Microalgae fractionation using steam explosion, dynamic and tangential cross-flow membrane filtration

In this study, the microalga Nannochloropsis gaditana was subjected to acid catalysed steam explosion treatment and the resulting exploded material was subsequently fractionated to separate the different fractions (lipids, sugars and solids). Conventional and vibrational membrane setups were used with several polymeric commercial membranes. Two different routes were followed: 1) filtration+lipid solvent extraction and 2) lipid solvent extraction+filtration. Route 1 revealed to be much better since the used membrane for filtration was able to permeate the sugar aqueous phase and retained the fraction containing lipids; after this, an extraction required a much lower amount of solvent and a better recovering yield. Filtration allowed complete lipid rejection. Dynamic filtration improved permeability compared to the tangential cross-flow filtration. Best membrane performance was achieved using a 5000Da membrane with the dynamic system, obtaining a permeability of 6L/h/m²/bar.

Effect of pre-treatments on the production of biofuels from Phaeodactylum tricornutum

Several characteristics make Phaeodactylum tricornutum potential candidate for biofuels production such as methane and biodiesel. For this reason, some alternatives are evaluated in this manuscript to improve the conversion of this microalgae into methane. One of these alternatives is the addition of sewage sludge to Phaeodactylum tricornutum for anaerobic co-digestion. Although the co-digestion resulted in lack of synergy, the absence of inhibition indicated that both substrates could be co-digested under certain circumstances, for example if microalgae are cultivated for wastewater treatment purposes. The extraction of lipids using organic solvents has been evaluated for biodiesel production but also as a pre-treatment for anaerobic digestion. The results revealed that the type of solvent influences lipid and biodiesel yields. The high polarity of the mixture methanol/hexane increased the lipid and the biodiesel yields from 10 ± 1 to 53 ± 2 gLipids/100 gVS and from 7 ± 1 to 11 ± 1 gBiodiesel/100 gVS compared with hexane. However, none of these solvents affected the composition of biodiesel. Regarding the methane production after the extraction, it yielded 257 ± 8 and 180 ± 6 mLCH4/gVS from lipid-extracted P. tricornutum using hexane and methanol/hexane respectively. The methane production from the raw microalga was 258 ± 5 mLCH4/gVS in the same experiment. The difference in methane production, mainly after the extraction with methanol/hexane, was a consequence of the changes in the composition of the microalgae after extraction. The extraction did not influence the biodegradability. The ultrasonic pre-treatment prior anaerobic digestion completely disrupted the microalgae cells, but the solubilisation of the organic fraction was scarce (<9.5%). The methane production from pre-treated samples was barely 10-11% higher than the obtained from non pre-treated samples, indicating that the refractory nature of the organic fraction in P. tricornutum is the main obstacle for the methane production.

Biorefinery concept in a microalgae pilot plant. Culturing, dynamic filtration and steam explosion fractionation

A 53 m(3) microalgae pilot plant with semi-closed photobioreactors has been operated in batch mode at Tarragona, where proper climatic conditions exist. Operations carried-out were microalgae culturing, concentration, cell disruption and lipid extraction. Culturing was performed with and without CO2 fertilization. pH was used to control CO2 dosing. With CO2 fertilization best microalgae concentrations were obtained. Productivities up to 19.9 g/m(2)/day were reached. Although sedimentation and centrifugation was performed, studies focused on dynamic membrane filtration as improved technique compared with conventional one. Significant fouling reduction was obtained by using a vibrational membrane setup. Cell disruption including product pre-extraction was performed by using steam explosion at moderate conditions, as novel technique for this application. Lipid extraction was performed by using conventional techniques with and without exploded material. The amount of lipids obtained from exploded material was higher than with non-exploded material, which shows that steam explosion provides a clear enhancement.

Isoflavone effect on gene expression profile and biomarkers of inflammation

The use of high throughput techniques to find differences in gene expression profiles between related samples (transcriptomics) that underlie changes in physiological states can be applied in medicine, drug development and nutrition. Transcriptomics can be used to provide novel biomarkers of a future pathologic state and to study how bioactive food compounds or drugs can modulate them in the early stages. In this study, we examine the expression pattern in order to determine the effect of the pathological-inflammatory state on the RAW 264.7 cell model and to ascertain how isoflavones and their active functional metabolites alleviate the inflammatory burst and the extent of gene modulation due to the presence of polyphenols. Results demonstrated that genistein (20 microM) and equol (10 microM) significantly inhibited the overproduction of NO and PGE(2) induced by LPS plus INF-gamma when a pre-treatment was performed or when administered during activation. Daidzein, however, did not exert similar effects. Moreover, both isoflavone treatments regulated gene transcription of cytokines and inflammatory markers, among others. The transcriptomic changes provide clues firstly into defining a differential expression profile in inflammation in order to select putative biomarkers of the inflammatory process, and secondly into understanding the isoflavone action mechanism at the transcriptional level. In conclusion, isoflavone modulates the inflammatory response in activated macrophages by inhibiting NO and PGE(2) and by modulating the expression of key genes defined by transcriptomic profiling.

