Showing papers in "Acta Biotechnologica in 1996"

Heavy metal sorption by microalgae

Abstract: Viable microalgae are known to be able to accumulate heavy metals (bioaccumulation). Against a background of the increasing environmental risks caused by heavy metals, the microalgae Chlorella vulgaris and Spirulina platensis and their potential for the biological removal of heavy metals from aqueous solutions were taken as an example for investigation. Small-scale cultivation tests (50 1) with Cd-resistant cells of Chlorella vulgaris have shown that approx. 40% of the added 10 mg Cd/l was removed from the solution within seven days. At this heavy metal concentration sensitive cells died. Non-viable microalgae are able to eliminate heavy metal ions in a short time by biosorption in uncomplicated systems, without any toxicity problems. Compared with original biomasses, the sorption capacity of microalgal by-products changes only insignificantly. Their low price makes them economical.

Investigations into the antibiotic activity of tea fungus/kombucha beverage

Abstract: Tea fungus/kombucha, an acetic acid flavoured fermented tea beverage, is widely consumed in various parts of the world and has more recently become a fad in the United States. This is due in part to the fact that it can be produced in the home, and it is reported to be medicinal, effective against arthritis, psoriasis, chronic fatigue, constipation, indigestion and metabolic diseases. Among 264 references from 1852 to 1961, there are reports of antibiotic activity against Agrobacterium tumefaciens and medicinal value against a variety of diseases. The medicinal value appears to be related to that attributed to vinegar, one of our most ancient foods. We decided to test tea fungus/kombucha for its antibiotic activity against Helicobacter pylori, a primary cause of gastritis related to peptic ulcers and gastric carcinoma, Escherichia coli, Staphylococcus (Micrococcus) aureus and Agrobacterium tumefaciens. Tea containing 4.36 g of dry tea per litre and 10% of sucrose and fermented with the tea fungus showed no antibiotic activity in the beverage beyond that caused by acetic acid, a primary product of the fermentation.

Heavy metal sorption by marine algae and algal by‐products

Abstract: All the oceans are plentiful with marine algae. Non-viable marine macroalgae are able to adsorb heavy metal ions. Compared with other biosorbents, such as fungi, bacteria, yeasts and microalgae, they have the advantage of being easily available, cheap and having high heavy metal sorption capacities. The by-products of marine phaeophyceae are even more cost-effective heavy metal biosorbers. Experiments of heavy metal sorption using non-viable Fucus vesiculosus, Ascophyllum nodosum and algal by-products were carried out to investigate the factors influencing and optimizing the heavy metal biosorption. The pH value, biomass concentration, heavy metal concentration, heavy metal species, competing ions, algal varieties and time were the most decisive parameters. The sorption isotherms showed increasing sorption capacities and decreasing sorption efficiencies with an increase in the initial heavy metal concentration. Sorption kinetics of different metals were established. Biomass concentration influenced the sorption efficiencies very much, but reduced the sorption capacity per g biomass. The pH value controlled the sorption (pH 3–7) and desorption (pH 1–2) decisively. Beside heavy metal contaminated model waters, actual industrial effluents were treated successfully by algal sorbents in batch experiments and continuous column tests. Transmission electron micrographs of different contaminated and untreated algal specimens are available.

The use of a thermotolerant fermentative Kluyveromyces marxianus IMB3 yeast strain for ethanol production

Abstract: An investigation was carried out on the growth and ethanol production of a novel thermotolerant ethanol-producing Kluyveromyces marxianus IMB3 yeast strain. It grew aerobically on glucose, lactose, cellobiose, xylose and whey permeate and fermented all the above carbon sources to ethanol at 45 degrees C. This strain was capable of growing under anaerobic chemostat fermentation conditions at 45 degrees C and a dilution rate of 0.15 h(-1) and produced less than or equal to 0.9 g/l biomass and 1.8% (v/v) ethanol. An increase in biomass (up to 10.0 g/l) and ethanol (up to 4.3% v/v at 45 degrees C and 7.7% v/v at 40 degrees C) were achieved by applying a continuous two-stage fermentation in sequence (one aerobic and one anaerobic stage) or a two-stage anaerobic fermentation with cell recycling. Potential applications, involving alcohol production systems, for use in dairy and wood related industries, were discussed.

