Undecaprenyl phosphate recycling comes out of age

The recycling of the lipid carrier undecaprenyl-phosphate (Und-P) requires the dephosphorylation of Und-PP, a reaction proposed to occur at the external or periplasmic side of the bacterial cell membrane. In this issue of Molecular Microbiology, experiments based on the analysis of lipopolysaccharide modifications in Escherichia coli demonstrate that the phosphorylation of lipid A at position 1 is catalysed by the membrane enzyme LpxT (formerly YeiU). This enzyme specifically transfers the distal phosphate group from Und-PP to lipid A 1-phosphate to produce lipid A 1-diphosphate. Furthermore, this reaction requires a functionally intact MsbA protein, which catalyses the transfer of lipid A across the membrane, confirming that the LpxT-mediated lipid A modification occurs on the periplasmic side of the membrane. These observations provide a novel and unexpected link between periplasmic lipid A modifications and the Und-PP recycling pathway.

An Escherichia coli undecaprenyl-pyrophosphate phosphatase implicated in undecaprenyl phosphate recycling

Undecaprenyl phosphate (Und-P) is a universal lipid carrier of glycan biosynthetic intermediates for carbohydrate polymers that are exported to the bacterial cell envelope. Und-P arises from the dephosphorylation of undecaprenyl pyrophosphate (Und-PP) molecules produced by de novo synthesis and also from the recycling of released Und-PP after the transfer of the glycan component to other acceptor molecules. The latter reactions take place at the periplasmic side of the plasma membrane, while cytoplasmic enzymes catalyse the de novo synthesis. Four Und-PP pyrophosphatases were recently identified in Escherichia coli. One of these, UppP (formerly BacA), accounts for 75 % of the total cellular Und-PP pyrophosphatase activity and has been suggested to participate in the Und-P de novo synthesis pathway. Unlike UppP, the other three pyrophosphatases (YbjG, YeiU and PgpB) have a typical acid phosphatase motif also found in eukaryotic dolichyl-pyrophosphate-recycling pyrophosphatases. This study shows that double and triple deletion mutants in the genes uppP and ybjG, and uppP, ybjG and yeiU, respectively, are supersensitive to the Und-P de novo biosynthesis inhibitor fosmidomycin. In contrast, single or combined deletions including pgpB have no effect on fosmidomycin supersensitivity. Experimental evidence is also presented that the acid phosphatase motifs of YbjG and YeiU face the periplasmic space. Furthermore, the quadruple deletion mutant DeltauppP-DeltaybjG-DeltayeiU-DeltawaaL has a growth defect and abnormal cell morphology, suggesting that accumulation of unprocessed Und-PP-linked O antigen polysaccharides is toxic for these cells. Together, the results support the notion that YbjG, and to a lesser extent YeiU, exert their enzymic activity on the periplasmic side of the plasma membrane and are implicated in the recycling of periplasmic Und-PP molecules.

The use of recycled demolition aggregate in precast concrete products – Phase III: Concrete pavement flags

A study undertaken at the University of Liverpool has investigated the potential for using construction and demolition waste (C&DW) derived aggregate in the manufacture of a range of precast concrete products, i.e. building and paving blocks and pavement flags. Phase III, which is reported here, investigated
concrete pavement flags. This was subsequent to studies on building and paving blocks. Recycled demolition aggregate can be used to replace newly quarried limestone aggregate, usually used in coarse (6 mm) and fine (4 mm-to-dust) gradings. The first objective was, as was the case with concrete building
and paving blocks, to replicate the process used by industry in fabricating concrete pavement flags in the laboratory. The ‘‘wet’’ casting technique used by industry for making concrete flags requires a very workable mix so that the concrete flows into the mould before it is compressed. Compression squeezes out water from the top as well as the bottom of the mould. This industrial casting procedure was successfully replicated in the laboratory by using an appropriately modified cube crushing machine and a special mould typical of what is used by industry. The mould could be filled outside of the cube crushing machine and then rolled onto a steel frame and into the machine for it to be compressed. The texture and mechanical properties of the laboratory concrete flags were found to be similar to the factory ones. The experimental work involved two main series of tests, i.e. concrete flags made with concrete- and
masonry-derived aggregate. Investigation of flexural strength was required for concrete paving flags. This is different from building blocks and paving blocks which required compressive and tensile splitting strength respectively. Upper levels of replacement with recycled demolition aggregate were determined
that produced similar flexural strength to paving flags made with newly quarried aggregates, without requiring an increase in the cement content. With up to 60% of the coarse or 40% of the fine fractions replaced with concrete-derived aggregates, the target mean flexural strength of 5.0 N/mm2 was still
achieved at the age of 28 days. There was similar detrimental effect by incorporating the fine masonry-derived aggregate. A replacement level of 70% for coarse was found to be satisfactory and also conservative. However, the fine fraction replacement could only be up to 30% and even reduced to 15% when used for mixes where 60% of the coarse fraction was also masonry-derived aggregate.

