Torbjörn Linden - Academia.edu (original) (raw)

Papers by Torbjörn Linden

Peritoneal Dialysis International, Jul 1, 2001

Objective: When glucose is present in a medical fluid, the heat applied during sterilization lead... more Objective: When glucose is present in a medical fluid, the heat applied during sterilization leads to degradation. The glucose degradation products (GDPs) give rise to bioincompatible reactions in peritoneal dialysis patients. The extent of the degradation depends on a number of factors, such as heating time, temperature, pH, glucose concentration, and catalyzing substances. In the present work, we investigated the influence of pH and concentration in order to determine how to decrease the amounts of GDPs produced. Design: Glucose solutions (1%-60% glucose; pH 1-8) were heat sterilized at 121°C. Ultraviolet (UV) absorption, aldehydes, pH, and inhibition of cell growth (ICG) were used as measures of degradation. Results: Glucose degradation was minimum at an initial pH (prior to sterilization) of around 3.5 and at a high concentration of glucose. There was considerable development of acid degradation products during the sterilization process when the initial pH was high. Two different patterns of development of UV-absorbing degradation products were seen: one below pH 3.5, dominated by the formation of 5-hydroxy-methyl-2-furaldehyde (5-HMF); and one above, dominated by degradation products absorbing at 228 nm. 3-Deoxyglucosone (3-DG) concentration and the portion of 228 nm UV absorbance not caused by 5-HMF were found to relate to the in vitro bioincompatibility measured as ICG; there was no relation between 5-HMF or absorbance at 284 nm and bioincompatibility. Conclusion: In order to minimize the development of bioincompatible GDPs in peritoneal dialysis fluids during heat sterilization, pH should be kept around 3.2 and the concentration of glucose should be high. 5-HMF and 284 nm UV absorbance are not reliable as quality measures. 3-DG and the portion of UV absorbance at 228 nm caused by degradation products other than 5-HMF seem to be reliable indicators of bioincompatibility.

Enzyme and microbial technology, Apr 1, 1993

ABSTRACT Three differently treated xylose isomerase preparations of Lactobacillus brevis DSM 2005... more ABSTRACT Three differently treated xylose isomerase preparations of Lactobacillus brevis DSM 20054 whole cells were compared with a commercial immobilized preparation, Maxazyme GI-immob., with respect to activity and stability. All isomerizations were performed in spent sulfite liquor. The activity (∼300 mg xylulose g−1 dry weight biocatalyst h−1) of one preparation, heat-, ethanol-, and glutaraldehyde-treated whole cells of L. brevis, was 30 to 40 times higher, at pH 5 and 5.5, respectively, than that of the commercial enzyme at pH 5.5. The commercial enzyme was not active at pH 5. During four repeated 24-h isomerizations, this L. brevis preparation retained 70% of the activity at pH 5.5 and 30% at pH 5, as compared with 66 and 0%, respectively, for the commercial preparation.

Applied Biochemistry and Biotechnology, Mar 1, 1992

Peritoneal Dialysis International, Dec 1, 2001

A patient on peritoneal dialysis (PD) uses 3-7 tons of PD fluid every year. The result is conside... more A patient on peritoneal dialysis (PD) uses 3-7 tons of PD fluid every year. The result is considerable stress on the peritoneal tissue. Aspects of PD fluids that have been considered responsible for bioincompatibility are low pH, high osmolality, high glucose and lactate concentrations, and the presence of glucose degradation products (GDPs). However, the relative importance of each factor in PD fluid has so far not been investigated. Discovering their relative importance was the aim of the present study. Two main methods for investigating biocompatibility were used in this study: cytotoxicity measured as in vitro inhibition of cell growth, and in vitro AGE formation measured as albumin-linked fluorescence. The two most important factors for determining in vitro bioincompatibility of PD fluids were the presence of GDPs, which caused both severe cytotoxicity and strong AGE promotion, and low pH, which induced severe cytotoxicity. The biocompatibility of PD fluids can be monitored through fairly simple in vitro methods such as cell proliferation and AGE formation. Bioincompatibility of PD fluids is caused mainly by the presence of GDPs and low pH. These findings correlate well with known clinical bioincompatibility.

Peritoneal Dialysis International, Nov 1, 2005

During heat sterilization and during prolonged storage, glucose in peritoneal dialysis fluids (PD... more During heat sterilization and during prolonged storage, glucose in peritoneal dialysis fluids (PDF) degrades to carbonyl compounds commonly known as glucose degradation products (GDPs). Of these, 3,4-dideoxyglucosone-3-ene (3,4-DGE) is the most cytotoxic. It is an intermediate in degradation between 3-deoxyglucosone (3-DG) and 5-hydroxymethyl-2-furaldehyde (5-HMF). We have earlier reported that there seems to be equilibrium between these GDPs in PDF. The aim of the present study was to investigate details of this equilibrium.

