Paracoccus sp. Strain LL1 as a Single Cell Factory for the Conversion of Waste Cooking Oil to Polyhydroxyalkanoates and Carotenoids

Background and objective: Polyhydroxyalkanoates have drawn significant attention as alternative to petroleum-based plastics; however, their industrial production is still hindered by the costly feed materials. Co-generation of other high-value products in addition to polyhydroxyalkanoate by the same microbial strains can be helpful in alleviating overall production cost up to 50%. This study for the first time demonstrates that polyhydroxyalkanoate and astaxanthin-rich carotenoids can be co-produced by Paracoccus sp. LL1 using waste cooking oil as substrate.Material and methods: The halophilic strain of Paracoccus sp. LL1 was grown under batch fermentation using mineral media supplemented with 1% (v v-1) waste cooking oil. Different surfactants were used to improve substrate utilization. Polyhydroxyalkanoate obtained after the fermentation was characterized by fluorescent microscopy, gas chromatography, and Fourier Transform Infra-Red spectroscopy.Results and conclusion: Oil as a substrate, led to 1.0 g l-1 poly (3-hydroxybutyrate-co-3-hydroxyvalerate) with concomitant production of 0.89 mg l-1 of carotenoids after 96 h. An enhancement of 2.7-folds in total cell dry mass was achieved when 0.1% (v v-1) Tween-80 was used as surfactant for ease in oil metabolism. Paracoccus sp. LL1 has the potential to serve as a single cell factory for bioconversion of cheap substrates into high value products.Conflict of interest: The authors declare no conflict of interest

Critical currents for vortex defect motion in superconducting arrays

We study numerically the motion of vortices in two-dimensional arrays of resistively shunted Josephson junctions. An extra vortex is created in the ground states by introducing novel boundary conditions and made mobile by applying external currents. We then measure critical currents and the corresponding pinning energy barriers to vortex motion, which in the unfrustrated case agree well with previous theoretical and experimental findings. In the fully frustrated case our results also give good agreement with experimental ones, in sharp contrast with the existing theoretical prediction. A physical explanation is provided in relation with the vortex motion observed in simulations.Comment: To appear in Physical Review

Spatiotemporal Stochastic Resonance in Fully Frustrated Josephson Ladders

We consider a Josephson-junction ladder in an external magnetic field with half flux quantum per plaquette. When driven by external currents, periodic in time and staggered in space, such a fully frustrated system is found to display spatiotemporal stochastic resonance under the influence of thermal noise. Such resonance behavior is investigated both numerically and analytically, which reveals significant effects of anisotropy and yields rich physics.Comment: 8 pages in two columns, 8 figures, to appear in Phys. Rev.

Dynamic transition and Shapiro-step melting in a frustrated Josephson-junction array

We consider a two-dimensional fully frustrated Josephson-junction array driven by combined direct and alternating currents. Interplay between the mode locking phenomenon, manifested by giant Shapiro steps in the current-voltage characteristics, and the dynamic phase transition is investigated at finite temperatures. Melting of Shapiro steps due to thermal fluctuations is shown to be accompanied by the dynamic phase transition, the universality class of which is also discussed

Precision genome engineering with programmable DNA-nicking enzymes

Zinc finger nucleases (ZFNs) are powerful tools of genome engineering but are limited by their inevitable reliance on error-prone nonhomologous end-joining (NHEJ) repair of DNA double-strand breaks (DSBs), which gives rise to randomly generated, unwanted small insertions or deletions (indels) at both on-target and off-target sites. Here, we present programmable DNA-nicking enzymes (nickases) that produce single-strand breaks (SSBs) or nicks, instead of DSBs, which are repaired by error-free homologous recombination (HR) rather than mutagenic NHEJ. Unlike their corresponding nucleases, zinc finger nickases allow site-specific genome modifications only at the on-target site, without the induction of unwanted indels. We propose that programmable nickases will be of broad utility in research, medicine, and biotechnology, enabling precision genome engineering in any cell or organism.

A STUDY ON THE TWO-ROW EFFECT IN THE SLOSHING PHENOMENON

In this study, changes in fluid impact loads inside a tank were examined according to a two-row tank arrangement in an LNG-FPSO (Liquefied Natural Gas-Floating Production Storage Offloading) vessel. The motion RAO (Response Amplitude Operator) of the LNG-FPSO, coupled with the sloshing phenomenon inside the tank, was calculated by using HydroStar by Bureau Veritas. The motion simulation in the tank was conducted under filling ratios of 30%H, 60%H, and 80%H. The RAO in each condition was calculated according to the one-row and the two-row tank arrangement. The motion response spectrum using the calculated RAO and the JONSWAP (Joint North Sea Wave Analysis Project) spectrum were computed by implementing irregular motion according to each filling ratio and tank arrangement. The sloshing phenomenon inside the tank was implemented by using a 6-DOF (Degree Of Freedom) sloshing motion platform; impact pressure on the walls of the tank was measured with pressure sensors installed inside the tank. The sloshing experiment was conducted under the three filling ratios in the one-row and the two-row tank arrangement and impact loads were compared under each filling ratio according to the one-row and the two-row tank arrangement