Optimisation of integrated biodiesel production. Part II: a study of the material balance

A study was made of the material balance for the fatty acid methyl ester (biodiesel) synthesis from sunflower oil using potassium hydroxide as the catalyst. A factorial design of experiments and a central composite design have been used to evaluate the influence of operating conditions on the process material balance. The responses chosen were the biodiesel yield and the yield losses due to triglyceride saponification and methyl ester dissolution in glycerol, while the variables studied were temperature, initial catalyst concentration and the methanol:vegetable oil molar ratio. The biodiesel yield increased and therefore the yield losses decreased by decreasing catalyst concentration and temperature. However, the methanol:sunflower oil molar ratio did not affect the material balance variables significantly. Second-order models were obtained to predict the biodiesel yield and both yield losses. Within the experimental range studied, these models largely matched the results from the experiments.     

均匀设计法优化高丽参多糖的提取

利用均匀设计法优化了高丽参多糖的提取过程.主要考察料液质量比、浸泡时间、提取温度和提取时间四个因素对提取率的影响.通过数学模型得到最优提取状况和3D曲面图.结果表明,提取温度对高丽参多糖得率影响最大,在料液质量比1:35、浸泡时间135 min、水提取温度81℃条件下提取156 min,高丽参多糖最大理论提取率为49.51%.最优化模型下实际多糖得率49.29%与理论得率相符.     

A teleonomic model describing performance (body, milk and intake) during growth and over repeated reproductive cycles throughout the lifespan of dairy cattle. 1. Trajectories of life function priorities and genetic scaling

The prediction of the control of nutrient partitioning, particularly energy, is a major issue in modelling dairy cattle performance. The proportions of energy channelled to physiological functions (growth, maintenance, gestation and lactation) change as the animal ages and reproduces, and according to its genotype and nutritional environment. This is the first of two papers describing a teleonomic model of individual performance during growth and over repeated reproductive cycles throughout the lifespan of dairy cattle. The conceptual framework is based on the coupling of a regulating sub-model providing teleonomic drives to govern the work of an operating sub-model scaled with genetic parameters. The regulating sub-model describes the dynamic partitioning of a mammal female's priority between life functions targeted to growth (G), ageing (A), balance of body reserves (R) and nutrient supply of the unborn (U), newborn (N) and suckling (S) calf. The so-called GARUNS dynamic pattern defines a trajectory of relative priorities, goal directed towards the survival of the individual for the continuation of the specie. The operating sub-model describes changes in body weight (BW) and composition, foetal growth, milk yield and composition and food intake in dairy cows throughout their lifespan, that is, during growth, over successive reproductive cycles and through ageing. This dynamic pattern of performance defines a reference trajectory of a cow under normal husbandry conditions and feed regimen. Genetic parameters are incorporated in the model to scale individual performance and simulate differences within and between breeds. The model was calibrated for dairy cows with literature data. The model was evaluated by comparison with simulations of previously published empirical equations of BW, body condition score, milk yield and composition and feed intake. This evaluation showed that the model adequately simulates these production variables throughout the lifespan, and across a range of dairy cattle genotypes.     

Nutritional influence on childhood development and genetic control of adolescent growth of Quechuas and Mestizos from the Peruvian Lowlands

The growth in height of 1,202 Quechua and Mestizo children aged 6 to 19 years of the province of Lamas in the Peruvian Eastern Lowlands was studied. As shown by evaluations of ABO, Rh systems, and skin reflectance measurements, the Quechuas are genetically different from the Mestizos. The heights of Quechuas and Mestizos were matched for nutritional status based on measurements of subcutaneous fat and body muscle. The study indicates that: (1) during childhood, Quechuas and Mestizos matched for the same nutritional status attain similar heights; (2) during adolescence (or after the age of 11 years), the Mestizos are significantly taller than the Quechuas of the same nutritional status; 3) during childhood, the relative difference in height between Quechuas and Mestizos matched for the same nutritional status is less than the difference between Quechuas (or Mestizos) of the same genetic composition characterized by good and poor nutritional status. These findings suggest that the influence of environmental factors, such as nutrition, have a greater influence in producing differences in body size during childhood than during adolescence. Conversely, the present findings support the hypothesis that the influence of genetic factors on body size are greater during adolescence than during childhood. However, comparison of adolescent samples of similar genetic composition (whether they be Quechuas or Mestizos), characterized by good and poor nutritional status, reveal large differences in height, suggesting that under conditions of malnutrition, the genetic control of growth is diminished.     

