Astaxanthin bioszintézis genetikai befolyásolása Phaffia rhodozyma-ban = Genetic influence on biosynthesis of astaxanthin in Phaffia rhodozyma

Az astaxanthin (3,3¢-dihydroxy-b,b-carotene-4,4¢-dione) termelő élesztők nagy biotechnológiai jelentőségűek. RAPD analízisen alapuló csoport analízist végrehajtva igazoltuk , hogy az astaxanthin-termelő izolátumok két fajba (Xanthopyllomyces dendrorhous és Phaffia rhodozyma) tartoznak. Különböző mutációs eljárásokat - gamma-, UV-sugárzás és kémiai mutagenezis, illetve ezek kombinációi - alkalmazva auxotróf és színmutánsokat izoláltunk mindkét élesztőfajból. Pigment- illetve astaxanthin túltermelő mutánsokat, melyek színanyag profilja jelentősen eltért hoztunk létre. Protoplaszt fúziós kísérleteket végeztünk és fúziós hibrideket izoláltunk és jellemeztünk. In vivo EPR vizsgálatokkal jellemeztük a különböző pigment-profilú mutánsok plazmamembránjának szerkezeti és dinamikus sajátosságait a hőmérséklettel összefüggésben. Meghatároztuk a X. dendrorhous 3-hydroxy-3-methylglutharyl coenzyme A reductase (HMG-CoA reductase) génjének részleges génszekvenciáját. Felfedeztük, hogy mind a P. rhodozyma és a X. dendrorhous képes lebontani az ochratoxin A-t ochratoxin alfává, feltehetően egy sejthez kötött karboxipeptidáz A aktivitás révén. | Astaxanthin (3,3¢-dihydroxy-b,b-carotene-4,4¢-dione) - accumulating yeasts are of great biotechnological interest. RAPD analysis involving astaxanthin-producing yeast strains was performed: cluster analysis based on RAPD markers differentiated isolates of Xanthopyllomyces dendrorhous and Phaffia rhodozyma (asexual) at an intraspecific level. Different mutation strategies, which involves *- and UV-irradiations, as well as chemical mutagenesis of cells was worked out to obtain auxotrophic and colour mutants from these astaxanthin-producing yeasts. Overproducer mutants exhibited different patterns of carotenoid production have also been isolated. Protoplast fusion experiment have been carried out and fusion hybrides have been isolated and characterized. Spin labelling methods were used to describe the structure and dynamic properties of various carotenoids containing X. dendrorhous’s plasma membranes in relation to temperature. A partial gene sequence of 3-hydroxy-3-methylglutharyl coenzyme A reductase (HMG-CoA reductase) of X. dendrorhous has been determined. Ochratoxin degrading activities of P. rhodozyma and X. dendrorhous isolates were discovered. P. rhodozyma is able to convert ochratoxin A to ochratoxin a (possibly mediated by a cell-bound carboxypeptidase A)

Functional diversity investigation of bacterial communities in distinct soil types with RISA after preculturing (RISA-APC) method

Microorganisms play a leading role in soil development and preservation; moreover, they could indicate the soil health and conditions. In this study, we analyzed the bacterial composition of three different soil types with a newly developed RISA-APC method. A novelty of this method is the pre-culturing step: this preculturing of the bacterial communities were performed on solid media supplemented with different carbon sources (e.g.: carboxy-methyl cellulose, xylan, chitin, starch, tributyrin, casein and protocatechuic acid). For the investigation of heavy metal tolerant bacteria, a preculturing on YEG media containing CuSO4 or CdCl2 were used. The mini-colonies developed after a short incubation time was investigated. This RISA-APC method proved to be a useful tool for the comparison of different soil types, and for the examination of changes in the soil bacterial community structure. It was clearly shown that the most diverse functional diversity values occurred in the forest soil and the less diverse bacterial community was detected in sandy soil samples

Disinfection action of some essential oils on stainless steel

Bacteria can attach to different surfaces and form biofilm. Biofilms can cause a big problem in food industry by contamination of food items and reduction of the effectiveness of machines. In the biofilm bacteria are less exposed to the different disinfectants, than the free living cells. Essential oils (EO) with known antimicrobial effect can also inhibit biofilm formation. In our experiments minimal inhibitory concentrations (MIC) and minimal bactericide concentrations (MBC) of the investigated EOs: cinnamon, juniper and lemon were determined by macro-dilution method on Pseudomonas putida and E.coli. Cinnamon showed the best antibacterial effect with MBC values of 2mg/ml forE. coli and 4mg/ml forP.putida. Thebactericidaleffect of EOsdependedontheactingtime. We established 80 minutes forP. putida and 120 (cinnamon EO) and 240 (juniper EO) min forE. coli. The disinfection potential of the EOs were studied on P. putida and E. coli 1 and 7 days old biofilms formed on industrial stainless steel surfaces. Each of the EO was effective. The number of P. putida cells was reduced up to 99% and we had similar result by 1 day old E. coli biofilm. The cell number of 7 days old E. coli biofilm was reduced by 62.5% with cinnamon EO and juniper EO reduced it by 87%

Effect of pesticides on the growth and secreted chymotrypsin-like activity of a biocontrol strain of bacillus amyloliquefaciens

Biocontrol is an alternative approach to reduce the harmful effects of pathogen species in the agriculture. Pesticide-tolerant biocontrol agents are preferred in the integrated pest management because they can be applied together with different fungicides, herbicides and insecticides. A potent biocontrol agent, Bacillus amyloliquefaciens SZMC 22206 strain was isolated and studied previously. It was revealed, that the extracellular chymotrypsin-like protease and fengycin secretion of the strain resulted its antagonistic effect. The aim of our present study was to analyse the effect of different pesticides on the growth and activity of the extracellular chymotrypsin-like proteases of this Bacillus strain. The tested pesticides were a fungicide (carbendazim), and three frequently used herbicides (linuron, chlortoluron and 2,4-dichlorophenoxyacetic acid). The tested Bacillus strain was able to grow in the presence of the pesticides, but the activities of the extracellular chymotrypsin-like proteases were significantly reduced in some cases