Immuntechnikák alkalmazása élelmiszerek vizsgálatára

A jelenleg ismert analitikai módszerek közül a legnagyobb specifikussággal az immunbiokémiai módszerek rendelkeznek. A szerző áttekintést ad az élelmiszeranalitikai célra alkalmazott immunkémiai módszerekről: gél-immun diffúzió, elektroimmundiffúziós és ELISA-technika, Röviden beszámol az immuntechnika élelmiszeranalitikai alkalmazásának néhány hazai eredményéről. The biochemical procedures have the largest specificity among the present time known analytical methods. The author gives a view about the immun-biochemical procedures, which are adopted for food analytics: gel-immundiffusion, electricimmundiffusion and ELISA-technique. The author reports on some domestic results of immuntechnique which is adopted for food analytics

COMPARISON OF STRESSED AND UNSTRESSED YEAST BY DIFFERENTIAL SCANNING CALORIMETRY (DSC) AND SDS-PAGE

Heat shock of Saccharomyces yeast strains resulted in the induction of a set of proteins referred to as shock protein (HSPs). SDS-PAGE analysis revealed that at least three induced HSPs were identified in a Saccharomyces cerevisiae CBS 1395 and seven in a Saccharomycespastorianus CBS 1503. One of these HSPs with molecular mass of approximately 41 KDa was also identified in two Illutant strains of Saccharomyces cerevisiae. Differential scanning calorimetry analysis of whole yeast cells revealed that heat shock treatment decreased the enthalpy of denaturation ~(H) of total cellular proteins. A direct correlation between the degree of HSP inducibility and protection against extreme temperatures was observed, These results suggest that prior heat shock treatment protects the protein of yeast cells from elevated temperatures

STUDY OF THE SULPHUR METABOLISM OF METHIONINE-RICH YEASTS

Mutants were produced by mild mutagenic agents such as DV-radiation and nitrite treat- ment, from yeast strains belonging to different genera. The primary selection has been based on an assumed higher sulphate requirement. Norleucine has been used as methionine antagonist and the resistance of the mutants was compared to that of the parent strains. Our assays showed that the mutants selected were more sensitive to norleucine as compared to the untreated strains. Thus, the higher methionine content cannot be attributed to homoserine-0-transsuccinase derepression. Simultaneously with the increased sulphate requirement, the mutants responded to a higher methyl donor concentration also by an enhanced growth. In methionine enriched mutants also the lipoic acid concentration of the yeast in- creased in parallel with the increase in the sulphurous amino acid concentration. The concentrations of both components react very sensitively to the aeration intensity applied during fermentation and these begin to fall at the value of 200 mmol O2h-11-1. Sulphur present in sulphate form has been found to be a much better sulphur source than methionine. Applying the latter, a slower cell growth can be observed due to sulphur limitation. Our experimental results indicate that with the mutants produced, the sulphate reduction step became more efficient and provided an increased methionine content

Környezeti tényezők hatása egyes laktobacillusok biogén amin és bakteriocin bioszintézisére = Effect of environmental factors on biogenic amine and bacteriocin biosynthesis of certain lactobacilli

Három autentikus laktobacillus törzs, Lb.plantarum 2142, Lb. casei subsp.casei 2750 ,és Lb. curvatus 2770, szaporodását és bakteriocin termelét vizsgáltuk a tápköözeg összetétel függvényében. Mindhárom esetben MRS tápközegben volt a legjobb szaporodás, de a pepton víz+ YE illetve pepton víz + y e3 glükóz-on is számottevő növekedés következett be. A növényi alapú tápoldtok közül TJ-on kisebb növekedés lépett fel mint cékla-illetve csicsókalén. A gátlóhatást vizsgálva ateszt mikroorganizmusokkal (baktérium, élesztő és penész) szembeni aktivitás termelő törzs függő. Egyazon törzs esetén a tápközeg összetételnek is hatása van, de a gátló aktivitás nem mutat összefüggést az adott táplén észlelt szaporodással ,ami arra mutat, hogy a bakteriocin termelés nem szaporodáshoz kötött, a stacioner azakszban lép fel.A biogén aminszintézist elsődlegesen a hozzáférhető szabad aminósav koncentráció, az aminósav dekarboxiláz (ADC) és az amonóoxidáz(AO) befolyásolja. Peptid kötésben levő aminósav szubsztrázum esetén a proteáz aktivitás a meghatározó. MRS tápközegben a legnagyobb proteáz aktivitású törzs termelt legnagyobb amin-koncentrációt. Mind az ADC mind az AOerős szubsztrát koncentráció függést mutat 0-1 mg/ml, ill. 0-0,004 mg/ml tartományban. A H2O2 szintézis a vizsgált törzsek estén jelentősen eltér, MRS-n szporítoot sejtek közül az Lb.2142, mig TJ. a 2770 volt legaktívabb.A képződött 0.03 mM H2Os nem okozott sejtkárosodást. | We investigated in case of 3 authentic lactobacilli (Lb. plantarum 2142, Lb. casei subsp. casei 2750 and Lb. curvatus 2770) the influence of medium composition on growth and bacteriocin production.For growth MRS was the best, but pepton water + YE andpepton water+YE3glucose resulted also considerabel growth. Among the plant-based media TJ resulted lower groth than red beet and Jerusalem artichoke juices. Inhibitory activity aginst test microorganisma (bacteria, yeaste, moulds) is dependent on the producer strain. in case of the same Lb. the medium composition has also influence, but inhibitory activity shows no correlation with growth rate in the same substrate, this means that bacteriocin sínthesis is not growth phase dependent it occurs in the stationary phase. Biogenic amins production is mainly influenced by the free amino acid present, the amino acid decarboxylae ADC) and aminooxidase8AO) activities. Whe n amino acid is peptide bound, the proteinase activity is rate limiting. In MRS medium highest amine content was detected by higheat protease activity Lb. strain. Both ADC and AO are highliy sutrate conc. dependent in the range of 0-1mg/ml and 0-0.004 mg/ml resp. H2O2 production of the strains is highly different, among MRS grown cells Lb.2142, while on TJ Lb. 2770 where most active producers. The synthesized concnetration 0.03mM did'nt result cell damage of the producer Lb.214