Acetate kinase production by Escherichia coli during steady-state and transient growth in continuous culture.

The synthesis of acetate kinase by Escherichia coli ATCC 9637 was studied during growth in anaerobic continuous cultures under steady-state and transient conditions. During growth in anaerobic, glucose-limited chemostats, acetate kinase synthesis was linearly associated with growth. Two types of non-steady-state transients were studied: the perturbation in one was the addition of glucose alone, and, in the second, glucose plus Casamino Acids. During the nutritional shift-up in the second case, but not in the first, the instantaneous specific acetate kinase activities and specific synthesis rates exceeded pre- and postshift values. Trajectory curves demonstrated that the increase in specific activity remained within the bounds of values obtainable under steady-state conditions with minimal and Casamino Acids media. Specific synthesis rates, however, greatly exceeded steady-state values. Enzyme yield values on glucose after the transient nutritional shift-up increased up to fivefold. Active protein synthesis is shown to be necessary to achieve the enhanced specific synthesis rates and enzyme yields. The results from these transient responses are discussed in terms of a conceptful model for metabolic regulation.     

Optimization of pulping conditions of abaca. An alternative raw material for producing cellulose pulp

The influence of temperature (150-170 degrees C), pulping time (15-45 min) and soda concentration (5-10%) in the pulping of abaca on the yield, kappa, viscosity, breaking length, stretch and tear index of pulp and paper sheets, was studied. Using a factorial design to identify the optimum operating conditions, equations relating the dependent variables to the operational variables of the pulping process were derived that reproduced the former with errors lower than 25%. Using a high temperature, and a medium time and soda concentration, led to pulp that was difficult to bleach (kappa 28.34) but provided acceptable strength-related properties (breaking length 4728 m; stretch 4.76%; tear index 18.25 mN m2/g), with good yield (77.33%) and potential savings on capital equipment costs. Obtaining pulp amenable to bleaching would entail using more drastic conditions than those employed in this work.     

Nutritional requirements of mycelial growth of Cordyceps sinensis in submerged culture

AIMS: The nutritional requirements for mycelial growth of Cordyceps sinensis in semi-synthetic liquid media were investigated. The results provide a basis for further physiological study and industrial fermentation of the fungus. METHODS AND RESULTS: Nutritional requirements, including 17 carbohydrates, 16 nitrogen compounds, nine vitamins, four macro-elements, four trace-elements and eight ratios of carbon to nitrogen, were studied for their effects on the mycelial growth in submerged cultures of C. sinensis by using one-factor-at-a-time and orthogonal matrix methods. Among these variables, sucrose, peptone, folic acid, calcium, zinc and a carbon to nitrogen ratio 12 : 1 were identified as the requirements for the optimum mycelial growth. The concentrations of sucrose, peptone and yeast extract were optimized and the effects of medium composition on mycelial growth were found to be in the order sucrose > yeast extract > peptone. The optimal concentration for mycelial growth was determined as 50 g l(-1) sucrose, 10 g l(-1) peptone and 3 g l(-1) yeast extract. CONCLUSIONS: Under optimal culture conditions, over 22 g l(-1) of mycelial biomass could be obtained after 40 days in submerged cultures. SIGNIFICANCE AND IMPACT OF THE STUDY: Cordyceps sinensis, one of the most valued medicinal fungi, is shown to grow in axenic culture. This is the first report on nutritional requirements and design of a simplified semi-synthetic medium for mycelial growth of this psychrophilic species, which grows slowly below 20 degrees C. The results of this study will facilitate research on mass production of the fungus under defined culture conditions.     

