a)
a) Univ. of Ljubljana,
Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia.
Review of authors
Language: Slovene
ABSTRACT
In the present list the authors who have published their papers in the Research
Rept. of the Biotechnical Fac. of Univ. of Ljubljana. Agricultural Issue.
Zootechny are sorted in alphabetical order. Each entry contains besides author’s
name the volume, year and number of the Research Reports as well as pages of the
published article. There are 288 authors. More than 50% of authors published
their articles once while 18 authors more than ten times.
a) and
Jože STOPAR
a) Univ. of Ljubljana, Biotechnical
Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia, Prof., Ph.D.
Review of authors
Language: Slovene
ABSTRACT
In the 25 years of publishing the special number of Research Reports (Research
Rept. Biotechnical Fac. Univ. of. Ljubljana. Agricultural Issue. Zootechny) 390
articles written by 288 authors appeared. Most of articles, 80%, are original
scientific papers, 9.5% are review papers; 23% of authors work at the
Zootechnical Department, 19% of authors are from abroad, 27% are young
researchers (graduates, post-graduates and doctoral candidates) and 31% are from
other institutions and enterprises.
Key words: authors / papers / types of papers / serial publications
a) a)
Swiss Federal Institute of Technology, Institute of Food Science, Laboratory of
Dairy Science, CH-8092 Zürich, Switzerland, Prof., Ph.D.
Review paper
Language: English
ABSTRACT
In general, the incentive for developing new technologies is determined by a)
the need for increased product safety, economy and protection of the environment
for existing products; b) the demand of consumers and the market for new dairy
products and for foods containing milk ingredients. Membrane technology for
separation and concentration of milk offers possibilities in the manufacture of
existing consumer products such as cheese, liquid and fermented milk products as
well as for the preparation of tailor-made products. One of the emerging
technologies is the use of ultra-high-pressure because of its marked influence
on milk proteins including enzymes, on lipids and on microorganisms. As this is
a very costly technology, its application within the dairy industry may,
therefore, be limited to special products. Despite the fact that the
manufacturing process for all fermented dairy products includes biological
operations, the introduction of new biotechnological methods to transform milk
ingredients, the production of specific metabolites and continuous fermentation
processes will increasingly gain importance in dairy plants. Energy saving in
dairy industry will remain an important task for the technologists of the
future. The milk industry is facing increasing product competition.
Consequently, the intensive co-operation between industry and basic research is
vital.
a) and
a)
University of Zagreb, Faculty of Food Technology and Biotechnology, Pierottijeva
6, HR-10000 Zagreb, Croatia, Prof., Ph.D.
Original scientific paper
Language: English
ABSTRACT
The concept of functional foods and probiotics is a novelty in former Eastern
block. The Croatian and Slovenian dairy industries are the first that launched
probiotic. In this work, samples of probiotic fermented milks purchased from
Slovenian market were stored within 25 days at three different temperatures (4°
C, 20° C, 37° C), and changes in acetaldehyde, ethanol and diacetyl were
determined. Above chemical compounds have a high impact on the desired product
flavour. At the same time sensory evaluation was carried out. Acetaldehyde and
ethanol concentration were determined by aldehyde dehydrogenase and alcohol
dehydrogenase methods. Diacetyl was measured by modification of the Hill’s
colorimetric method. Sensory analysis was conducted by five member panel, using
a scoring system with weighted factors in the 20-point scale. The concentration
of these flavour compounds changed during storage depending on duration and
temperature in depot. Acetaldehyde content decreased at each temperature level
during 25-days storage. Diacetyl and ethanol content increased with duration at
all temperature levels. Sensoric quality decreased with duration and was closely
related to changes in the content of aroma compounds. Changes of all
investigated parameters were pronounced on higher temperature levels. Thus,
there were no significant changes during the refrigerated storage at 4° C
while at the other two temperature levels results pointed out significant
differences between the values before and after storage.
a), Aleš
KUHAR and Emil ERJAVEC
a) Univ. of Ljubljana,
Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia,
higher lecturer., Ph.D., M.Sc.
