Jan Bárta

Chemical composition and nutritional value of protein concentrates isolated from potato (Solanum tuberosum L.) fruit juice by precipitation with ethanol or ferric chloride.

Effects of protein precipitators, ethanol and ferric chloride, on yield, resolubility, chemical composition and nutritional value of protein concentrates isolated from industrial potato fruit juice (PFJ) were studied. Optimum precipitating concentrations of ethanol and ferric chloride in PFJ were 4 M (23.1% v/v) and 20 mM (2% w/v), resulting in yield of 69% and 86.5% of total protein, respectively. Contents of total glycoalkaloids and potassium in both protein concentrates were significantly lower (P < 0.05) as compared with contents in PFJ dry matter. Both protein concentrates exhibited high nutritional value; values of essential amino acid index (EAAI) were 81.7% and 82.7%, respectively. Fraction of patatin proteins (39-43 kDa) represented with EAAI value of 86.1% the nutritionally improving protein component. Lipid acyl hydrolase activity of patatin family was not negatively affected by cooled ethanol precipitation. It can be thus suggested that biological and enzymatic activities of this protein family are utilizable after this type of precipitation.

Cultivar Variability of Patatin Biochemical Characteristics: Table versus Processing Potatoes (Solanum tuberosum L.)

Biochemical characteristics of patatin proteins purified by ion-exchange and affinity chromatography from tubers of 20 potato cultivars were studied to evaluate their genotype differences with respect to utility groups, table potato cultivars (TPCs) and processing potato cultivars (PPCs). Both groups of cultivars showed similar values of protein content in dry matter (3.98-7.39%) and of patatin relative abundance (5.40-35.40%). Three mass levels (∼40.6, 41.8, and 42.9 kDa) of purified patatins were found by MALDI-TOF MS within all cultivars. Differences among mass levels corresponding with the mass of sugar antenna (∼1.2 kDa) confirmed the previous concept of different glycosylation extentsin patatin proteins. It was showed that the individual types of patatin varying in their masses occur in the patatin family in a ratio specific for each of the cultivars, with the lowest mass type being the major one. Electrophoretic analyses demonstrated wide cultivar variability in number of patatin forms. Especially 2D-PAGE showed 17-23 detected protein spots independently on the utility group. Specific lipid acyl hydrolase (LAH) activity of purified patatins from the individual tested cultivars varied between 0.92 and 5.46 μmol/(min mg). Patatin samples within most of the TPCs exhibited higher values of specific LAH activity than samples of PPCs. It may be supposed that individual patatin forms do not have similar physiological roles.

UTILIZATION OF DNA MARKERS BASED ON MICROSATELLITE POLYMORPHISM FOR IDENTIFICATION OF POTATO VARIETIES CULTIVATED IN THE CZECH REPUBLIC

In the year 2007, there were one hundred and seventy-eight potato varieties enlisted in the Czech list of registered potato varieties. The classical morphometric approach to characterization is not effective for such a number of varieties especially for identification at the level of tubers. The needfulness of variety identification at the level of tubers is important mainly for trade aspect. The Czech law no.110/1997 Sb. about the food-stuff and tobacco products and the consequential ordinance (MZe c. 332 / 1997 Sb.) require guarantee of variety declaration in commercial relation for table potato. In this study we analyzed twenty potato varieties (Solanum tuberosum L.) cultivated in the Czech Republic. Every variety was represented by four independent replicates. This set of samples was analyzed by methods of PCR-SSR (Simple Sequence Repeats) and PCR-ISSR (Inter Simple Sequence Repeats). We discovered that both of tested methods afford sufficient polymorphism for variety identification, but the method of PCR-ISSR is not utilizable, because we observed the variability within variety. For outright identification of the whole set of potato varieties cultivated in the Czech Republic we recommend to use SSR, AFLP and retrotransposene-based markers as well as morphological markers.

N-Glycome Profiling of Patatins from Different Potato Species of Solanum Genus

It is hypothesized that oligosaccharides are another potential source of immunological cross-reaction between different plant allergens. Patatin is the most abundant glycoprotein in potato and has been described to have an oligosaccharide of composition Man3(Xyl)GlcNAc2(Fuc). In this work, N-glycosylation profiles of patatin proteins isolated from tubers of different potato species were investigated and compared. Oligosaccharides were released by enzymatic digestion with PNAGase A and analyzed primarily by matrix-assisted laser desorption ionization mass spectrometry. For glycan labeling, a modified version of on-target derivatization with phenylhydrazine was applied. This study found the presence of glycan structures not described previously in patatins of potato tubers, and their glycan profiles significantly differed. This knowledge about the glycosylation of potato patatins may be helpful for correct choice of potato species to decrease the presence of specific glycan epitopes causing food allergy as well as for utilization of potatoes for the manufacture of therapeutic proteins.

Soil nitrogen variability in relation to seasonal nitrogen cycling and accumulation of nitrogenous components in starch processing potatoes

Abstract Seasonal dynamics of total soil nitrogen, ammonium and nitrate ions contents were evaluated for a processing potato field experiment conducted on three sites with different altitudes. Fertilization levels of 100 and 200 kg N ha−1 applied before potato crop planting were compared. Content of soil ammonium and nitrate ions ranged from 1.5 to 149 mg kg−1 and from 3.0 to 108 mg kg−1 on soil dry matter basis, respectively and showed strong seasonal dynamics with a rapid increase of the content during June and subsequent fall down to initial values. The nitrogen fertilization level had minimal effect on seasonal dynamic of total soil nitrogen, ammonium and nitrate ions contents. The higher fertilization level significantly increased crude protein content in potato tubers and yield of crude protein per area unit. The factors of starch content in potato tubers and yield per area unit were affected negatively by the higher dose of nitrogen fertilization. It could be concluded that the dose of 100 kg N ha−1 is sufficient for production of potato tubers with high content of both crude protein and starch, especially in production areas with higher altitude. The dose of 200 N is justifiable only in production areas with lower altitude (below 400 m a.s.l.) that are not so suitable for accumulation of crude protein and starch in potato tubers.

Preventing the mixed detergent micelle effect in two-dimensional electrophoresis on Tris-Tricine gels

Application of Tris‐N‐[Tris(hydroxymethyl)methyl]glycine gels for 2DE is hampered by formation of mixed CHAPS–SDS micelles resulting in typical swirling pattern in the low mass range, which makes reliable quantitative and qualitative gel evaluation impossible. Modification of 2DE strip equilibration procedure prevented the direct interaction between both detergents during equilibration process, thus substantially improving gel separation.