Ian Maddox | Massey University (original) (raw)
Papers by Ian Maddox
Can J Microbiol, 1987
An investigation was made into some methods of culture maintenance and inoculum development proce... more An investigation was made into some methods of culture maintenance and inoculum development procedures by which the production of solvents by Clostridium acetobutylicum could be maximized. Storage of the organism as spores in nonnutrient media at either 4 or −20 °C proved to be the most effective method of culture maintenance. On revival of stock cultures, neither heat shocking nor treatment with aqueous ethanol or butanol gave improvements in solvent production during the subsequent fermentation. However, significantly improved production was obtained when culture transfers during the inoculum development procedure were made at the time of maximum cell motility.
Letters in Applied Microbiology, Aug 1, 1996
ABSTRACT N.A. GUTIERREZ AND I.S. MADDOX. 1996. Evidence is provided that there are two separate s... more ABSTRACT N.A. GUTIERREZ AND I.S. MADDOX. 1996. Evidence is provided that there are two separate systems for galactose uptake in Clostridium acetobutylicum P262, a phosphoenolpyruvate-dependent phosphotransferase system and a proton motive force-driven system. Glucose uptake involves the former but not the latter. When present on their own in a semi-synthetic medium, glucose and galactose were consumed by the bacterium at rates of 1.00 mmol 1−1 h−1 and 0.79 mmol 1−1 h−1, respectively. However, when present as a mixture, glucose was used preferentially, and there was a lag period before galactose utilization commenced. The subsequent consumption rates were 0.97 mmol 1−1 h−1 and 0.38 mmol 1−1 h−1, for glucose and galactose, respectively. These data provide evidence for repression of galactose utilization by glucose.
Journal of Industrial Microbiology and Biotechnology, Nov 14, 2003
Food and Bioproducts Processing, 2005
World Journal of Microbiology and Biotechnology, Mar 31, 2000
Beneficial Microbes, Feb 11, 2015
The objective of the study was to design and produce calcium alginate beads that can deliver immo... more The objective of the study was to design and produce calcium alginate beads that can deliver immobilised Lactobacillus reuteri DPC16 to a target site of the colon in the gastrointestinal (GI) tract. In this study, several factors that might affect the effectiveness of calcium alginate gel beads entrapping L. reuteri DPC16 cells were investigated. An in vitro GI tract model was used to simulate the pH variation and the existence of enzymes. Firstly, by varying the concentration of alginate at a constant concentration of CaCl2 the survival of immobilised DPC16 cells in simulated gastric fluid (SGF) was observed; secondly, the physical stability of calcium alginate beads containing skim milk during sequential incubation in the GI fluids was observed using optimal concentrations of alginate; finally, the survival of DPC16 cells immobilised within alginate beads containing skim milk were compared when the beads were incubated for different times during sequential exposure to the simulated fluids. The results demonstrated that non-encapsulated DPC16 cells were sensitive to an acidic environment, and no viable cells were detected after 90 min exposure in SGF (pH 1.2). With the protection of calcium alginate gel, the survival rate of immobilised DPC16 cells was slightly improved. An alginate concentration of 4% (w/v) was the most effective of those tested, but due to the irregular shape it formed, an alginate concentration of 3% (w/v) was used in further investigations. When skim milk (8% (w/v)) was added to the alginate solution, the cell survival was improved markedly. The optimal concentration of calcium chloride was 0.3 M, because the beads maintained their integrity in SGF and simulated intestinal fluid while disintegrating in simulated colonic fluid. The beads made from 3% alginate, 8% skim milk and 0.3 M CaCl2 proved to be an effective delivery and release system for DPC16 cells.
Journal of Industrial Microbiology and Biotechnology, Feb 2, 2006
Applied Microbiology and Biotechnology, 1986
Journal of Industrial Microbiology, 1991
Summary Using a defined medium in chemostat culture, an inverse relationship between the biomass ... more Summary Using a defined medium in chemostat culture, an inverse relationship between the biomass concentration and the specific butanol productivity has been observed. It is suggested that this is due to the cell population not being homogeneous, and that a change in the nutrient balance leads to a cha in the relative proportions of acidogenic, solventogenic and inert cells (spores).
Applied and environmental microbiology, 1987
The motility of Clostridium acetobutylicum has been investigated during a typical batch fermentat... more The motility of Clostridium acetobutylicum has been investigated during a typical batch fermentation process for solvent production. The motility is characterized by "runs" during the early phase of sugar utilization and acid production, but this changes to "tumbles" during the onset of solventogenesis. Sugars and undissociated acetic and butyric acids have been shown to be attractants for the bacterium, while acetone, butanol, ethanol, and dissociated acetate and butyrate are repellents. It is suggested that chemotactic responses explain why highly motile cells are strongly solventogenic.
Enzyme and Microbial Technology, 1992
... Product inhibition in a nonmotile mutant of Clostridium acetobutylicum Noemi A. Gutierrez and... more ... Product inhibition in a nonmotile mutant of Clostridium acetobutylicum Noemi A. Gutierrez and Ian S. Maddox Department of Biotechnology, Massey University, Palmerston North, New Zealand Growth inhibition studies have ... 1981, 11, 567-579 Lin, YL and Blaschek, HP Appl. ...