Use of a Controlled-Nutrient Experiment to Test Heterosis Hypotheses

A controlled-nutrient (CN) experiment was conducted to test three heterosis hypotheses with reference to tomato yield, and its components, for a set of two inbred lines and their hybrid that had previously exhibited considerable heterosis under field conditions. The CN treatments consisted of periodic applications of differential doses of nutrient solution to plants reared individually in containers filled with vermiculite. Ripe fruit were harvested, counted and weighed over a period of 340 days. The data permitted the partitioning of yield into a closed system of five component variables. Heterosis was not exhibited by yield, nor yield components, at any of the four nutrient levels. Hence the total heterosis phenomenon was classified as nutrient-dependent: heterosis occurring under field conditions, but not under the nutritional restrictions of the CN experiment. Three heterosis hypotheses were examined for their ability to explain all of the nutrient-dependent aspects of the heterosis phenomenon. Hypothesis 1: Heterosis is a consequence of a more efficient hybrid metabolic system in that it can produce more product with equal input. Hypothesis 2: Heterosis is a consequence of the somatic multiplication of additive component traits. Hypothesis 3: Heterosis is a consequence of a faster hybrid growth rate. Although none of the hypotheses are rejected by the field data, the first two are rejected by the CN experimental results. The third hypothesis fits all aspects of the nutrient-dependent heterosis phenomenon remarkably well. It is speculated that the indeterminate pattern of plant development responsible for yield and its components is due to two major gene systems: genes that determine morphogenetic, and genes that determine growth rate manifestations of growth. Under this hypothesis, the CN technique permits separation of the responses due to these two gene systems.     

Ethyleneglycol pulp from tagasaste

In this work, we examined the influence of operational variables [viz. Ethyleneglycol concentration (50-70%), temperature (155-185 degrees C), time (30-90 min) and number of PFI beating revolutions (500-1500)] in the ethyleneglycol pulping of tagasaste (Chamaecytisus proliferus) on pulp yield and the breaking length, stretch, burst index, tear index and brightness of paper sheets formed from it. Application of a fuzzy neural network model in combination with an experimental factorial design allowed the results for the dependent variables to be predicted as a function of the operating conditions used with errors less than 15% in all cases. The operating conditions of choice provided pulp with a high yield (56.85%) and a low brightness (22.51%) which may thus be useful to obtain non-white paper.     

Phenotypic plasticity to photon flux density of physiological,anatomical and growth traits in a modern Criollo cocoa clone

Cocoa grows under shade, but some cultivars develop successfully in full sunlight. In order to characterize the response to photosynthetic photon flux density (PPFD) of a Modern Criollo cocoa clone, gas exchange, photochemical activity and leaf traits, and their relation to growth were measured in seedlings growing in a greenhouse at three different values of PPFD, as well as in adults in full sunlight and shade in the field. Plants showed changes in physiological, biochemical, and morpho‐anatomical traits in response to the different light conditions, and in the phenotypic plasticity of these variables. Seedlings subjected to high PPFD in the greenhouse showed decreases in photosynthetic rate, apparent quantum yield of CO₂ fixation and photochemical quenching, and increases in non‐photochemical quenching, suggesting down‐regulation of PSII. In contrast, trees under full sunlight in the field showed a marked reduction in maximum quantum yield of PSII, indicating photoinhibition and supporting that cocoa is a shade tolerant crop. Cocoa showed higher plasticity of physiological and biochemical variables than morpho‐anatomical variables in response to PPFD. Effects of time under treatment in the greenhouse and plant age (greenhouse vs field) on plasticity were observed. The acclimation observed in some of the variables studied after 6 months in high light did not represent a particular advantage to seedlings, since relative growth rate was lower than in low‐ and medium‐light seedlings.     

