Effects of partial substitution of fishmeal by soybean meal in Nile tilapia (Oreochromis Niloticus) diet

The experimental trial was conducted in saline water to determine the replacement level of fish meal with locally available plant protein source, the soybean meal on growth performance, survival and body composition of Nile Tilapia (Oreochromis niloticus) juveniles reared in floating net cages. Four types of diet (35% crude protein) were formulated where fishmeal was replaced by soybean meal, partially up to 0%, 25%, 50% and 75% designated as treatment T1, T2, T3 and T4 respectively. The diet T1 was the control diet where a fish meal was the main ingredient and sole source of protein. A triplicate group of thirty healthy fish, juveniles (15.58g average initial weight) were stocked in each floating net cage (1.2 x 1.2 x 1.2m). Feeding was done at the rate of apparent visual satiation twice daily for a period of six weeks. At the end of the trial results indicates that there were no significant differences (P>0.05) in percent weight gain (%), specific growth rate (SGR %), average daily weight gain (g/ind/day), and feed conversion ratio (FCR) up to 50% fishmeal replacement by comparing with the control diet without soybean meal. However, deterioration in growth performance was noted in fish receiving more than 50% dietary soybean meal. Feed conversion ratio was poorer by increasing the soybean meal over 50%, T4 (2.81±0.74) and T3, (2.55±0.36), which is significantly different from T1 (2.21±0.12) and T2 (2.34±0.34). Survival was 94.99% in all the treatment groups. No significant differences (P>0.05) were found in fish final body carcass composition of protein, ash and moisture contents, but, the lipid level of the fish's body increased (P<0.05) significantly with an increasing fish oil and soybean meal in the diets. As a result, 50% soybean meal in the diet can substitute fishmeal without jeopardizing the growth and health condition of Nile tilapia

Chemical microenvironments and single-cell carbon and nitrogen uptake in field-collected colonies of Trichodesmium under different pCO2

Gradients of oxygen (O2) and pH, as well as small-scale fluxes of carbon (C), nitrogen (N) and O2 were investigated under different partial pressures of carbon dioxide (pCO2) in field-collected colonies of the marine dinitrogen (N2)-fixing cyanobacterium Trichodesmium. Microsensor measurements indicated that cells within colonies experienced large fluctuations in O2, pH and CO2concentrations over a day–night cycle. O2 concentrations varied with light intensity and time of day, yet colonies exposed to light were supersaturated with O2 (up to ~200%) throughout the light period and anoxia was not detected. Alternating between light and dark conditions caused a variation in pH levels by on average 0.5 units (equivalent to 15 nmol l−1 proton concentration). Single-cell analyses of C and N assimilation using secondary ion mass spectrometry (SIMS; large geometry SIMS and nanoscale SIMS) revealed high variability in metabolic activity of single cells and trichomes of Trichodesmium, and indicated transfer of C and N to colony-associated non-photosynthetic bacteria. Neither O2 fluxes nor C fixation by Trichodesmium were significantly influenced by short-term incubations under different pCO2 levels, whereas N2fixation increased with increasing pCO2. The large range of metabolic rates observed at the single-cell level may reflect a response by colony-forming microbial populations to highly variable microenvironments

Flavour-active wine yeasts

The flavour of fermented beverages such as beer, cider, saké and wine owe much to the primary fermentation yeast used in their production, Saccharomyces cerevisiae. Where once the role of yeast in fermented beverage flavour was thought to be limited to a small number of volatile esters and higher alcohols, the discovery that wine yeast release highly potent sulfur compounds from non-volatile precursors found in grapes has driven researchers to look more closely at how choice of yeast can influence wine style. This review explores recent progress towards understanding the range of ‘flavour phenotypes’ that wine yeast exhibit, and how this knowledge has been used to develop novel flavour-active yeasts. In addition, emerging opportunities to augment these phenotypes by engineering yeast to produce so-called grape varietal compounds, such as monoterpenoids, will be discussed.Antonio G. Cordente, Christopher D. Curtin, Cristian Varela, Isak S. Pretoriu