Original scientific paper
Language: Slovene
ABSTRACT
Significant level of market-price support measures for milk production is a
reality of European agricultural policy. However, simultaneously with reduction
of support to agriculture, various types of budget support measures are becoming
increasingly important to compensate declined farmers’ incomes. It has not yet
been decided whether also the candidate countries are going to participate in
these support schemes. The paper aims at an assessment of the impact of direct
payments and structural support measures on Slovenian milk market. Their effects
on incomes of dairy farmers as well as on producers’, consumers’ and taxpayers’
welfare are analysed. Policy Analysis Matrix (PAM) in combination with
Agricultural Policy Analysis Simulator (APAS) methodology has been applied for
simulation of different policy scenarios’ effects on these important economic
indicators. Analysis of different levels of CAP measures is carried out for the
period after accession. Results obtained show extreme importance of both direct
payments and structural support measures for all indicators under investigation
and therefore argue for their complete implementation. In the case of Slovenian
accession before next reform of Common market organisation for milk, structural
mechanisms have higher impact, but increasing importance of direct payments is
foreseen after 2005/06. Absence of one or another leads to stagnation of
Slovenian milk production, which due to its low competitiveness has no good
prospects also under optimistic scenarios. In the case of appropriate
pre-accession agricultural policy strategy, satisfactory outcome of accession
negotiations seems to be more realistic.
Key words: milk production / agricultural policy / compensatory payments /
structural payments / modelling / Slovenia / EU
a) and
Jože VERBIČ
a) Agricultural
Institute of Slovenia, Hacquetova 17, SI-1001 Ljubljana, Slovenia, research
adviser, Ph.D., M.Sc.
Original scientific paper
Language: Slovene
ABSTRACT
Concentration of metabolizable energy (ME) and net energy for lactation (NEL) of
19 samples of green forage, 5 samples of grass silage and one sample of hay with
known in vivo measured digestibility were estimated according to official
German system (DLG, 1997). Energy value and organic matter digestibility (dOM)
were comparatively estimated on the basis of chemical composition and
digestibilities from tables. It was established that on the basis of data form
DLG tables dOM was underestimated for 2.1 ± 3.95%, concentration of ME for 0.29
± 0.52 MJ and concentration of NEL for 0.21 ± 0.37 MJ kg-1 dry matter
(DM). Somewhat lower deviation from in vivo estimates were obtained in
estimation of ME (0.04 ± 0.45 MJ kg-1 DM) and NEL (0.03 ± 0.33 MJ kg-1
DM) on the basis of chemical composition and regression equations from
literature (GfE, 1998). By the use of Hohenheim gas production test (in vitro)
and adequate regression equations from literature the accuracy of estimate was
increased markedly. Relatively precise was found to be the equation by (Menke
and Steingass, 1987), which in comparison to in vivo estimation
underestimated the concentration of ME for 0.12 ± 0.26 MJ and concentration of
NEL for 0.09 ± 0.19 MJ kg-1 DM. Equations by Aiple et al.
(1995) overestimated in vivo estimated concentration of ME for 0.15 ±
0.24 MJ kg-1 DM and concentration of NEL for 0.10 ± 0.17 MJ kg-1
DM. The major part of variability in concentration of ME can be explained with
multiple regression equation on the basis of gas production, which is developed
during the incubation of samples with rumen liquor and concentration of crude
fat (R2 = 0.96).
Key words: forage / grassland / energy value / chemical composition /
digestibility
a), Andrej
LAVRENČIČ and Jože STOPAR
a) Univ. of Ljubljana, Biotechnical
Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia, Prof., Ph.D.
Original scientific paper
Language: Slovene
ABSTRACT
In 1997 on seven different plots of the same ground in four periods and in
different stages of growth in each period ten samples of red clover (Trifolium
pratense) and Italian ryegrass (Lolium multiflorum) and eight samples
of timothy (Phleum pratense), perennial ryegrass (Lolium perenne),
meadow fescue (Festuca pratensis), red fescue (Festuca rubra) and
orchardgrass (Dactylis glomerata) were collected. In the soil sample the
pH value of 7.2 and 75.8 mg zinc kg-1 were established. On the
average grass samples contained 20.36 mg and red clover 26.43 mg zinc kg-1
DM. The lowest zinc concentration was found in samples of red fescue (16.92 mg
kg-1
DM). In perennial ryegrass the zinc content was 18.13 mg, in meadow fescue 18.66
mg and in orchard grass 20.84 mg kg-1 DM. The highest value was found
in timothy (23.66 mg kg-1 DM) and in Italian ryegrass (23.77 mg kg-1
DM). Differences between grasses were statistically significant. In the
first harvest a statistically significant change in zinc concentration with
maturity of plants was demonstrated (22.44 mg, 19.57 mg and 16.47 mg kg-1
DM for vegetative, heading and flowering stage of growth respectively). Between
zinc concentrations in samples of first harvest and of second harvest there were
no significant differences (19.49 mg and 20.22 mg kg-1 DM,
respectively). In samples collected in the third harvest zinc concentration was
higher (24.29 mg kg-1 DM), P< 0.05) than in first and second harvest.
