Dr Craig Evans

Ruminal acidosis is a prevalent disorder among dairy cows and feedlot cattle, which can significantly impair their health and productivity. This study, involving seven different strains of dairy propionibacteria, represents an in vitro investigation of the feasibility of using these organisms as direct-fed microbials to control lactic acid acumulation in the rumen. Interactions between the propionibacteria, Streptococcus bovis and Megasphaera elsdenii were evaluated in terms of effects on lactic, acetic and propionic acid metabolism, following co-incubation. Spot resistance tests showed slight but varying degrees of growth inhibition by S. bovis among the propionibacteria, while no inhibition was observed between M. elsdenii and the different strains of dairy propionibacteria. In the co-culture experiments comprising S. bovis in nutrient broth, significant differences in pH and the levels of production of lactic, acetic and propionic acid, were observed between treatments following inoculation with various propionibacteria and/or M. elsdenii. In general, lactic acid concentrations at the end of the incubation were significantly lower in the cultures containing propionibacteria compared with cultures comprising either S. bovis only or S. bovis + M. elsdenii, although efficacy of lactate metabolism varied between species and strains. Moreover,the accumulation of acetic and propionic acid in the combined cultures, but not in the solo S. bovis culture, indicated that these compounds were produced as a result of the metabolism of lactic acid by the propionibacteria and M. elsdenii.

Seven different types of fermented drinking milk were made from goats' milk using various culture compositions of Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12 and novel putative probiotic Propionibacterium jensenii 702. Probiotic viability, physico-chemical and sensory properties of fermented milk were measured during 3 weeks of storage at 4 °C. All three probiotics were able to maintain high viability (>107 cfu mL-1) during fermentation and subsequent storage regardless of the culture composition in goats' milk without major antagonistic effects. Acidity of all fermented milk samples increased during storage, however there were no significant differences among preparations for organoleptic properties. Generally, lower sensory acceptability was recorded for the samples stored for 3 weeks than the respective fresh products.

Sweat contains amino acids and electrolytes derived from plasma and athletes can lose 1-2L of sweat per hour during exercise. Sweat may also contain contributions of amino acids as well as urea, sodium and potassium from the natural moisturizing factors (NMF) produced in the stratum corneum. In preliminary experiments, one participant was tested on three separate occasions to compare sweat composition with surface water washings from the same area of skin to assess contributions from NMF. Two participants performed a 40 minute self-paced cycle session with sweat collected from cleansed skin at regular intervals to assess the contributions to the sweat load from NMF over the period of exercise. The main study investigated sweat amino acid composition collected from nineteen male athletes following standardised endurance exercise regimes at 32-34°C and 20-30% RH. Plasma was also collected from ten of the athletes to compare sweat and plasma composition of amino acids. The amino acid profiles of the skin washings were similar to the sweat, suggesting that the NMF could contribute certain amino acids into sweat. Since the sweat collected from athletes contained some amino acid contributions from the skin, this fluid was subsequently referred to as "faux" sweat. Samples taken over 40 minutes of exercise showed that these contributions diminished over time and were minimal at 35 minutes. In the main study, the faux sweat samples collected from the athletes with minimal NMF contributions, were characterised by relatively high levels of serine, histidine, ornithine, glycine and alanine compared with the corresponding levels measured in the plasma. Aspartic acid was detected in faux sweat but not in the plasma. Glutamine and proline were lower in the faux sweat than plasma in all the athletes. Three phenotypic groups of athletes were defined based on faux sweat volumes and composition profiles of amino acids with varying relative abundances of histidine, serine, glycine and ornithine. It was concluded that for some individuals, faux sweat resulting from exercise at 32-34°C and 20-30% RH posed a potentially significant source of amino acid loss.

A mixture of probiotic Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12 and novel potential probiotic Propionibacterium jensenii 702 was resuspended in reconstituted (20% w/v) goat's milk, spray dried in a mini spray dryer (inlet temperature=195°C and outlet temperature=85°C) and the spray dried powder was stored in air tight glass jars at 4°C and 30°C for 24 weeks. Powder quality and probiotic viability after spray drying and subsequent storage were measured. Spray drying probiotics in reconstituted goat's milk resulted in a significant reduction in the viability of all three probiotics. However, all three probiotics were able to maintain satisfactory viability levels (106-108cfu/g) after spray drying. While storage temperature did not appear to have a significant effect on moisture content, the viability of all three strains declined dramatically when stored at 30°C but lactobacilli and propionibacteria remained virtually unaffected under storage at 4°C, satisfying recommendations regarding the level of viable cells in probiotic foods.