Peritoneal Dialysis International, Jul 1, 2004

Bioincompatible glucose degradation products (GDPs) develop during heat sterilization of peritone... more Bioincompatible glucose degradation products (GDPs) develop during heat sterilization of peritoneal dialysis (PD) fluids. However, degradation may also take place during storage. Consequently, storage may add to the bioincompatibility caused by heat sterilization. The aim of the present study was to investigate how different factors such as the sterilization procedure, pH, glucose concentration, and temperature influence GDP production during storage. ♦ ♦ ♦ ♦ ♦ Design: Degradation in glucose solutions was followed

Applied and Environmental Microbiology, May 1, 1992

From a continuous spent sulfite liquor fermentation plant, two species of yeast were isolated, Sa... more From a continuous spent sulfite liquor fermentation plant, two species of yeast were isolated, Saccharomyces cerevisiae and Pichia membranaefaciens. One of the isolates of S. cerevisiae, no. 3, was heavily flocculating and produced a higher ethanol yield from spent sulfite liquor than did commercial baker's yeast. The greatest difference between isolate 3 and baker's yeast was that of galactose fermentation, even when galactose utilization was induced, i.e., when they were grown in the presence of galactose, prior to fermentation. Without acetic acid present, both baker's yeast and isolate 3 fermented glucose and galactose sequentially. Galactose fermentation with baker's yeast was strongly inhibited by acetic acid at pH values below 6. Isolate 3 fermented galactose, glucose, and mannose without catabolite repression in the presence of acetic acid, even at pH 4.5. The xylose reductase (EC 1.1.1.21) and xylitol dehydrogenase (EC 1.1.1.9) activities were determined in some of the isolates as well as in two strains of S. cerevisiae (ATCC 24860 and baker's yeast) and Pichia stipitis CBS 6054. The S. cerevisiae strains manifested xylose reductase activity that was 2 orders of magnitude less than the corresponding P. stipitis value of 890 nmol/min/mg of protein. The xylose dehydrogenase activity was 1 order of magnitude less than the corresponding activity of P. stipitis (330 nmol/min/mg of protein).

Enzyme and microbial technology, May 1, 1994

ABSTRACT High-purity d-xylulose > 97% was prepared from d-xylose in gram quantities using ... more ABSTRACT High-purity d-xylulose > 97% was prepared from d-xylose in gram quantities using a simple three-step procedure; enzymatic isomerization with commercial glucose isomerase (xylose isomerase EC. 5.3.1.5), ethanol precipitation, and ion-exchange chromatography on an anionic resin in sulfite form. In the chromatographic step, 0.7–1.4 g xylulose was produced within 10–15 h. Impurities in the preparation are of sugar origin and may consist of glucose, ribulose, and xylose. Fractions of high purity, > 99%, but in small amounts, could be produced in the chromatographic step. When the procedure was simplified by performing the precipitation in a saturated isomerization solution, almost identical results were obtained. If the precipitation step was excluded, it resulted in poorer separation in the chromatographic step, but xylulose could still be produced with a purity with a purity of 96–97%, though in smaller amounts, 0.35–0.74g.

Biotechnology Techniques, Mar 1, 1989

ABSTRACT In the concentration range appropriate for enzymatic xylose isomerization, xylulose was ... more ABSTRACT In the concentration range appropriate for enzymatic xylose isomerization, xylulose was measured in a lignocellulose hydrolysate using HPLC with two hydrogen loaded ion exchange columns in series. Spent sulphite liquour (SSL) was used as a model for lignocellulose hydrolysates. In buffer the separation took 22 minutes and in SSL the analysis time was 47 minutes due to the presence of ethanol. The enzymatic isomerization of xylose to xylulose was followed directly in SSL, providing a method for the direct determination of xylose isomerase activity in lignocellulose hydrolysates.

Enzyme and microbial technology, Sep 1, 1989

Untreated spent sulfite liquor (SSL) was fermented with five yeasts, Candida tropicalis, Pichia s... more Untreated spent sulfite liquor (SSL) was fermented with five yeasts, Candida tropicalis, Pichia stipitis, Pachysolen tannophilus, Schizosaccharomyces pombe, Saccharomyces cerevisiae, and a co-culture of P. tannophilus and S. cerevisiae, in the presence of commercial xylose (glucose) isomerases and 4.6 mM azide. The highest yield of ethanol, 0.41 g g ~ total sugar, was obtained with S. cerevisiae. The yield based on consumed sugars and per gram cell dry weight was also highest with this yeast. C. tropicalis and P. tannophilus produced considerable amounts of polyoles, mainly xylitol. With P. stipitis sugar uptake was rapidly inhibited in untreated SSL. The presence of azide contributed to the yield by about 0.04, mainly due to the fermentation of stored carbohydrates. The fermentation of hydrogen fluoride-pretreated and acid-hydrolysed wheat straw with S. cerevisiae, xylose isomerase, and azide gave a yield of O.40 g ethanol g-Z total sugar. In this substrate the xylose utilization was 84% compared with 51% in SSL, which is discussed in relation to the salt sensitivity of xylose isomerases.