Optimisation of Inulinase Production by Aspergillus niger Using Simplex and Classical Method

The simplex method has been used to optimise the inulinase production by Aspergillus niger strain 13/36 with respect to 5 components of the medium. The extracellular enzyme activity was almost 80 U/mL, and over 1.6-fold higher than the results obtained by the classical »one-factor-at-a-time« method. The greatest advantage of the simplex method is that the optimum factor levels were determined in only 12 iterative steps, shortening a typical optimum search process considerably. This is the first use of the simplex method for optimising inulinase production

Thermal inactivation and conformational lock studies on glucose oxidase

In this study, the dissociative thermal inactivation and conformational lock theories are applied for the homodimeric enzyme glucose oxidase (GOD) in order to analyze its structure. For this purpose, the rate of activity reduction of glucose oxidase is studied at various temperatures using b-D-glucose as the substrate by incubation of enzyme at various temperatures in the wide range between 40 and 70 �C using UV–Vis spectrophotometry. It was observed that in the two ranges of temperatures, the enzyme has two different forms. In relatively low temperatures, the enzyme is in its dimeric state and has normal activity. In high temperatures, the activity almost disappears and it aggregates. The above achievements are confirmed by dynamic light scattering. The experimental parameter ‘‘n’’ as the obvious number of conformational locks at the dimer interface of glucose oxidase is obtained by kinetic data, and the value is near to two. To confirm the above results, the X-ray crystallography structure of the enzyme, GOD (pdb, 1gal), was also studied. The secondary and tertiary structures of the enzyme to track the thermal inactivation were studied by circular dichroism and fluorescence spectroscopy, respectively. We proposed a mechanism model for thermal inactivation of GOD based on the absence of the monomeric form of the enzyme by circular dichroism and fluorescence spectroscopy

A Novel Strategy to Construct Yeast Saccharomyces cerevisiae Strains for Very High Gravity Fermentation

Very high gravity (VHG) fermentation is aimed to considerably increase both the fermentation rate and the ethanol concentration, thereby reducing capital costs and the risk of bacterial contamination. This process results in critical issues, such as adverse stress factors (ie., osmotic pressure and ethanol inhibition) and high concentrations of metabolic byproducts which are difficult to overcome by a single breeding method. In the present paper, a novel strategy that combines metabolic engineering and genome shuffling to circumvent these limitations and improve the bioethanol production performance of Saccharomyces cerevisiae strains under VHG conditions was developed. First, in strain Z5, which performed better than other widely used industrial strains, the gene GPD2 encoding glycerol 3-phosphate dehydrogenase was deleted, resulting in a mutant (Z5ΔGPD2) with a lower glycerol yield and poor ethanol productivity. Second, strain Z5ΔGPD2 was subjected to three rounds of genome shuffling to improve its VHG fermentation performance, and the best performing strain SZ3-1 was obtained. Results showed that strain SZ3-1 not only produced less glycerol, but also increased the ethanol yield by up to 8% compared with the parent strain Z5. Further analysis suggested that the improved ethanol yield in strain SZ3-1 was mainly contributed by the enhanced ethanol tolerance of the strain. The differences in ethanol tolerance between strains Z5 and SZ3-1 were closely associated with the cell membrane fatty acid compositions and intracellular trehalose concentrations. Finally, genome rearrangements in the optimized strain were confirmed by karyotype analysis. Hence, a combination of genome shuffling and metabolic engineering is an efficient approach for the rapid improvement of yeast strains for desirable industrial phenotypes

Yeasts in sustainable bioethanol production: a review

Bioethanol has been identified as the mostly used biofuel worldwide since it significantly contributes to the reduction of crude oil consumption and environmental pollution. It can be produced from various types of feedstocks such as sucrose, starch, lignocellulosic and algal biomass through fermentation process by microorganisms. Compared to other types of microoganisms, yeasts especially Saccharomyces cerevisiae is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars. However, there are some challenges in yeast fermentation which inhibit ethanol production such as high temperature, high ethanol concentration and the ability to ferment pentose sugars. Various types of yeast strains have been used in fermentation for ethanol production including hybrid, recombinant and wild-type yeasts. Yeasts can directly ferment simple sugars into ethanol while other type of feedstocks must be converted to fermentable sugars before it can be fermented to ethanol. The common processes involves in ethanol production are pretreatment, hydrolysis and fermentation. Production of bioethanol during fermentation depends on several factors such as temperature, sugar concentration, pH, fermentation time, agitation rate, and inoculum size. The efficiency and productivity of ethanol can be enhanced by immobilizing the yeast cells. This review highlights the different types of yeast strains, fermentation process, factors affecting bioethanol production and immobilization of yeasts for better bioethanol production

The Iconography of a Peacock in Ancient and Early Christian Art

Tematem i celem pracy jest systematyczna prezentacja kontekstów występowania wizerunku pawia w sztuce starożytnej i wczesnochrześcijańskiej, uzupełniona powstałymi wtedy tekstami literackimi. Ma to zobrazować ich różnorodność i zmienność w czasie oraz służyć próbie odpowiedzi na pytanie o charakter związków łączących przedstawienia pawi z wyrażaniem treści chrześcijańskich. Rozważania oparte są na przykładzie artystycznych reprezentacji pawia do VII wieku występujących na obszarze objętym do tego czasu ekspansją chrześcijaństwa. Dodatkowym celem pracy jest próba charakterystyki ewolucji znaczeń nadawanych symbolom w pierwszych wiekach chrześcijaństwa na przykładzie omawianego motywu. Główną częścią pracy jest katalog zabytków w układzie tematycznym, w którym przeprowadzono ikonograficzną analizę reprezentatywnych przedstawień. Na podstawie omawianego motywu zasygnalizowane zostały pytania na stałe związane z badaniami ikonograficznymi i interpretowaniem dzieł sztuki późnej starożytności, przede wszystkim: jak rozdzielić wymowę pogańską od chrześcijańskiej, w jaki sposób odróżnić element dekoracyjny od niosącego głębsze treści znaczeniowe oraz na ile możliwa jest analiza nie całego programu, a motywu, niebędącego najczęściej samodzielnym tematem kompozycji. Dodatkowo motyw pawia zestawiony został z przedstawieniami mitycznego feniksa. Określenie możliwości badawczych jest więc wstępem do prezentacji kontekstów występowania obu ptaków i próby interpretacji ich wzajemnych, skomplikowanych zależności. Łączący symbolikę tych ptaków temat odrodzenia rozumiany jest w pracy zgodnie z teorią archetypów Carla Gustava Junga, która w badaniach ikonograficznych jest szczególnie pociągająca dzięki możliwości przypisania ludziom różnych kultur i czasów uniwersalnego zestawu nieświadomych odniesień.The subject and purpose of this thesis is the systematic presentation of contexts in which the images of a peacock appear in ancient and early Christian art, completed with literary texts of those periods. It is supposed to provide a picture of their diversity and variability in time as well as struggle to answer the question about the relations between the use of peacock images and expression of Christian ideas. The author of the thesis also undertakes an effort to characterize the evolution of meaning imposed upon symbols in the first centuries of Christianity.The considerations are based upon numerous examples of artistic representations of peacocks found in the area covered by Christian expansion until 7th century.The main part of the thesis is the catalogue of historical pieces of art preceded by a map carefully created as an innovative tool for the sake of statistics and clarity