Published Article / The growth of Saccharomyces cerevisiae strain W303-1A(a) was evaluated in complex and chemically defined media. The use of chemically defined medium allowed the complete utilisation of glucose within 20 h. as well as all of the produced ethanol within 45 h. Maximum specific growth rates (µmax) were increased from 0.28 h-1 to 0.42 h-1 and the volumetric rate of ethanol production increased from 0.204 g l-1 h-1 to 0.597 g l-1 h-1. However, when the ethanol concentration exceeded a threshold value of 10 g l-1, the µmax value was significantly decreased. These observations suggest that ethanol metabolism related growth experiments for the relevant strain should be carried out in chemically defined medium with ethanol concentrations below 10 g l-1.

The small intestine and the liver regulate several physiological functions together including the absorption and bioavailability of drugs and bile and nitrogen homeostasis. It is important to study these two organs together to gain a holistic understanding of their communication with each other. However, there is a lack of culture models that investigate the use of primary cells/tissues from the liver and the intestine to study their interaction and importance in manifestation of drug toxicity. The studies described in this dissertation were conducted using inverted rat intestinal explants obtained from three regions of the jejunum, named as the proximal, medial and distal jejunum. Markers of enterocyte, goblet cell and Paneth cell function in the jejunum followed in vivo – like spatial trends reported for the entire small intestine. Jejunum explants were integrated with hepatocytes to model the intestine-liver axis. Integration of jejunum explants from the proximal region with hepatocytes had a beneficial effect on both hepatocyte urea secretion and jejunum mucin secretion, hinting at communication between these organs in culture. Integrated cultures of the rat jejunum and hepatocytes were used to investigate ethanol toxicity in vitro. Trends in activities of enzymes involved in ethanol metabolism and mucus secretion in integrated cultures with proximal jejunum explants corroborated with in vivo reports on ethanol toxicity. Various metabolites secreted and metabolized in vitro were also identified using mass spectrometry. Spatial trends in concentrations of several lipids including bile acids, lysophosphatidylcholines and fatty acids corroborated with in vivo reports of lipid metabolism. The integrated intestine-liver cultures can be used as a platform for future investigations of drug toxicity, lipid metabolism and inter-organ communication. / Doctor of Philosophy / The small intestine and the liver perform several functions together. The small intestine is responsible for the digestion of food, absorption of nutrients and metabolism of oral drugs. The liver is involved in the metabolism of glucose, protein, lipids and drugs. It is important to study these two organs together to gain a holistic understanding of their communication with each other. However, there is a lack of culture models that investigate the use of cells/tissues directly obtained from animal liver and intestine to study their interaction and importance in manifestation of drug toxicity. The studies described in this dissertation were conducted using tissues obtained from three regions of the jejunum segment of the rat small intestine. Functional markers of various cell types in the jejunum followed in vivo – like spatial trends reported for the entire small intestine. Jejunum tissues were integrated with liver cells to model the intestine-liver axis. Integration of jejunum tissues from the proximal region with liver cells had a beneficial effect on both liver and intestinal markers, hinting at communication between these organs in culture. Integrated cultures of the rat jejunum and liver cells were used to investigate alcohol toxicity in vitro. Trends in activities of enzymes involved in alcohol metabolism and mucus secretion in integrated cultures with jejunum tissues corroborated with in vivo reports on alcohol toxicity. Various metabolites secreted and metabolized in vitro were also identified using mass spectrometry. Spatial trends in concentrations of lipids including bile acids, lysophosphatidylcholines and fatty acids within the jejunum corroborated with in vivo reports of lipid metabolism. The integrated intestine-liver cultures can be used as a platform for future investigations of drug toxicity, lipid metabolism and inter-organ communication.