Ian Maddox

Massey University, School of Engineering and Advanced Technology, Emeritus

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40 years experience in industrial microbiology and fermentation processes.
Clostridial fermentation processes are a speciality.
Experience in brewing and pharmaceutical industries.
Extensive consulting experience in New Zealand and overseas.

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Papers by Ian Maddox

Consumption of antimicrobial manuka honey does not significantly perturb the microbiota in the hind gut of mice

PeerJ, 2016

The aim of this study was to test the hypothesis that consuming manuka honey, which contains anti... more The aim of this study was to test the hypothesis that consuming manuka honey, which contains antimicrobial methylglyoxal, may affect the gut microbiota. We undertook a mouse feeding study to investigate whether dietary manuka honey supplementation altered microbial numbers and their production of organic acid products from carbohydrate fermentation, which are markers of gut microbiota function. The caecum of C57BL/6 mice fed a diet supplemented with antimicrobial UMF® 20+ manuka honey at 2.2 g/kg animal did not show any significantly changed concentrations of microbial short chain fatty acids as measured by gas chromatography, except for increased formate and lowered succinate organic acid concentrations, compared to mice fed a control diet. There was no change in succinate-producing Bacteroidetes numbers, or honey-utilising Bifidobacteria, nor any other microbes measured by real time quantitative PCR. These results suggest that, despite the antimicrobial activity of the original ho...

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High‐throughput microbial bioassays to screen potential New Zealand functional food ingredients intended to manage the growth of probiotic and pathogenic gut bacteria

International Journal of Food Science & Technology, 2008

SummaryA spectrophotometric bioassay was used to screen selected food ingredients intended for de... more SummaryA spectrophotometric bioassay was used to screen selected food ingredients intended for development of functional foods designed to influence the growth of gut bacteria. Dose–response profiles displaying Δgrowth, the magnitude of deviation from growth of controls, were generated for probiotics Lactobacillus reuteri, Lactobacillus rhamnosus, Bifidobacterium lactis and pathogens Escherichia coli, Salmonella Typhimurium and Staphylococcus aureus. Ingredients were manuka honey UMF™20+(dose‐dependently increased probiotics and decreased pathogens); bee pollen (biphasic growth effects against all); Rosehips and BroccoSprouts® (increased all dose‐dependently); blackcurrant oil (little effect) and propolis (inhibited all strains). Ingredients were also bioassayed in pairs to assess desirable or undesirable synergistic interactions. Observed synergies included manuka honey (predominantly desirable); rosehips or BroccoSprouts® (desirable and undesirable); blackcurrant oil (desirable) a...

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The contribution of dietary broccoli sprouts towards the microbial metabolite profile in the hind gut of mice

International Journal of Food Science & Technology, 2012

1 Food and Nutrition Group, The New Zealand Institute for Plant & Food Research Limited, Food... more 1 Food and Nutrition Group, The New Zealand Institute for Plant & Food Research Limited, Food Industry Science Centre, Batchelar Rd, Palmerston North 4410, New Zealand 2 The University of Queensland School of Medicine, Greenslopes Private Hospital, Greenslopes, Qld 41201, Australia 3 College of Sciences, Massey University, Albany Campus, Albany, Auckland 1311, New Zealand 4 Animals Department, Harper Adams University College, Newport, Shropshire TF10 8NB, UK 5 Food and Wellness Group, The New Zealand Institute for Plant & Food Research Limited, Mt Albert Research Centre, 120 Mt Albert Rd, Sandringham, Auckland 1025, New Zealand

The effect of some culture maintenance and inoculum development techniques on solvent production by Clostridium acetobutylicum

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.

Galactose transport in Clostridium acetobutylicum P262

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.