Nutritional, growth, and reproductive responses of maize (Zea mays L.) to arbuscular mycorrhizal inoculation during and after drought stress at tasselling

The effects of root colonization by the arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck & Smith on nutritional, growth, and reproductive attributes of two tropical maize cultivars with different sensitivities to drought were studied. Freshly regenerated seeds of selection cycles 0 (cv. C0, drought-sensitive) and 8 (cv. C8, drought-resistant) of the lowland tropical maize population "Tuxpeño sequía" were used in this greenhouse experiment. Maize plants were subjected to drought stress for 3 weeks following tasselling (75–95 days after sowing) and rewatered for the subsequent 5 weeks until harvest. Mycorrhizal (M+) plants had significantly higher uptake of N, P, K, Mg, Mn, and Zn into grain than non-mycorrhizal (M–) plants under drought conditions. AM inoculation also produced significantly greater shoot masses in C0 and C8 regardless of the drought-stress treatment. In the sensitive cultivar C0, drought stress reduced the shoot mass and grain yield by 23% and 55%, respectively, when roots were not colonized, while the reductions were only 12% and 31%, respectively, with mycorrhizal association. In addition, the emergence of tassels and silks was earlier in M+ plants than in M– plants under drought conditions. Mycorrhizal response was more pronounced under both well-watered and drought conditions in C0 than in the C8 cultivar. The overall results suggest that AM inoculation affects host plant nutritional status and growth and thereby alters the reproductive behaviour of maize under drought conditions.     

Effect of Post-Infiltration Soil Aeration at Different Growth Stages on Growth and Fruit Quality of Drip-Irrigated Potted Tomato Plants (Solanum lycopersicum)

Soil hydraulic principles suggest that post-infiltration hypoxic conditions would be induced in the plant root-zone for drip-irrigated tomato production in small pots filled with natural soil. No previous study specifically examined the response of tomato plants (Solanum lycopersicum) at different growth stages to low soil aeration under these conditions. A 2 × 6 factorial experiment was conducted to quantify effects of no post-infiltration soil aeration versus aeration during 5 different periods (namely 27–33, 34–57, 58–85, 86–99, and 27–99 days after sowing), on growth and fruit quality of potted single tomato plants that were sub-surface trickle-irrigated every 2 days at 2 levels. Soil was aerated by injecting 2.5 liters of air into each pot through the drip tubing immediately after irrigation. Results showed that post-infiltration aeration, especially during the fruit setting (34–57 DAS) and enlargement (58–85 DAS) growth stages, can positively influence the yield, root dry weight and activity, and the nutritional (soluble solids and vitamin C content), taste (titratable acidity), and market quality (shape and firmness) of the tomato fruits. Interactions between irrigation level and post-infiltration aeration on some of these fruit quality parameters indicated a need for further study on the dynamic interplay of air and water in the root zone of the plants under the conditions of this experiment.     

Catalytic cracking of palm oil for the production of biofuels: optimization studies

Oil palm is widely grown in Malaysia. Palm oil has attracted the attention of researchers to develop an 'environmentally friendly' and high quality fuel, free of nitrogen and sulfur. In the present study, the catalytic cracking of palm oil to biofuel was studied over REY catalyst in a transport riser reactor at atmospheric pressure. The effect of reaction temperature (400-500 degrees C), catalyst/palm oil ratio (5-10) and residence time (10-30s) was studied over the yield of bio-gasoline and gas as fuel. Design of experiments was used to study the effect of operating variables over conversion of palm oil and yield of hydrocarbon fuel. The response surface methodology was used to determine the optimum value of the operating variables for maximum yield of bio-gasoline fraction in the liquid product obtained.     