A streamlined life-cycle assessment and decision tool for used tyres recycling

In order to achieve progress towards sustainable resource management, it is essential to evaluate options for the reuse and recycling of secondary raw materials, in order to provide a robust evidence base for decision makers. This paper presents the research undertaken in the development of a web-based decision-support tool (the used tyres resource efficiency tool) to compare three processing routes for used tyres compared to their existing primary alternatives. Primary data on the energy and material flows for the three routes, and their alternatives were collected and analysed. The methodology used was a streamlined life-cycle assessment (sLCA) approach. Processes included were: car tyre baling against aggregate gabions; car tyre retreading against new car tyres; and car tyre shred used in landfill engineering against primary aggregates. The outputs of the assessment, and web-based tool, were estimates of raw materials used, carbon dioxide emissions and costs. The paper discusses the benefits of carrying out a streamlined LCA and using the outputs of this analysis to develop a decision-support tool. The strengths and weakness of this approach are discussed and future research priorities identified which could facilitate the use of life cycle approaches by designers and practitioners.

Development and application of a multiple linear regression model to consider the impact of weekly waste container capacity on the yield from kerbside recycling programmes

The paper describes the development and application of a multiple linear regression model to identify how the key elements of waste and recycling infrastructure, namely container capacity and frequency of collection affect the yield from municipal kerbside recycling programmes. The overall aim of the research was to gain an understanding of the factors affecting the yield from municipal kerbside recycling programmes in Scotland. The study isolates the principal kerbside collection service offered by 32 councils across Scotland, eliminating those recycling programmes associated with flatted properties or multi occupancies. The results of a regression analysis model has identified three principal factors which explain 80% of the variability in the average yield of the principal dry recyclate services: weekly residual waste capacity, number of materials collected and the weekly recycling capacity. The use of the model has been evaluated and recommendations made on ongoing methodological development and the use of the results in informing the design of kerbside recycling programmes. The authors hope that the research can provide insights for the ongoing development of methods to optimise the design and operation of kerbside recycling programmes.

Chlorobenzenes in rivers draining industrial catchments

Eleven chlorobenzenes (out of a total of 12 in the congener series) were monitored weekly on four industrialized rivers (Aire, Calder, Don and Trent) of the Southern Humber Catchment in whole water samples. 1,2- and 1,4-dichlorobenzene were present at relatively high levels on both the Aire and Calder, having mean concentrations of approximately 30 ng/l. They were both at lower concentrations on the Don and Trent, although the 1,4-isomer dominated. All other chlorobenzenes monitored were routinely found on all the rivers, with the exception of hexachlorobenzene, which was only regularly detected on the Trent. Again, the rivers fell into two classes with respect to their total chlorobenzene concentrations, with the Aire and Calder being more polluted. The higher levels of chlorobenzenes (excluding hexachlorobenzene which was used widely as a agricultural pesticide) on the Aire and Calder, and the dominance of the 1,4-dichlorobenzene congener (accounting for 60-70% of sigma chlorobenzenes) on the Don and Trent, indicated that the Aire and Calder were predominately contaminated with chlorobenzenes through industrial sources, while the Don and Trent were mainly contaminated through domestic sources (1,4-dichlorobenzene is widely used as a toilet deodorant). 1,4-Dichlorobenzene dominated flux, with the Aire, Don and Trent exporting 52.5 kg/year into the Humber estuary, followed by the 1,2-dichlorobenzene at 38.8 kg/year. Sigma chlorobenzenes exported to the Humber was 133 kg/year. This is the first study to calculate chlorobenzene fluxes to the North Sea from a UK catchment.

Inscribing value on business model innovations: Insights from industrial projects commercializing disruptive digital innovations

In this paper we seek to show how marketing activities inscribe value on business model innovation, representative of an act, or sequence of socially interconnecting acts. Theoretically we ask two interlinked questions: (1) how can value inscriptions contribute to business model innovations? (2) how can marketing activities support the inscription of value on business model innovations? Semi-structured in-depth interviews were conducted with the thirty-seven members from across four industrial projects commercializing disruptive digital innovations. Various individuals from a diverse range of firms are shown to cast relevant components of their agency and knowledge on business model innovations through negotiation as an ongoing social process. Value inscription is mutually constituted from the marketing activities, interactions and negotiations of multiple project members across firms and functions to counter destabilizing forces and tensions arising from the commercialization of disruptive digital innovations. This contributes to recent conceptual thinking in the industrial marketing literature, which views business models as situated within dynamic business networks and a context-led evolutionary process. A contribution is also made to debate in the marketing literature around marketing's boundary-spanning role, with marketing activities shown to span and navigate across functions and firms in supporting value inscriptions on business model innovations.