Valores de referencia de oxalato, calcio, citrato, ácido úrico, fósforo, magnesio, sulfato y sodio urinarios en alumnos de la carrera de bioquímica de la Universidad Nacional del Litoral, Argentina / Reference values for urinary oxalate, calcium, citrate, uric acid, phosphate, magnesium, sulphate and sodium in biochemistry students at Universidad Nacional del Litoral, Argentina

INTRODUCCIÓN: La urolitiasis (UL) es una alteración frecuente, cuya incidencia ha aumentado en el último cuarto del siglo XX. Para su diagnóstico se realizan estudios metabólicos para lo cual es necesario contar con valores de referencia (VR) establecidos para la población en cuestión. OBJETIVO: El objetivo del trabajo fue determinar VR de calcio, oxalato, citrato, úrico, fósforo, magnesio, sulfato y sodio en orina de 24 horas de alumnos de la Facultad de Bioquímica y Ciencias Biológicas de la Universidad Nacional del Litoral, Santa Fe, Argentina. Con los VR hallados se determinó la frecuencia de alteraciones y se la comparó con datos bibliográficos. MATERIAL Y MÉTODOS: Se utilizó la guía NCCLSC28-A3, 2008. La muestra de referencia fue de 69 alumnos. Se utilizaron métodos enzimáticos-colorimétricos, espectrofotómetro Metrolab 1600 plus, electrodos ion selectivo DIESTRO. RESULTADOS: Los VR hallados (IC 95%) fueron para el oxalato: 1,96-45,08; calcio: 20,65-250,74; citrato: 112,78-666,01; ácido úrico 58,73-782,17; fósforo 238,37-1051,44; magnesio 28,7-146,67 todos en mg/24h; sulfato 3,15-25,18 mmol/24h y sodio 42,81-285,3 mEq/24h. Se encontró un 3% hiperoxaluria, 12% hipercalciuria, 3% hipocitraturia y 6% hiperuricosuria, 6% hiperfosfaturia, 6% hipomagnesuria, 7% hipernatriuria, 0% hipersulfaturia. Los VR comparados mostraron coincidencias para algunos analitos y para otros amplias diferencias. CONCLUSIONES: El diagnóstico de la alteración metabólica para el estudio de UL varía según el valor de referencia utilizado. Adoptar valores establecidos para otras poblaciones, incluidos los de los fabricantes de los kits comerciales, conducen a un diagnóstico que puede no ser acorde a la situación clínica del paciente

INTRODUCTION: Urolithiasis (UL) is a common disease whose incidence increased in the last quarter of the twentieth century. Metabolic evaluation is necessary for diagnosis, which requires the establishment of reference values (RV) for the population in question. OBJECTIVE: To determine the RV for calcium, oxalate, citrate, uric acid, phosphate, magnesium, sulphate and sodium in 24-hour urine belonging to students from the School of Biochemistry and Biological Sciences at Universidad Nacional del Litoral, province of Santa Fe, Argentina. Once RV were established, a frequency of alterations was determined and then compared with literature data. METHODS: The NCCLSC28-A3 guideline (2008) was used. The study group included 69 students. The enzymatic colorimetric method, a Metrolab 1600 plus spectrophotometer and a DIESTRO ion-selective electrode were also employed. Results: The RV found (95 % CI) were the following: oxalate, 1.96-45.08; calcium, 20.65-250.74; citrate, 112.78-666.01; uric acid, 58.73-782.17; phosphate, 238.37-1051.44; magnesium, 28.7-146.67, all these values expressed as mg/24h; sulphate, 3.15-25.18 mmol/24h, and sodium, 42.81-285.3 mEq/24h. These findings emerged as well: hyperoxaluria, 3%; hypercalciuria 12%; hypocitraturia, 3%; hyperuricosuria, 6%; hyperphosphaturia, 6%; hypomagnesuria, 6%; hypernatriuria, 7%, and hypersulphaturia, 0%. When RV were compared, some analyte levels were similar and others showed a considerable difference. CONCLUSIONS: The diagnosis of UL through the study of metabolic changes is different according to the reference value used. Applying reference values established for other populations, including those of commercial kits manufacturers, may lead to a diagnosis which does not match the clinical condition of the patient

