Industrial yeast strains engineered for controlled flocculation

Thesis (PhD (Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2009.In many industrial fermentation processes, Saccharomyces cerevisiae yeast should ideally meet two partially conflicting demands. During fermentation a high suspended yeast count is of paramount importance to maintain a rapid fermentation rate, whilst efficient flocculation should ideally be initiated only on completion of the primary alcoholic fermentation, so as to enhance product clarification and recovery. Most commercial wine yeast strains are non-flocculent, probably because this trait was counter-selected to avoid fermentation problems. In this study, we assessed molecular strategies to optimise the flocculation behaviour of non-flocculent laboratory and wine yeast strains. For this purpose, the chromosomal copies of three dominant flocculation genes, FLO1, FLO5 and FLO11, of a non-flocculent S. cerevisiae laboratory strain (FY23) and two commercial wine yeast strains (BM45 and VIN13) were placed under the transcriptional control of the stationary phase-inducible promoters of the S. cerevisiae ADH2 or HSP30 genes. Under standard laboratory media and culture conditions, all six promoter-gene combinations resulted in specific flocculation behaviours in terms of timing and intensity. The data show that the strategy resulted in the expected and stable expression patterns of these genes in both laboratory and industrial wine yeast strains. Most importantly, the data confirm that inducible expression of the native FLO1 and FLO5 open reading frames, albeit to varying degrees, are responsible for a quantifiable cell-cell adhesion phenotype that can be characterized as a Flo1 flocculation phenotype. On the other hand, we found that inducible expression of the native FLO11 ORF under these conditions resulted in flor/biofilm formation and invasive growth phenotypes. However, the specific impact of the expression of individual dominant FLO genes with regard to characteristics such as flocculation efficiency, cell wall hydrophobicity, biofilm formation and substrate adhesion properties showed significant differences between the commercial strains as well as between commercial and laboratory strains. These adhesion phenotype differences may at least in part be attributed to wine yeast FLO gene open reading frames containing significantly smaller intragenic repeat regions than laboratory strains. The data show that the ADH2 regulatory sequences employed in this study were unsuitable for the purpose of driving FLO gene expression under wine-making conditions. However, HSP30p-based FLO1 and FLO5 wine yeast transformants displayed similar flocculent phenotypes under both synthetic and authentic red wine-making conditions, and the intensities of these phenotypes were closely aligned to those observed under nutrient-rich YEPD conditions. The fermentation activities of HSP30p-based transgenic yeast strains were indistinguishable from that of their parental host wine yeast strains. The chemical composition of wines obtained using transgenic yeast strains were similar to those produced by parental strains. The BM45-derived HSP30p-FLO5 transformant in particular was capable of generating compacted or ‘caked’ lees fractions, thereby providing a distinct separation of the fermented wine product and lees fractions. Furthermore, in this study we report a novel FLO11 induced flocculation phenotype that seems to exclusively develop under authentic red wine-making conditions. This strong FLO11 flocculation phenotype was not wine yeast strain dependant, possessed both Ca2+-dependant and Ca2+-independent flocculation characteristics and was insensitive to inhibition by both glucose and mannose. A distinct advantage of this unique FLO11 phenotype was highlighted in its ability to dramatically promote faster lees settling rates. Moreover, wines produced by HSP30p-FLO11 wine yeast transformants were significantly less turbid than those produced by their wild type parental strains. The benefit of this attractive property is it facilitates simpler and faster recovery of wines and also promotes greater volume recovery of the wine product

Potential for interactive design simulations in discrete element modelling

This study investigates the potential for combining lower fidelity models with high performance solution strategies such as efficient graphical processing unit (GPU) based discrete element modelling (DEM) to not only do simulations faster but differently. Specifically this study investigates interactive simulation and design for which the simulation environment BlazeDEM-GPU was developed that allows researchers and engineers to interact with simulations. The initial results prove to be promising and warranting extensive research to be conducted in future which may allow for the development of alternative paradigms. In addition to the design cycle, the role that this interactive simulation and design will play in education is invaluable as an in-house corporate training tool for young engineers to actively train and develop understanding for specific industrial processes. This would also allow engineers to conduct just-in-time (JIT) simulation based assessment of processes before commencing on actual site visits, allowing for shorter and more focussed site excursions