The highest value was found in samples of the autumn harvest (26.91 mg kg-1
DM, P< 0.05). Differences between zinc concentrations in timothy, perennial
ryegrass and Italian ryegrass samples collected in the first harvest and in
autumn harvest were very high (+78.4%, +68.0% and +58.4%, respectively).
Marija RAJČEVIČ a), Anton ILC, Peter
KUMPand Marijan NEČEMER
a)
Poslovni sistem
Mercator, d.d., Dunajska 107, SI-1113 Ljubljana, Slovenia, senior scientist.,
Ph.D., M.Sc.
Original scientific paper
Language: English
ABSTRACT
In 1999 5 samples of pasture grass, 13 samples of grass silage, 6 samples of hay
and 7 samples of maize silage were taken at random. All samples were from the
defined region, and the forage was produced in similar soil and weather
conditions. The grass botanical composition was comparable as well. The pasture
and grasslands were manured by pig and bovine slurry. The content of sulphur and
chlorine was determined by roentgen fluorescent analysis. Grass dry matter
contained 2.56 ± 0.70 g of sulphur (CV = 27.29%) and 9.15 ± 4.18 g of chlorine
(CV = 45.49%), grass silage 2.38 ± 0.49 g of sulphur (CV = 20.67%) and 7.19 ±
1.89 of chlorine (CV = 26.34%), hay 1.93 ± 0.48 g of sulphur (CV = 24.84%) and
5.72 ± 1.98 of chlorine (CV = 34.68%), and maize silage contained 0.88 ± 0.25 g
of sulphur (CV = 28.14%) and 1.98 ± 0.86 g of chlorine (CV = 43.39%). Some
results for sulphur as well as for chlorine deviated a great deal from the mean
value and median. More attention should be paid to collection and preparation of
samples for the analysis and determination of ash insoluble in hydrochloric
acid.
FATTY ACID COMPOSITION OF EDAM, EMMENTAL AND GOUDA CHEESES PRODUCED IN
SLOVENIA IN AUTUMN 1997
a) and
Vekoslava STIBILJ
a) Univ. of Ljubljana,
Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia.
Original scientific paper
Language: English
ABSTRACT
The aim of our work was to determine fatty acid composition of three different
types of cheeses - Edam, Gouda and Emmental, produced in Slovenia in autumn
1997. The analysed Edam and Gouda cheese was produced by three and Emmental
cheese by two different producers. All samples were purchased in the local
supermarkets twice in the period of three months in autumn 1997. The methyl
esters of the fatty acids were prepared by in situ transesterification
(ISTE) and determined by gas chromatography. The average total SAT (saturated
fatty acids) content was 56.80 wt % (relative percentage for each fatty acid of
the total fatty acids) for Emmental cheese, 56.62 wt % for Edam cheese and 57.49
wt % for Gouda cheese. The average total MUFA (monounsaturated fatty acids)
content was 34.26 wt % for Emmental cheese, 34.28 wt % for Edam cheese and 33.45
wt % for Gouda cheese. The average total PUFA (polyunsaturated fatty acids)
content was 5.30 wt % for Emmental cheese, 5.74% for Edam cheese and 5.64% for
Gouda cheese. No great difference was found between three types of cheese
concerning the fatty acid profile (wt %).
a) and
Milena KOVAČ
a) Univ. of Ljubljana, Biotechnical Fac.,
Zootechnical Dept., Groblje 3,
SI-1230 Domžale, Slovenia, Assist.
Review paper
Language: Slovene
ABSTRACT
Performance of breeding animals is frequently measured on successive intervals,
like milk traits, growth, feed intake, and exterior. The traits collected at
different time or different places are not independent. Their average as well as
standard deviation changes over time, and the correlation depends on the
distance among them. For such kind of data, random regression models (RRM)
describing production functions combined with covariance functions accommodating
time- (place-)dependent (co)variance components are the method of choice. The
models are compared to lactation yield models, to test interval model, and fixed
regression models based on literature review, and illustrated using data from
Slovenian black-white dairy-cattle population. RRMs reflect better biological
background of animal performance over time and allow selection on the overall
production level as well as the shape of production curve. They are in favor of
more flexible recording scheme and thus, cost reduction for data collection.