Regulation of ammonia-metabolizing enzymes expression in the liver of obese rats: differences between genetic and nutritional obesities

OBJECTIVE

To determine the expression of carbamoylphosphate synthetase (CPS) and glutamine synthetase (GS) in two different models of obese rats: genetically obese rats and diet obese rats.

SUBJECTS

Lean and genetically obese (fa/fa) Zucker rats were used.

DESIGN

Lean animals (30-60 d old) were fed for 30 d with standard chow pellets or with a hypercaloric cafeteria diet. Genetically obese rats were fed with standard chow pellets.

MEASUREMENTS

Enzyme activity, protein (Western blot) and mRNA (Northern blot) contents of CPS and GS were measured in liver homogenates.

RESULTS

In genetically obese animals CPS mRNA content was higher, and GS mRNA content was lower than in control animals; CPS protein content did not change and CPS activity was lower than in control rats. Diet-obese rats had higher levels of CPS and GS mRNAs than control animals; GS protein content and activity was higher than in the control group and at the same time, CPS activity was very low.

CONCLUSIONS

In the genetically obese animals the expression of CPS and GS is mainly regulated at the pre-translational level, whereas in the diet obese rats there is a noticeable post-translational component. A reciprocal regulation between CPS and GS can be established at pre-translational levels, whereas at post-transcriptional levels it cannot. It can be concluded that in diet-obese animals the mechanisms involved in retaining nitrogen (low CPS activity) are modulated at the post-translational level.

[Disseminated acute encephalomyelitis with fatal evolution: clinicopathological study]

INTRODUCTION

Disseminated acute encephalomyelitis is a monophasic demyelinating disease which progresses rapidly and is often fatal. It is an autoimmune condition, mediated by T lymphocytes, in which the immune response is directed against the myelin antigens.

CLINICAL CASE

We describe the clinical, radiological and neuropathological findings in the case of a 31 year old woman who, ten days after complaining of a clinical condition of upper respiratory tract inflammation, presented with unilateral focal neurological signs, subsequent rapid deterioration of consciousness and death. On autopsy the neuropathological characteristics of disseminated acute encephalomyelitis were seen.

CONCLUSIONS

The relative rarity of this condition at the present time makes clinical diagnosis difficult. The differential diagnosis with other conditions may be difficult also. Thus, this disease often leads to a neuropathological diagnosis.

Regulation of glutamate dehydrogenase expression in the developing rat liver: control at different levels in the prenatal period

To study the regulation of the expression of glutamate dehydrogenase (Glu-DH) in rat liver during development, the Glu-DH mRNA concentration in the liver of rats ranging in age from 14 days prenatal development to 3 months after birth was determined. This concentration increased up to two days before birth, decreased rapidly between two days before and one day after birth and increased again in the second and third postnatal week. The ratio of Glu-DH mRNA/protein decreased more than 10-fold in the prenatal period, whereas it did not change significantly after birth. Thus, whereas the ratio between the Glu-DH monomer protein molecules and Glu-DH mRNA molecules is found to be approximately 1400 at 14 days of prenatal development, it is approximately 1700 four weeks after birth. We argue than an increase in the translational efficiency after birth is the most likely cause of the observed developmental changes in Glu-DH mRNA/protein ratio. Our results suggest that the expression after birth is predominantly regulated at the pretranslational level, whereas the prenatal Glu-DH expression is regulated both at the translational level and at the pretranslational level.

Changes in alanine turnover rate due to nutritional and genetic obesity in the rat

The changes in alanine turnover were determined in Zucker rats, which were either genetically obese (fa/fa) or rendered obese by dietary treatment (cafeteria fed). The whole body rate of alanine turnover was higher in genetically obese rats than in rats in which obesity was induced by diet (cafeteria). This is possibly due to variations in the rate of the amino acid incorporation into proteins, since the rate of whole body alanine degradation is the same for both groups. Thus, the different pattern followed by alanine turnover rate in these types of obese animals reflects the differences in the nitrogen economy of these animals, pointing to a higher alanine utilization in the genetically obese animals and a conservative management of alanine in the cafeteria-fed animals.

Long-term effects of cafeteria diet feeding on young Wistar rats

The long-term effects of cafeteria diet feeding were studied by comparing the circulating levels of glucose, lactate, glycerol, 3-hydroxybutyrate and urea, and liver glycogen in female Wistar rats offered the diet from birth (CB) or from 30 days (C30) after birth, compared with controls fed on a standard reference diet. Body weight was maximal for CB, distinctly higher than that of C30, which in turn were heavier than controls. Growth rates, however, were similar for most of the period studied. Plasma glucose homeostasis was maintained fully in all three groups, with a remarkable lack of changes in liver glycogen concentration. The patterns of lactate and glycerol concentration changed with age. Different initial settings converged to adult values in all groups. The higher ability of cafeteria rats to use lipids as energy fuel is in agreement with their higher circulating levels of 3-hydroxybutyrate, a factor that may be essential in the shift to increased fat deposition that characterizes prolonged cafeteria feeding. Urea levels were highest in controls, and lowest in cafeteria rats fed from day 30, a consequence of the different setting of nitrogen sparing induced by the timing of initiation of cafeteria feeding. From the results presented it can be postulated that the type of diet onto which the rats are weaned may significantly affect their weight and metabolic correlations much later in life.