Influences of phenolic compounds on citric acid productivity by Aspergillus niger in stirred fermentor

Influences of phenol, alpha-naphtol and beta-naphtol, which are toxic chemicals, on citric acid biosynthesis and biomass in the artificial culture setting of Aspergillus niger using batch fermenter are examined in the most favorable fermentation conditions, and a model is proposed. Addition of certain concentrations of phenol, alpha-naphtol and beta-naphtol to the culture increases the citric acid production. According to this model, maximum citric acid concentration is 48.3 g L-1 in a culture that does not contain any toxic chemicals, whereas the maximum concentrations obtained in cultures containing 25 mg L-1 phenol, 25 mg L-1 alpha-naphtol and 15 mg L-1 beta-naphtol are 62.5 g L-1, 78.1 g L-1 and 86.0 g L-1, respectively. Moreover, addition of toxic chemicals to the culture reduces fermentation time by 24 hrs.

Valorization of raw glycerol for citric acid production by Yarrowia lipolytica yeast

In the present report, citric acid production from raw glycerol in two fed-batch systems by acetate negative-mutants of Yarrowia lipolytica: Wratislavia 1.31 and Wratislavia AWG7 was compared. In the system, in which the total glycerol concentration was 200 g∙L-1, the substrate was added by pulsed additions, and in the other, in which the total glycerol concentration was 300 g∙L-1, the substrate was added at a constant feeding rate of 1.4 g∙h-1. Despite high citric acid concentrations (155.2 and 157.5 g∙L-1 with Y. lipolytica Wratislavia 1.31 and Y. lipolytica Wratislavia AWG7, respectively) obtained from 300 g∙L-1 of glycerol, the yield of citric acid was similar, i.e. about 0.6 g∙g-1. The volumetric citric acid productivity was markedly higher (1.05 and 0.94 g∙L-1h-1 with Y. lipolytica Wratislavia 1.31 and Y. lipolytica Wratislavia AWG7 strains, respectively) in the cultures containing 200 g∙L-1 of carbon source.

Citric acid production from glucose by yeast Candida oleophila ATCC 20177 under batch, continuous and repeated batch cultivation

The effect of air saturation on citric acid production in batch, repeated batch and chemostat cultures has been studied. It was shown that, under continuous fermentation (chemostat mode), the highest concentration of citric acid equal of 98 g/l was produced at 20% of air saturation. In contrary to continuous fermentation, displaying an optimum at 20%, 80% air saturation yielded higher values in repeated batch fermentation process. 167 g/l citric acid were produced continuously with the fill and drain technique at 4.85 days, at 80% air saturation, compared with 157.6 g/l achieved within 5.4 days at 20%. Under repeated batch fermentation, the formation rate of the generic product (Rj) as well as the specific citric acid productivity (mp) reached a maximum of 1.283 g/(l x hr) at 4.01 days and of 0.0375 g/(g x hr) at 4.58 days, respectively. The glucose consumption rate (Rx) reached a maximum value of 3.33 g/(l x hr) entering stationary phase after 2.56 days at a glucose concentration of 131.2 g/l.

Selection of 5-fluorocytosine-resistant mutants from an Aspergillus niger citric acid-producing strain

Mutants of Aspergillus niger N402, induced by UV mutagenesis, were selected and tested for resistance or sensitivity to 5-fluorocytosine. Some mutants showed increased citric acid production, which did not correlate with the intracellular amount of protein or ammonium ion. The resistance to 5-fluorocytosine proved to be a rational approach for isolation of new mutants with improved production of citric acid. The best mutant (FR13) accumulated double the amount of citric acid produced by the parental strain.

