production-chemicals-klebsiella-pneumoniae-using-bamboo-hydrolysate

Production of Chemicals by <em>Klebsiella pneumoniae</em> Using Bamboo Hydrolysate as Feedstock

Bamboo is an important biomass, and bamboo hydrolysate is used by Klebsiella pneumoniae as a feedstock for chemical production. Here, bamboo powder was ...

Chinese Academy of Sciences

Phase effect of the optical duobinary (ODB) modulation on the chromatic dispersion (CD) tolerance is more important than the ODB modulation-induced bandwidth effect. To show this, we evaluate, respectively, the filter bandwidth effect and the phase effect of the partial bit delay correlative modulation (PBDCM) on the CD tolerance. Due to the cancellation between the CD-induced and the PBDCM-induced phase effects, the PBDCM method can increase the CD-limited transmission to 2 ??? 3 times of that using standard 1-bit delay modulation, while the optimized filter bandwidth method can increase the transmission by 50% or less, depending on the input signal format. The PBDCM can be physically realized by adjusting the delay time of the delay-and-add circuit in the conventional duobinary transmitter (without lower-pass filter). These conclusions are also valid for systems having non-negligible polarization-mode dispersion (PMD) and polarization dependent loss (PDL).

Partial bit delay correlative modulation used to improve the dispersion tolerance of an optical duobinary system.

A new analytical evaluation of polarization-induced error probability for optical systems consisting of both PMD and PDL is presented. Using a simplified model containing a lumped PMD-PDL fiber, an amplifier with ASE noise, an idealized optical filter, and an electrical filter with integrate-and-dump response, a closed-form of the probability density of the filtered current is obtained. This allows us to evaluate the BER affected by the PMD and PDL. Based on this, two polarization related effects, i.e., the PMD and PDL directional coupling and the polarization-induced intersymbol interference (ISI), are studied. We show that the PMD and PDL directional coupling can be strongest when the PMD vector perpendicularly correlates with both the PDL vector and the input signal polarization in the 3D Stokes space. Besides, its impact on bit-error-rate (BER) strongly depends on the PDL value. We also find that, for an optical system with realistic parameters, the impact of polarization-induced ISI on the BER is mostly caused by the two closest neighbors of the desired bit. Related with these two polarization effects is the PMD value fluctuation. Large PMD value variation can play an overwhelming role in impairing the optical performance.

Combined PMD-PDL effects on BERs in simplified optical systems: an analytical approach.

New forms using Dirac bra-ket notations and their transformations to express electrically filtered currents are presented for optical systems using either binary differential phase-shift keying (2-DPSK) or ON-OFF keying (OOK) with lumped first-order PMD and PDL, arbitrary optical and electrical filtering and pulse shaping. Based on these forms, the moment generating functions (MGFs) and bit-error-ratios (BERs) for different systems are obtained. Our results show that, for a given BER, 2-DPSK requires ~ 5dB lower input signal-to-noise ratio than OOK. By comparing BERs for different polarization systems, we also show that the PDL-induced partially polarized noise can significantly improve system performance and reduce BER variation caused by the random couplings between signal polarization, PDL and PMD vectors.

Accurate BER evaluation for lumped DPSK and OOK systems with PMD and PDL.

A fourth-order Runge-Kutta in the interaction picture (RK4IP) method is presented for solving the coupled nonlinear Schr odinger equation (CNLSE) that governs the light propagation in optical fibers with randomly varying birefringence. The computational error of RK4IP is caused by the fourth-order Runge-Kutta algorithm, better than the split-step approximation limited by the step size. As a result, the step size of RK4IP can have the same order of magnitude as the dispersion length and/or the nonlinear length of the fiber, provided the birefringence effect is small. For communication fibers with random birefringence, the step size of RK4IP can be orders of magnitude larger than the correlation length and the beating length of the fibers, depending on the interaction between linear and nonlinear effects. Our approach can be applied to the fibers having the general form of local birefringence and treat the Kerr nonlinearity without approximation. Our RK4IP results agree well with those obtained from Manakov-PMD approximation, provided the polarization state can be mixed enough on the Poincar e sphere.

A fourth-order Runge-Kutta in the interaction picture method for numerically solving the coupled nonlinear Schrodinger equation.

In a nonlinear optical fiber communication (OFC) system with signal power much stronger than noise power, the noise field in the fiber can be described by linearized noise equation (LNE). In this case, the noise impact on the system performance can be evaluated by moment-generating function (MGF) method. Many published MGF calculations were based on the LNE using continuous wave (CW) approximation, where the modulated signal needs to be artificially simplified as an unmodulated signal. Results thus obtained should be treated carefully. Reliable results can be obtained by replacing the CW-based LNE with the accurate LNE proposed by Holzlöhner et al in Ref. [1]. In this work we show that, for the case of linearized noise amplified by EDFAs, its MGF can be obtained by calculating the noise propagator directly from the accurate LNE. Our results agree well with the experimental data of multi-span DPSK systems.

Moment-generating function method used to accurately evaluate the impact of the linearized optical noise amplified by EDFAs.

The glucose oxidation pathway is important for glucose catabolism in Klebsiella pneumoniae. Gluconic acid and 2-ketogluconic acid are intermediates of this pathway, and the production of these two chemicals has been developed in K. pneumoniae mutants. Catalysis characteristic research in this study has shown that xylose is a suitable substrate of the glucose dehydrogenase of this pathway. Here, using xylose as substrate, xylonic acid was accumulated in the broth of K. pneumoniae culture, and this process was dependent upon acidic conditions. Using a mixture of glucose and xylose as substrates, a mixture of xylonic acid and gluconic acid was produced by the Δgad mutant of K. pneumoniae; gluconic acid was synthesized early, and xylonic acid synthesis began after most glucose was consumed. Using the hydrolysate of bamboo as substrate, mixture of 33 g/L gluconic acid and 14 g/L xylonic acid were produced by K. pneumoniae Δgad. In fed-batch fermentation, 103 g/L xylonic acid was produced after 79 h culture, with a conversion ratio of 1.11 g/g. This is the first report of xylonic acid produced by K. pneumoniae. Production of xylonic acid and gluconic acid using bamboo hydrolysate is a novel approach for biomass utilization.

Zhongxi Zhang

Lab of Biorefinery,
Shanghai Advanced Research Institute,
Lab of Biorefinery, Shanghai Advanced Research Institute

Chinese Academy of Sciences

Production of Chemicals by Klebsiella pneumoniae Using Bamboo Hydrolysate as Feedstock

Zhongxi Zhang

Lab of Biorefinery,Shanghai Advanced Research Institute,Lab of Biorefinery, Shanghai Advanced Research Institute

Chinese Academy of Sciences

Production of Chemicals by Klebsiella pneumoniae Using Bamboo Hydrolysate as Feedstock

Lab of Biorefinery,
Shanghai Advanced Research Institute,
Lab of Biorefinery, Shanghai Advanced Research Institute