A contributing factor in recurrent Listeria monocytogenes (L. monocytogenes) food contamination is that this bacterium produces biofilms on surfaces to persist in food-processing environments. Quorum sensing (QS) is a cell-to-cell communication system utilized by bacteria within biofilms to collaborate and adapt to environmental stresses. However, the details of how the QS-dependent network contributes to biofilm development of L. monocytogenes have yet to be well understood. By comparing the transfer rates of planktonic and biofilm (sessile) L. monocytogenes from stainless steel blades to bologna slices, we found that sessile bacteria had reduced transferability onto a single slice but caused the increase in the number of contaminated slices. This suggests that physiological adaptions derived during biofilm development affect bacterial dissemination. Given the contribution of proteins and environmental temperatures to the extracellular polymeric substances (EPS) synthesis and biofilm integrity, we evaluated the exoproteomes of biofilms formed at 25 and 37°C using 2D-gel electrophoresis and LC-MS/MS. We found exoproteases Lmo0186, Cwh, and Spl exclusively in biofilms formed at 25°C and their greater expression in the gene level at 25°C. By using the zymography and crystal-violet-staining assay with a protease inhibitor, we observed a greater proteolytic activity at lower temperatures and showed that the attenuated proteolytic activity of proteases is positively correlated with increased biofilmorming ability at 25°C. Considering the transcriptional role of QS systems during biofilm development, we investigated how the accessory gene regulator (Agr)-based and metabolite S-Adenosylmethionine (SAM)-involved QS systems modulate nutrient availability and EPS synthesis. The results revealed that the SAM signal interacts with the Agr QS at the transcriptional level during biofilm development, whereas SAM and Agr QS regulate distinct EPS synthesis pathways. Additionally, this interaction is dependent on bacterial life modes (planktonic and sessile). Overall, we conclude that L. monocytogenes manipulates the synthesis of EPS with the coregulation of metabolism and QS for biofilm formation and the production of exoproteases for biofilm dispersion. These precise regulations on EPS enable L. monocytogenes to prolong its survival and promote its dissemination in environments.

Gegenstand dieser Arbeit ist die Entwicklung einer Metadatensystematik zur Ausarbeitung der wesentlichen Einflussgrößen auf das Betriebsverhalten von Verarbeitungsmaschinen und -anlagen. Sie dient als Grundlage, um Erkenntnisse aus verschiedenartigen Prozess- und Betriebsanalysen zu ziehen und somit das Wissen über die vorherrschenden Verarbeitungsvorgänge zu vergrößern. Die Metadaten werden als Einflussgrößen, die im Rahmen einer Betriebsanalyse ergänzend erfasst und verarbeitet werden können, definiert. Zunächst erfolgt die Entwicklung eines ganzheitlichen Modellansatzes zur Erarbeitung der Einflussarten auf das Verhalten eines Maschinensystems. Dieses Modell bildet die Grundlage für die Metadatensystematik. Für die Erstellung der Systematik findet eine Klassifikation und eine Kategorisierung der Metadaten statt. Anschließend wird eine Metadatenerfassungsprioritätszahl eingeführt, welche eine Abschätzung der Erfassungsrelevanz der einzelnen Metadaten ermöglicht. Des Weiteren werden Empfehlungen zur Verarbeitung der Daten gegeben und ein Arbeitsablaufplan zur systematischen Vorbereitung einer Metadatenerfassung vorgestellt. Die Metadatensystematik soll dabei helfen, die Einflussgrößen auf das Betriebsverhalten systematisch zu erfassen, Daten verschiedener Prozessanalysen zu vergleichen und das Verständnis sowie die Interpretation der Kennzahlen eines Maschinensystems zu fördern.:Kurzfassung I Abstract I Symbolverzeichnis IV Abkürzungsverzeichnis VII 1 Einleitung 1 1.1 Motivation 1 1.2 Zielsetzung und Lösungsansatz 2 1.3 Aufbau der Arbeit 2 2 Stand der Wissenschaft und Technik 5 2.1 Einführung der Wissenshierarchieebenen 5 2.1.1 Differenzierung zwischen Zeichen, Daten, Informationen und Wissen 5 2.1.2 Differenzierung zwischen Basiszahlen und Kennzahlen 5 2.1.3 Allgemeine Definition von Metadaten 6 2.2 Grundlagen der Betriebsanalyse 6 2.2.1 Definition des Betriebsverhaltens von Verarbeitungsanlagen 6 2.2.2 Zwecke und Ziele einer Betriebsanalyse 7 2.2.3 Arten von Betriebsanalysen 7 2.2.4 Kennzahlen zur Bewertung des Betriebsverhaltens 8 2.2.5 Vorgehensweise zur Analyse des Betriebsverhaltens 12 2.2.6 Datensysteme eines Unternehmens 13 2.3 Methoden der Systemtheorie 15 2.3.1 Grundlagen der Systemtheorie 15 2.3.2 Definition des Systembegriffs 15 2.3.3 Systemmodelle der Verarbeitungstechnik 16 2.3.4 Technisches System 17 2.3.5 Funktionsstruktur und Funktionsbereiche 18 2.3.6 Innermaschinelles Verfahren 19 2.3.7 Modell der Wirkpaarung 19 2.3.8 Mensch-Technik-Organisation-Modell 19 3 Präzisierte Aufgabenstellung 21 4 Einflussgrößen auf das Betriebsverhalten von Verarbeitungsanlagen 25 4.1 Systemtheoretischer Modellansatz für Betriebsanalysen 25 4.1.1 Problemstellungen bei der Modellbildung 