Anthony McHale

Ethanol production at elevated temperatures and alcohol concentrations: part I - yeasts in general

There are a number of process advantages which could be exploited through the use of thermophilic microorganisms for ethanol production. Energy savings through reduced cooling costs, higher saccharification and fermentation rates, continuous ethanol removal and reduced contamination have stimulated a search for routes to thermophilic or thermotolerant yeasts. These routes have included screening existing culture collections, temperature adaptation, mutagenesis and molecular techniques and finally isolating new strains. Varying success has been achieved, however, the most thermotolerant yeasts have come from fresh isolations from environments which experience high temperatures. Thermotolerant yeasts have been investigated for the following potential applications: simultaneous saccharification and fermentation of cellulose, where the high fermentation temperature allows more rapid and efficient enzymatic cellulose hydrolysis; whey fermentation, where high salt and low fermentable substrate concentrations make conditions difficult; and fermentation of D-xylose and cellobiose, which is essential for efficient conversion of woody biomass to ethanol. Ethanol and temperature tolerance are important characteristics for commercial yeast strains. Both characteristics are interactive and generally decrease with increasing temperature and ethanol concentration. Considerable research has been directed towards investigation of fatty acid composition changes in response to these stresses and the role of heat shock proteins in tolerance mechanisms. If thermotolerant yeasts are to be used in commercial processes, bioreactor configuration will play an important part in the design of production processes. Batch and fed-batch systems have been shown to be useful in some circumstances as have continuous flow systems, however, some of the newly isolated thermotolerant yeasts such as Kluyveromyces marxianus do not show the high growth rate under anaerobic conditions that is characteristic of Saccharomyces cerevisiae. Various immobilization techniques appear to offer a means of presenting and maintaining high biomass in anaerobic continuous flow reactors.

Optimising ultrasound-mediated gene transfer (sonoporation) in vitro and prolonged expression of a transgene in vivo: Potential applications for gene therapy of cancer

Therapeutic approaches using gene-based medicines promise alternatives or adjuncts to conventional cancer treatment. Because of its non-invasive nature, ultrasound, as a membrane-permeabilising stimulus has the potential to be highly competitive with viral gene delivery and existing non-viral alternatives. In optimising ultrasound-mediated, microbubble-assisted (MB101) gene tranfection in vitro, we demonstrate efficiencies of up to 18% using ultrasound at 1 MHz at a duty cycle of 25% at intensities ranging from 1 to 4 W cm(-2). Using ultrasound-mediated transfection together with an episomal plasmid-based gene expression system, we demonstrate prolonged functional gene expression of luciferase in mouse hind leg muscle and in tumours in vivo.

Studies on the biosorption of uranium by Talaromyces emersonii CBS 814.70 biomass

Residual biomass, produced by the thermophilic fungus, Talaromyces emersonii CBS 814.70, following growth on glucose-containing media, was examined for its ability to take up uranium from aqueous solution. It was found that the biomass had a relatively high observed biosorption capacity for the uranium (280 mg/g dry weight biomass). The calculated maximum biosorption capacity obtained by fitting the data to a Langmuir model was calculated to be 323 mg uranium/g dry weight biomass. Pretreatment of the biomass with either dilute HCl or NaOH brought about a significant decrease in biosorptive capacity for uranium. Studies on the effects of variation in temperature on the biosorptive capacity demonstrated no significant change in binding between 20°C and 60°C. However, a significant decrease in biosorptive capacity was observed at 5°C. Binding of uranium to the biomass at all temperatures reached equilibrium within 2 min. While the routine binding assays were performed at pH 5.0, adjustment of the pH to 3.0 gave rise to a significant decrease in biosorption capacity by the biomass. The biosorptive capacity of the biomass for uranium was increased when extraction from solution in sea-water was examined.

Oxygen carrying microbubbles for enhanced sonodynamic therapy of hypoxic tumours

Tumour hypoxia represents a major challenge in the effective treatment of solid cancerous tumours using conventional approaches. As oxygen is a key substrate for Photo-/Sono-dynamic Therapy (PDT/SDT), hypoxia is also problematic for the treatment of solid tumours using these techniques. The ability to deliver oxygen to the vicinity of the tumour increases its local partial pressure improving the possibility of ROS generation in PDT/SDT. In this manuscript, we investigate the use of oxygen-loaded, lipid-stabilised microbubbles (MBs), decorated with a Rose Bengal sensitiser, for SDT-based treatment of a pancreatic cancer model (BxPc-3) in vitro and in vivo. We directly compare the effectiveness of the oxygen-loaded MBs with sulphur hexafluoride (SF6)-loaded MBs and reveal a significant improvement in therapeutic efficacy. The combination of oxygen-carrying, ultrasound-responsive MBs, with an ultrasound-responsive therapeutic sensitiser, offers the possibility of delivering and activating the MB-sensitiser conjugate at the tumour site in a non-invasive manner, providing enhanced sonodynamic activation at that site.