Neural fuzzy model applied to ethylene-glycol pulping of non-wood raw materials

We studied the influence of the operational variables (viz. ethylene-glycol concentrations of 50-70%, temperatures of 155-185 degrees C, times of 30-90 min and numbers of PFI beating revolutions of 500-1500) on pulp yield and various paper properties (breaking length, stretch, burst index, tear index and brightness) obtained in the ethylene-glycol pulping of vine shoots, cotton stalks, leucaena (Leucaena leucocephala) and tagasaste (Chamaecytisus proliferus). The fuzzy neural network models used reproduced the experimental results with errors less than 15% and smaller than those provided by second-order polynomial models in all cases. An ethylene-glycol concentration of 65% at 180 degrees C for 75 min and 1500 PFI beating revolutions were found to provide substantial savings in energy, chemicals and facility investments as a result of operating under milder conditions than the strongest ones studied in this work. Tagasaste was found to be the most suitable raw material among those tested as it provided the paper sheets with the highest breaking length (4644 m), stretch (2.87%), burst index (2.46 kN/g), tear index (0.33 m Nm(2)/g) and brightness (40.92%); its pulp yield was also high (62.88%), which reflects efficient use of this raw material.     

Evaluation and modelling the utility of SCCO2 to support efficient lipase mediated esterification

Supercritical fluids offer environmental advantages over chemical solvents, while providing enhanced separation and chemical selectivity. The use of supercritical fluids for the recovery of products from biomass and the transformation of selected molecules (to add value) was studied. Free fatty acids were bio-catalytically transformed to fatty acid esters using lipase within a supercritical fluid environment. A central composite rotatable design was used to evaluate the influence of operating conditions on the enzymatic esterification process and a response surface equation was optimized to identify the most favourable process conditions for maximum free fatty acid conversion. Based on the model equation the process conditions under which it was predicted a yield of 100% esters could be obtained were: pressure 200 bar, temperature 60 °C, ethanol concentration 2.0 M, enzyme concentration 11 wt.% and time 60 min. Experiments conducted under these conditions gave an ester yield of 94.3% (close to predicted results). The activity per unit mass of biocatalyst was found to be 1585 μmol/min/g_cat. The results support the use of supercritical fluids for process integration.     

Microbial production of polyhydroxybutyrate with tailor-made properties: an integrated modelling approach and experimental validation

The microbial production of polyhydroxybutyrate (PHB) is a complex process in which the final quantity and quality of the PHB depend on a large number of process operating variables. Consequently, the design and optimal dynamic operation of a microbial process for the efficient production of PHB with tailor-made molecular properties is an extremely interesting problem. The present study investigates how key process operating variables (i.e., nutritional and aeration conditions) affect the biomass production rate and the PHB accumulation in the cells and its associated molecular weight distribution. A combined metabolic/polymerization/macroscopic modelling approach, relating the process performance and product quality with the process variables, was developed and validated using an extensive series of experiments and measurements. The model predicts the dynamic evolution of the biomass growth, the polymer accumulation, the consumption of carbon and nitrogen sources and the average molecular weights of the PHB in a bioreactor, under batch and fed-batch operating conditions. The proposed integrated model was used for the model-based optimization of the production of PHB with tailor-made molecular properties in Azohydromonas lata bacteria. The process optimization led to a high intracellular PHB accumulation (up to 95% g of PHB per g of DCW) and the production of different grades (i.e., different molecular weight distributions) of PHB.     

Effect of Extraction Procedures on Functional Properties of Eruca sativa Seed Mucilage

The effect of different extraction procedures on functional properties of mucilage extracted from Eruca sativa seed were investigated using response surface methodology. A Central Composite Face Design (CCFD) with three independent variables: temperature (25–85 °C), pH (4–10) and water to seed ratio (20:1–60:1) was used to study the response variables (yield, viscosity, emulsion stability, foam stability, solubility and water absorption capacity). For each response, a second-order polynomial model was developed using multiple linear regression analysis. The results indicated that extraction temperature and pH significantly (p < 0.05) affected all functional properties. Applying desirability function method, optimum operating conditions were found to be extraction temperature of 65.5 °C, pH: 4 and water to seed ratio of 60:1. At this optimum point, maximum extraction yield, viscosity, emulsion stability (ES), foam stability (FS), solubility and water absorption capacity (WAC) were found to be 10.3 (%), 357 (mPas), 87 (%), 87.5 (%), 28.5 (%) and 9.3 (g/g), respectively.     