Changes induced in amino acid-enzymes of developing rats by a high-energy diet and glucose gavage

Liver and muscle amino acid enzyme activities and plasma proteins, urea, amino acids, glucose, lactate, 3-hydroxybutyrate and acetoacetate concentrations were studied in growing rats undergoing adaptation to high-fat, high-energy diet and glucose gavage. Liver and muscle were used for the estimation of alanine transaminase (GPT, EC 2.6.1.1.), adenylate deaminase (AMD, EC 3.5.4.6.), glutamine synthetase (GST, EC 6.3.1.2) and serine dehydratase (SDH, EC 4.2.1.13) activities, the latter only in liver samples. The most important modifications produced in muscle enzyme activities by glucose gavage were observed in rats fed a cafeteria diet. Glucose gavage affects liver enzyme activities in the same sense than cafeteria diet. Energy plasma components were affected in opposite way by glucose gavage according to diet administered.

Effect of diet and essential amino acids gavage on young rat amino acid metabolism enzymes

1. The effects of a high-fat, high-energy diet and essential plus semi-essential amino acid gavage on pup rats have been studied (60-65 animals). 2. The activities of alanine transaminase, adenylate deaminase, glutamine synthetase and serine dehydratase have been tested in liver and muscle. 3. Plasma was used for the estimation of proteins, urea, amino acids, glucose, lactate, 3-hydroxybutyrate and acetoacetate. 4. Liver and muscle glutamine synthetase activities are increased by diet and gavage administered. Hepatic serine dehydratase is inhibited by a cafeteria diet but activated by amino acid gavage. Adenylate deaminase is inhibited by diet and gavage in the liver, but gavage does not affect this enzyme activity in muscle. Liver alanine transaminase is increased by the diet; in the muscle, cafeteria diet and amino acid gavage showed the highest values for this enzyme. 5. In the plasma, the increase in lactate produced by the diet is inhibited by the amino acids provided. Cafeteria-fed pups showed lower urea levels and higher 3-hydroxybutyrate concentrations in the plasma. 6. Intracellular glucose is diminished by cafeteria diet. In contrast, the blood cell amino acid concentration increases with diet and gavage supplied.

Postnatal development of amino acid metabolism enzymes in the liver and muscle of 'cafeteria' rats

The effect of feeding a high-energy highly palatable cafeteria diet on the liver and muscle ontogenesis of serine dehydratase, alanine transaminase, glutamine synthetase and adenylate deaminase during postnatal development of the rat has been studied. The results are in agreement with the lower amino acid utilization in cafeteria rats, both adults and during postnatal development. The feeding of excess energy coupled with high-quality protein resulted in changes in the ontogenesis of the studied enzymes that coincide with the development of protein synthesis and overall pup growth even before they had direct access to this rich diet, suggesting that cafeteria feeding already affects the amino acid metabolism of the pup through the dam's milk.

Effects of lactation on circulating plasma metabolites in 'cafeteria-fed' rats

1. The effects of 'cafeteria feeding' on primiparous Wistar rats during lactation have been studied by measuring circulating levels of glucose, amino acids, lactate, urea and ammonia as well as glycogen levels in liver and muscle. 2. No significant changes in glucose levels were observed despite alterations in blood glucose compartmentation. 3. Compared with controls, the dams given the cafeteria diet had higher liver glycogen stores which were more easily mobilized at the peak of lactation. 4. Rats given the cafeteria diet showed a lower amino acid utilization than controls and adequately maintained circulating levels, as determined by the lower circulating levels of ammonia and urea. 5. No significant differences in body-weight were observed in the period studied despite increasing dam weight after weaning in the cafeteria-fed group. 6. The size of pups of cafeteria-fed dams was greater than that of controls, and the differences were marked after weaning, when the metabolic machinery of the cafeteria pup maintained high protein accretion and body build-up using fat as the main energy substrate characteristic of the preweaning stage. The controls, however, changed to greater utilization of amino acids as an energy substrate and adapted to high-protein (low-biological-quality) diets with a significantly different pattern of circulating nitrogen distribution.

[Hepatic cirrhosis and primary pulmonary hypertension. A case report (author's transl)]

The present report deals with the clinical history and autopsy findings of a 41 year-old male patient with hepatic cirrhosis, surgical splenorenal shunt and severe pulmonary hypertension. Since the original description of Mantz and Craige several series have been reported, both in children and in adults, of the association between pulmonary hypertension and liver disease and/or portal hypertension. However, the type of hepatic alteration associated to pulmonary hypertension and the mechanisms responsible for this association remain unclarified. In the present case prominent plexiform and/or angiomatoid lesions of the pulmonary vasculature were observed, prompting the authors to speculate on the possibility that non-identified vasoconstrictor substances might contribute to the production of morphological lesions in the arterio-venous pulmonary shunts.