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O objetivo deste trabalho foi estudar a produção do antitumoral retamicina por células imobilizadas de Streptomyces olindensis ICB20 em biorreatores. A imobilização das células foi conseguida após uma etapa inicial de cultivo em erlenmeyers (reativação e pré-imobilização) e posterior envolvimento em gel, utilizando-se alginato de cálcio 3%; as esferas produzidas tinham diâmetro médio de 3,0 ± 0,2 mm. Foram utilizados neste trabalho os biorreatores tipo cesta (2,4 L de volume útil) e coluna de bolhas (1,6 L de volume útil), efetuando-se cultivos em batelada simples, bateladas repetidas e contínuos, visando-se uma comparação dos diferentes sistemas empregados. Também foram realizados alguns cultivos com células livres, a fim de efetuar uma comparação com os sistemas com células imobilizadas nos diferentes biorreatores. Os ensaios consistiram em empregar diferentes condições de agitação (300 e 500 rpm) e aeração (0,4 e 1 vvm) para o biorreator cesta em sistema com células imobilizadas, assim como diferentes vazões de aeração no biorreator coluna de bolhas (1, 2 e 3 vvm). Os cultivos em bateladas repetidas e contínuos foram operados a partir das melhores condições obtidas nos cultivos descontínuos. Foram aplicadas nos sistemas contínuos com células imobilizadas, as vazões específicas de alimentação de 0,05 e 0,2 h -1 no biorreator cesta e vazões de 0,015 a 0,05 h -1 no biorreator coluna de bolhas. A comparação entre os sistemas com células livres e imobilizadas mostrou que as limitações difusionais afetaram significativamente as cinéticas dos ensaios com células imobilizadas, considerando-se apenas uma batelada. A operação do biorreator cesta em sistema de bateladas repetidas apresentou os maiores valores de produção da retamicina (em torno de 1,5 a 1,7 UA), porém sua operação foi possível por apenas três bateladas. O sistema contínuo operado com vazão específica de alimentação de 0,03 h-1, com células imobilizadas no biorreator coluna de bolhas, mostrou ser o mais adequado dentre todos os ensaios realizados com células imobilizadas, apresentando estabilidade na produção, em torno de 0,8 UA, durante 96 horas de alimentação (cerca de três tempos de residência). / The purpose of this study was to investigate the production of the antitumor antibiotic retamycin by immobilized cells of Streptomyces. olindensis ICB20 in bioreactors. Cells were immobilized by entrapment in Ca-alginate gel (3%) after being grown in Erlenmeyers (reactivation and pre-immobilization cultures). The average diameter of the Ca-alginate beads was 3.0 ± 0.2 mm. Aiming to compare different cell systems, immobilized cell cultures were carried out in a 2.4L working volume basket-type stirred tank reactor (BSTR) and a 1.6 L working volume bubble column reactor (BCR) in batch, repeated-batch and continuous modes. Free cell suspension cultures were also performed and the results obtained compared to those in immobilized cell systems. Different agitation rates (300 and 500 rpm) and air flow rates (0.4 and 1.0 v.v.m.) were employed in the BSTR immobilized cell experiments.The BCR cultures were conducted at 1.0, 2.0 and 3.0 v.v.m. The optimal operating conditions for the batch mode were used in the repeated-batch and continuous cultures. Immobilized cells were grown in continuous mode at feed dilution rates of 0.05 and 0.2 h-1 in the BSTR and at 0.015 and 0.05 h-1 in the BCR. The comparative evaluation of the batch cultures with free and immobilized cells showed that diffusion limitations had affected the kinetics of cell growth and retamycin production in the immobilized cell systems. The highest average values of retamycin content (from 1.5 to 1.7 AU) were achieved in repeated batch cultures conducted in the basket-type reactor (BSTR) in spite of a limited number of batches (3 batches). Of all the systems, the continuous cell immobilized culture carried out in the BCR at a dilution rate of 0.03 h-1 proved to be the most adequate for retamycin production as retamycin levels remained stable (around 0.8 AU) over 96 hours (about 3 residence times).