Biotechnology Letters, 1982
Biotechnology and Bioengineering, 1988
Bioresource Technology, 1995
Biotechnology and Bioengineering, 1991
Can J Microbiol, 1987
An investigation was made into some methods of culture maintenance and inoculum development proce... more An investigation was made into some methods of culture maintenance and inoculum development procedures by which the production of solvents by Clostridium acetobutylicum could be maximized. Storage of the organism as spores in nonnutrient media at either 4 or −20 °C proved to be the most effective method of culture maintenance. On revival of stock cultures, neither heat shocking nor treatment with aqueous ethanol or butanol gave improvements in solvent production during the subsequent fermentation. However, significantly improved production was obtained when culture transfers during the inoculum development procedure were made at the time of maximum cell motility.
Letters in Applied Microbiology, Aug 1, 1996
ABSTRACT N.A. GUTIERREZ AND I.S. MADDOX. 1996. Evidence is provided that there are two separate s... more ABSTRACT N.A. GUTIERREZ AND I.S. MADDOX. 1996. Evidence is provided that there are two separate systems for galactose uptake in Clostridium acetobutylicum P262, a phosphoenolpyruvate-dependent phosphotransferase system and a proton motive force-driven system. Glucose uptake involves the former but not the latter. When present on their own in a semi-synthetic medium, glucose and galactose were consumed by the bacterium at rates of 1.00 mmol 1−1 h−1 and 0.79 mmol 1−1 h−1, respectively. However, when present as a mixture, glucose was used preferentially, and there was a lag period before galactose utilization commenced. The subsequent consumption rates were 0.97 mmol 1−1 h−1 and 0.38 mmol 1−1 h−1, for glucose and galactose, respectively. These data provide evidence for repression of galactose utilization by glucose.
Journal of Industrial Microbiology and Biotechnology, Nov 14, 2003
Food and Bioproducts Processing, 2005
World Journal of Microbiology and Biotechnology, Mar 31, 2000
Beneficial Microbes, Feb 11, 2015
The objective of the study was to design and produce calcium alginate beads that can deliver immo... more The objective of the study was to design and produce calcium alginate beads that can deliver immobilised Lactobacillus reuteri DPC16 to a target site of the colon in the gastrointestinal (GI) tract. In this study, several factors that might affect the effectiveness of calcium alginate gel beads entrapping L. reuteri DPC16 cells were investigated. An in vitro GI tract model was used to simulate the pH variation and the existence of enzymes. Firstly, by varying the concentration of alginate at a constant concentration of CaCl2 the survival of immobilised DPC16 cells in simulated gastric fluid (SGF) was observed; secondly, the physical stability of calcium alginate beads containing skim milk during sequential incubation in the GI fluids was observed using optimal concentrations of alginate; finally, the survival of DPC16 cells immobilised within alginate beads containing skim milk were compared when the beads were incubated for different times during sequential exposure to the simulated fluids. The results demonstrated that non-encapsulated DPC16 cells were sensitive to an acidic environment, and no viable cells were detected after 90 min exposure in SGF (pH 1.2). With the protection of calcium alginate gel, the survival rate of immobilised DPC16 cells was slightly improved. An alginate concentration of 4% (w/v) was the most effective of those tested, but due to the irregular shape it formed, an alginate concentration of 3% (w/v) was used in further investigations. When skim milk (8% (w/v)) was added to the alginate solution, the cell survival was improved markedly. The optimal concentration of calcium chloride was 0.3 M, because the beads maintained their integrity in SGF and simulated intestinal fluid while disintegrating in simulated colonic fluid. The beads made from 3% alginate, 8% skim milk and 0.3 M CaCl2 proved to be an effective delivery and release system for DPC16 cells.
Journal of Industrial Microbiology and Biotechnology, Feb 2, 2006
Applied Microbiology and Biotechnology, 1986
Journal of Industrial Microbiology, 1991
Summary Using a defined medium in chemostat culture, an inverse relationship between the biomass ... more Summary Using a defined medium in chemostat culture, an inverse relationship between the biomass concentration and the specific butanol productivity has been observed. It is suggested that this is due to the cell population not being homogeneous, and that a change in the nutrient balance leads to a cha in the relative proportions of acidogenic, solventogenic and inert cells (spores).
Applied and environmental microbiology, 1987
The motility of Clostridium acetobutylicum has been investigated during a typical batch fermentat... more The motility of Clostridium acetobutylicum has been investigated during a typical batch fermentation process for solvent production. The motility is characterized by "runs" during the early phase of sugar utilization and acid production, but this changes to "tumbles" during the onset of solventogenesis. Sugars and undissociated acetic and butyric acids have been shown to be attractants for the bacterium, while acetone, butanol, ethanol, and dissociated acetate and butyrate are repellents. It is suggested that chemotactic responses explain why highly motile cells are strongly solventogenic.
Enzyme and Microbial Technology, 1992
... Product inhibition in a nonmotile mutant of Clostridium acetobutylicum Noemi A. Gutierrez and... more ... Product inhibition in a nonmotile mutant of Clostridium acetobutylicum Noemi A. Gutierrez and Ian S. Maddox Department of Biotechnology, Massey University, Palmerston North, New Zealand Growth inhibition studies have ... 1981, 11, 567-579 Lin, YL and Blaschek, HP Appl. ...
Biotechnology Letters, 1982
Biotechnology and Bioengineering, 1988
Bioresource Technology, 1995
Biotechnology and Bioengineering, 1991