Enzymatic and metabolic activities in four anaerobic sludges and their impact on methane production from ensiled sorghum forage.

BMP tests were used in order to evaluate the anaerobic digestibility of ensiled sorghum forage. Being a batch test, the BMP assay is strongly dependent on initial conditions especially on the nature of the anaerobic sludge inoculum. The inoculum selection may have a relevant impact on both biomethanization rate an final BMP value after a selected operative digestion time. These aspects can make BMP values difficult to compare. To explain the origin of the observed differences on methane production, BMP tests were run on sorghum forage using four inocula (urban, agricultural, mixture of agricultural and urban, granular sludge) and metabolic and enzymatic activities were measured during the course of BMP tests. Results indicate that lower differences were observed in terms of BMP values with a slight higher value when agricultural sludge was used as inoculum, possibly due to the adaptation of the bacterial consortium to similar agricultural wastes. Significant differences can be observed among different inocula, in terms of biomethanization rate. The fastest biomethanization occurred when using the urban sludge while the slowest one was obtained from the agricultural sludge, in agreement with the observed hydrolytic activities. Differences on the hydrolytic and enzymatic activities are also discussed

Impact of different types of pre-treatment on methane production of two agricultural substrates.

The aim of this study was to compare the effects of different types of pretreatment (thermal, alkaline, enzymatic and combination of them) on chemical composition and anaerobic biodegradability of ensiled sorghum forage and wheat straw. All the pre-treatments tested led to a solubilisation of fibrous fractions for both substrates. The highest lignin reduction, compared to untreated samples, was found at 100°C with 10% NaOH dosage (53% and 72% for wheat straw and sorghum, respectively). Under this pre-treatment condition a high hemicelluloses reduction yield was also found (63% for both substrates). The highest increase in methane yield (up to 29%), compared to the untreated substrate was observed at 40°C with 10% NaOH for sorghum. As for wheat straw, significant increases in methane yield were observed at 40°C with 10% NaOH (49%), at 100°C with 1-10% NaOH (55 and 75%, respectively), and after enzymatic pretreatment (40%)

Anti-Listeria bacteriocin Sakacin-A: biotechnological and biochemical approaches for high-yield food-grade production

Cases of listeriosis, a serious food-borne infection, increased sharply between 2002 and 2006, and remained constant afterward, with severe illness and a 20% mortality reported. Food exceeding the safety criterion for L. monocytogenes was highest in Ready to Eat fishery products, followed by meat products and by fresh cheeses. Among antimicrobial agents that can be used to reduce food-related risks, bacteriocins are a class of small bacterial peptides with a greater potential. Sakacin-A is a class IIa bacteriocin, produced by the GRAS bacterium Lactobacillus sakei, showing a specific anti-Listeria activity. Its application as food preservative in active packaging - through appropriate devices - may offer many advantages, but requires low production cost and high conversion yield. Two biochemical approaches were followed: the investigation of L. sakei specific nutritional requirements as well as its overexpression and isolation in a food-grade form. HPLC analysis of free aminoacids present into culture supernatant showed arginine to be the only component totally depleted during L. sakei growth and sakacin-A production. Arginine supplementation helps maintaining culture pH levels around 6, thanks to the arginine deaminase pathway. Overexpression of sakacin-A under food-grade requirements was attempted in the GRAS yeast Kluyveromyces lactis. Competent wild-type strain of K. lactis were transformed by employing an integrative plasmid carrying the his-tagged sakacin-A gene optimized for codon-usage. The highest producer clone was select by RT-PCR. Practical applications of sakacin-A need to control the diffusion rate from the packaging to the food. Hydrophobic (polystyrene) and negatively charged (cellulose) nanoparticles are being tested, taking advantage of the amphipathic nature of sakacin-A. Preliminary results show a good adhesiveness of Sakacin-A onto hydrophobic nanoparticles, thus paving the way to the application of this natural antimicrobial in food packaging

Seeing in 3-D With Just One Eye

Humans can perceive depth when viewing with one eye, and even when viewing a two-dimensional picture of a three-dimensional scene. However, viewing a real scene with both eyes produces a more compelling three-dimensional experience of immersive space and tangible solid objects. A widely held belief is that this qualitative visual phenomenon (stereopsis) is a by-product of binocular vision. In the research reported here, we empirically established, for the first time, the qualitative characteristics associated with stereopsis to show that they can occur for static two-dimensional pictures without binocular vision. Critically, we show that stereopsis is a measurable qualitative attribute and that its induction while viewing pictures is not consistent with standard explanations based on depth-cue conflict or the perception of greater depth magnitude. These results challenge the conventional understanding of the underlying cause, variation, and functional role of stereopsis. </jats:p