L(+)-Lactic acid is a commonly occurring organic acid, which is valuable due to its wide use in food and food-related industries, and its potential for the production of biodegradable and biocompatible polylactate polymers. The aim of this study was to optimize and scale-up a biotechnological process of L(+)-lactic acid production by suspended cells of R. arrhizus DAR 36017 with waste potato starch as the substrate. Commonly used inorganic and organic nitrogen sources, including ammonium sulphate, ammonium nitrate, urea, yeast extract and peptone, were assessed in conjunction with various ratios of carbon to nitrogen (C:N). Fermentation media with a low C:N ratio enhanced the production of lactic acid, biomass and ethanol, while a high C:N ratio led to production of more fumaric acid as a by-product. The use of organic nitrogen sources (yeast extract, peptone and urea) resulted in a significant reduction of lactic acid yields by 15% - 34% with a decrease of C:N from 168 to 28. The use of inorganic nitrogen sources (ammonium nitrate and ammonium sulphate) led to a high lactic acid yield of 84% - 91% at a C:N below 168. Therefore, ammonium nitrate and ammonium sulphate were considered to be better nitrogen sources for lactic acid production. Small pellets are the favoured morphological form for many fermentation processes by filamentous fungi. However, to control filamentous Rhizopus sp in the pellet form in a submerged fermentation system is difficult due to its filamentous characteristics. An acidadapted preculture technique was developed to induce the formation of the pellet form in bioreactors. Using the acid-adapted precultures, the fungal biomass can be controlled in small dispersed pellets as a dominant morphological form. With these small pellets, a lactic acid yield of 86-89%, corresponding to a concentration of 86-89g/L, was obtained in a laboratory scale process using a stirred tank reactor (STR) and a bubble column reactor (BCR). A batch bioprocess for lactic acid production was successfully scaled-up from shake flasks to laboratory scale bioreactors. Results from a simulated scale-up process revealed that the concentration and productivity of lactic acid decreased with the increase of the scale-up steps because of increased pellet size. This suggested that a one-step scale-up process using the acid-adapted preculture may be feasible in an industrial-scale bioreactor system. A comprehensive investigation of the impact of cultivation parameters on the morphology of R. arrhizus and lactic acid production was carried out in the BCR. The results showed that the fungal morphology was significantly influenced by carbon sources, pH, starch concentrations, sparger designs and aeration rates. The favoured morphology for lactic acid production was freely dispersed small pellets, which could be retained as a dominant morphology under operation conditions at pH 5.0 – 6.0, starch concentrations of 60 – 120 g/L and aeration rates of 0.2 – 0.8 vvm, using a sintered stainless steel disc sparger. The optimal cultivation conditions at pH 6.0 and aeration rate of 0.4 vvm resulted in the formation of the freely dispersed small pellets and production of 103.8 g/L lactic acid, with a yield of 87%, from 120 g/L liquefied potato starch in 48 h. This study shows a technically feasible and economically promising process for the production of lactic acid from waste potato starch. The use of waste potato starch instead of pure glucose or starch as substrate can significantly reduce the production cost, making this technology environmentally and economically attractive. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339122 / Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2008

O objetivo deste trabalho foi estudar a produção do antitumoral retamicina por células imobilizadas de Streptomyces olindensis ICB20 em biorreatores. A imobilização das células foi conseguida após uma etapa inicial de cultivo em erlenmeyers (reativação e pré-imobilização) e posterior envolvimento em gel, utilizando-se alginato de cálcio 3%; as esferas produzidas tinham diâmetro médio de 3,0 ± 0,2 mm. Foram utilizados neste trabalho os biorreatores tipo cesta (2,4 L de volume útil) e coluna de bolhas (1,6 L de volume útil), efetuando-se cultivos em batelada simples, bateladas repetidas e contínuos, visando-se uma comparação dos diferentes sistemas empregados. Também foram realizados alguns cultivos com células livres, a fim de efetuar uma comparação com os sistemas com células imobilizadas nos diferentes biorreatores. Os ensaios consistiram em empregar diferentes condições de agitação (300 e 500 rpm) e aeração (0,4 e 1 vvm) para o biorreator cesta em sistema com células imobilizadas, assim como diferentes vazões de aeração no biorreator coluna de bolhas (1, 2 e 3 vvm). Os cultivos em bateladas repetidas e contínuos foram operados a partir das melhores condições obtidas nos cultivos descontínuos. Foram aplicadas nos sistemas contínuos com células imobilizadas, as vazões específicas de alimentação de 0,05 e 0,2 h -1 no biorreator cesta e vazões de 0,015 a 0,05 h -1 no biorreator coluna de bolhas. A comparação entre os sistemas com células livres e imobilizadas mostrou que as limitações difusionais afetaram significativamente as cinéticas dos ensaios com células imobilizadas, considerando-se apenas uma batelada. A operação do biorreator cesta em sistema de bateladas repetidas apresentou os maiores valores de produção da retamicina (em torno de 1,5 a 1,7 UA), porém sua operação foi possível por apenas três bateladas. O sistema contínuo operado com vazão específica de alimentação de 0,03 h-1, com células imobilizadas no biorreator coluna de bolhas, mostrou ser o mais adequado dentre todos os ensaios realizados com células imobilizadas, apresentando estabilidade na produção, em torno de 0,8 UA, durante 96 horas de alimentação (cerca de três tempos de residência). / The purpose of this study was to investigate the production of the antitumor antibiotic retamycin by immobilized cells of Streptomyces. olindensis ICB20 in bioreactors. Cells were immobilized by entrapment in Ca-alginate gel (3%) after being grown in Erlenmeyers (reactivation and pre-immobilization cultures). The average diameter of the Ca-alginate beads was 3.0 ± 0.2 mm. Aiming to compare different cell systems, immobilized cell cultures were carried out in a 2.4L working volume basket-type stirred tank reactor (BSTR) and a 1.6 L working volume bubble column reactor (BCR) in batch, repeated-batch and continuous modes. Free cell suspension cultures were also performed and the results obtained compared to those in immobilized cell systems. Different agitation rates (300 and 500 rpm) and air flow rates (0.4 and 1.0 v.v.m.) were employed in the BSTR immobilized cell experiments.The BCR cultures were conducted at 1.0, 2.0 and 3.0 v.v.m. The optimal operating conditions for the batch mode were used in the repeated-batch and continuous cultures. Immobilized cells were grown in continuous mode at feed dilution rates of 0.05 and 0.2 h-1 in the BSTR and at 0.015 and 0.05 h-1 in the BCR. The comparative evaluation of the batch cultures with free and immobilized cells showed that diffusion limitations had affected the kinetics of cell growth and retamycin production in the immobilized cell systems. The highest average values of retamycin content (from 1.5 to 1.7 AU) were achieved in repeated batch cultures conducted in the basket-type reactor (BSTR) in spite of a limited number of batches (3 batches). Of all the systems, the continuous cell immobilized culture carried out in the BCR at a dilution rate of 0.03 h-1 proved to be the most adequate for retamycin production as retamycin levels remained stable (around 0.8 AU) over 96 hours (about 3 residence times).