Production of ethanol and n-butanol from hexose/pentose mixtures using consecutive fermentations with Saccharomyces cerevisiae and Clostridium acetobutylicum

Biotechnol Lett, 1982

PRODUCTION OF ETHANOL AND n-BUTANOL FROM HEXOSE/PENTOSE MIXTURES USING CONSECUTIVE FERMENTATIONS WITH SACCHAROMYCES CEK"V!F:AE AND CLOSTRIDIL'N ACETOBL'TYLICUM

Biotechnol Lett, 1982

Fermentation performance of an exopolysaccharide-producing strain of Lactobacillus delbrueckii subsp. bulgaricus

Journal of Industrial Microbiology and Biotechnology, Nov 14, 2003

The formation of exopolysaccharide (EPS) and extracellular metabolites was studied in a strain of... more The formation of exopolysaccharide (EPS) and extracellular metabolites was studied in a strain of Lactobacillus delbrueckii subsp. bulgaricus (NCFB 2483), grown under batch culture conditions in a semidefined medium incorporating lactose and casein hydrolysate. Performance parameters were derived from the fermentation data, and kinetic models were applied in order to describe the production of EPS, extracellular metabolites, and biomass produced. Lactose was split intracellularly, with the resultant galactose being exported from the cell, and the glucose being metabolised further to EPS and lactic acid. Production of EPS, lactate, and galactose was closely growth-associated and followed a pattern of primary kinetics. A marginally lower galactose level relative to the modelled levels throughout most of the time course of the fermentation suggests that not all galactose is exported from the cell, and that a low level of flux to other metabolites, such as EPS, might exist. Keywords Exopolysaccharide AE Lactobacillus delbrueckii subsp. bulgaricus AE Fermentation modelling Materials and methods Fermentation medium The medium used was that described by Kimmel and Roberts [16], modified by the replacement of glucose with lactose as the sole sugar source (KM-l). This medium was based on the MRS medium

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Reduction in butanol inhibition by perstraction: Utilization of concentrated lactose/whey permeate by Clostridium acetobuuylicum to enhance butanol fermentation economics

Food and Bioproducts Processing, 2005

A cetone-butanol-ethanol (ABE) were produced from whey permeate medium, supplemented with lactose... more A cetone-butanol-ethanol (ABE) were produced from whey permeate medium, supplemented with lactose, in a batch reactor using Clostridium acetobutylicum P262, coupled with ABE removal by perstraction. ABE (98.97 gL 21) were produced from lactose (227 gL 21) at a yield of 0.44 and productivity of 0.21 gL 21 h 21. It should be noted that the ratio of acids to solvents was significantly lower in the perstraction experiment compared to the control batch process suggesting that acids were converted to solvents. The perstraction experiment results are superior to the control batch fermentation where 9.34 gL 21 ABE was produced. It was determined that lactose at 250 gL 21 was a strong inhibitor to the cell growth of C. acetobutylicum and fermentation. A membrane with an area of 0.1130 m 2 was used as the perstraction membrane while oleyl alcohol as the perstraction solvent. Removal of ABE by perstraction was faster than their production in the reactor, and the maximum concentration of ABE in the oleyl alcohol was 9.75 gL 21. It is viewed that recovery of ABE from oleyl alcohol (at this concentration) would be more economical than recovery from the fermentation broth. It is suggested that a new membrane be developed which can offer a higher ABE flux. Alternately, silicalite membranes that were successfully developed for pervaporation could be used for perstraction. Using such an integrated system would reduce process streams and save significant processing costs. It is also viewed that the process of concentrated lactose-whey permeate fermentation to butanol can be adapted in the existing solvent fermentation industries without making significant changes.

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A proposed biochemical mechanism for citric acid accumulation by Aspergillus niger Yang No. 2 growing in solid state fermentation

World Journal of Microbiology and Biotechnology, Mar 31, 2000

Aspergillus niger Yang No. 2 and its mutant strain SL1 were grown in solid state fermentation. Sa... more Aspergillus niger Yang No. 2 and its mutant strain SL1 were grown in solid state fermentation. Samples were taken after 2, 4 and 6 days of incubation and the mycelia were analysed for their intracellular concentrations of some organic acids and adenylates and the activities of selected enzymes. Strain Yang No. 2 contained high concentrations of citrate with very little oxalate, while strain SL1 contained lower concentrations of citrate but considerably higher concentrations of oxalate. As the fermentation proceeded, strain Yang No. 2 showed a much higher ratio of ATP:AMP than did strain SL1. In addition, the enzyme ATP:citrate lyase became undetectable during citrate accumulation in strain Yang No. 2, while its activity remained high during oxalate accumulation in strain SL1. It is proposed that citrate accumulation by strain Yang No. 2 during solid state fermentation is due to blockage of its metabolism in the mitochondrion via inhibition of isocitrate dehydrogenase by the high ATP:AMP ratio, and in the cytosol by repression of ATP:citrate lyase activity.

