Madeleine Bussemaker

Manipulation of ultrasonic effects on lignocellulose by varying the frequency, particle size, loading and stirring.

The parameters, including ultrasonic frequency, still versus stirring, biomass particle size and biomass loading were concurrently investigated for the ultrasonic treatment of wheat straw. Experiments were conducted at three different frequencies; 40, 376, and 995 kHz using three different solid to liquid ratios, 1/50, 1/20, and 1/15(g/ml), with and without mechanical stirring. Additional treatments in different particle size ranges, 0-0.5, 0.5-1, and 1-2mm were performed at the solid to liquid ratio of 1/20(g/ml). Fractionation was improved at 40 and 995 kHz via different mechanisms. Delignification was favored at the ultrasonic treatment frequency of 40 kHz, biomass loading 1/20(g/ml) with stirring and particle size range of 0.5-1mm. However at 995 kHz carbohydrate solubilization was favored, especially in the particle size range of <0.5mm. The treatment efficacies highlighted the use of ultrasound for physical and chemical effects at different frequencies.

A parametric review of sonochemistry: Control and augmentation of sonochemical activity in aqueous solutions

In this review the phenomenon of ultrasonic cavitation and associated sonochemistry is presented through system parameters. Primary parameters are defined and considered, namely; pressure amplitude, frequency and reactor design; including transducer type, signal type, vessel-transducer ratio, liquid flow, liquid height, liquid temperature and the presence of a reflective plate. Secondary parameters are similarly characterised and involve the use of gas and liquid additives to influence the chemical and physical environments. Each of the parameters are considered in terms of their effect on bubble characteristics and subsequent impact on sonochemical activity. Evidence suggests that via parametric variation, the reaction products and efficiency may be controlled. This is hypothesised to occur through manipulation of the structural stability of the bubble.

A phenomenological investigation into the opposing effects of fluid flow on sonochemical activity at different frequency and power settings. 1. Overhead stirring

The effect of flow in an ultrasonic reactor is an important consideration for practical applications and for the scale-up of ultrasonic processing. Previous literature on the influence of flow on sonochemical activity has reported conflicting results. Therefore, this work examined the effect of overhead stirring at four different frequencies, 40, 376, 995 and 1179 kHz, in two different reactor configurations. Comparable power settings were utilised to elucidate the underlying mechanisms of interactions between the flow and sonochemical activity. The sonochemical activity was determined by the yield of hydrogen peroxide, measured by iodide dosimetry, and the active region was visualised with sonochemiluminescence imaging. The overhead stirring in the low frequency reactor altered the yield of hydrogen peroxide so it produced the maximum yield out of the four frequencies. The increase in hydrogen peroxide yield was attributed to a reduction in coalescence at 40 kHz. However at the higher frequencies, coalescence was not found to be the main reason behind the observed reductions in sonochemical yield. Rather the prevention of wave propagation and the reduction of the standing wave portion of the field were considered.

A phenomenological investigation into the opposing effects of fluid flow on sonochemical activity at different frequency and power settings. 2. Fluid circulation at high frequencies

Sonochemical activity is dependent on flow patterns within the reactor and either no affect or a decrease in activity was observed at 376, 995, and 1179 kHz from overhead stirring. The interaction of fluid flow with ultrasound was further investigated in this study with circulatory flow. The effect of fluid circulation on radical production was investigated at two circulation speeds, with and without surface stabilisation. The sonochemical activity was determined by the yield of hydrogen peroxide, measured by iodide dosimetry. The sonochemically active region was pictured using sonochemiluminescence imaging and the flow fields were visualised with dyed flow videos. At 376 and 995 kHz, an increase in sonochemical activity was observed with the slower flow rate; however at 1179 kHz, the sonochemical activity was either not affected or decreased. The observed changes in sonochemical activity were attributed to an increase in asymmetry of the bubble collapse brought about by fluid motion.

Formation of methanol from methane and water in an electrical discharge

Matrix isolation FTIR experiments have shown that methanol is a major product when argon gas doped with water and methane is exposed to an electrical discharge and condensed to a solid matrix at 11 K. Experiments with (2)H, (17)O and (18)O-labeled isotopologues show the mechanism for the methanol production is likely to be insertion of an excited oxygen atom in the (1)D state into a C-H bond of a methane molecule. In light of these experiments, the possibility of oxygen atom insertion into methane should be considered as a possible mechanism for the production of methanol in interstellar ices.