Substrate specificity of laccase from Lentinus edodes

Abstract: In previous studies, the white-rot basidiomycete Lentinus edodes, strain SC-495, was proved to be a “selective” lignin degrader and its extracellular crude preparations arising from solid-state cultures were successfully employed in biopulping experiments on annual plants. This fungus produced extracellular laccase as the predominant phenoloxidase when growing in solid-state fermentation on corn stalks. Laccase from this strain was purified and partially characterized, as an initial approach towards the study of its ligninolytic complex. Laccase was purified 69.6-fold by anion-exchange chromatography and two affinity-chromatography steps with an overall yield of 7.45%. The native enzyme exhibited a molecular mass of 74 kDa, an isoelectric point of 3.42 and a carbohydrate content of 7.5%. The absorption spectrum of laccase showed a maximum at 605 nm, typical of blue-copper oxidases. The optimum pH and temperature for the activity of laccase were 4.0–4.2 and 50°C, respectively. Kinetic experiments, performed with a wide range of phenolic compounds, showed that the reaction rate and the substrate affinity greatly varied depending on the nature of substituents and their reciprocal positions on the aromatic ring. In particular, the enzyme showed high affinity to phenolic compounds bearing methoxyl or methyl groups, but no affinity to those bearing the nitro group directly attached to the benzene ring, nor to non-phenolic lignin-related compounds, such as trans-cinnamic acid or 3,4-dimethoxycinnamic acid. The huge differences in terms of reactivity of the enzyme towards phenolic compounds suggests that a preliminary systematic screening should be advisable when using laccase in effluent treatment applications.

Xylitol formation by Candida guilliermondii grown in a cane bagasse hemicellulosic hydrolysate: Effect of aeration and inoculum adaptation

Abstract: The xylose conversion into xylitol by Candida guilliermondii was evaluated in sugar cane bagasse hemicellulosic hydrolysate. The effect of air flow rates of 0.4, 0.6 and 0.8 vvm on xylitol formation was studied. In addition, inoculum previously adapted to the hydrolysate was also tested in the fermentation carried out at 0.6 vvm. The results showed that xylitol production depends markedly on the aeration rate and on the previous adaptation of the yeast to the hydrolysate. When the fermentations were carried out at an air flow rate of 0.8 vvm and non-adapted inoculum was used, the highest productivity of xylitol was 0.39 g/l x h. However, during the fermentation carried out at an air flow rate of 0.6 vvm with adapted inoculum, the productivity increased to 0.65 g/l x h. Furthermore, the adapted cells performed quite well in the presence of acetic acid concentrations of about 4.5 g/l in the medium.

Isolation and characterization of an alkaliphilic bacterium capable of growing on 2,4‐dichlorophenoxyacetic acid and 4‐chloro‐2‐methylphenoxyacetic acid

Abstract: A bacterial strain, called P4a, was isolated from debris of concrete samples of a demolished herbicide factory. The samples were contaminated with chlorinated and methylated phenoxyalkanoic acids. Strain P4a was able to utilize 2,4-dichloro- (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) as the sole source of carbon and energy ; degradation of 2,4-dichlorinated and 4-chloro-2-methylated phenoxypropionic acid and -butyric acid derivatives was not found. Growth on 2,4-D was observed from a pH of 5.6 up to a pH of about 10, with optimum growth at around 8.5. No supplements were found to be required for growth on 2,4-D, but the presence of yeast extract increased the growth rate from less than 0.05 h -1 to 0.2 h -1 . The strain was metabolically active up to pH values of 12, which corresponded to the pH of aqueous eluates from such material. It was able to degrade 2,4-D under these conditions up to an initial concentration of 400 mg/l and in fact did degrade 1,600 mg/l of 2,4-D at an initial pH value of 11. Strain P4a was tentatively identified as Comamonas acidovorans on the basis of the substrate utilization pattern (BIOLOG), fatty acid profile (MIS) and G+C content.

