Craig Evans

Probiotic viability and physico-chemical and sensory properties of plain and stirred fruit yogurts made from goat’s milk

Probiotic plain and stirred fruit yogurts were made from goats milk using bacterial cultures comprising, Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12 and Propionibacterium jensenii 702. The products were stored at 4°C for 4weeks, during which time the viability of the yogurt starter culture and probiotic bacteria was analysed weekly. P. jensenii 702 demonstrated the highest viability (10(8)cfu/g) in all types of yogurt throughout the storage period, while the viability of the bifidobacteria (∼10(7)cfu/g) also remained above the minimum therapeutic level. The viability of L. acidophilus LA-5 fell below 10(6)cfu/g in yogurts, however, the addition of fruit juice appeared to support the viability of lactobacilli, with higher microorganism numbers observed in fruit yogurts than in plain yogurt throughout the shelf life. Addition of fruit juice significantly increased the syneresis, and decreased viscosity and water holding capacity of yogurts (p<0.05), and also enhanced their sensory acceptability.

Altered amino acid excretion in children with autism

Abstract Autism is a complex and life-long behavioural disorder of unknown aetiology. Recent reports have indicated the involvement of digestive tract dysfunction and possible complications from inadequate nutrition. In this study, 34 autistic children (12 untreated and 22 receiving therapeutic treatments related to digestive function and nutritional uptake) and 29 control subjects (all 5–15 years of age) were investigated to determine whether there were any anomalies in the urinary excretion of amino acids, glucose, sucrose, arabinose and tartaric acid using GC/FID and GC/MS analysis techniques. Significantly lower relative urinary levels of essential amino acids were revealed for both the untreated (mean ± SEM, 32.53 ± 3.09%) and treated (31.98 ± 2.87%) autistic children compared with the controls (37.87 ± 1.50%). There were no significant differences in measured excretions of sugars or tartaric acid. It was concluded that the untreated autistic children had evidence of altered metabolic homeostasis.

Extensive bacterial diversity indicates the potential operation of a dynamic micro-ecology within domestic rainwater storage systems

The concept that domestic rainwater storage tanks may host sustainable microbial ecosystems has not previously been addressed. The bacterial diversity, cultivated from more than 80 samples from 22 tanks at various locations across eastern Australia, is presented here as prima facie evidence for the potential operation of a functional micro-ecology within rainwater storage systems. Cultivated isolates were found to comprise members of four major bacterial divisions; Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, including more than 200 species from 80 different genera. The pattern of abundance distribution was typical of that observed in most natural communities, comprising a small number of abundant taxa and a multitude of rare taxa, while the specific composition resembled that previously described in a number of natural aquatic systems. Although Proteobacteria from alpha, beta and gamma sub-classes were dominant, a set of core taxa comprising representative genera from all four phyla could be identified. Coliform and other species specifically associated with faecal material comprised <15% of the species identified, and represented <1.5% of total average abundance. The composition of the cultivated populations and scope of diversity present, suggested that rainwater tanks may support functional ecosystems comprising complex communities of environmental bacteria, which may have beneficial implications for the quality of harvested rainwater.

Rainwater tanks and microbial water quality: Are the indications clear?

Abstract Deriving maximum economic and water savings benefits from rainwater harvesting in the urban environment requires the use of rainwater for internal applications, including showering/bathing, laundry and toilet flushing. Widespread use of rainwater for these applications has been hindered by uncertainty over quality and perceptions of health risk. This study examined the presence and abundance of the faecal indicators E. coli, enterococci and total coliform in over 100 water samples collected from rainwater tanks in eastern Australia. A large proportion of samples were compliant with the requirements of mains water drinking standards, especially among those collected via a hot water system, while almost universal compliance with bathing water quality standards was observed. Indicator species were found to represent a very small proportion of total bacterial contamination and no significant correlation between faecal indicator counts and heterotrophic plate counts was observed. Furthermore, enterococci were not significantly correlated with the other indicator groups. On average, heterotrophic counts were found to be dominated by Pseudomonas spp and several other widely distributed environmental organisms. The implications of these findings with regard to the scope of domestic rainwater use in the urban environment, and the difficulty in achieving reliable risk assessment, have been discussed.

Sweat facilitated amino acid losses in male athletes during exercise at 32-34 ˚C

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.

Potential influence of dairy propionibacteria on the growth and acid metabolism of Streptococcus bovis and Megasphaera elsdenii

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.

In vitro investigation of the effect of dairy propionibacteria on rumen pH, lactic acid and volatile fatty acids

Abstract Ruminal acidosis is a prevalent disorder in ruminants such as dairy cows and feedlot beef cattle, caused primarily by the inclusion of a high percentage of readily fermentable concentrates in the diet. The disorder presents as an accumulation of lactic acid, a decrease of pH in the rumen and a subsequent imbalance of the rumen fermentation process with detrimental impacts on the animals health and productivity. Dairy propionibacteria, a group of bacteria characterised by utilization of lactic acid as the favoured carbon source, with propionic acid produced as a by-product, were evaluated in this study as potential direct-fed microbials for use in controlling ruminal acidosis. Acidosis was simulated by introduction of high concentrations of lactic acid into rumen fluid samples and a multi-strain in vitro analysis was conducted, whereby changes in pH and lactic acid metabolism were compared in identical acidified rumen samples, following inoculation with various propionibacteria. This was followed by a study to evaluate the effect of bacterial inoculation dosage on acid metabolism. The results indicated that lactic acid levels in the rumen fluid were significantly reduced, and propionic acid and acetic acid concentrations both significantly increased, following addition of propionibacteria. Significant ‘between strains’ differences were observed, with Propionibacterium acidopropionici 341, Propionibacterium freudenreichii CSCC 2207, Propionibacterium jensenii NCFB 572 and P. jensenii 702 each producing more rapid reduction of lactic acid concentration than P. freudenreichii CSCC 2206, P. acidopropionici ATCC 25562 and Propionibacterium thoenii ATCC 4874. Furthermore, the efficacy of this application was dosage related, with the rates of reduction in lactic acid levels and production of propionic acid, both significantly greater for the higher (10 10 cfu mL −1 ) compared with lower (10 5 cfu mL −1 ) dosage inoculation. The results confirmed that the introduction of propionibacteria could promote more rapid reduction of lactic acid levels than would occur without their addition, demonstrating their potential in controlling ruminal acidosis.