In managing water quality in catchments and estuaries, faecal contamination is typically assessed using microbial indicators, such as faecal coliform bacteria. Bacteriological indicators however cannot be used to distinguish whether the faecal contamination has been derived from human or animal sources. The ability to track contamination and distinguish between sources is particularly important where water is used for potable supply, recreational purposes and where commercial aquaculture for human consumption is undertaken. Various chemicals associated with human metabolism and activities which are present in faecal material (such as faecal sterol, pharmaceutical and fluorescent whitening compounds present in wastewaters) can be utilized to identify a human signal and therefore whether the faecal contamination in water is likely to have been derived from human sources. This paper demonstrates an approach and methodology for future work using a combination of these methods to distinguish human contaminant sources in stormwater runoff in an estuary where aquaculture is practised.

Gastrointestinal tolerance, adhesion to intestinal epithelium and immunomodulation are critical factors in maintaining probiotic efficacy. Seven different types of fermented milk were made from goat's milk using various culture compositions of three probiotics: Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12 and Propionibacterium jensenii 702 and in vitro gastrointestinal tolerance, adhesion ability and stimulation of cytokine production by probiotics were evaluated. All probiotics and combinations demonstrated significantly lower viability after exposure to simulated gastric (pH 2.0) and intestinal (with 0.3% bile, pH 8.0) fluids (p < 0.05). The ability of probiotics to adhere to Caco-2 cells appeared to be influenced by the specific probiotic strains with which they were combined in the manufacturing of fermented milk. Only monocultures of lactobacilli and bifidobacteria and their co-cultures were able to induce low levels of IL-6 and TNF-a production from Caco-2 cells. It seems likely that co-cultures of various probiotics may affect their functional properties. © 2014 Elsevier Ltd.

The secondary metabolites geosmin and 2-methylisoborneol (2-MIB) provide soil with its characteristic earthy-musty odour, being notably produced by the abundant spore-forming filamentous bacterial genus Streptomyces, among other Actinobacteria. Taste and odour (T&O) problems attributed to these compounds affect drinking water supplies worldwide, often occurring sporadically and untraced to their biological origins. A number of prokaryotic and eukaryotic organisms are recognised geosmin and 2-MIB producers in aquatic environments. However, the focus of this paper is to assess the potential contribution of Actinobacteria to this water quality issue. To date, the aquatic ecology of these bacteria remains poorly understood and debate surrounds whether they exist solely as dormant spores of terrestrial origin or are capable of growing and biosynthesising these odourous compounds in aquatic environments. The Actinobacteria which are known to produce geosmin and 2-MIB are identified and a critical assessment of habitats within aquatic environments in which they may be metabolically active residents and thus potential sources of T&O is provided. Current understandings of the chemical ecology and biosynthetic pathways of geosmin and 2-MIB, as well as the conditions under which these secondary metabolites are produced by Streptomyces, are reviewed. © IWA Publishing 2013.

Computer programs that model the fate and transport of organic contaminants through porous media typically use Fick's first law to calculate vapor phase diffusion. Fick's first law, however, is limited to the case of a single, dilute species diffusing into a stagnant, high concentration, bulk vapor phase. When dealing with more than one diffusing species and at higher concentrations, the multicomponent coupling effects on vapor phase diffusion and advection of the various constituents become significant. VLEACH, a one-dimensional finite difference model developed for the U.S. Environmental Protection Agency (USEPA), is typical of the models using Fick's first law to model vapor-phase diffusion. The VLEACH model was modified to accommodate up to 10 components and to calculate the binary diffusion coefficients for each of the components based on molecular weight, molecular volume, temperature and pressure, and to address the coupling effects on multiple component vapor phase diffusion and its impact on ground water. The resulting model was renamed MC-CHEMSOIL. At low vapor phase concentrations, MC-CHEMSOIL predicts identical ground water impacts (dissolved phase loading) to those from VLEACH 2.2a. At higher vapor phase concentrations, however, the relative difference between the models exceeded 20 percent.