Sucrose medium osmolality as a regulator of anabolic and catabolic parameters in Zymomonas culture

Abstract: This study focuses on the growth of Zymomonas mobilis strain 113 S and its ethanol and levan production under the conditions of increasing sucrose medium osmolality caused by NaCl, KCl, sorbitol or maltose. The increase in medium osmolality (700-1,500 mosml/kg) was accompanied by the inhibition of growth (growth rate, biomass yield) and ethanol production (specific productivity and yield). In contrast, levan synthesis was less affected or even stimulated and, as a consequence, levan specific productivity was increased significantly. A decrease in the anabolic growth parameters correlated with a parallel inhibition of glucose-6-P dehydrogenase and alcohol dehydrogenase (isoenzyme ADH II) activities. A significant inverse linear relationship (r = - ().932, 1 - P = 0.01) was observed between the values of the specific productivities of ethanol and levan. This relationship was confirmed independently by a controlled reduction of growth and ethanol productivity (3.75-4.75 mM sodiumbisulphite as an acceptor of acetaldehyde formed in the pyruvate decarboxylase reaction). As further support of this relationship, a significant inverse correlation was observed between levan specific productivity and ATP concentration in Zymomonas mobilis cells, most probably demonstrating that a reduced level of energetic metabolism is favourable for levan production.

Enhancement of the biological degradation of soils contaminated with oil by the addition of compost

Abstract: The fundamentals of the biological treatment of contaminated soils were investigated in bioreactors with the aim to optimize the processes of biological soil treatment in order to achieve the highest possible degree of degradation within the shortest period of time. Preinvestigations using test systems at different scales have provided information about the possibilities of enhancing the decomposition processes which are dependent on various factors, such as milieu conditions, additives, etc., that must be known before remedial actions are taken. The investigations made so far have shown that compost is a favourable additive when oil-contaminated soils are biologically treated. The degradation of contaminants can be enhanced by the addition of compost. This positive effect is attributed to various mechanisms. In this paper, results of a variety of test systems at different scales are presented. In test series, different amounts of biocompost were added to investigate the influence on the degradation of diesel fuel. It was demonstrated that by increasing the compost content – the cumulative O2 consumption caused by the degradation of the diesel fuel contaminants increased. It could be shown that the reduction of the diesel fuel contaminants in the soil was independent of the compost age and amounted to approximately 94% of the initial quantity. The addition of biocompost could also enhance the degradation of real contaminants. After a test period of 162 days in set-ups with compost addition, more than 75% of the lubricating oil contaminants disappeared, while less than 37% of the contaminants disappeared in set-ups without compost addition. Moreover, by the addition of compost, the formation of pellets during the dynamic treatment of soil materials could be reduced.

Media for the detection of Bacillus larvae spores in honey

Abstract: Bacillus larvae, the causative agent of American foulbrood in honey bees completes its life cycle of germination, outgrowth and sporulation in young honey bee larvae by killing them and often bringing about the destruction of the entire hive. While B. larvae germinates and outgrows on complex organic media in vitro, the literature suggests, for reasons that are not at all clear, that a relatively large number of spores of B. larvae are required to yield each visible colony (colony forming units, CFU) on media. Various researchers have reported that from 16 to 3,000 or more spores of B. larvae are required to yield a single colony on an agar plate. HANSEN in Denmark designed a useful method of spreading approximately 80 mg of honey directly on the surface of a PETRI plate containing “J” agar medium to determine if B. larvae spores are present in the honey. In the present study, selected media were tested for the ability to recover B. larvae spores in honeys in the form of visible colonies (CFU) using HANSEN's strek method. A modification of a medium (TMYGP) developed by DINGMAN and STAHLY, (T-HCL-YGP agar), recovered considerably more viable B. larvae spores in the form of visible colonies (CFU) than HANSEN's “J” medium. When “J” medium was fortified with 0.1% sodium pyruvate, it was comparable to modified T-HCL-YGP medium in its recovery of B. larvae spores. Brain heart infusion agar (BHIA) with the addition of thiamine recovered more spores in the form of viable colonies than did “J” medium but it was not as efficient as T-HCL-YGP medium. Serial dilution from 100 to 10,000 times of weighed samples of honey with deionized water led to higher spore counts (CFU per g honey) than that indicated by undiluted honeys plated at 80 mg levels directly onto the surface of media by the HANSEN procedure.