Validation of the gpu based blaze-dem framework for hopper discharge

Understanding the dynamical behavior of particulate materials is extremely important to many industrial processes, with typical applications that range from hopper flows in agriculture to tumbling mills in the mining industry. The discrete element method (DEM) has become the defacto standard to simulate particulate materials. The DEM is a compu- tationally intensive numerical approach that is limited to a moderate amount (thousands) of particles when considering fully coupled densely packed systems modeled by realistic par- ticle shape and history dependent constitutive relationships. A large number (millions) of particles can be simulated when the coupling between particles is relaxed to still accurately simulated lesser dense systems. Massively large scale simulations (tens of millions) are possi- ble when particle shapes are simplified, however this may lead to oversimplification when an accurate representation of the particle shape is essential to capture the macroscopic transport of particulates. Polyhedra represent the geometry of most convex particulate materials well and when combined with appropriate contact models predicts realistic mechanical behavior to that of the actual system. Detecting collisions between polyhedra is computationally ex- pensive often limiting simulations to only hundreds of thousands of particles. However, the computational architecture e.g. CPU and GPU plays a significant role on the performance that can be realized. The parallel nature of the GPU allows for a large number of simple independent processes to be executed in parallel. This results in a significant speed up over conventional implementations utilizing the Central Processing Unit (CPU) architecture, when algorithms are well aligned and optimized for the threading model of the GPU. We recently introduced the BLAZE-DEM framework for the GPU architecture that can model millions of pherical and polyhedral particles in a realistic time frame using a single GPU. In this paper we validate BLAZE-DEM for hopper discharge simulations. We firstly compare the flow-rates and patterns of polyhedra and spheres obtained with experiment to that of DEM. We then compare flow-rates between spheres and polyhedra to gauge the effect of particle shape. Finally we perform a large scale DEM simulation using 16 million articles to illustrate the capability of BLAZE-DEM to predict bulk flow in realistic hoppers

endo-11-(Dibenzyl­amino)­tetra­cyclo­[5.4.0.03,10.05,9]undecane-8-one

The structure of the title compound, C25H27NO, is a mono-ketone penta­cyclo­undecane (PCU) mol­ecule bearing a tertiary amine group. One of the methyl­ene groups in the PCU is disordered over two orientations with site-occupancy factors of 0.621 (7) and 0.379 (7)

tert-Butyl N-[(11-exo-benzyl­oxy­carbonyl-8-oxopenta­cyclo­[5.4.0.02,6.03,10.05,9]undecane-11-endo-yloxy)carbon­yl­methyl]carbamate

The structure of the title compound, C26H29NO7, at 173 K has an inter­molecular N—H⋯O hydrogen bond. This is one of the few examples where a mono-ketone penta­cyclo­undecane (PCU) mol­ecule exibits hydrogen bonding in the solid state. The dihedral angles of the amide and ester groups are normal and unaffected by the cage structure. A longer than normal C—C bond [1.571 (4) Å] was found within the cage structure

3D laser scanning technique coupled with DEM GPU simulations for railway ballasts

Spheres with complex contact models or clumped sphere models are classically used to model ballast for railway applications with the Discrete Element Method (DEM). These simplifications omits the angularity of the actual ballast by assuming the ballast is either round or has rounded edges. This is done by necessity to allow for practically com- putable simulations that may consist of a few hundred particles. This study demonstrates that an experimentally validated DEM simulation environment, BlazeDEM-3DGPU, that computes on the graphical processing unit (GPU) is able to simulate railway ballast with a more realistic shapes that includes angularity for railway applications. In particular, a procedure is developed that extracts polyhedral shaped ballast geometries digitized from 3D-laser scanning for use in DEM simulations. The results show that much larger number of particles can be successfully modelled allowing for new possibilities offered by the GPUs to investigate model railway problems using DEM. Specifically, in this study a typical experimental ballast box that contains up to 60 000 polyhedral particles have been simulated with the BlazeDEM-3DGPU computing environment within reasonable computing times

Numerical study on the effect of particle shape on mixers

Homogenization of particulate systems is a critical part in the processing of particulate materials to achieve consistency and ensure product quality. Homogenization is achieved by mixing, the aim is to obtain a final mixture that is homogeneous when mixing individual particulate constituents, in the sense of a uniform spatial mass distribution. Although there is always some measure of heterogeneity in a mixture this can be quantified by Gys sampling theory. This is critical for pharmaceutical industries in which it is essential that the variance of the active ingredients between tablets are within specified bounds. Although there have been numerous numerical studies on mixing using the Discrete Element Method (DEM), most studies to date have incorporated significant simplifications to reduce the computational time such as using mono-disperse size distributions, scaling up of particle size and spherical estimations of shape. The development of GPU based DEM simulations in the past few years significantly increased the number of spherical particles however most often at the expense of simplifying the physical interaction between particles. This oversimplification of particle shape has much wider primary implications as primary contact mechanisms such as angularity and locking are omitted. This is important in the pharmaceutical industry where the feed powders are often made from crystalline solids in which the shape of the individual particles are polyhedral. As this study demonstrates, this is significant in that the underlining dynamics of polyhedral particles is vastly different to that of spherical particles, resulting in tighter packing fractions different flow patterns, and percolation. In this paper we use the GPU based DEM code BlazeDEM3D-GPU to study and quantify the effect of particle shape in a high shear blade mixer

New advances in large scale industrial DEM modeling towards energy efficient processes

