Biologic processing of fossil fuels. Rśumé of the Bioconversion Session of ICCS'97.
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Bacteria↗
Biomedical subjects
H J Rehm
Publications and source records attributed to H J Rehm.
Changes in the contents of fat-soluble vitamins and provitamins during tempe fermentation.
The content and formation of fat-soluble vitamins and provitamins during tempe fermentation was studied with 14 different strains of Rhizopus sp. All strains investigated form carotenoids in small amounts during fermentation, but beta-carotene formation was only found in fermentations with six Rhizopus strains. The highest increase of beta-carotene production was to be seen from 34 to 48 h of fermentation. Soybean seeds did not contain ergosterol in detectable amounts. Ergosterol was produced by all Rhizopus strains in concentrations of up to 750 microg g(-1) tempe dry weight (dw) during a 34 h fermentation period and of up to 1610 microg g(-1) tempe dw during a 96 h fermentation period. The amounts of gamma-tocopherol in soybeans ranged from 192.4 to 231.8 microg g(-1) dw. Soybean seeds contained only free, not esterified tocopherols. During fermentation the total amount of vitamin E remained constant but the content of free tocopherols decreased. The content of vitamin K1 in soybeans is not strongly effected by tempe fermentation with pure cultures of Rhizopus sp.
Chromatography, High Pressure Liquid↗
Biodegradation of 2-chloroethanol by freely suspended and adsorbed immobilized Pseudomonas putida US2 in soil.
The degradation of 2-chloroethanol by Pseudomonas putida US2 was investigated in batch, repeated batch and continuous cultures especially in a packed-bed fermenter with sand. The degradation of 2-chloroethanol was connected with a release of protons, which led to a decrease of the pH in the medium. Higher initial concentration than 25 mM 2-chloroethanol were not degraded completely because they entailed a decrease of the pH to 5.0, which inhibited further growth and degradation. P. putida US2 showed a typical repression of catabolites and diauxic growth with succinate as cosubstrate. The addition of succinate as a second substrate caused a decrease in degradation of 2-chloroethanol. Activated sludge added to adsorbed cultures in a continuous fermentation did not lead to a decrease in metabolic activity. After 2 weeks of continuous cultivation the specialized strain could be retained.
Adsorption↗
Development of a continuous system for the degradation of a cyanuric acid by absorbed Pseudomonas sp. NRRL B-12228.
Cyanuric acid in high concentrations (15.5 mM) was degraded completely by Pseudomonas sp. NRRL B-12228 independently of glucose concentration. In the batch fermentations there was a relation between the glucose concentration, on the one hand, and the liberation of ammonia or production of protein, on the other. The greater the supply of carbon, the more biomass was produced, and fewer NH4+ ions were released. Continuous fermentations using adsorbed cells could be performed to degrade cyanuric acid. In spite of different glucose feeding there was only a negligible difference in residues of s-triazine. In a one-step continuous system with dilution rates between 0.021 h-1 and 0.035 h-1, even a ratio of 0.65 between glucose and cyanuric acid was not sufficient to degrade the cyanuric acid supplied (320-540 mumol l-1 h-1) completely. When a continuous two-step system was applied with dilution rates between 0.035 h-1 and 0.056 h-1, the consumption of carbon source could be minimized while s-triazine degradation up to 860 mumol l-1 h-1 was complete. In this way the ratio between glucose and cyanuric acid could be increased to 0.25 (molar C:N ratio = 0.33:1). Thereby the process was made considerably more economic.
Adsorption↗
Utilization of chlorinated s-triazines by a new strain of Klebsiella pneumoniae.