Selection of hemicellulosic hydrolysate pretreatments and fermentation conditions to stimulate xylitol production by ethanol-producing yeasts

Abstract: Xylitol production from hardwood hemicellulosic hydrolysates by well-known ethanol-producing yeasts was stimulated through an experimental schedule including pretreatments of the hydrolysate, the choice of the best xylitol producer and the selection of the optimum fermentation conditions. The xylitol or ethanol yields obtained on consumed xylose demonstrated that their production was stimulated under completely different conditions, as to be expected by the fact that these catabolites are the final products of different metabolic pathways. In particular, the catabolism of Pachysolen tannophilus, that is the best ethanol producer from this natural substrate, could be targeted towards xylitol rather than towards ethanol production by ensuring a strongly reducing environment through a suitable pretreatment of the hydrolysate. The final removal of fermentation inhibitors by adsorption onto highly adsorbing substances allowed a further 20% xylitol yield increase.

Studies on polyphosphate and poly-β-hydroxyalkanoate accumulation in Acinetobacter johnsonii 120 and some other bacteria from activated sludge in batch and continuous culture

Abstract: Twelve bacterial isolates, four of them assigned to the genus Acinetobacter, were taken from sewage of a treatment plant with Enhanced Biological Phosphorus Removal (EBPR) and screened for phosphorus uptake, polyphosphate (polyP) accumulation and adsorption under limited carbon and nitrogen conditions. In addition, poly-β-hydroxyalkanoate (PHA) production was studied under carbon, nitrogen, phosphorus, and oxygen limitation. Under C limitation, the uptake of phosphorus was highest, ranging up to 66 mg P per g dry weight (dw) for the Acinetobacter isolates, whereas the highest amount of polyP was detected under limited N conditions (up to 25 mg PolyP / g dw). Extra-cellular polyP was detected, however to a minor extent, accounting for a maximum of 10% of the total polyP in one Acinetobacter isolate. The highest PHA concentration (given as 3-hydroxybutyrate, 3 HB) with 211 mg 3 HB / g dry weight (21% of the dried cell mass) was found for A. johnsonii 120 under nitrogen limitation, but also under P and O2 limitation, PHA, mainly poly-β-hydroxybutyrate and poly-β-hydroxyvalerate, were produced. Three isolates, assigned to the genus Pseudomonas, showed even higher values (345–427 mg 3 HB / g dw) under N limitation. Studies with Acinetobacter johnsonii 120 in continuous culture, simulating the aerobic/anaerobic periods of a waste-water treatment plant, resulted in a P elimination of 36% at an anaerobic contact time of 0.6 h. This value increased to 51% at an anaerobic contact time of 3.1 h. No release of phosphate and no uptake of acetate could be detected during the anaerobic period. In addition, Acinetobacter johnsonii 120 was not able to synthesize PHA under anaerobic conditions. By changing the anaerobic conditions to aerobic, a continuous decrease of the polyP content relative to the totalP content from 45% (day 1 of the aerobic process) to 19% (day 17 of the aerobic process) was observed. The amount of PHA increased to 50.4 mg 3 HB/g dw under aerobic conditions. The results indicate again that the EPBR process cannot be defined by simply applying the knowledge of the metabolic processes, observed or assumed in Acinetobacter pure cultures, to the complexity of the process in sewage treatment plants.