Granular material processing is crucial to a number of industries such as pharmaceuticals, construction, mining, geology and primary utilities. The handling and processing of granular materials represents roughly 10% of the annual energy consumption [1]. A recent study indicated that in the US alone, current energy requirements across Coal, Metal and Mineral Mining amounts to 1246 TBtu/yr, whereas the practical minimum energy consumption is estimated to be 579 TBtu/yr, while the theoretical limited is estimated around 184 TBtu/yr [2]. It is evident that design modification allowing for process optimization can play a significant role in realizing a more energy efficient industry sector that can have significant implications on the annual global energy demands. The status quo in industry when facing the complex physics governing granular materials, is that current industry developed strategies to handle granular materials remain overly conservative and often energy-wasteful to prevent or reduce industrial-related bulk material handling problems like segregation, arching formation, insufficient handleability. Granular scale approaches have also been developed to both understand the fundamental physics governing granular flow and to study industrial applications, especially to improve the understanding and estimation of energy dissipation and energy efficiency of granular flow processes. The Discrete Element Method (DEM) proposed by Cundall and Strack [3] is starting to mature and evolve into a systematic approach to estimate and predict the response of granular systems. However, DEM is computationally intensive and is limited by the number of particles that can be considered realistically are limited to hundreds of thousands or low millions. However, before DEM can be practically considered for industrial applications the number of particles need be increased to tens of millions particles for a sufficient amount of processing time. This study discusses new advances and perspectives made possible by the Graphical Processor Unit (GPU) when simulating discrete element models, specifically for granular industrial applications. Attention is specifically focussed on the newly developed BlazeDEM3D-GPU framework for an industrial flow investigation [4]. Note that BlazeDEM3D-GPU is an open-source DEM code developed by Govender et al. [5] that has been validated for industrial ball mill simulations and hopper discharge applications using ten of millions of particles using a single NVIDIA GPU card on a desktop computer [4, 6]. The industrial granular flow investigation considered in this study is of the storage silos located at the industrial concrete central in France. The typical silo diameter is 8m with a height of around 17m. Three dimensional DEM studies were been performed to investigate the influence of particle sizes and inter-particle cohesion on the bulk flow rate and induced shear stresses for various hopper designs located at concrete central. As required for this industrially relevant application, up to 32 million particles were required to be simulated within a reasonable computing time. These simulations were performed within these requirements but only made possible by the utilization of GPUs. These results show that the GPU computing allows for realistically relevant number of simulated particles for the 3D DEM applications within a reasonable time frame. This makes large-scale analysis practically relevant but more importantly allows for a number of analyses to be conducted to steer granular processing solutions towards an increased efficiency in energy utilization

Body image and antiretroviral therapy adherence among people living with HIV: a protocol for a systematic review and meta-analysis.

HEARD, 2021.Introduction Adherence to antiretroviral therapy (ART) remains a key challenge to achieving the fast-track goal of ending the HIV epidemic by 2030. To provide a more comprehensive indication of whether interventions designed to promote ART adherence might benefit from targeting body image perceptions, we aim to conduct a systematic review to synthesise existing evidence on the association between body image and ART adherence. Methods and analysis A systematic review of peer-reviewed observational studies and randomised controlled trials that have investigated the association between body image and adherence to ART will be performed. JSTOR, PsycARTICLES, PsycINFO, PubMed, ScienceDirect and Web of Science databases will be searched from 1 January 2000 to 31 March 2021. Eligible records will consider body image as either an independent variable or a mediator, whereas ART adherence will be assessed as an outcome variable. Study selection will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and study quality will be assessed using relevant tools developed by the National Institute of Health. If sufficient data are available, a meta-analysis will be conducted. Effect size estimates will be aggregated using a random effects meta-analysis approach. Publication bias and its impact will be evaluated through the use of a funnel plot and the trim-and-fill method. The Grading of Recommendations Assessment, Development and Evaluation approach will be used to report on the overall quality of evidence

Green Synthesis of Metal Nanoparticles for Antimicrobial Activity

The development and extensive spread of multi-drug resistant bacteria are considered as a major public health concern. Failures to control severe infections due to antibiotic resistance have augmented healthcare costs as well as patient morbidity and mortality. Presently, natural product-based therapeutics are gaining significant attention both for their antimicrobial effectiveness and for not persuading drug resistance. Furthermore, recent developments in nanoscience on new drug delivery systems built on nanostructured materials from plants and microbes have emerged which focus on targeted delivery and controlled release of therapeutic agents. This review examines the recent investigations on the biological activities of plant and bacterial biological material for silver nanoparticle (AgNP) synthesis. Also, the underlying mechanism of antimicrobial activities of silver nanoparticles against human pathogens will be discussed. A fact of the biological activities and/or chemical responses of plants is required, not only for the discovery of new therapeutic agents, but because such evidence may be of value in disclosing new sources of already known biologically active compounds