Biogas generation from sewage in four public universities in Ghana: A solution to potential health risk

Apart from waste treatment, anaerobic digestion is a reliable method for biogas generation. The digested sludge from anaerobic digesters can also be used to enhance the fertility of the soil. This paper assesses the biogas potential from the sewage generated in four public universities in Ghana for the 2008/2009 academic year. In the estimation of the amount of sewage generated in each university, the population was used and was categorized into residential and non-residential staff and students. The population of the universities varies throughout the year due to the vacation periods hence the sewage generated varies accordingly. The estimated population for the four universities was 100,313 when in session and 20,903 on vacation and the estimated daily sewage generated is 1379.9 m³ and 327.8 m³, when the universities were in session and on vacation respectively. This study revealed that an annual biogas potential of about 815,109 m³ could be obtained which is equivalent to about 4,891 MWh of energy or can replace about 4532 tonnes of firewood or 326.4 tonnes of LPG which can reduce the pressure on the forest and the use of LPG.     

Non-Linear Mechanical Behavior of Plasma Sprayed Alumina Under Mechanical and Thermal Loading

Mechanical response of plasma sprayed ceramic coatings to mechanical and thermal loading of various extents was studied. Coated samples were subjected to four-point bending (4PB), with coatings loaded in tension and compression, respectively. Thermal loading was provided by heating the samples, while stresses were generated by thermal mismatch between the coatings and substrates. In both cases, cyclic loading was applied. Non-linear behavior and significant hysteresis were observed, indicating inelastic phenomena taking place. The tests were complemented by structural observations in SEM and indentation tests. Relevant structural features and possible mechanisms underlying this behavior are discussed.     

Initial Droplet Size Impacts pH‐Induced Structural Changes in Phase‐Separated Polymer Dispersions

The effect of pH change on the morphology of whey protein isolate (WPI)–pectin dispersions obtained from phase‐separated systems after mild shear was studied. The purpose of this study was to examine the impact of mixing speed on the initial particle size of biopolymer complexes and their structure morphology after sequentially changing the pH. Therefore, solutions of WPI and pectin were combined at pH 6.1, allowed to phase separate and were then mildly homogenized at 50, 100, and 150 rpm, respectively, to form a dispersion containing differently sized WPI droplets in a surrounding pectin‐rich phase. Each dispersion was then subjected to a pH change, such as 6.1 to 5.2 and 3.2, by slowly adding hydrochloric acid. The systems morphology, size, appearance, rheology, and storage stability was then characterized by optical microscopy, static light scattering, visual inspections, and steady shear rheometry to gain insights into the structural rearrangements. Results indicated substantial changes in the structure of the dispersion when the pH was changed. Formation of core‐shell structures from the WPI droplets was observed at an intermediate pH. There, initial droplet size was found to affect structures formed, that is, core‐shell type particles would only form if droplets were large (>1.5 μm) prior to pH change. Insights gained may be of importance to food manufacturers intending to create new structures from mixtures of proteins and carbohydrates.     

Evaluation of heterologous α‐amylase production in two expression platforms dedicated for Yarrowia lipolytica: commercial Po1g–pYLSC (php4d) and custom‐made A18–pYLTEF (pTEF)

In view of the constantly increasing demand for cost‐effective, low‐energy and environmentally friendly industrial processes and household care products, enzyme production occupies an essential place in the field of biotechnology. Along with increasing demand for industrial and household care enzymes, the demand for heterologous expression platforms has also increased. Apart from the conventional hosts, e.g. Escherichia coli, Saccharomyces cerevisiae and Pichia pastoris, routinely used in heterologous protein expression, the non‐conventional ones have become more and more exploited in this field. Among the available yeast host systems, Yarrowia lipolytica appears to be an attractive alternative. The aim of this study was to compare efficiency of two Yarrowia‐based expression platforms, commercial Po1g–pYLSC and custom‐made A18‐pYLTEF, in expression of an insect‐derived, raw‐starch‐digesting α‐amylase, to select the ‘champion’ system for further studies on this valuable enzyme. Both expression platforms were compared with respect to copy number of the integrated expression cassette/transformed genome, and the recombinant strains performance (Po1g–pYLSC‐derived 4.29 strain, and A18‐pYLTEF‐derived B9 strain) during batch bioreactor cultures. Our results demonstrate that the average number of integration events into the recipient's genome was comparable for both expression systems under investigation, but with varying distribution of the multicopy integrants; and the number of the recombinant gene copies was highly correlated with the acquired amylolytic activity of the strains. Due to severe susceptibility of the recombinant AMY1 polypeptide to native proteases of the custom‐made expression system, the final yield of the enzyme was substantially lower when compared to the commercial Po1g–pYLSC (reaching a maximum level of 142.84 AU/l). Copyright © 2015 John Wiley & Sons, Ltd.     