A NEW WAY OF IDENTIFICATION OF YEASTS: USE OF NIR TECHNIQUE

Four strains of Saccharomyces genera were investigated: S. pastorianus CBS 1503, S. cerevisiae CBS 1395, S. cerevisiae CB 67 and S. cerevisiae CB 89. The aim of our work was to test the suitability of NIR technique for rapid identification of different yeasts. Yeasts were grown in batch culture and samples were taken from the exponential and stationary growth stages, later ones were divided into parts and one of them was heat-shocked. The four yeasts tested were morphologically different, the CBS signed showed oval, the CB signed ones had round shaped cells. Optimum growth temperatures were all in the range of 30-35 ⁰C, and at 30⁰C growth rates of mixed cultures did not differ significantly from those of monocultures. The SDS-PAGE protein prints of the four strains were different both in the number of subfractions apd their molecular mass distributions. This method is suitable to characterize and differentiate the investigated yeasts . Quantitative evaluation ofthe SDS-PAGE patterns enables us to detect infections in the pure culture . NIR spectra of the investigated strains were significantly different. The growth stage or heat-shock treatment had serious effect on the spectrum. Mixtures of two pure cultures (0, 10, 20 ... 90% 'infection') showed NIR spectra in between those of the pure culture and even 10% contamination caused a significant difference

A NEW METHOD FOR THE EVALUATION OF THE RESISTANCE OF MAIZE HYBRIDS TO FUSARIAL EAR ROT - THE TOXIN-MOULD-INDEX (TMI)

30 maize hybrids grown in Hungary representing the groups FAO 200 - 299, FAO 300 399, FAO 400 - 499, and FAO 500 - were studied in order to gain information about genotypic resistance to Fusarium moulds. The plants grown on an experimental farm were artificially infected using the tooth pick method with F. graminearum and F. oxysporum resp. In addition maize grain meals were also inoculated with isolates of moulds. The surface area of ears covered by moulds 9 weeks after inoculation and the toxin content (zearalenone and T-2 toxin) of infected maize grain meals were measured. Big differences were observed in the mould-covered area of the ear surface (2.00 to 38.88%) and also in the zearalenone content (2.73 to 80.33 mg per kg) and T-2 toxin content (5.37 to .52.33 mg per kg) between genotypes. Poor correlation was found between the mould-covered area and the toxin content measured in the maize grain meal of the same genotypes. For characterization of resistance resp. susceptibility of different genotypes, a new method was introduced using the toxin-mould-index (TMI) taking in to consideration both the growth rate of moulds and their toxin production. In every FAO group resistant genotypes were found confirming the view that not only the duration of the vegetation period influences the resistance or susceptibility

STUDY OF THE EFFECTS OF N-FERTILIZATION AND PLANT DENSITY ON THE RESISTANCE OF MAIZE HYBRIDS TO FUSARIAL EAR ROT

Eight maize hybrids grown in Hungary were studied in order to investigate the effects of some agrotechnical factors (N-fertilization and plant density) on the resistance to Fusarium moulds. The plants grown on an experimental farm were artificially infected using the tooth pick method with F. graminearum and F. culmorum. In addition, maize grain meals were also inoculated with isolates of moulds. The surface area of ears covered by moulds 9 weeks after inoculation and the toxin content (Zearalenone and T2 toxin) of infected grain meals were measured. For characterization of resistance, the toxin-mould index (TMI) was introduced which takes into consideration both the growth rate of moulds and their toxin production. A slight decrease in the mould-covered surface area of ears was observed with growing N-supply, and surprisingly no significant differences were found in the toxin content with higher plant density