A bacterium utilizing 2-chloro-4,6-diamino-s-triazine (CAAT) as sole nitrogen source was isolated under a N2-free atmosphere and identified as Klebsiella pneumoniae. Concomitant to CAAT degradation the protein content increased and chloride was released into the medium. Under air and a N2-atmosphere no reduction of CAAT degradation resulted, though this strain is able to fix molecular nitrogen, but the decomposition accelerated under anaerobic conditions. The degradation rate increased continuously with increasing CAAT concentration. A continuous CAAT degradation without CAAT accumulation was possible up to a influx rate of 4.8 mumol.l-1h-1 (dilution rate = 0.007 h-1). K. pneumoniae A2 was also able to utilize deethylsimazine (CEAT) and deethylatrazine (CIAT) as nitrogen source. Both under aerobic and anaerobic conditions CEAT could be degraded faster than CIAT. The degradation sequence of mixed s-triazines was cyanuric acid < CAAT < CEAT < CIAT, which was reflected by the degradation times of single compounds. Complete degradation was assumed for all investigated s-triazine derivatives.
Atrazine↗
Tempe fermentation: some aspects of formation of gamma-linolenic acid, proteases and vitamins.
During a tempe fermentation the concentrations of linoleic, and alpha-linolenic acids (ALA) decreased while the concentration of oleic acid increased. During fatty acid synthesis Rhizopus sp. produced only gamma-linolenic acid (GLA) instead of ALA. The amount of GLA in tempe were influenced by varying external parameters. The proteolytic capacity of 36 strains of the genus Rhizopus isolated from Indonesian tempe or tempe inocula was examined. There was a distinct increase in the amount of free amino acids during tempe fermentation. Fermentations with mixed populations of bacteria and Rhizopus yielded a lower level of free amino acids, but an increase in total amount of amino acids. In comparison to intracellular, and extracellular proteases the proteases of the cell wall fraction are most responsible for proteolytic capacity of the different Rhizopus strains. Two isolated strains of Citrobacter freundii were found to be the best vitamin B(12) producers during the soaking of soybeans. In the solid substrate fermentation the Rhizopus molds formed vitamin B(6), riboflavin, and nicotinic acid. The addition of bacteria to the solid substrate fermentation resulted in a strong increase of active vitamin B(12) in tempe. In the presence of the Rhizopus mold, the vitamin B(12) formation by C. freundii was three times higher than that of a fermentation without the mold.
Journal Article↗
Long-Term Production of Ergot Peptides by Immobilized Claviceps purpurea in Semicontinuous and Continuous Culture.
The semicontinuous and continuous production of pharmaceutically useful ergot peptides with immobilized Claviceps purpurea could be demonstrated. A key aspect was the presence of high concentrations of CaCl(2) (96.9 mM) to give marked prolongation of the productive phase, and cultivation in a bubble column reactor became possible. Restriction of the phosphate supply avoided an otherwise problematic massive increase of outgrowing hyphae.
Journal Article↗
Fatty acid impurities in alginate influence the phenol tolerance of immobilized Escherichia coli.
A short time after the immobilization of Escherichia coli in calcium alginate substantial modifications of the fatty acid patterns of the cells were observed. This effect could be related to lipid impurities in the commercial alginate product used, which could be taken up, at least in part by the microorganisms. The impurities were mainly free fatty acids but sterols were also detected. Immobilization of the cells in alginate material extracted by chloroform or ethanol decreased the tolerance of the cells to phenol as compared with cells immobilized in raw alginate. This effect was diminished if the immobilized cells were exogenously supplied with palmitic acid, which is the main constituent of the fatty acids extracted from alginate. These results indicate that not only fatty acids but also other ingredients of commercial alginate have physiological effects on cells entrapped in this gel material.
Alginates↗
Biodegradation of 4-chlorophenol by adsorptive immobilized Alcaligenes sp. A 7-2 in soil.
