Fachbereich Ingenieur- und Naturwissenschaften
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The study aimed at comparing the effects of three coffee processing methods on aroma profiles and sensory quality of Ruiru 11 and SL 28 coffee varieties. The processing methods varied on stages of processing and method of mucilage removal. The green coffee beans obtained from the three processing methods were graded and roasted, ground and analyzed for the aroma profiles and sensory quality. Headspace Solid phase Microextraction fibre (SPME) technique were used for the extraction of aroma compounds from coffee samples and characterization of the compounds with use of gas chromatography mass spectrometry (GC-MS). Sensory quality were analyzed by an expert panelist. Various volatile aroma compounds were identified in roasted coffee and classified into their chemical classes involving furans, ketones, pyrazines ketones pyridines, pyrroles and acids. The intensity of aroma compounds were compared in terms of their peak areas and variations were noted between the processing methods with the ecopulper showing higher levels of pyrazines such as 2-methylpyrazine, 2-ethyl-6-methylpyrazine, and wet pulper showing higher levels of furans such as furfuryl formate and furfuryl alcohol, acetate. The hand pulper was high in the level of acids and esters such as acetic acid and propanoic acid, ethyl ester. Similar aroma compounds were identified in headspace of Ruiru 11 and SL 28 and there were variations in the intensities of aroma groups such as pyrroles and pyridines. It was concluded that the eco-pulper and hand pulper methods gives better aroma quality than the wet pulper while SL 28 variety gives higher sensory quality than Ruiru 11.
Ethanol production via genetically engineered cyanobacteria is a promising solution for the production of biofuels. Through the introduction of a pyruvate decarboxylase and alcohol dehydrogenase direct ethanol production becomes possible within the cells. However, during cultivation genetic instability can lead to mutations and thus loss of ethanol production. Cells then revert back to the wild type phenotype.
A method for a rapid and simple detection of these non-producing revertant cells in an ethanol producing cell population is an important quality control measure in order to predict genetic stability and the longevity of a producing culture. Several comparable cultivation experiments revealed a difference in the pigmentation for non-producing and producing cells: the accessory pigment phycocyanin (PC) is reduced in case of the ethanol producer, resulting in a yellowish appearance of the culture. Microarray and western blot studies of Synechocystis sp. PCC6803 and Synechococcus sp. PCC7002 confirmed this PC reduction on the level of RNA and protein.
In the last few decades, MALDI-TOF MS has become a useful technique not only in proteomics, but also as a fast and specific tool for whole cell analysis through intact cell mass spectrometry (IC-MS). The present study evaluated IC-MS as a novel tool for the detection of distinct patterns that can be observed after exposure to a certain toxin or concentration by utilizing the eukaryotic fish cell line RTL-W1. Two different viability assays were performed to define the range for IC-MS investigations, each of which employing copper sulfate, acridine, and β-naphthoflavone (BNF) as model compounds for several classes of environmental toxins. The IC-MS of RTL-W1 cells revealed not only specific spectral patterns for the various toxins, but also that the concentration used had an effect on RTL-W1 profiles. After the exposure with copper sulfate and acridine, the spectra of RTL-W1 showed a significant increase of certain peaks in the higher mass range (m/z >7000), which is probably attributed to the apoptosis of RTL-W1. On the contrary, exposure to BNF showed a distinct change of ion abundances only in the lower mass range (m/z <7000). Furthermore, a set of mass peaks could be identified as a specific biomarker for a single toxin treatment, so IC-MS demonstrates a new method for the distinction of toxic effects in fish cells. Due to fast sample preparation and high throughput, IC-MS offers great potential for ecotoxicological studies to investigate cellular effects of different substances and complex environmental samples.
Für den simultanen Nachweis mehrerer Analyten innerhalb einer Probe ist die Bead-basierte Multiplexanalytik ein häufig verwendetes Verfahren und wird beispielsweise zur Quantifizierung von Proteinen genutzt. Die aufwendige Durchführung der Assays soll durch Automatisierung einerseits dem Anwender abgenommen werden, während andererseits die Genauigkeit und Reproduzierbarkeit der Analyse gesteigert wird. Die Automatisierung des Bio-Plex Pro™ Assays ist mit dem Pipettierroboter Tecan Freedom EVO 200 umgesetzt worden. Es ist ein Skript mit der Software Freedom EVOware® entwickelt worden, welches die Probenvorbereitung des Assays vollständig übernimmt. Für einen Vergleich der manuellen und automatisierten Methode sind die humanen Zytokine IL-2, IL-4, IL-10, GM-CSF, IFN-γ und TNF-α in einer achtstufigen Standardverdünnungsreihe und in unterschiedlich konzentrierten Proben gemessen worden. Die Berechnung der Streuungen (Standardabweichung und Variationskoeffizient) der einzelnen Standardverdünnungsreihen sowie der Vergleich von gemessenen und erwarteten Konzentrationen der automatisierten und manuellen Methode zeigen, dass die Automatisierung neben der zeitlichen Optimierung auch die Genauigkeit und Reproduzierbarkeit der Analyse verbessert.