Modeling the contribution of point sources and non-point sources to Thachin River water pollution

Major rivers in developing and emerging countries suffer increasingly of severe degradation of water quality. The current study uses a mathematical Material Flow Analysis (MMFA) as a complementary approach to address the degradation of river water quality due to nutrient pollution in the Thachin River Basin in Central Thailand. This paper gives an overview of the origins and flow paths of the various point- and non-point pollution sources in the Thachin River Basin (in terms of nitrogen and phosphorus) and quantifies their relative importance within the system. The key parameters influencing the main nutrient flows are determined and possible mitigation measures discussed.The results show that aquaculture (as a point source) and rice farming (as a non-point source) are the key nutrient sources in the Thachin River Basin. Other point sources such as pig farms, households and industries, which were previously cited as the most relevant pollution sources in terms of organic pollution, play less significant roles in comparison. This order of importance shifts when considering the model results for the provincial level. Crosschecks with secondary data and field studies confirm the plausibility of our simulations. Specific nutrient loads for the pollution sources are derived; these can be used for a first broad quantification of nutrient pollution in comparable river basins. Based on an identification of the sensitive model parameters, possible mitigation scenarios are determined and their potential to reduce the nutrient load evaluated.A comparison of simulated nutrient loads with measured nutrient concentrations shows that nutrient retention in the river system may be significant. Sedimentation in the slow flowing surface water network as well as nitrogen emission to the air from the warm oxygen deficient waters are certainly partly responsible, but also wetlands along the river banks could play an important role as nutrient sinks.     

Microstructure and Creep Behavior of a Si3N4–SiC Micronanocomposite

The microstructure and its influence on the creep behaviour of carbon derived Si₃N₄-SiC micro/nanocomposite tested in bending at temperatures from 1200° to 1400°C in air has been studied. No phase and microstructure change after creep test implied that material is stable at tested temperature range. After creep test only partial crystallization of glassy intergranular phase has been observed. Creep parameters n close to 1, apparent activation energy around 350 kJ/mol together with TEM observation indicated that the main creep mechanisms is solution precipitation controlled by interface reaction in combination with grain boundary sliding caused by the amorphous intergranular phases present in microstructure. However, the grain boundary sliding is hindered by local SiC particles interlocking neighboring Si₃N₄ grains.     

Phenylalanine ammonia‐lyase and phenolic compounds in leaves and fruits of Olea europaea L. cv. Picual during ripening

BACKGROUND: The kinetic and molecular properties of phenylalanine ammonia‐lyase (PAL) in leaves and fruit of the olive tree (Picual variety) have been studied during the seasonal process of fruit maturation. The concentrations of total phenolic compounds, oleuropein, hydroxytyrosol and tyrosol, have also been determined. This study has been made in rainfed 30‐year‐old olive trees in Jaén, Spain, cultivated by the traditional method. RESULTS: PAL specific activity was assayed and hyperbolic kinetics were observed in both organs. The K_m value for L ‐Phe was 0.22 mmol L^?1 in leaf and 0.26 mmol L^?1 in fruit. In leaf, the highest PAL specific activity was found in the stage prior to veraison. By immunoblot, a PAL‐immunoreactive 75 kDa polypeptide was detected in leaf and fruit. In leaf, the level of this protein progressively rose until the last stages of ripening at the same time that total phenols increased. In fruit, PAL activity and protein change as in two series coinciding with different fruit‐maturation period. By immunohistochemistry under light microscopy, PAL was located in the epidermis and parenchyma cells of leaf and fruit. CONCLUSION: These results demonstrate the involvement and regulation of PAL during fruit ripening of olive, cv. Picual. Copyright © 2008 Society of Chemical Industry