Alcaligenes sp. A 7-2 immobilized on granular clay has been applied in a percolator to degrade 4-chlorophenol in sandy soil. Good adsorption rates on granular clay were achieved using cell suspensions with high titres and media at pH 8.0. The influence of various parameters such as aeration rate, pH, temperature, concentration of 4-chlorophenol and size of inoculum on the degradation rate were investigated. During fed-batch fermentations under optimal culture conditions, concentrations of 4-chlorophenol up to 160 mg.l-1 could be degraded. Semicontinuous culture experiments demonstrated that the degradation potential in soil could be well established and enhanced by the addition of immobilized bacteria. Continuous fermentation was performed with varying 4-chlorophenol concentrations in the feed and different input levels. The maximum degradation rate was 1.64 g.l-1.day-1.
Alcaligenes↗
Aspects of biotechnology in a united Germany.
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Biotechnology↗
Increase of phenol tolerance of Escherichia coli by alterations of the fatty acid composition of the membrane lipids.
In the presence of sublethal concentrations of phenol, 4-chlorophenol, and p-cresol in the growth medium, cells of Escherichia coli modified the fatty acid composition of their lipids. The results of these changes was an increase in the degree of saturation of lipids probably in order to compensate an increase of fluidity of the membrane induced by the phenols. Supplementation of the growth medium with saturated fatty acids could also enhance the degree of lipid saturation due to the incorporation of the acyl chains in the phospholipids. At the same time the growth of cells was less inhibited than in unsupplemented cells. The increase of tolerance of cells by manipulating the lipid composition indicates that the membrane structure plays a crucial role in the mode of action of phenols.
Cell Membrane↗
Influence of phenols on growth and membrane permeability of free and immobilized Escherichia coli.
The inhibition of the exponential growth of Escherichia coli K-12 by different phenolic compounds was examined. Cells entrapped in calcium alginate showed a greater tolerance than cells grown in suspension. The extent of inhibition of growth of the immobilized cells depended on the period of growth in the gel matrix. After the addition of bacteriostatic concentrations of phenol or 4-chlorophenol, a dose-dependent efflux of metabolites such as ATP and of K+ ions was elicited. Provided that glucose was supplied as an energy substrate, a reaccumulation of K+ ions at low phenol concentrations was observed. The restoration of the membrane gradient for K+ always preceded the continuation of growth in the presence of the toxic compounds. Compared with free cells, those cells immobilized and grown in alginate suffered a smaller loss of cations after the addition of 4-chlorophenol. The reestablishment of gradients was observed at higher concentrations of the pollutants with entrapped cells than with free cells. Corresponding to the increase in tolerance, the membrane damage was reduced in cells grown in immobilized form for longer times. These data offer a mechanistic explanation of the protection of immobilized microorganisms from phenolic solvents. The data point to the membrane as an important cell component in the toxicity of these pollutants.
Adenosine Triphosphate↗
Phenol-induced membrane changes in free and immobilized Escherichia coli.
Membranes of Escherichia coli cells grown in the presence of phenol were examined after isolation of the cytoplasmic and outer membrane fractions. Both membrane types showed reduced lipid-to-protein ratios compared to cells grown without phenol. Phenol-induced differences in the expression of individual proteins of the inner membrane were established. Different proteins of the outer membrane, probably involved in the uptake of iron, were expressed in smaller quantities after phenol addition. Growth in the presence of phenol increased the respiratory activity of the cytoplasmic membrane, whereas the direct inhibition of O2 consumption by phenol was not affected by the presence of this compound in the growth medium. E. coli cells grown entrapped in calcium alginate showed low lipid-to-protein ratios even without phenol in the growth medium. Immobilization of cells also markedly changed the protein pattern of the outer membrane.
Bacteriological Techniques↗
Coupled reductive and oxidative degradation of 4-chloro-2-nitrophenol by a co-immobilized mixed culture system.