Furthermore, the genetic evaluation can be performed before lactation is
finished shortening the generation interval and can be done more frequently
giving a useful tool for herd management.
a), Andrej
OREŠNIK and Milena KOVAČ
a) Univ. of Ljubljana, Biotechnical
Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia, Assist.
Language: Slovene
Professional paper
ABSTRACT
In 1996 on 17 family farms in Bohinj area data on 193 lactations were analysed.
Diferent cattle breeds were reared on farms: Simmental (51.4%), Black-and-White
(31.3%), Brown (2.5%), Pinzgau (2.5%) and unknown breeds (12.3%). Milk yield and
fertility traits were analysed for 156 cows. Thirty-seven cows were culled for
different reasons. The average milk yield in the lactation was 5590 ± 1988 kg
and in standard lactation 5178 ± 1687 kg, and milk yield per feeding day was
14.2 ± 4.8 kg. Calving to conception interval lasted on average 113.8 ± 62.3
days. Calving interval was 400.2 ± 69.1 days. Conception rate was on average
65.2%. Calving interval, parity and breeder significant by affected on milk
yield per feeding day (FD). The highest milk yield per FD was achieved with
calving intervals between 341 and 365 days. Prolonged calving interval increased
the average milk yield in standard lactation. Calving to conception interval was
significantly correlated (P< 0.0001) with all fertility traits, milk yield in
lactation, and milk yield in standard lactation. Number of inseminations was
correlated with milk per FD (r = -0.1769, P< 0.0271). Distribution analyses of
diferent fertility traits showed that low heat detection rate (62.1%) folowed by
prolonged insemination to conception interval was a major problem that caused
the prolongation of calving interval on analised farms. On four farms, where
heat detection rate was 100%, calving to conception interval lasted 83 days and
first insemination to conception interval 21 days on average.
The paper is a
part of graduation thesis (justification September 14, 1998), supervisor
prof. Andrej Orešnik, Ph.D., co-advisor assoc.prof. Milena Kovač, Ph.D.
Marija UREMOVIÆ a), Zvonimir
UREMOVIÆ and Zoran LUKOVIÆ
a)
Faculty of
Agriculture, University of Zagreb, Department for animal science, HR-10000
Zagreb, Croatia, Prof., Ph.D.
Preliminary report
Language: English
ABSTRACT
The paper discusses the situation in the endangered autochthonous Black
Slavonian Breed, developed in Croatia. A program for preserving this breed was
initiated in 1996, which allowed the size of effective population (Ne) to grow
from 18.46 to 32.32. Production properties of the Black Slavonian Breed are
presented, i.e. litter size and fattening properties. According to the obtained
results, production properties of this breed are rather limited. The number of
liveborn and reared pigs per litter is 6.89 and 5.76 respectively. Under
extensive conditions of fattening, daily gain in body mass starting at 27.20 and
reaching 106.05 kg was 478 g, meat percentage being 42.95%.
Key words: pigs / autochthonous breeds / Black Slavonian breed / production
properties / litter size / daily gain / meat percentage
Simona SUŠNIK,
a), Jurij
POHAR and Peter DOVČ
a) Univ. of Ljubljana, Biotechnical
Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia, Assist., Ph.D.,
M.Sc.
Original scientific paper
Language: Slovene
ABSTRACT
The mode of inheritance of 18 microsatellite loci in grayling genome was
studied. At fifteen microsatellite loci two alleles were found and additional
amplification products at three loci. The possibility that additional products
would be the consequence of non-specific amplification, was rejected. There is
an indication that some regions of grayling genome reflect partial tetrasomic
state of the genome or duplication of some chromosomal regions.
This paper is a
part of disertation thesis, supervisor assoc.prof. Peter Dovč Ph.D.
PREPARATION OF PEROXIDASE
CONJUGATED MONOCLONAL ANTIBODIES AGAINST G CLASS OF CHICKEN IMMUNOGLOBULINS
(IgY)*
Mateja REJC,
a), Dušan
BENČINA and Franc HABE
a) Univ. of Ljubljana,
Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia,
Ass.Prof., Ph.D., M.Sc.