Ethanol production at elevated temperatures and alcohol concentrations : Part II : Use of Kluyveromyces marxianus IMB3

It is clear that only a small proportion of all micro-organisms have been isolated and identified. The simple technique of seeking a thermotolerant fermentative yeast from a suitable hot environment has yielded a number of strains. These organisms, identified as strains of Kluyveromyces marxianus var. marxianus, have been shown to have a wide range of metabolic capabilities that could be used in industrial applications. Not only have the metabolic capabilities been elucidated but possible bioreactor configurations and process application options have been investigated. It appears that there are a number of specific situations where this thermotolerant yeast could find industrial applications. A full-scale industrial ethanol production trial using this yeast was successfully carried out in India. K. marxianus IMB3s performance in terms of the ethanol concentrations achieved was comparable to that obtained using the distillerys own yeast strain with an added advantage of eliminating cooling.

Exploiting ultrasound-mediated effects in delivering targeted, site-specific cancer therapy

Although the concept of employing ultrasound for the treatment of cancer is not a new one, virtually all existing ultrasound-based clinical cancer treatments are based on hyperthermic ablation. This review seeks to highlight the potential offered by more subtle ultrasound-triggered phenomena such as sonoporation in delivering novel targeted cancer treatment modalities.

Studies on neutral, cationic and biotinylated cationic microbubbles in enhancing ultrasound-mediated gene delivery in vitro and in vivo

Ultrasound-mediated gene transfer is emerging as a practical means of facilitating targeted gene expression and is significantly enhanced in the presence of exogenously added microbubbles. This study explores the influence of microbubble surface modifications on their interaction with plasmid DNA and target cells, and the functional consequences of those interactions in terms of ultrasound-mediated gene transfer. Polyethylene glycol-stabilized, lipid-shelled microbubbles with neutral (SDM201), cationic (SDM202) and biotinylated cationic (SDM302) surfaces were compared in terms of their abilities to interact with a luciferase-encoding reporter plasmid DNA and with target cells in vitro. The results demonstrate that the biotinylated cationic microbubble>cationic microbubble>neutral microbubble, in terms of their abilities to interact with target cells and to enhance ultrasound-mediated gene transfer, particularly at low microbubble concentration. The presence of a net positive charge on both cationic microbubbles promoted the formation of microbubble-nucleic acid complexes, although preformation of the complexes prior to addition to target cells inhibited the interaction between the microbubbles and target cells in vitro. The impact of these findings on potential in vitro or ex vivo therapeutic applications of microbubble-enhanced ultrasound-mediated gene transfer is discussed. All three microbubble preparations could be used to facilitate gene transfer in vivo and the potential advantages associated with the use of the cationic microbubbles for targeted gene delivery are discussed.

Ethanol production at 45° by an alginate-immobilized thermotolerant strain of Kluyveromyces marxianus following growth on glucose-containing media

SummaryIn comparing ethanol production by free and Ca-alginate immobilized cultures of the thermotolerant yeast, Kluyveromyces marxianus IMB3, on glucose-containing media at 45°C, it was found that initial yields produced by the immobilized culture lagged behind those produced by cultures in free suspension. However, in subsequent batch-feed experiments it was demonstrated that the ethanol-producing ability of the immobilized preparation increased with successive feeds, while production by the free suspension reduced significantly.

Treating cancer with sonodynamic therapy: A review

Abstract Sonodynamic therapy (SDT) has emerged as a promising option for the minimally invasive treatment of solid cancerous tumours. SDT requires the combination of three distinct components: a sensitising drug, ultrasound, and molecular oxygen. Individually, these components are non-toxic but when combined together generate cytotoxic reactive oxygen species (ROS). The major advantage of SDT over its close relative photodynamic therapy (PDT), is the increased penetration of ultrasound through mammalian tissue compared to light. As a result, SDT can be used to treat a wider array of deeper and less accessible tumours than PDT. In this article, we critically review the current literature on SDT and discuss strategies that have been developed in combination with SDT to enhance the therapeutic outcome.

Removal of uranium from solution using residual brewery yeast: Combined biosorption and precipitation

Whilst unwashed preparations of biomass from a local brewery had an apparentmaximum biosorption capacity for uranium of 360mg/g (dry weight biomass) washingreduced this maximum to 150mg/g. Homogenization of both biomass preparations andrecovery of cellular debris had no significant effect on the maximum biosorptioncapacities although at lower equilibrium concentrations of uranium differences inthe biosorption capacities were detected. When unwashed biomass was retained by asemi-permeable membrane 40% of uranium used in the experiments precipitated outsidethat membrane. Therefore a significant proportion of the uranium removed fromsolution, and previously attributed to biosorption by the yeast biomass,resulted from precipitation brought about by interaction with low molecularweight components loosely associated with the biomass.