BiOnto: An Ontology for Biomass and Biorefining Technologies

This paper presents design and implementation of the BiOnto ontology in the domain of biorefining. The ontology models both biomass types and composition and biorefining processing technologies. The designed ontology is verified by a case study in the domain of Industrial Symbiosis.

Sonodynamic therapy combined with novel anti-cancer agents, sanguinarine and ginger root extract: Synergistic increase in toxicity in the presence of PANC-1 cells in vitro

The presence of ultrasound-induced cavitation in sonodynamic therapy (SDT) treatments has previously enhanced the activity and delivery of certain sonosensitisers in biological systems. The purpose of this work was to investigate the potential for two novel anti-cancer agents from natural derivatives, sanguinarine and ginger root extract (GRE), as sonosensitisers in an SDT treatment with in vitro PANC-1 cells. Both anti-cancer compounds had a dose-dependent cytotoxicity in the presence of PANC-1 cells. A range of six discreet ultrasound power-frequency configurations were tested and it was found that the cell death caused directly by ultrasound was likely due to the sonomechanical effects of cavitation. Combined treatment used dosages of 100μM sanguinarine or 1mM of GRE with 15s sonication at 500kHz and 10W. The sanguinarine-SDT and GRE-SDT treatments showed a 6% and 17% synergistic increase in observed cell death, respectively. Therefore both sanguinarine and GRE were found to be effective sonosensitisers and warrant further development for SDT, with a view to maximising the magnitude of synergistic increase in toxicity.

An ontological approach to chemical engineering curriculum development

Continuous reflection and evolution of curricula in chemical engineering is beneficial for adaptation to evolving industries and technologies and for improving student experience. To this end it was necessary to develop a method to enable a holistic reflection on the curriculum and to examine potential areas of improvement and change. The curriculum was modelled using knowledge modelling through the development of an ontology, Chemical Engineering Education Ontology (ChEEdO) in the Protege 3.5 environment. ChEEdO models topics, taught modules and the learning outcomes of the modules within the domain of chemical engineering. The learning outcomes were related to the topics using verb properties from Bloom’s taxonomy and the context of each learning outcome. The functionality of semantic reasoning via the ontology was demonstrated with a case study. The modelling results showed that the ontology could be successfully utilised for curriculum development, horizontal and vertical integration and to identify appropriate pre-requisite learning.

Utilising Semantics for Improved Decision Making in Bio-refinery Value Chains

This paper presents an effort to utilise semantics to improve the decision making process in biorefinery value chains. In more detail, an ontology describing biomass and biorefineries is used to facilitate the identification of the best options for the population of the optimisation problem. In addition to that, the reasoning capabilities of ontologies are used to enhance search of information. The approach has been verified with a case study for biomass available in Scotland.

Modelling the microbial dynamics and antimicrobial resistance development of Listeria in viscoelastic food model systems of various structural complexities

Minimal processing for microbial decontamination, such as the use of natural antimicrobials, is gaining interest in the food industry as these methods are generally milder than conventional processing, therefore better maintaining the nutritional content and sensory characteristics of food products. The aim of this study was to quantify the impact of (i) structural composition and complexity, (ii) growth location and morphology, and (iii) the natural antimicrobial nisin, on the microbial dynamics of Listeria innocua. More specifically, viscoelastic food model systems of various compositions and internal structure were developed and characterised, i.e. monophasic Xanthan gum-based and biphasic Xanthan gum/Whey protein-based viscoelastic systems. The microbial dynamics of L. innocua at 10 °C, 30 °C and 37 °C were monitored and compared for planktonic growth in liquid, or in/on (immersed or surface colony growth) the developed viscoelastic systems, with or without a sublethal concentration of nisin. Microscopy imaging was used to determine the bacterial colony size and spatial organisation in/on the viscoelastic systems. Selective growth of L. innocua on the protein phase of the developed biphasic system was observed for the first time. Additionally, significant differences were observed in the colony size and distribution in the monophasic Xanthan gum-based systems depending on (i) the type of growth (surface/immersed) and (ii) the Xanthan gum concentration. Furthermore, the system viscosity in monophasic Xanthan gum-based systems had a protective role against the effects of nisin for immersed growth, and a further inhibitory effect for surface growth at a suboptimal temperature (10 °C). These findings give a systematic quantitative insight on the impact of nisin as an environmental challenge on the growth and spatial organisation of L. innocua, in viscoelastic food model systems of various structural compositions/complexities. This study highlights the importance of accounting for system structural composition/complexity when designing minimal food processing methods with natural antimicrobials.