Original scientific paper
Language: Slovene
ABSTRACT
Infections of poultry with pathogen microorganisms are relatively frequent and
can cause great economic loss. Most of bacterial or virus infections can be
indirectly detected by demonstration of specific antibodies. The most frequently
used are indirect immunoenzyme assays where specific serum imunoglobulins of
class Y (IgY), which is an avian homologue of mammals’ class G (IgG), are
demonstrated. Beside the appropriate antigen in such assays, the secondary
antibodies against chicken IgY, conjugated with enzyme are necessary. IgY
isolated from chicken egg yolk were used for immunization of BALB/c mice and
monoclonal antibodies (mAb), designated M2 were designed and conjugated with
horseradish peroxidase (M2-p). MAb M2 recognized determinants on chicken,
turkey, pheasant and peacock IgY. Determinant is a part of heavy chain of
chicken IgY and is probably not glycosilated. For use of conjugate M2-p in
direct immuno-enzyme assays pH optimum, optimal working dilution and affinity
were determined. Very wide range of pH (from 3 to 11) values, where mAb M2
reacts with IgY indicates a high affinity of binding. Results obtained so far
indicate that our conjugate M2-p is appropriate for use in immunoenzyme assays
for detection of specific antibodies IgY in chicken, turkey, pheasant and
peacock.
Univ. of Ljubljana,
Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia,
Assoc.Prof., Ph.D., M.Sc.
Original scientific paper
Language: English
ABSTRACT
Sampling and extraction procedures were elaborated for DNA isolation suitable
for subsequent PCR amplification and other molecular manipulation experiments
from horse excrements. Eleven Lipizzaner horses were split into two age groups
and faecal excrements were collected as soon as possible after defecation and
the DNA was isolated immediately after arrival to the laboratory. The excrements
collected from the group of younger horses yielded on average 3-4 fold higher
amounts of DNA than from the group of older horses. The variability of the DNA
yield isolated on successive days from the same horse remained within 15% of the
average yield. The DNA yield isolated on successive days from the same faecal
excrement increased gradually from 4.61 to 7.96 μg g-1
faeces until 48 hrs after defecation and dropped only slightly to 7.51 μg g-1
after further four days. Our results indicate, that substantial microbial growth
is taking place in the faecal excrements at least until two days after
defecation. It is of utmost importance therefore, that the sampling is done as
soon as possible after defecation if microbial community structure analysis of
the equine colon and faeces is to be performed.
Univ. of Ljubljana,
Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia,
Assoc.Prof., Ph.D., M.Sc.
Review paper
Language: English
ABSTRACT
In recent years, molecular genetics and genome analysis provided extensive
evidence that gene loss and acquisition are likely to be the primary mechanisms
by which bacteria genetically adapt to novel or changed environments and by
which bacterial populations diverge and form separate, evolutionary distinct
species. Three mechanisms of gene transfer have been identified in
microorganisms: transformation, conjugation and transduction, but our knowledge
concerning horizontal gene transfer in the environment was and still is very
limited. Animal gut and in particular the rumen belong to the most complex
microbial ecosystems. Conditions in the rumen potentially favour horizontal gene
transfer with conjugation and transduction, due to large, diverse and dense
bacterial and bacteriophage populations, however, there is very little evidence
supporting theoretical assumptions. A brief review of current knowledge on
horizontal gene transfer is presented with the emphasis on the available data
and views concerning the process going on in the rumen.
ISOLATION OF THE btsT
GENE ENCODING THIOESTERASE AND CONSTRUCTION OF VECTOR FOR ITS INSERTION
MUTAGENESIS IN Bacillus licheniformis
*
a)
a) Krka, Pharmaceutical,
Šmarješka cesta 6, SI-8000 Novo mesto, Slovenia.
Original scientific paper
Language: Slovene
ABSTRACT
Next to almost all prokaryotic operons encoding peptide synthetases, which are
involved in the synthesis of peptide antibiotics, distinct genes have been
detected that encode proteins with strong sequence similarity to thioesterases.
The mechanism and function of thioesterases in peptide synthesis is not known.
