13Polyhydroxyalkanoates (PHAs) are bioplastics that can replace conventional 14 petroleum derived products in various applications. One of the major barriers for 15 their widespread introduction in the market is the higher production costs when 16 compared with their petrochemical counterparts. In this work, a process was 17 successfully implemented with high productivity based on wheat straw, a cheap 18 and readily available agricultural residue, as raw material. The strain 19Burkholderia sacchari DSM 17165 which is able to metabolize glucose, xylose 20 and arabinose, the main sugars present in wheat straw hydrolysates (WSH), 21 was used. Results in shake flask showed that B. sacchari cells accumulated ca 22 * Corresponding author. Tel.: +351 21 8419137; fax: +351 21 8419062.e-mail address: teresa.cesario@ist.utl.pt 2 70 % g P(3HB)/g cell-dry-weight with a yield of polymer on sugars (Y P/S ) of 0.18 23 g/g when grown on a mixture of commercial C6 and C5 sugars (control), while 24 these values reached ca 60 % g P(3HB)/g cell-dry-weight and 0.19 g/g, 25 respectively, when WSHs were used as carbon source. In fed-batch cultures 26 carried out in 2L stirred tank reactors on WSH, a maximum polymer 27 concentration of 105 g/L was reached after 61 h of cultivation corresponding to 28 an accumulation of 72% of CDW. Polymer yield and productivity were 0.22 g 29 P(3HB)/g total sugar consumed and 1.6 g/L . h, respectively. The selected 30 feeding strategy successfully overcame the carbon catabolite repression 31 phenomenon observed in sugar mixtures containing hexoses and pentoses. 32 This is the first work describing fed-batch cultivations aiming at PHA production 33 using real lignocellulosic hydrolysates. Additionally, the P(3HB) volumetric 34 productivities attained are, by far, the highest achieved ever on agricultural 35 wastes hydrolysates. 36
Keywords 37Wheat straw hydrolysates ; poly 3-hydroxybutyrate; Burkholderia sacchari; carbon
This paper focuses on the commodification processes and the aestheticization practices that shape gated communities and on the way these are connected to their segregational dimension, which is illustrated through the case of the Lisbon Metropolitan Area (LMA). First, I discuss the (increasing) aestheticization of commodities, emphasising some of the more problematic theoretical issues it involves. Following this discussion I present and analyse the 'Lisbon case'. I provide a brief overview of gated communities in the LMA and then present and analyse the results obtained through a content analysis of LMA gated community advertisements and observation of their site semantics as conveyed through general built form, including physical location, planning, architecture, landscaping, and toponymy. I relate these findings to the LMA gated community market characteristics and to the broader prevailing socio-spatial context regarding their emergence.
Efficient production of poly-3-hydroxybutyrate (P(3HB)) based on glucose-xylose mixtures simulating different types of lignocellulosic hydrolysate (LCH) was addressed using Burkholderia sacchari, a wild strain capable of metabolizing both sugars and producing P(3HB). Carbon catabolite repression was avoided by maintaining glucose concentration below 10g/L. Xylose concentrations above 30g/L were inhibitory for growth and production. In fed-batch cultivations, pulse size and feed addition rate were controlled in order to reach high productivities and efficient sugar consumptions. High xylose uptake and P(3HB) productivity were attained with glucose-rich mixtures (glucose/xylose ratio in the feed=1.5w/w) using high feeding rates, while with xylose-richer feeds (glucose/xylose=0.8w/w), a lower feeding rate is a robust strategy to avoid xylose build-up in the medium. Xylitol production was observed with xylose concentrations in the medium above 30-40g/L. With sugar mixtures featuring even lower glucose/xylose ratios, i.e. xylose-richer feeds (glucose/xylose=0.5), xylonic acid (a second byproduct) was produced. This is the first report of the ability of Burkholderia sacchari to produce both xylitol and xylonic acid.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.