Efecto de metales traza sobre la morfología celular, actividad enzimßtica y producción de ácido cítrico en una cepa de Aspergillus wentii / Effect of trace metals on cell morphology, enzyme activation, and production of citric acid in a strain of Aspergillus wentii

Data concerning the effect of very low concentrations of metals on citric acid production by microorganisms, as well as on the activity of enzymes presumptively involved in the process, are confuse. The bulk of information was obtained mainly studying selected strains of Aspergillus niger. Information concerning other citric acid producer filamentous fungi, such as A. wentii, is scanty. In the present article we report the effect of different cations on the growth pattern of A. wentii P1 as well as on the related citric acid production and the activity of several enzymes. It was found that without any addition to the culture medium the fungus developed a pelleted form of growth, pellets being about 1.5 mm in diameter. The citric acid yield was about 90. The addition of Cu2+ impaired the sugar uptake, as well as the production of citric acid and biomass. The uptake of sugar increased in the presence of Zn2+, and there was a marked increase of the biomass production, which could account for the low citric acid production. The addition of Fe2+ impaired the citric acid production and, as sulfate, the sugar uptake. The presence of Fe3+ markedly impaired the citric acid production and increased the sugar uptake. There is no agreement about the enzymes involved in the accumulation of citric acid by microorganisms. In spite of this, aconitase (Ac), isocitrate lyase (IL), isocitrate dehydrogenase NAD(+)-dependent (ICDH- NAD+) and isocitrate dehydrogenase NADP(+)-dependent (ICDH-NADP+) are often postulated as key enzymes. In our case, these enzymes were active during the standard fermentation, although with variations, particularly concerning Ac and IL. The behavior of enzymes might be different when tested in vivo or in vitro, mainly from the quantitative point of view. Nevertheless, the activity determined in vitro might give some indication concerning the effect on fermentation of substances present in the medium. It was found that all the enzymes tested increased their activity in the presence of Fe2+ and Fe3+. The addition of Cu2+ improved the activity of Ac, IL and ICDH-NADP+, while that of ICDH-NAD+ was impaired. The presence of Zn2+ decreased the activity of the enzymes excepting that of ICDH-NADP+ which increased. It must be pointed out that according to these results there are differences concerning the behavior of ICDH-NAD+ and ICDH-NADP+ in the presence of Cu2+ or Zn2+.

Some aspects of citrate metabolism in renal-stone patients from northeastern Thailand.

In our previous nephrolithiasis studies in the northeast region of Thailand, hypokaliurea and hypocitraturia were the 2 most commonly encountered metabolic abnormalities. This led us to believe that people prone to forming renal-stones in this area were in a state of potassium depletion, a condition which probably caused the low urinary excretion of citrate. Further studies on some aspects of citrate metabolism in these subjects were carried out. Two groups of adult male subjects were included in the study protocol. Group 1 consisted of 20 urban dwellers who were used as normal controls, and group 2 was comprised of 36 renal-stone patients residing in rural villages outside the municipal area. Fasting clotted venous blood and one 24-hour urine specimens were collected and analyzed for creatinine, citrate, calcium, phosphate, magnesium, sodium, potassium, chloride, bicarbonate and uric acid. Values for: creatinine and citrate clearances, the filtered load of citrate and the tubular reabsorption of citrate were then calculated. The results showed that, for both groups, the concentrations of most of the above parameters were within the normal ranges both serum and urine. An exception to this was that the levels of serum potassium and of urinary excretions of sodium, potassium and citrate in people in group 2 were significantly less than those in group 1 (p < 0.005, p < 0.001, p < 0.001 and p < 0.0001, respectively). With respect to citrate metabolism, while the serum citrate levels and the filtered load of citrate were not different between the 2 groups, the average percentage of renal tubular reabsorption of group 2 (95 +/- 1.1%) increased significantly (P < 0.0001)in comparison to group 1 (85 +/- 1.6%). Moreover when results from both groups were combined, a significant negative correlation between the renal tubular reabsorption of citrate and the urinary excretion of potassium was clearly seen (r = 0.4001, p < 0.007). Our data suggests that potassium depletion may affect the renal tubular cells in some manner which, consequently, causes an increase in renal tubular reabsorption of citrate. The final outcome of these changes in these renal stone subjects was hypocitraturia.