Antibiotic bacitracin, produced by Bacillus licheniformis, is synthesised
by a large multienzyme complex composed of the three bacitracin synthetases BA1,
BA2 and BA3. Genes encoding bacitracin synthetases are organised in the bac
operon. Upstream of the bac operon is btsTgene encoding
thioesterase. In order to investigate the influence of thioesterase on
bacitracin biosynthesis 1.2 kb fragment was isolated from chromosomal DNA B.
licheniformis by using PCR . This fragment consists of almost entire btsT
gene and complete promotor region of bac operon. Fragment has been
hybridised with B. licheniformis BA1 chromosomal DNA. In addition the Tc
resistance gene (tetM) was inserted into the fragment to construt vector
for insertion mutagenesis of the btsT gene.
Univ. of Ljubljana,
Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia,
Assoc.Prof., Ph.D., M.Sc.
Original scientific paper
Language: Slovene
ABSTRACT
Three strains of rumen spirochetes have been isolated from the rumen fluid
sample. Phase-contrast and epifluorescence microscopy have been used for
morphological observation of isolated strains. For further characterisation
rapid biochemical tests (API 50CH) and molecular biological analysis have been
used. The morphological observations showed that two of the isolated strains SM1
and SM3 are similar and differ significantly from the strain SM2. All three
isolated strains of rumen spirochetes are Gram-negative. The SM1 and SM3 cells
were smaller than SM2 cells. Smaller were also the amplitude and the wavelength
of coils of SM1 and SM3 cells. SM1 and SM3 strains utilised seven of 49 tested
charbohydrates, whereas strain SM2 utilised additional 14 sugars. The literature
data describing sugar fermentation in T. bryantii and T.
saccharophilum showed significant differences between type strains T.
bryantii and T. saccharophilum and strains SM1 and SM3. The strain
SM2 seems to be similar to the type strain of T. saccharophilum. Large
differences between analysed strains were found with theoretical and
experimental RFLP analysis using different restriction enzymes of the 16S rRNA
gene.
Darja FERME, Jerneja
AMBROŽIČ, Miklavž GRABNAR, Maja RAVNIKAR and
a)
a) Univ. of Ljubljana,
Biotechnical Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia,
Assoc.Prof., Ph.D., M.Sc.
Original scientific paper
Language: English
ABSTRACT
Sampling, inoculation and extraction procedures were elaborated for the
isolation of bacteriophages from cattle rumen fluid. Several strains from four
different species of rumen bacterial genus Prevotella were used as
indicator organisms as well as Escherichia coli, Salmonella sp.
and Yersinia enterocolitica strains. Only one strain, i.e. P.bryantii
TC1-1 was successfully infected with filter sterilised rumen fluid inoculum
containing rumen bacteriophages. Two plaque morphotypes were observed, both
being turbid and rather small but clearly different in size. The preliminary
transmission electron microscopy analysis showed that all observed
bacteriophages have presumably icosahedral symmetry. The infection trials of
other Prevotella strains with isolated bacteriophages from the strain
TC1-1 were successful only with type strains of species P.bryanti and
P.brevis
respectively. Bacteriophage purification and long term storage procedures were
elaborated.
THE INFLUENCE OF SUBSTRATE CONCENTRATION AND GROWTH PHASE ON EXPRESSION OF
Butyrivibrio sp. Mz5 ENDOXYLANASES
a), Romana
MARINŠEK LOGAR, Tadej ČEPELJNIK and Franc V. NEKREP
a) Univ. of Ljubljana, Biotechnical
Fac., Zootechnical Dept., Groblje 3, SI-1230 Domžale, Slovenia.
Original scientific paper
Language: English
ABSTRACT
Butyrivibria represent a significant proportion of bacterial isolates from
different ruminants. The strain Butyrivibrio sp. Mz5 was originally
isolated from the rumen of a black and white Frisian cow. It possesses very high
xylanolytic activity, at least 1.65 times higher than any of the tested
anaerobic bacteria, as shown earlier. The inducibility by substrate, the
influence of substrate concentration and growth phase on expression of its
endoxylanases were tested in the present work. Xylanase activity of
Butyrivibrio
sp. Mz5 was found to be inducible, the specific activity of cells grown on xylan
being increased 34-fold in comparison with cells grown on soluble carbon
sources. The 51 kDa- and 145 kDa-endoxylanases are constitutive. The highest
xylanolytic activity was detected after 16 hours growth and at 0.5% xylan
concentration in growth medium. The majority of the xylanolytic activity was
cell bound. Lower concentrations of xylan promoted the release of xylanolytic
enzymes into the medium. The 26.7 kDa endoxylanase showed resistence to lower
pH. The data obtained will help to achieve maximal xylanolytic activity for the
needs of enzyme purification.