The restriction of oxygen transfer in Ca-alginate beads used for the immobilization of microbial cells was applied to a coupled reductive and oxidative microbial degradation of the xenobiotic 4-chloro-2-nitrophenol (CNP). The conversion of CNP by Enterobacter cloacae under anaerobic conditions led to the formation of 4-chloro-2-aminophenol (CAP, 81%) and 4-chloro-2-acetaminophenol (CAAP, 16%) after 50 h incubation. CAP, the main reduction product, was further degraded under aerobic conditions by Alcaligenes sp. TK-2, a hybrid strain isolated by conjugative in-vivo gene transfer. Whereas both degradation steps excluded one another in homogeneous systems with free cells, a coupled reductive and oxidative degradation of CNP was observed in one aerated reactor system after co-immobilization of both strains in Ca alginate. The diameter of the alginate beads used for immobilization was recognized as one main factor determining the properties of this mixed culture system.
Aerobiosis↗
Multistep reactions with immobilized microorganisms.
This review presents some examples of new semicontinuous and continuous processes for product formation and for degradation of xenobiotics with immobilized microorganisms. A semicontinuous process for glycerol formation with Saccharomyces cerevisiae cells, adsorbed on sintered glass, and a continuous production of citric acid with Aspergillus niger, entrapped in calcium alginate, are given as examples of the production of primary metabolites. The production of ergot alkaloids with entrapped Claviceps purpurea demonstrates the possibilities of production of secondary metabolites. The continuous degradation of phenolic substances and that of 4-chlorophenol by entrapped and adsorbed microorganisms are given as examples of the possibility of a continuous degradation of xenobiotics by immobilized microorganisms. The continuous degradation of these substances was successful not only in artificial solutions but also in sterile and nonsterile wastewater.
Aspergillus niger↗
Semicontinuous and continuous production of citric acid with immobilized cells of Aspergillus niger.
The citric acid excretion of Ca-alginate-immobilized cells of Aspergillus niger in batch culture decreased with a half-time of approximately 19 days. Reactivation of the biocatalysts by regeneration in growth medium was possible, but it was followed by a submerged sporulation of the fungus, and medium was highly contaminated with free cells. Citric acid production could better be prolonged by semicontinuous cultivation with medium exchange every 7 or 14 days, respectively. After 32 days the remaining activity in semicontinuous culture was 1.4-fold higher than in comparable batch experiments. Similar improvements were obtained with a continuous process at a dilution rate of 0.125 v/v X d, whereby medium efflux kept completely free of detaching mycelia.
Aspergillus niger↗
[Degradation of aflatoxin b1 by various microorganisms (author's transl)].
The degradation of aflatoxin B1 by various representatives of bacteria, yeasts and moulds in growing and resting cultures was investigated. We found that growing cultures of Corynebacterium rubrum degraded the added aflatoxin nearly quantitatively. -- Growing cultures of anascosporogenous yeasts degraded most of aflatoxin B1 while no degradation of this substance by ascosporogenous yeasts could be stated. Moulds degraded aflatoxin B1 to a high extent. -- With regard to the course of degradation three types can be distinguished. -- In the cultures of moulds two blue fluorescing compounds were found beside aflatoxin B1.
Aflatoxins↗
[Microorganisms in gums. IV. Microbial degradation of plant exudates and seaweed extracts (author's transl)].
The three plant exudates gum traganth, gum arabic, and gum karaya and the two seaweed extracts carrageenan and alginate were degraded by five different Bacilli which were isolated from these gums: Bacillus coagulans, B. lentus, B. cereus, B. licheniformis, and B. firmus. After 14 days all the gums have been degraded by these Bacilli to a different extent after addition of trace elements. The fractions of degraded gums by TLC, GLC, and IR-spectroscopy have been examined with the following results: 1. Except the already known monomers of the above mentioned gums no other monosaccharides could be found. 2. The microbial degradation of gum karaya and alginate resulted in products with a high molecularweight. Monomers could not be determined. 3. Carrageenan has been degraded to oligosaccharides with molecularweights of about 500, 3,6-anhydrogalactose has been partly identified. 4. Gum arabic has been partly degraded to rhamnose and arabinose. 5. Gum traganth has been partly degraded to arabinose and xylose and partly to polysaccharides with molecularweights under 3000.
Acacia↗