uniform random request sequences. We prove this for small paths and indicate it experimentally for larger graphs.     

Short-term temporal variations in speciation of Pb, Cu, Zn and Sb in a shooting range runoff stream

This study was designed to explore the changes in physico-chemical forms of Pb, Cu, Zn and Sb in a stream draining a contaminated shooting range, located at Steinsjøen in the South-Eastern part of Norway, during a period of 21 days. To obtain information on the element species distribution, an interphased size and charge fractionation system was applied, where membrane filtration (0.45 µm) and ultrafiltration using hollow fibre (nominal cut off 10 kDa) were performed prior to charge fractionation using chromatography (cationic and anionic exchange resins). The results show that Pb mainly was present as particulate and colloidal high molecular mass (HMM) species, Cu as colloidal (HMM) and low molecular mass (LMM) species, while Sb and Zn were mainly present as LMM species. The total element concentrations of Pb, Cu, Zn and Sb were positively correlated to water flow and dissolved organic carbon (DOC), suggesting these are important factors in controlling the run-off of the investigated elements in this catchment. During episodes of higher water flow, the increase in element concentration was mainly in the colloidal fraction. Partial redundancy analysis (pRDA) revealed that variations in pH, HMM organic carbon (HMM OC) and LMM organic carbon (LMM OC) explained 47% of the variation in size distribution of the elements, while variations in precipitation and water flow explained 48% of the variation in the charge distribution of the elements. The variation in concentrations during the period varied by a factor of 4, also stressing the importance of frequent sampling opposed to spot sampling in environmental surveys and risk assessments.     

New potato fibre for improvement of texture and colour of wheat bread

The aim of this project was to compare the functional properties of five fibre fractions by baking of wheat bread by substitution 0, 4, 8 and 12 w/w% of wheat flour using dry potato pulp (Fibre 1), a commercial potato fibre (Fibre 2), two fibre prepared from potato pulp by enzymatic hydrolysis (Fibre 3 and 4), and one solubilised fibre (Fibre 5). The effect of chemical composition of fibre on texture, colour, specific weight and volume of wheat bread was studied using objective methods for measurement of texture characteristics, colour (L, a, b) and sensory analysis. Dry potato pulp, Potex (Fibre 2) and two enzymatically prepared fibre powders (Fibre 3 and 4) with a high concentration of lignin and insoluble non-starch polysaccharides (INCP) had a detrimental effect on bread quality by substitution of more than 8% of the wheat flour by fibre. The detrimental effect was mainly due to increased hardness, deformation energy, modulus and gumminess. Multiple linear regression analysis with forward selection was used for determination of the relationship between quality characteristics and of soluble non-starch polysaccharides (SNSP), insoluble non-starch polysaccharides (INCP), cellulose and lignin. The enzymatic solubilised fibre (Fibre 5) with a high concentration of soluble fibre and a low concentration of cellulose and lignin could be used for substitution of at least 12% wheat flour for baking of bread with an attractive colour, delicious texture and flavour.     

Evaluation of energy and dietary intake estimates from a food frequency questionnaire using independent energy expenditure measurement and weighed food records

Background  

We have developed a food frequency questionnaire (FFQ) for the assessment of habitual diet, with special focus on the intake of fruit, vegetables and other antioxidant-rich foods and beverages. The aim of the present study was to evaluate the relative validity of the intakes of energy, food and nutrients from the FFQ.     

Effects of Chemical and Enzymatic Modification on Dough Rheology and Biscuit Characteristics

ABSTRACT: The effect of addition of sodium meta-bisulfite and a commercial protease on dough rheological properties and biscuit characteristics was studied on 7 biscuit wheat cultivars. Sodium meta-bisulfite (SMS) (360 mg/kg flour) or protease (300 mg/kg flour) was added to semisweet biscuit dough. Rheological studies included creep recovery and shear oscillation. SMS and protease increased maximum strain, recovery strain, and phase tan Δ, and lowered storage modulus, G', and the relative recovery, % recovery. The effects varied among cultivars and between SMS and protease. Biscuit eccentricity (width/length) was significantly reduced by addition of SMS or protease, but the effect varied among the cultivars, and between SMS and protease. Partial least squares regression analysis of the rheological parameters and the dimensional characteristics showed that biscuit contraction and spread were mostly correlated to % recovery of the dough, and protein and gluten content of the flour. Correlations between predicted and measured contraction and spread were r = 0.70 and r = 0.43, respectively.