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Viability and delivery of immobilised Lactobacillus reuteri DPC16 within calcium alginate gel systems during sequential passage through simulated gastrointestinal fluids

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.

Metabolism associated with raised metabolic flux to sugar nucleotide precursors of exopolysaccharides in Lactobacillus delbrueckii subsp. bulgaricus

Journal of Industrial Microbiology and Biotechnology, Feb 2, 2006

Exopolysaccharide (EPS) metabolism was studied in a galactose-negative strain of Lactobacillus de... more Exopolysaccharide (EPS) metabolism was studied in a galactose-negative strain of Lactobacillus delbrueckii subsp. bulgaricus, using two different approaches. Firstly, using both the parent strain and a chemically induced mutant with higher yield and specific productivity of EPS than the parent, comparative information was obtained relating to enzyme activities and metabolite levels associated with EPS formation when grown on lactose. Under continuous culture conditions (D=0.10 h À1), the higher metabolic flux towards EPS formation in the mutant strain relative to the parent appeared to be mediated by raised levels of UDP-glucose pyrophosphorylase (UGP). Marginally raised UDPgalactose 4-epimerase (UGE) activity in the mutant strain suggested that this enzyme could also play a role in EPS overproduction. The second approach involved investigating the effect of growth rate on sugar nucleotide metabolism in the parent, as it is known that EPS production is growth-associated in this strain. UGE activity in the parent strain appeared to increase when the growth rate was elevated from 0.05 to 0.10 h À1 , and further to 0.35 h À1 , conditions that can be associated with higher levels of metabolic flux to EPS formation. Concurrent with these increments, intracellular ATP levels in the cell were raised. In both investigations glucose-6-phosphate accumulated pointing to a constriction at this branchpoint, and a limitation in the flow of carbon towards fructose-6-phosphate or glucose-1-phosphate. The changes in metabolism associated with enhanced flux to EPS provide guidance as to how the yield of Lactobacillus delbrueckii subsp. bulgaricus EPS can be improved.

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Isolation and partial characterization of a non-motile mutant of Clostridium acetobutylicum

Biotechnol Lett, 1990

A non-motile mutant of Clostridium acetobutylicurn, morphologically indistinguishable from the mo... more A non-motile mutant of Clostridium acetobutylicurn, morphologically indistinguishable from the motile parent, was capable of solvent production, suggesting that motility is not a regulatory trigger for solventogenesis. However, solventogenesis was considerably weaker than that of the parent, providing evidence of a positive relationship between solvent production and motility.

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Effect of pH and lactose concentration on solvent production from whey permeate using Clostridium acetobutylicum

A study was performed to optimize the production of solvents from whey permeate in batch fermenta... more A study was performed to optimize the production of solvents from whey permeate in batch fermentation using Clostridiurn acetobutylicurn P262. Fermentations performed at relatively low pH values resulted in high solvent yields and productivities, but lactose utilization was incomplete. At higher pH values, lactose utilization was improved but acid production dominated over solvent production. When operating at the higher pH values, an increase in the initial lactose concentration of the whey permeate resulted in lower rates of lactose utilization, and this was accompanied by increased solvent production and decreased acid production. Analysis of data from several experiments revealed a strong inverse relationship between solvent yield and lactose utilization rate. Thus, conditions which minimize the lactose utilization rate, such as low culture pH values or high initial lactose concentrations, favor solventogenesis at the expense of acid production.

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The effect of methanol on critic acid production from galactose by Aspergillus niger

Applied Microbiology and Biotechnology, 1986

Effect of biomass concentration on the specific solvent productivity of Clostridium acetobutylicum in chemostat culture

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).

Role of Chemotaxis in Solvent Production by Clostridium acetobutylicum

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.

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Microbial Production of 2,3-Butanediol

Biotechnology Set, 2001

Product inhibition in a nonmotile mutant of Clostridium acetobutylicum

Enzyme and Microbial Technology, 1992

... Product inhibition in a nonmotile mutant of Clostridium acetobutylicum Noemi A. Gutierrez and... more

Use of silicalite for the adsorption of n-butanol from fermentation liquors

Biotechnology Letters, 1982

Silicalite, a zeolite analogue~ has been used to adsorb n-butanol from fermentation liquors. 85 m... more

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