Ce travail concerne la mesure et la caractérisation du transfert thermique à la paroi externe d’un faisceau de tube de refroidissement inséré dans des colonnes à bulles type « slurry ». La valeur du coefficient de transfert de chaleur est estimée à partir des équations de la chaleur. Une colonne de 0,15 m de diamètre et de 4 m de haut, équipée de deux tubes en U (3 cm de diamètre externe), a été utilisée pour mettre au point la métrologie nécessaire. L’eau a servi de fluide de refroidissement. Le mélange diphasique air-huile Syltherm XLT®, puis le mélange triphasique air-huile Syltherm XLT®-microbilles d’alumine poreuses (dS ~ 80 μm), ont servi de fluides modèles. L’incertitude de nos mesures a été estimée à environ 8 %. En système diphasique, les variations du coefficient de transfert de chaleur avec la vitesse superficielle du gaz ont pu être corrélées par une loi semblable à celle de Deckwer (1980). Cependant, la valeur de la constante de corrélation semble dépendre de l’orientation du faisceau de tubes par rapport à l’axe de la colonne. Un tel comportement n’a jamais été rapporté dans la littérature. L’écart du faisceau à un faisceau idéal (i.e. parfaitement droit et symétrique) peut être un paramètre crucial pour le transfert de chaleur. En système triphasique, la valeur du coefficient ne varie pas de façon significative jusqu’à une concentration massique d’environ 18,8 %, avant de diminuer d’environ 10 % pour une concentration massique de 21,3 %. Ce résultat est surprenant. Les variations rapportées dans la littérature sont en effet souvent contradictoires, mais toujours continues dans la gamme de concentrations testée. La métrologie mise au point a été implantée dans une colonne de 1 m de diamètre et de 5 m de haut, équipée de 24 tubes en U (6 cm de diamètre externe). Celle-ci est jugée représentative d’un réacteur pour le procédé Fischer-Tropsch. Les premiers résultats indiquent que la caractérisation thermique de l’installation sera plus délicate que pour la petite colonne / This work investigates the measure and characterisation of heat transfer in slurry bubble column reactors equipped with a bundle of cooling tubes. The value of the shell-tube heat transfer coefficient is estimated at thermal steady-state regime using heat transfer equations. A 15 cm in diameter, 4 m high bubble column, equipped with a two U-tubes (3 cm O.D.) bundle has been used to assess the metrology selected. The cooling fluid was water. Air-Syltherm XLT® heat transfer fluid and air-Syltherm XLT® heat transfer fluid-porous alumina particles (dS ~ 80 μm) were successively used as shell fluids. The uncertainty of our measures has been estimated to be around 8 %. The variations of the shell-tube heat transfer coefficient with superficial gas velocity can be modelled using the well-known correlation by Deckwer (1980). However, a smaller constant value than indicated by Deckwer et al. (1980) was obtained and it was found to be dependent upon the orientation of the tube bundle relatively to the column axis. This has never been reported in the literature and implies that any difference relatively to the ideal tube bundle – perfectly straight and symmetric – might be critical for heat transfer. Addition of solid particles has little effect on heat transfer for solid concentrations below 18.8 %w/w. A further increase up to 21.3 %w/w induced a 10 % decrease of the value of the shell-tube heat transfer coefficient. This was surprising, as existing literature results display continuous variations of the heat transfer coefficient values in the range of solid concentrations tested, even though trends of variation could be opposite. The assessed metrology was implemented into a 1 m in diameter, 5 m high bubble column equipped with a 24 U-tubes (6 cm O.D.) bundle. This pilot plant was considered to be large enough to mock up a slurry bubble column reactor for the Fischer-Tropsch process. First results indicate that thermal characterisation will be more complex than for the smaller diameter column