Transcription regulation of the Escherichia coli pcnB gene coding for poly(A) polymerase I: roles of ppGpp, DksA and sigma factors

Poly(A) polymerase I (PAP I), encoded by the pcnB gene, is a major enzyme responsible for RNA polyadenylation in Escherichia coli, a process involved in the global control of gene expression in this bacterium through influencing the rate of transcript degradation. Recent studies have suggested a complicated regulation of pcnB expression, including a complex promoter region, a control at the level of translation initiation and dependence on bacterial growth rate. In this report, studies on transcription regulation of the pcnB gene are described. Results of in vivo and in vitro experiments indicated that (a) there are three σ70-dependent (p1, pB, and p2) and two σS-dependent (pS1 and pS2) promoters of the pcnB gene, (b) guanosine tetraphosphate (ppGpp) and DksA directly inhibit transcription from pB, pS1 and pS2, and (c) pB activity is drastically impaired at the stationary phase of growth. These results indicate that regulation of the pcnB gene transcription is a complex process, which involves several factors acting to ensure precise control of PAP I production. Moreover, inhibition of activities of pS1 and pS2 by ppGpp and DksA suggests that regulation of transcription from promoters requiring alternative σ factors by these effectors of the stringent response might occur according to both passive and active models

Cosmic ray oriented performance studies for the JEM-EUSO first level trigger

JEM-EUSO is a space mission designed to investigate Ultra-High Energy Cosmic Rays and Neutrinos (E > 5 ⋅ 1019 eV) from the International Space Station (ISS). Looking down from above its wide angle telescope is able to observe their air showers and collect such data from a very wide area. Highly specific trigger algorithms are needed to drastically reduce the data load in the presence of both atmospheric and human activity related background light, yet retain the rare cosmic ray events recorded in the telescope. We report the performance in offline testing of the first level trigger algorithm on data from JEM-EUSO prototypes and laboratory measurements observing different light sources: data taken during a high altitude balloon flight over Canada, laser pulses observed from the ground traversing the real atmosphere, and model landscapes reproducing realistic aspect ratios and light conditions as would be seen from the ISS itself. The first level trigger logic successfully kept the trigger rate within the permissible bounds when challenged with artificially produced as well as naturally encountered night sky background fluctuations and while retaining events with general air-shower characteristics

Badania nad izomeryzacją D-glukozy do D-fruktozy przy zastosowaniu unieruchomionej izomerazy glukozowej maxazyme G I.

The aim if the work was to study the influence of three parameters, i.e. type of substrate, addition of calcium ions and short-lasting effect of increased temperature on the action of enzyme, imrriobilized glucose isomerase Maxazyme G I, a preparation produced by Gist Brocades Company, the Netherlands. Isomerization of D-glucose into D-fructose was carried out applying the continuous column process. The obtained results reveal the influence of the above mentioned factors upon the activity, stability and productivity of the enzyme.Wzrost produkcji syropu fruktozowego w świecie związany jest z rozwojem produkcji unieruchomionej izomerazy glukozowej. W pracy przebadano wpływ niektórych czynników na aktywność, stabilność i produkcyjność preparatu izomerazy glukozowej Maxazyme GI unieruchomionej na żelatynie przez okluzję, a mianowicie: - wpływ rodzaju substratu, - wpływ dodatku jonów wapnia, - wpływ krótkotrwałego działania wysokiej temperatury. Badania izomeryzacji prowadzono sposobem ciągłym, kolumnowym, utrzymując konwersję na poziomie 4$0/o fruktozy. Zawartość fruktozy mierzono metodą polarymetryczną, a aktywność, produkcyjność i okres półtrwania obliczono na podstawie Współczynnika Thiele dla temp. 70°C i czasu 75-165 godz. mierzonego od momentu rozpoczęcia procesu. W pracy przedstawiono wyniki procesu izomeryzacji roztworu krystalicznej glukozy oraz pszennego i ziemniaczanego hydrolizatu glukozowego przez 2 partie preparatu Maxazyme GI. Wartości początkowe zastosowanych substratów były zbliżone. Stwierdzono również hamujące działanie jonów wapnia, wskazujące na bezwzględną konieczność maksymalnej demineralizacji substratu, bowiem obecność jonów wapnia nawet w ilości 5 ppm obniża o ok. 10% szybkość początkową, z jaką należy wprowadzać sok na kolumnę w celu utrzymania konwersji na wymaganym poziomie. Badania nad wpływem 30 min utrzymywania preparatu w podwyższonej temperaturze Wykazały, że zastosowanie temp. 75, 80 i 85°C wymaga obniżenia o 5-6% szybkości Przepływu soku przez kolumnę, a zastosowanie temp. 90°C - o 13%

The unconventional single stage hydrolysis of potato starch

Enzymatic depolymerisation of starch to glucose or maltose is carried out by starch- degrading amylases during a two-stage hydrolysis: liquefaction using bacterial α-amylase followed by saccharification with glucogenic (fungal amylase) or maltogenic (fungal or bacterial) amylases. As a rule, these enzymes are applied separately, following the recommendations concerning their action provided by the enzyme manufacturers. The study presents our attempts to determine the reaction conditions for a simultaneous action of liquefying and saccharifying enzymes on pre-treated potato starch. Hydrolysis was run by Liquozyme Supra, Maltogenase 4000L and San Super 360L enzymes (Novozymes) at different temperatures. During the single-stage method of starch hydrolysate production the most desirable results was obtained for the maltose hydrolysate at 80°C (51.6 DE) and for the glucose hydrolysate at 60°C (96 DE). The analyses indicate that the application of a single-stage hydrolysis of starch to maltose or glucose makes it possible to obtain a degree of starch saccharification comparable with that obtained in the traditional two-stage hydrolysis

High pressure impact on changes in potato starch granules

Air dry potato starch (84.9% d.s.) was subjected to pressurizing under the pressure of 50, 100, 250, 500, 750, 1000 and 2000 MPa for 1 h. The physical properties of pressurized starch, such as morphology, surface and crystalline structure, gelatinization parameters, were studied by means of scanning and atomic force microscopy (SEM/AFM), X-ray diffraction (X-ray), differential scanning calorimetry (DSC). The susceptibility to the amylolytic enzyme (α-amylase) was also measured. Application of pressure in the range of 50–2000 MPa results in an increase in the compressed potato starch bulk density, change in the contours of the granules from oval to polyhedral, increase in the roughness of the granule surface, vanishing of the X-ray reflexes generated by the orthogonal structure and weakening of the reflexes generated by the hexagonal structure, lowering of the enthalpy of starch gelatinization, and the enhancement of hydrolytic susceptibility of starch granules to the amylolytic enzyme