Production of citrinin by Monascus ruber submerged culture in chemically defined media

Abstract: Following our investigations on citrinin production by Monascus ruber in a chemically defined medium, the kinetic behaviour of this toxin in the fermenter was studied with relation to production of pigments, biomass and nutrient consumption. Showing a secondary metabolite pattern, citrinin was produced when dμ/dt and dQ s /dt were ≤ 0, while a high specific production rate of pigments occurred when dμ/dt and dQ s /dt were > 0. No trophophase-idiophase transition was detected during the cultivation, and the behaviour of pigment production was similar to that of a primary metabolite.

Performance of industrial scale bioreactors with modified RUSHTON turbine agitators

Abstract: The data presented here with respect to the behaviour of industrial scale stirred tank bioreactors equipped with modified RUSHTON turbine agitators in the biosynthesis processes of antibiotics are valid for that case that the power consumption is the same as it is in standard RUSHTON turbine agitators. Each modified RUSHTON turbine agitator was obtained through the variation of the blade surface by adding perforations so that the ratio between the perforation surface area and the full surface area (or the surface fraction of the perforations) is 0.36. In the fermentations of Streptomyces aureofaciens, Streptomyces rimosus and Penicillium chrysogenum producing tetracycline, oxytetracyline and penicillin, respectively, in bioreactors equipped with modified RUSHTON turbine agitators, the relative antibiotic production is increased by more than 30% compared to standard bioreactors.

Kinetic study of the anaerobic degradation of toluene by a mixed culture

Abstract: Toluene was anaerobically degraded by an enriched mixed culture under methanogenic conditions. The mixed culture was originally developed from cow-dung and sludge from a laboratory reactor, in which benzene was anaerobically degraded by sulphate-reducing bacteria. First the mixed culture was enriched on toluene over a year with and without the use of sulphate in the medium. For the evaluation of growth-kinetic and maintenance parameters, namely μ max , K S , k d and Y o X/S , the anaerobic degradation of toluene was carried out in batch as well as in continuous reactor systems. The gas volume and the methane content in the produced gas was somewhat lower than the theoretical value expected, indicating an incomplete degradation of some of the complex intermediates of the toluene degradation pathway. However, the mixed culture was able to transform 41.3% of the toluene carbon into methane.

Evolutionary biotechnology-theory, facts and perspectives

Abstract: Molecular evolution has recently been applied in biotechnology which consist of the development of evolutionary strategies in the design of biopolymers with predefined properties and functions. At the heart of this new technology are the in vitro replication and random synthesis of RNA or DNA molecules, producing large libraries of genotypes that are subjected to selection techniques following DARWIN's principle. By means of these evolutionary methods, RNA molecules were derived which specifically bind to predefined target molecules. Ribozymes with new catalytic functions were obtained as well as RNA molecules that are resistant to cleavage by specific RNases. In addition, the catalytic specificities of group I introns, a special class of ribozymes, were modified by variation and selection. Efficient applications of molecular evolution to problems in biotechnology require a fundamental and detailed understanding of the evolutionary process. Two basic questions are of primary importance: (i) How can evolutionary methods be successful as the numbers of possible genotypes are so large that the chance of obtaining a particular sequence by random processes is practically zero, and (ii) how can populations avoid being caught in evolutionary traps corresponding to local fitness optima? This review is therefore concerned with an abridged account of the theory of molecular evolution, as well as its application to biotechnology. We add a brief discussion of new techniques for the massively parallel handling and screening of very small probes as is required for the spatial separation and selection of genotypes. Finally, some imminent prospects concerning the evolutionary design of biopolymers are presented.

A new version of an in situ sampling system for bioprocess analysis

Abstract: In this article, attention is focussed on an on-line sampling device for bioreactors and its characterization regarding sterility and response time. The integration of this device into analytical systems for biotechnology (FIA with biosensors) resulted in on-line analysis systems for bioprocess control. The new ESIP version of an in situ sampling system for bioprocess analysis produced by the EPPENDORF-NETHELER-HINZ GmbH, Germany, had a short response time of 8 min (99%), which was determined by means of conductivity measurement after an increase of the medium conductivity due to the gradual addition of KCl. Effectiveness and reliability of the module were tested by bubble point measurement resulting in a bubble point pressure of 2.1 bars. The sampling probe was tested successfully for use in a broad variety of microorganisms and cultivations.

