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Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy July 2012... more Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy July 2012 Department of Chemical Engineering UNIVERSITY OF CAPE TOWN I would like to thank the following people: My supervisor Prof Sue Harrison for her insight, wisdom, support, encouragement and financial assistance throughout this study. In allowing me to spend some time away to explore other avenues in the enzyme field (BBI Enzymes SA (Pty) Ltd and the University of Stellenbosch). My co-supervisor Prof Kim Clarke (Process Engineering, University of Stellenbosch) for her continued interest and assistance. To Sue Jobson for looking after all the admin, finance, and housekeeping matters, Fran Pocock as CeBER's very resourceful and knowledgeable lab manager, Joe Macke for maintenance of the babies (Chemaps) and Bill Randall and Granville le Cruz for all the electronic maintenance of the ancillary equipment. To Helen Divey and Stephanie Snoek for assistance in the analytical laboratory. To all the Chemeng and CeBER people (past and present) that has assisted me in various ways.
The Nexus: Energy, Environment and Climate Change, 2017
The wastewater biorefinery (WWBR) bridges the gap between the concepts of the biorefinery (BR) an... more The wastewater biorefinery (WWBR) bridges the gap between the concepts of the biorefinery (BR) and wastewater (WW) treatment. A WWBR aims to generate a product, or products, of sufficient value to make the process economically viable and enhance resource productivity, while simultaneously remediating wastewater to an acceptable quality. It is centred on the conversion of the organic carbon, nitrogen, phosphorous and associated trace nutrients in the wastewater stream to value added products, while concomitantly providing clean or ‘fit for use’ water as a product. The WWBR is increasingly recognised for its potential contribution to the bio-based economy, as well as its potential to augment the industrial sector. The concept of a WWBR contributes to valuing wastewater treatment as an integrated component of a wider system rather than a unit process for ‘end-of-pipe treatment’, as is generally the state of current operation, a significant paradigm shift which has the potential to increase plant profitability and reduce environmentally deleterious effluents. It provides a link between the users of water and those responsible for its management, leading to the recovery of resources in closed loop cycles and thus contributing to progressing towards the concept of a circular economy, where valuable nutrients and components are recovered and reused. This chapter examines the pedagogy around the design and implementation of WWBRs with a focus on the classification of wastewaters for WWBR design, selection of potential products, flow sheet development and the criteria for reactor selection.
Biotechnology and Bioengineering, 2008
Glucose oxidase (GO) is an important industrial enzyme typically purified from Penicillium and As... more Glucose oxidase (GO) is an important industrial enzyme typically purified from Penicillium and Aspergillus sp. As GO distribution within the cultures influences process design for maximal product recovery, distribution of GO activity in Penicillium sp. CBS 120262 and Aspergillus niger NRRL-3, during mid-exponential and stationary phases, is compared. On progression from mid-exponential to stationary phase, the percentage GO activity in the cytoplasm decreased 1.6- and 1.3-fold in Penicillium sp. and A. niger respectively. In Penicillium sp., a concomitant 1.8- and 1.9-fold decrease in the percentage GO activity in the cell envelope and slime mucilage respectively, translated into a 2.0-fold increase in the extracellular fluid. In A. niger, decreasing cytoplasmic GO activity was accompanied by 1.3-fold increases in the cell envelope and slime mucilage, with a 1.3-fold decrease in the extracellular fluid. Similar trends were observed in specific GO activities. As final GO activity recovered is governed by the purification program, recovery from the extracellular fluid plus cell extract or from the extracellular fluid only were compared through simulating processes of varying complexity. A critical yield for each purification stage was identified above which recovery from the extracellular fluid plus cell extract exceeded that from extracellular fluid alone. These results highlight the influence of microorganism, harvest time and efficiency of downstream process on GO activity delivered. In the systems studied, Penicillium sp. is the organism of choice and should be harvested during stationary phase. The purification process chosen should be informed by both enzyme distribution and individual purification stages yields.
Applied Microbiology and Biotechnology, 2005
The production of the enzyme glucose oxidase by Aspergillus niger is well documented. However, it... more The production of the enzyme glucose oxidase by Aspergillus niger is well documented. However, its distribution within the fungal culture is less well defined. Since the enzyme location impacts significantly on enzyme recovery, this study quantifies the enzyme distribution between the extracellular fluid, cell wall, cytoplasm and slime mucilage fractions in an A. niger NRRL-3. The culture was separated into the individual fractions and the glucose oxidase activity was determined in each. The extracellular fluid contained 38% of the total activity. The remaining 62% was associated with the mycelia and was distributed between the cell wall, cytoplasm and slime mucilage in the proportions of 34, 12 and 16%, respectively. Intracellular cytoplasmic and cell wall sites were confirmed using immunocytochemical labelling of the mycelia. In the non-viable cell, the mycelial-associated enzyme was distributed between these sites, whereas in the viable cell, it was predominantly associated with the cell wall. The distribution of the enzyme activity indicates that recovery from the solids would result in a 38% loss, whereas recovery from the extracellular fluid would result in a 62% loss. The results also suggest, however, that this 62% loss could be reduced to around 34% by disintegrating the solids prior to separation due to the contribution of the enzyme in the cytoplasm and slime mucilage. This was confirmed by independently establishing the percentage activity in the liquid and solid portions of a disintegrated culture as 62 and 38%, respectively.
Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy July 2012... more Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy July 2012 Department of Chemical Engineering UNIVERSITY OF CAPE TOWN I would like to thank the following people: My supervisor Prof Sue Harrison for her insight, wisdom, support, encouragement and financial assistance throughout this study. In allowing me to spend some time away to explore other avenues in the enzyme field (BBI Enzymes SA (Pty) Ltd and the University of Stellenbosch). My co-supervisor Prof Kim Clarke (Process Engineering, University of Stellenbosch) for her continued interest and assistance. To Sue Jobson for looking after all the admin, finance, and housekeeping matters, Fran Pocock as CeBER's very resourceful and knowledgeable lab manager, Joe Macke for maintenance of the babies (Chemaps) and Bill Randall and Granville le Cruz for all the electronic maintenance of the ancillary equipment. To Helen Divey and Stephanie Snoek for assistance in the analytical laboratory. To all the Chemeng and CeBER people (past and present) that has assisted me in various ways.
The Nexus: Energy, Environment and Climate Change, 2017
The wastewater biorefinery (WWBR) bridges the gap between the concepts of the biorefinery (BR) an... more The wastewater biorefinery (WWBR) bridges the gap between the concepts of the biorefinery (BR) and wastewater (WW) treatment. A WWBR aims to generate a product, or products, of sufficient value to make the process economically viable and enhance resource productivity, while simultaneously remediating wastewater to an acceptable quality. It is centred on the conversion of the organic carbon, nitrogen, phosphorous and associated trace nutrients in the wastewater stream to value added products, while concomitantly providing clean or ‘fit for use’ water as a product. The WWBR is increasingly recognised for its potential contribution to the bio-based economy, as well as its potential to augment the industrial sector. The concept of a WWBR contributes to valuing wastewater treatment as an integrated component of a wider system rather than a unit process for ‘end-of-pipe treatment’, as is generally the state of current operation, a significant paradigm shift which has the potential to increase plant profitability and reduce environmentally deleterious effluents. It provides a link between the users of water and those responsible for its management, leading to the recovery of resources in closed loop cycles and thus contributing to progressing towards the concept of a circular economy, where valuable nutrients and components are recovered and reused. This chapter examines the pedagogy around the design and implementation of WWBRs with a focus on the classification of wastewaters for WWBR design, selection of potential products, flow sheet development and the criteria for reactor selection.
Biotechnology and Bioengineering, 2008
Glucose oxidase (GO) is an important industrial enzyme typically purified from Penicillium and As... more Glucose oxidase (GO) is an important industrial enzyme typically purified from Penicillium and Aspergillus sp. As GO distribution within the cultures influences process design for maximal product recovery, distribution of GO activity in Penicillium sp. CBS 120262 and Aspergillus niger NRRL-3, during mid-exponential and stationary phases, is compared. On progression from mid-exponential to stationary phase, the percentage GO activity in the cytoplasm decreased 1.6- and 1.3-fold in Penicillium sp. and A. niger respectively. In Penicillium sp., a concomitant 1.8- and 1.9-fold decrease in the percentage GO activity in the cell envelope and slime mucilage respectively, translated into a 2.0-fold increase in the extracellular fluid. In A. niger, decreasing cytoplasmic GO activity was accompanied by 1.3-fold increases in the cell envelope and slime mucilage, with a 1.3-fold decrease in the extracellular fluid. Similar trends were observed in specific GO activities. As final GO activity recovered is governed by the purification program, recovery from the extracellular fluid plus cell extract or from the extracellular fluid only were compared through simulating processes of varying complexity. A critical yield for each purification stage was identified above which recovery from the extracellular fluid plus cell extract exceeded that from extracellular fluid alone. These results highlight the influence of microorganism, harvest time and efficiency of downstream process on GO activity delivered. In the systems studied, Penicillium sp. is the organism of choice and should be harvested during stationary phase. The purification process chosen should be informed by both enzyme distribution and individual purification stages yields.
Applied Microbiology and Biotechnology, 2005
The production of the enzyme glucose oxidase by Aspergillus niger is well documented. However, it... more The production of the enzyme glucose oxidase by Aspergillus niger is well documented. However, its distribution within the fungal culture is less well defined. Since the enzyme location impacts significantly on enzyme recovery, this study quantifies the enzyme distribution between the extracellular fluid, cell wall, cytoplasm and slime mucilage fractions in an A. niger NRRL-3. The culture was separated into the individual fractions and the glucose oxidase activity was determined in each. The extracellular fluid contained 38% of the total activity. The remaining 62% was associated with the mycelia and was distributed between the cell wall, cytoplasm and slime mucilage in the proportions of 34, 12 and 16%, respectively. Intracellular cytoplasmic and cell wall sites were confirmed using immunocytochemical labelling of the mycelia. In the non-viable cell, the mycelial-associated enzyme was distributed between these sites, whereas in the viable cell, it was predominantly associated with the cell wall. The distribution of the enzyme activity indicates that recovery from the solids would result in a 38% loss, whereas recovery from the extracellular fluid would result in a 62% loss. The results also suggest, however, that this 62% loss could be reduced to around 34% by disintegrating the solids prior to separation due to the contribution of the enzyme in the cytoplasm and slime mucilage. This was confirmed by independently establishing the percentage activity in the liquid and solid portions of a disintegrated culture as 62 and 38%, respectively.