Compost Pile Monitoring Using Different Approaches:GC-MS, E-nose and dynamic olfactometry

peer reviewedThe evaluation of odour emissions associated to the composting process is complex because these emissions depend on several factors such as the raw material to be composted, the different stages of the composting process, meteorological conditions, and others. For this reason, the aim of this paper is to compare complementary approaches to monitor odours. The odour source selected for this study is green waste compost at different maturity stages. The study site is a composting facility located in the south of Belgium. The compared approaches were: a portable e-nose developed by the Environmental Monitoring Research team (Arlon, Belgium) to monitor odorous emissions from the composting piles; chemical analyses performed in the laboratory using a GC–MS (manufactured by Thermo) to analyse volatile organic compounds which were collected by active sampling on Tenax TA sorbent simultaneously to the in situ e-nose measurements and olfactometric measurements to determine the odour concentration (ouE/m3) using the Odile olfactometer (Odotech). The portable e-nose was also used in the laboratory with compost odour samples collected in bags. The large numbers of data sets obtained were explored by statistical methods such as principal components analysis. The results obtained highlight the advantages of monitoring the composting process with these three approaches. Each approach gives different information about the composting process and the emissions generated. While the e-nose is capable of identifying some chemical family emissions and some activities such as turning steps, the GC–MS identifies each chemical compound emitted and dynamic olfactometry quantifies the odour concentration (ouE/m3) in relationship with these emissions

Distinct Prion Domain Sequences Ensure Efficient Amyloid Propagation by Promoting Chaperone Binding or Processing <i>In Vivo</i>

<div><p>Prions are a group of proteins that can adopt a spectrum of metastable conformations <i>in vivo</i>. These alternative states change protein function and are self-replicating and transmissible, creating protein-based elements of inheritance and infectivity. Prion conformational flexibility is encoded in the amino acid composition and sequence of the protein, which dictate its ability not only to form an ordered aggregate known as amyloid but also to maintain and transmit this structure <i>in vivo</i>. But, while we can effectively predict amyloid propensity <i>in vitro</i>, the mechanism by which sequence elements promote prion propagation <i>in vivo</i> remains unclear. In yeast, propagation of the [<i>PSI</i>^<i>+</i>] prion, the amyloid form of the Sup35 protein, has been linked to an oligopeptide repeat region of the protein. Here, we demonstrate that this region is composed of separable functional elements, the repeats themselves and a repeat proximal region, which are both required for efficient prion propagation. Changes in the numbers of these elements do not alter the physical properties of Sup35 amyloid, but their presence promotes amyloid fragmentation, and therefore maintenance, by molecular chaperones. Rather than acting redundantly, our observations suggest that these sequence elements make complementary contributions to prion propagation, with the repeat proximal region promoting chaperone binding to and the repeats promoting chaperone processing of Sup35 amyloid.</p></div