Effect of activated carbon on the biological treatment of oil-water emulsions

Abstract: Waste water, derived from the reprocessing of used emulsions or suspensions, contains high concentrations of emulsified mineral oil and stabilizers, as well as different additives that are needed during the treatment process. Two stirred-tank reactors and two fixed-bed reactors were used to study the biodegradation of these waste-water compounds during two-stage biological treatment. The waste water was first proceesed in an activated sludge reactor to remove easily biodegradable substances. The effluent from the first stage was treated in three parallel operating reactors: an activated sludge tank containing different amounts of powdered activated carbon (PAC, between 0 and 2%), an upflow anaerobic fixed-bed reactor and an aerobic fixed-bed reactor (trickling filter). The results from the continuous treatment were compared with laboratory batch experiments. About 60% of the influent TOC was reduced by the first activated sludge treatment. The removal efficiency increased to about 70% by using a second activated sludge stage. This degradation was comparable to the maximum degree of degradation measured in laboratory batch experiments. PAC addition to the second activated sludge tank resulted in increased degradation rates. The removal efficiency increased to about 76% when 0.1% PAC was added and to 96% with 1% PAC. The removal efficiency decreased to 84% when the proportion of PAC was further increased to 2%. Variations in the amount of PAC addition per unit influent volume in the range of 50 and 200 mg/l had no significant effect on the TOC removal. Degradation models based on the MONOD-type equation were found to be in close correlation with the results obtained from batch experiments. However, the biological removal rates measured in batch experiments did not reflect the removal capacity determined in continuous operating treatment systems.

Relationship between citric acid and extracellular acid phosphatase production by Aspergillus niger

Abstract: Optimum conditions for citric acid production by Aspergillus niger in submerged culture were established. Some correlation was found between the ability of the fungus to produce citric acid and its capability to accumulate extracellular acid phosphatase. Mutagenization and passage on sodium citrate (10-25%) medium gave rise to eleven A. niger strains able to grow when the concentration was 25%. Two mutants showed an increase in citric acid production (8.8-25.7%), accompanied by the highest activity of acid phosphatase (43.1-46.6%).

Application of an airlift bioreactor to the nystatin biosynthesis

Abstract: Pilot plant studies were performed using a concentric-tube airlift bioreactor of 2.5 m3 fermentation volume. The results have proven the relative merits of such a system in the biosynthesis of nystatin, produced by Streptomyces noursei, in submerged aerobic cultivation and batch operation mode. The results were compared to those obtained in a pilot-scale stirred tank bioreactor of 3.5 m3 fermentation volume. The fermentation processes in the two fermentation devices were similar with respect to substrate utilization, biomass production and nystatin biosynthesis. In the riser section, the dissolved oxygen concentration was higher than that in the downcomer. The volumetric oxygen mass transfer coefficient was dependent on the rheological behaviour of the biosynthesis liquids, which was not constant during the fermentation process. The total energy consumption for nystatin production in the airlift bioreactor was 56% of that in the stirred tank, while the operating costs represented 78% of those in the stirred tank bioreactor.

Production of extracellular polysaccharides by a Rhizobium species from the root nodules of Tephrosia purpurea Pers

Abstract: The Rhizobium sp., isolated from the root nodules of the leguminous climbing herb, Tephrosia Purpurea Pers., produced high amounts of extracellular polysaccharides (EPS) in yeast extract mannitol medium. Growth and EPS production started simultaneously, but the production reached its maximum in the stationary growth phase of the bacteria. Attempts were made to optimize the cultural requirements for growth and maximum EPS production. The EPS production was increased by 72.5% over the control when the medium was supplemented with mannitol (2%), thiamine hydrochloride (5 μg/ml) and KN0 3 (0.1%). The EPS contained glucose, galactose and mannose monomers. The possible role of the rhizobial EPS was discussed.

