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        Evolution of E. coli Phytase for Increased Thermostability Guided by Rational Parameters

        ( Jiadi Li ),( Xinli Li ),( Yuanming Gai ),( Yumei Sun ),( Dawei Zhang ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.3

        Phytases are enzymes that can hydrolyze phytate and its salts into inositol and phosphoric acid, and have been utilized to increase the availability of nutrients in animal feed and mitigate environmental pollution. However, the enzymes’ low thermostability has limited their application during the feed palletization process. In this study, a combination of B-value calculation and protein surface engineering was applied to rationally evolve the heat stability of Escherichia coli phytase. After systematic alignment and mining for homologs of the original phytase from the histidine acid phosphatase family, the two models 1DKL and 1DKQ were chosen and used to identify the B-values and spatial distribution of key amino acid residues. Consequently, thirteen potential amino acid mutation sites were obtained and categorized into six domains to construct mutant libraries. After five rounds of iterative mutation screening, the thermophilic phytase mutant P56214 was finally yielded. Compared with the wild-type, the residual enzyme activity of the mutant increased from 20% to 75% after incubation at 90°C for 5 min. Compared with traditional methods, the rational engineering approach used in this study reduces the screening workload and provides a reference for future applications of phytases as green catalysts.

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        On Deploying Relays for Connected Indoor Sensor Networks

        Yanmin Zhu,Cuiyao Xue,Haibin Cai,Jiadi Yu,Lei Ni,Minglu Li,Bo Li 한국통신학회 2014 Journal of communications and networks Vol.16 No.3

        This paper considers the crucial problem of deployingwireless relays for achieving a connected wireless sensor networkin indoor environments, an important aspect related to the managementof the sensor network. Several algorithms have been proposedfor ensuring full sensing coverage and network connectivity. These algorithms are not applicable to indoor environments becauseof the complexity of indoor environments, in which a radiosignal can be dramatically degraded by obstacles such as walls.Wefirst prove theoretically that the indoor relay placement problem isNP-hard. We then predict the radio coverage of a given relay deploymentin indoor environments. We consider two practical scenarios;wire-connected relays and radio-connected relays. For thenetwork with wire-connected relays, we propose an efficient greedyalgorithmto compute the deployment locations of relays for achievingthe required coverage percentage. This algorithm is proved toprovide a Hn factor approximation to the theoretical optimum,whereHn = 1+ 12 +· · ·+ 1n = ln(n)+1, and n is the number ofall grid points. In the network with radio-connected relays, relayshave to be connected in an ad hoc mode. We then propose an algorithmbased on the previous algorithm for ensuring the connectivityof relays. Experimental results demonstrate that the proposedalgorithms achieve better performance than baseline algorithms.

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