25 4.1.2 Erstellung eines ganzheitlichen Modellansatzes 26 4.1.3 Arten von Einflussgrößen auf das Betriebsverhalten 32 4.2 Möglichkeiten der Datenerfassung 32 4.3 Gegenüberstellung der Einflussarten und der Erfassungsmöglichkeiten 33 5 Metadaten des Betriebsverhaltens 35 5.1 Systematik der Metadaten 35 5.1.1 Bestandteile der Systematik 35 5.1.2 Klassifikation der Metadaten 36 5.1.3 Kategorisierung der Metadaten 37 5.2 Abschätzung der Relevanz der Metadaten 40 5.3 Empfehlungen zur Verarbeitung der Metadaten 43 5.3.1 Empfehlungen zur Erfassung der Metadaten 43 5.3.2 Empfehlungen zur Speicherung der Metadaten 45 5.3.3 Empfehlungen zur Auswertung der Metadaten 45 5.4 Vorgehensmodell zur Metadatenerfassung 47 6 Zusammenfassung und Ausblick 51 Thesen der Arbeit 53 Literaturverzeichnis IX Abbildungsverzeichnis XV Tabellenverzeichnis XVI Anhang XVII

A multistage production system consists of a number of production stages that are interrelated, that is the output from one stage forms input to the next stage. There are constraints associated with each stage as well as constraints imposed by the overall system. Besides, there are multiple objectives that need to be satisfied, and in numerous cases, these objectives conflict with each other. What is required is an efficient technique to allocate and schedule resources so as to provide a balance between the conflicting objectives within the system constraints. This study is concerned with the problem of scheduling multistage production systems in food processing industry. The system and products have complex structure and relationships. This makes the system difficult to be solved analytically. Therefore, the problem is solved by developing a heuristic algorithm that considers most of the constraints. The output generated by the algorithm includes a production schedule which specifies the starting and completion times of the products in each stage and the machines where the products are to be processed. In addition, a summary of system performances including throughput times, resources' utilizations, and tardy products is reported. / Graduation date: 1992

Thesis (MSc Food Sc )--Stellenbosch University, 2002. / ENGLISH ABSTRACT: South Africa is a developing country that relies heavily on its agricultural sector for economical welfare especially in the Western Cape Province. However, development gives rise to new technologies, new products, economical stability and unfortunately also to the production of larger volumes of liquid and solid waste. Anaerobic composting is becoming a very attractive treatment option for solid waste disposal because of its unique operational advantages and two valueadded by-products, compost and biogas. Over the last decade progress has been made in anaerobic digestion of solid wastes, but no literature could be found on the anaerobic composting of apple and peach pomace. The main objective of this study was to develop a method to anaerobically compost apple and peach pomace. In the first phase important operational parameters were identified and a method was developed to optimise the parameters. In the second phase of the study, the scaling-up and optimisation of the process were the major objectives. During the first phase of this research 2 L modified glass containers were used as composting units. The most important operational parameters (leachate pH, inoculum source and size, and initial moisture levels) were identified. Anaerobic compost from previous tests, brewery granules and anaerobic sludge were also used as inocula and evaluated for the best source of microbes. After optimising all the identified parameters, good results were obtained, which included higher biogas production, good volume reductions, less bad aromas and a compost product with a neutral pH. After developing the 2 L laboratory-scale method to compost the apple pomace anaerobically, the next step was to ascertain if the method would work if larger volumes of solid fruit waste were composted. A special 20 L composting unit made of PVC was designed to suit the operational requirements of the anaerobic composting process. It was also decided to mix apple pomace and peach pulp together and to use this solid waste source as part of the composting substrate. Different inocula, including cattle manure, anaerobic sludge, brewery granules and anaerobic compost produced in the previous tests, were used. Although good results were obtained with the anaerobic compost and cattle manure as inoculum, the aim was also to decrease the composting period by shortening the pH stabilisation period. To achieve this, it was decided to add NaHC03 to the substrate to be composted to facilitate a faster pH stabilisation. The composting period was subsequently shortened to 25 days with satisfactory results, which included a volume reduction, biogas production and faster pH stabilisation. An upflow anaerobic sludge blanket (UASB) bioreactor was also used to assist the composting process by facilitating the removal of the VFA's present in the composting leachate. This proved to be a valuable addition to the composting process