Mixing times in an external‐loop airlift bioreactor with static mixers

Abstract: The influence of static mixers on mixing time and circulation time in an external-loop airlift bioreactor with gas-induced and forced-liquid circulation was investigated. The study was carried out with water and three viscous, non-Newtonian starch solutions. The mixing time was determined for the overrall flow loop using a classical tracer response technique. It was found that the mixing time is highly dependent on the superficial gas velocity and the presence of static mixers. The shortest mixing time is achieved in a forced-loop airlift reactor without static mixers, where the average mixing time value is only 1/3 of the time necessary for mixing in the airlift reactor with gas-induced liquid circulation and static mixers. The pseudoplasticity of the liquid phase insignificantly influences the mixing time and the circulation time.

Cloning and expression of the porA gene of the Neisseria meningitidis strain B : 4 : P1.15 in Escherichia coli. Preliminary characterization of the recombinant polypeptide

Abstract: The gene coding for the class 1 outer membrane protein from the Neisseria meningitidis strain B385 (B : 4 : P1.15) was isolated by the Polymerase Chain Reaction (PCR) and cloned into the Sma I cut M13mp 18 vector. Then, a Xba I restriction site was created by using an oligonucleotide-directed in vitro mutagenesis system at the start of the coding fragment. In order to express the protein, this fragment was fused to 180 base pairs corresponding to 60 amino acids from the N terminus of interleukin-2 under the control of the tryptophan promoter (Ptrp). The expression was confirmed by Western-blotting where the recombinant protein (PILM28) was detected by bactericidal monoclonal antibodies (MABs). The recombinant polypeptide was partially purified and used to elicit murine antibodies, able to recognize the meningococcal class 1 subtype 15.

Hydrolyzed whey as a medium for propionic acid fermentation

Abstract: Whey, hydrolyzed by using pure enzymes and enzymatic preparations, was fermented by propionic acid bacteria in batch cultures. The course of propionic acid fermentation was examined by the determination of cell dry weight, lactose utilization, production of volatile free acids and biosynthesis of vitamin B 12 . The production of propionic acid by Propionibacteria increased when hydrolyzed whey was used as a medium. It rose from 6.3 to 6.7 g/l in the control compared to 8.0-8.8 g/l when pepsin, papain, alcalase, or pescalase were applied as hydrolyzing agents. A significant decrease in the biosynthesis of vitamin B 12 (more than 50%) was observed in all cases compared to the control (cultivation on medium without hydrolysis).

Penicillium citrinum protoplasts: Preparation, regeneration and lipolytic activity of regenerants

Abstract: The conditions for an optimum formation of protoplasts from mycelium of Pencillium citrinum, which produces extracellular lipase, were examined. The best results were achieved using Novozyme 234 in combination with β-glucuronidase. Chitinase or β-glucuronidase alone were not able to produce protoplasts under the given conditions. For the regeneration frequency, the type of osmotic stabilizer was important. The highest regeneration frequency (84.6% protoplasts) was achieved by using 0.6 M KCl as an osmotic stabilizer. Some regenerants were more effective in producing lipase than the parent. In particular, strain no. P-8 showed a three times higher lipolytic activity than the parent strain, but this high enzyme activity was unstable after subculture.

Immobilization of glucose oxidase and peroxidase to a urea derivative of granulated microcrystallized cellulose

Abstract: Glucose oxidase and peroxidase were immobilized individually to a urea derivative of granulated microcrystallized cellulose activated by formaldehyde. The catalytic properties of the immobilized enzymes were studied and compared to those of the soluble enzymes. The immobilized glucose oxidase and peroxidase were used for the manual determination of the concentration of glucose in sera. The developed method is characterized by high analytical reliability and comparatively low cost. The results correlated well with those obtained by using a BECKMAN glucoanalyzer, utilizing soluble glucose oxidase.