Importance of soil-water relations in assessing the endpoint of bioremediated soils

This study was conducted during 1992–1994 under semi-arid conditions in Burkina Faso. Our aim was to assess the influence of different mulch materials on soil variables affecting crop growth; i.e. water content, nutrient contents and temperature. The grain yield of Sorghum bicolor was used as a bioindicator, i.e. as an integrated measure of mulch effects.Six treatments were tested, two of which were leaf mulches of special interest for agroforestry. The treatments were chosen to represent mulch materials differing in nutrient content and decomposability (assumed to influence the duration of the impact on soil water content and temperature). The treatments were as follows: (1) control (no addition), (2) Azadirachta indica (neem) leaves, (3) neem leaves + aerobic compost of sorghum straw, (4) aerobic compost, (5) Acacia holocericea (acacia) phyllodes, and (6) wild grass. The mulching rate was 5 t dry matter ha^-1, and base mineral fertilizers were applied to all plots.It was shown that the neem leaves, neem leaves + compost, wild grass and acacia phyllodes treatments all significantly influenced the soil by conserving water and reducing temperatures compared with the control or the treatment with compost alone. Plots treated with either neem leaves, neem leaves + compost or compost alone gave higher yields than the three other treatments, generally poorer in nutrients, between which there was little difference. Neem leaves gave the numerically highest response: 1.54 × control, corresponding to a grain yield increase of 554 kg dry mass ha^-1 yr^-1 when averaged over the three years of study.Thus, yields did not always increase in spite of increased soil moisture and decreased soil temperatures. It was concluded that nutrients were more limiting than water or high soil temperatures under the conditions studied. The highest yields were achieved with a mulch that combines high nutrient delivery with water conservation and temperature reduction, namely mulch from neem leaves.     

Compensating for a bad start: catch-up growth in juvenile lizards (Amphibolurus muricatus, Agamidae)

In most natural environments, food availability varies unpredictably through space and time, and growth rates of individual organisms respond accordingly. However, growth rates are not necessarily a simple function of current nutritional conditions: growth rates can be affected by earlier nutritional experience as well as current circumstances. Thus, even a brief period of dietary restriction early in life might influence growth rates later on: either reducing them (if early experience sets subsequent rates, as in the "silver spoon" effect) or increasing them (if underfed individuals can compensate by growing more rapidly to cancel out the early decrement). Alternatively, later growth may be unaffected by earlier rates of growth. We experimentally manipulated food supply (and thus, growth rates) of hatchling lizards (Amphibolurus muricatus) for 1 month post-hatching, then maintained both high-food and low-food animals under identical nutritional conditions in outdoor enclosures for another 6 months. Low food abundance early in life significantly reduced juvenile growth, but these previously underfed animals exploited the subsequent (common garden) conditions to grow much faster than their larger (initially better-fed) siblings. Thus, the two groups were indistinguishable in body size at 6 months of age. Intriguingly, the compensatory growth occurred in winter, a period that is generally unsuitable for rapid growth in ectotherms.     

Effects of nitrogen fertilization in shrub willow short rotation coppice production – a quantitative review

Sustained interest in producing renewable energy from dedicated woody biomass crops, such as shrub willow (Salix spp.), through short rotation coppice (SRC) has resulted in a substantial amount of published research on SRC over the past few decades. One area of constant focus has been the nutritional requirements for optimal growth and yield. Inconsistency in the results of individual research trials has likely been a driver of repeated experimentation. This review is intended to provide a quantitative examination of the effect of fertilization treatments on willow biomass yield in field conditions. Data from the literature were collected and summarized to test for significant sources of variation in willow biomass nitrogen (N) pools of common SRC genotypes used in North American and European research programs. A meta‐analysis was conducted on studies comparing synthetic or organic sources of N willow fertilization to an unfertilized control treatment to test for yield response. Overall, the majority of responses to fertilization were positive, although variation by species, N source material, and crop age were found. While no clear pattern in N dosage response was observed, the level of yield response was correlated with geographic and climatic variables. Nitrogen export levels were fairly predictable, and the synthesis presented here can be used to refine current guidelines. Environmental and economic aspects are also considered.