as the UASB bioreactor also provided the composting units with a 'moisturising liquid', which was 'enriched' with a consortium of active anaerobic bacteria when the effluent from the bioreactor was re-added to the composting units. With all the operational parameters in place, good results were obtained and these included a volume reduction of 60% (m/m), a good biogas production, a composting period of only 25 days, a compost that was free of bad aromas, a final compost pH of > 6.5, final leachate COD values of less than 3 000 rnq.l", and a final leachate VFA's concentration of between 0 and 250 rnq.l". If in future research further scaling-up is to be considered, it is recommended that the composting unit be coupled directly to the UASB bioreactor, thus making the process continuous and more practical to operate. If the operational period of the anaerobic composting set-up could be further shortened and the inoculum adapted so that the process could be used for the treatment of other difficult types of solid wastes, it would probably be advantageous for the fruit processing industry to use this method as an environmental control technology. / AFRIKAANSE OPSOMMING: Suid-Afrika is 'n ontwikkelende land wat baie afhanklik is van die sukses van die landbousektor vir ekonomiese welstand, veral in die Wes Kaap Provinsie. Ontwikkeling gaan gepaard met nuwe tegnologie, nuwe produkte, ekonomiese stabiliteit en daarmee saam gaan die produksie van groter volumes vlooiebare en soliede afvalprodukte. Anaërobiese kompostering is tans besig om opgang te maak as en doeltreffende behandelingstegnologie vir vaste afvalstowwe. Tydens die laaste dekade is baie vooruitgang gemaak in die veld van anaërobiese vertering asook kompostering van afvalmateriaal met en hoë vaste stof inhoud. Anaërobiese kompostering van appel- en perskepulp, afkomstig van die versappingsindustrie, het tot dusver min aandag geniet. Die hoofdoel van hierdie navorsing was om 'n anaërobiese komposterings metode te ontwikkel vir die beheer van vrugte afval om sodoende die basis neer te lê vir en nuwe tegnologie wat baie voordele (biogas en kompos) inhou. In die eerste fase is die belangrikste operationele parameters geïdentifiseer om sodoende beter beheer oor die anaërobiese proses uit te oefen. In die tweede fase is die anaërobiese proses wat gedurende die eerste fase ontwikkel is, opgeskaal om optimum resultate te verkry. Gedurende die eerste fase van hierdie verhandeling was 2 L gemodifiseerde glas houers gebruik as komposteringseenhede. Die belangrikste operasionele parameters (pH beheer, inokulasie grootte, vloeistofvlakke en hoeveelheid vog asook vlugtige vetsuur produksie en verwydering) vir die beheer van die anaërobiese komposteringsproses was geïdentifiseer en gebruik as uitgangspunt om 'n anaërobiese komposteringsmetode te ontwikkel. Anaërobiese slyk, brouery granules en anaërobiese kompos van vorige eksperimente was as inokula gebruik. Gedurende hierdie studies was goeie resultate verkry en het 'n hoë biogas produksie, goeie volume reduksies, vermindering van slegte aromas en kompos met 'n neutrale pH ingesluit. . Nadat hierdie goeie resultate met die 2 L laboratorium-skaal metode verkry was, was groter volumes vaste vrugte afval gebruik om te bepaal of dieselfde metode toegepas kan word op en groter skaal. Spesiale 20 L komposteringseenhede was ontwerp om aan die operasionele vereistes van 'n anaërobiese proses te voldoen. Dit was ook besluit om appel pulp met perske pulp te meng en te gebruik as deel van die komposteringssubstraat. Verskeie inokula was weereens gebruik en het die volgende ingesluit: vars beesmis, anaërobiese slyk, brouery granules en anaërobiese kompos van vorige eksperimente. Hoewel baie goeie resultate met vars beesmis en anaërobiese kompos as inokula verkry was, was 'n volgende doel gewees om die kompoterings tydperk te verkort deur die pH vinniger te stabiliseer. Daar was besluit om NaHC03 by die komposteringssubstraat te voeg en so 'n vinniger pH stabilisasie te fasiliteer. 'n UASB ('upflow anaerobic sludge blanket') bioreaktor was ook gebruik om die komposteringsproses aan te help deur die vlugtige vetsure wat in die kompostloog teenwoordig was, te verwyder. Die insluiting van die bioreaktor in die anaërobiese komposteringsproses het bygedra tot die sukses van die proses deurdat die uitvloeisel as 'n vogmiddel vir die komposteringseenhede gebruik was en 'n konsortium van aktiewe anaërobiese bakterieë bevat het. Nadat al die operationele parameters in plek was, was goeie resultate bereik en het die volgende ingesluit: 'n volume reduksie van 60% (m/m), goeie biogas produksie, 'n komposteringstyd van 25 dae, 'n kompos wat vry was van slegste aromas, 'n finale kompos pH van >6.5, finale loog CSB van <3 000 rnq.l' en 'n finale vetsuur konsentrasie van tussen 0 en 250 mq.l'. lndien verdere navorsing onderneem word, word dit aanbeveel dat die UASB bioreaktor direk aan die komposteringseenheid gekoppel word om sodoende die proses meer aaneenlopend en die proses prakties makliker uitvoerbaar te maak. Indien die operationele tydperk nog korter gemaak kan word en die inokulum aanpasbaar kan wees om moeilik verteerbare afvalprodukte te akkomodeer, sal hierdie tegnologie baie voordelig wees as 'n metode om omgewingsbesoedeling te beheer