Modelling the stability of the pBR322 plasmid derivative pBB210 in Escherichia coli TG1 under non-selective and selective conditions

Abstract: A mathematical model has been developed to describe the stability behaviour of the pBR322 plasmid derivative pBB210 with the β-lactamase gene and the human interferon-α1 gene in Escherichia coli TG1 under non-selective, selective and modified selective conditions in a chemostat The model was formulated on the basis of experimental investigations It includes the interaction between β-lactam antibiotics (ampicillin and sulbactam) and cells (with and without plasmids), in particular the correlation between the growth rate of plasmid-free cells and ampicillin concentration in the medium; ampicillin transport into the periplasm of the plasmid-bearing cells; ampicillin degradation in the periplasm by by plasmid-encoded β-lactamase and the inhibition of the latter by sulbactam The results obtained by the simulation of chemostat cultivations under various conditions and by steady state analyses are closely related to the results of experiments Under non-selective conditions, the fraction of plasmid-bearing cells was approaching zero Under selective and modified selective conditions, a coexistence between plasmid-free and plasmid-bearing cells was reached at steady state Under these conditions, the steady state fraction of plasmid-bearing cells was proportional to the ampicillin concentration in the feed and inversely proportional to the cell concentration in the chemostat During high-density cultivation, a large amount of ampicillin is necessary to suppress plasmid-free cells Even small concentrations of the β-lactamase inhibitor sulbactam in the feed increased the steady state fraction of plasmid-bearing cells (from 172% to 996% at sulbactam-Na concentrations of 0 to 5 mg/l)

Extracellular acid phosphatase as a minor enzyme during the production of proteinases by Humicola lutea 120–5

Abstract: Extracellular acid phosphatase was studied as a minor enzyme of the fungal strain Humicola lutea 120-5 having a clear relation to the secretion of acid proteinases. A medium lacking in mineral orthophosphates ensured a fivefold higher yield of phosphatase while the proteinase production was reduced. An acid phosphatase fraction free of proteinase activity was isolated demonstrating a maximum hydrolysis of 4-nitrophenyl-phosphate at a pH of 4.0 and 50 °C. The phosphatase catalyzed a partial dephosphorylation of up to 30% of casein at a pH of 3.0 causing a complete substrate precipitation. Both proteinase and phosphatase biosynthesis increased twofold when natural casein was replaced by partially dephosphorylated casein in the cultivation medium.

Effect of the peptide and vitamin composition of casein hydrolysates on the β‐galactosidase activity of Kluyveromyces bulgaricus cells

Abstract: Instead of yeast extracts, casein hydrolysates from several suppliers were added to culture media and analyzed with respect to their ability to stimulate β-galactosidase activity in Kluyveromyces bulgaricus cells. Four enzymatic casein hydrolysates caused a significantly higher stimulation of enzyme activity, while acid casein hydrolysates clearly reduced the enzyme activity. Enzymatic casein hydrolysates, inducing high and low lactase activity, were analyzed with respect to average peptide length (APL), vitamins (niacin, panthothenate) as well as free and bound amino acids. The molecular weights of these casein hydrolysates were estimated by gel filtration. No correlation was found between the degree of enzyme stimulation and the vitamin contents, the APL values and the free amino acid contents of the casein hydrolysates. Casein hydrolysates stimulating the lactase activity were less soluble in water and, in a gel filtration column, they showed three peaks with slightly lower molecular weights than the three peaks seen in hydrolysates which had no effect on activity. APL values of alcoholic precipitates of casein hydrolysates showed an inverse correlation to lactase activity. The molecular weights of alcoholic precipitates of lactase stimulating digests were also lower compared to non-stimulating ones. Alcoholic precipitates with lactase-stimulating activity were more hydrophilic, as was shown by a smaller proportion absorbed in a C18 column and by amino acid analysis. Our results suggest that alcoholic precipitates could probably be important in the lactase stimulation and their composition should be further investigated. The mechanism is nevertheless complex and may be caused by various simultaneous factors.