South Africa has over 19 500 different indigenous plant species. Most of these are of ethnobotanical significance and are still used by local rural communities as medicine, food and for making beverages. The relatively little research that has been conducted on indigenous plant species has focused mainly on their medicinal potential. However, in view of the rapidly growing size of the global and local beverage industry and their constant search for new products, beverage-making indigenous plant species may have commercial development potential. To date, no detailed studies have been conducted on these plants, especially in the species-rich Limpopo province. The aim of this study was, therefore to evaluate the potential of indigenous plants for commercial beverage production. In order to achieve this, a survey was conducted in the Limpopo province to identify beverage-making plants and to document beverage preparation methods. Selected beverages were analysed and evaluated for their nutrient and sensory characteristics and a market product acceptability survey was conducted to identify those beverages with the greatest potential for development. Sixty three different beverage-plant species were identified in three study areas within the Limpopo province. These were used for the preparation of teas, fruit juices and alcoholic beverages. Plants that received further research attention were selected on the basis of their status as indigenous plants, frequency of use, nature of harvesting methods and availability. Some of the selected beverages were found to be rich in nutrients, especially with respect to vitamin C and mineral content. Furthermore, sensory analyses and market surveys indicated that four species, namely, Doyvalis caffra, Garcinia livingstonei, Grewia flavescens and Englerophytum magalismontanum have potential for further development for the beverage industry while Athrixia phylicoides has commercialisation potential as a herbal tea. However, further research is required to improve and refine preparation methods and to ensure compliance with quality standards. The availability of sufficient plant material for the industry must also be ensured. This research has indicated that South African indigenous plants have untapped market potential for the beverage industry which, if developed sustainably, could contribute to economic growth of the rural parts of South Africa. / Environmental Sciences / D. Ed. (Environmental Management)

South Africa has over 19 500 different indigenous plant species. Most of these are of ethnobotanical significance and are still used by local rural communities as medicine, food and for making beverages. The relatively little research that has been conducted on indigenous plant species has focused mainly on their medicinal potential. However, in view of the rapidly growing size of the global and local beverage industry and their constant search for new products, beverage-making indigenous plant species may have commercial development potential. To date, no detailed studies have been conducted on these plants, especially in the species-rich Limpopo province. The aim of this study was, therefore to evaluate the potential of indigenous plants for commercial beverage production. In order to achieve this, a survey was conducted in the Limpopo province to identify beverage-making plants and to document beverage preparation methods. Selected beverages were analysed and evaluated for their nutrient and sensory characteristics and a market product acceptability survey was conducted to identify those beverages with the greatest potential for development. Sixty three different beverage-plant species were identified in three study areas within the Limpopo province. These were used for the preparation of teas, fruit juices and alcoholic beverages. Plants that received further research attention were selected on the basis of their status as indigenous plants, frequency of use, nature of harvesting methods and availability. Some of the selected beverages were found to be rich in nutrients, especially with respect to vitamin C and mineral content. Furthermore, sensory analyses and market surveys indicated that four species, namely, Doyvalis caffra, Garcinia livingstonei, Grewia flavescens and Englerophytum magalismontanum have potential for further development for the beverage industry while Athrixia phylicoides has commercialisation potential as a herbal tea. However, further research is required to improve and refine preparation methods and to ensure compliance with quality standards. The availability of sufficient plant material for the industry must also be ensured. This research has indicated that South African indigenous plants have untapped market potential for the beverage industry which, if developed sustainably, could contribute to economic growth of the rural parts of South Africa. / Environmental Sciences / D. Ed. (Environmental Management)