Enzymatic Treatment of Selected Pesticides in Aqueous System

Widely applied pesticides have been detected in water bodies, which threatens the environment and non-target life. Thus, a promising treatment method, soybean peroxidase (SBP)-catalyzed process was studied to remove two halogenated benzonitrile pesticides Bromoxynil and Ioxynil through enzymatic oxidation from synthetic wastewater. SBP can be extracted from soybean hulls, a by-product of the soybean industry. First, the experiments studied the viability of SBP-catalyzed removal on these two compounds, then the operational parameters including pH, the molar ratio between hydrogen peroxide and substrate and minimum effective enzyme concentration were optimized. The first-order rate constant and half-life of each substrate were also determined under the established optimum conditions. The results demonstrated SBP is robust enzyme to achieve more than 95% removal efficiency for both compounds. In addition, the possible oligomeric products after enzymatic treatment were characterized by mass spectrometry and both dehalogenation and hydroxylation were observed after the reaction

Insights into the enzymatic degradation of mannan (in situ) and pectin utilization by Bacteroides thetaiotaomicron

PhD ThesisThe cell walls of plants are extremely complex and dynamic, and serve as the most abundant organic carbon source on the planet. These cell walls represent a potential alternative to fossil substrate for several industries such as the biofuel and chemical sectors. Plant cell walls also represent a significant nutrient for the microorganisms that inhabit the human distal gut. Understanding how the plant cell wall is degraded by microbial enzymes is critical to the industrial use of these composite structures, but also in the design of human promoting novel pre- and probiotics. In this thesis work is described that has analysed the importance of non-catalytic carbohydrate binding modules (CBMs) in the enzymatic degradation of -mannanas in plant cell walls, and the mechanism by which complex pectins are utilized by gut bacteria. Plant cell wall degrading enzymes often contain one or more CBMs. Work presented in this thesis evaluated the contribution of the specificities displayed by the catalytic modules and CBMs of endo-1,4-mannanases (mannanases) and esterases, to the enzymatic degradation of intact plant cell walls of both Nicotiana tabacum (tobacco) and Physcomitrella patens (moss). The data showed that CBMs greatly potentiated the activity of mannanases and esterases against intact plant cell walls. The cellulose and mannan binding CBMs have the greatest impact on the removal of mannan from tobacco and Physcomitrella cell walls, respectively. Finally, rather than improving the efficiency of mannan degradation by promoting enzyme substrate proximity, CBM32, which binds to the non-reducing end of mannan chains, enhanced the hydrolytic activity of a mannanase by preventing transglycosylation reactions. This work provides insights into the biological significance in vivo for the complex array of hydrolytic enzymes expressed by plant cell wall degrading organisms. Chapter 4 and 5 focused on the mechanism by which a prominent human gut bacterium, Bacteroides thetaiotaomicron, degraded the complex pectins rhamnogalacturonan I (RGI) and rhamnogalacturonan II (RGII). RGII is particularly complex consisting of 13 different monosaccharides and over 20 linkages and is believed to be highly resistant to microbial digestion. In this study proteins encoded by the RGI and RGII utilization loci of B. thetaiotaomicron were expressed in Escherichia coli, and their activity against RGI and RGII were assessed. With respect to RGII BT1010 was shown to be an -L-galactosidase that removes the terminal sugar on chain A. BT3662is an -L-arabinofuranosidase that hydrolysed the -1,3-linkage between arabinofuranosyl units and the polygalacturonic acid backbone. Both enzymes displayed novel activities for their respective CAZy families, GH95 (BT1010) and GH43 (BT3662). With respect to RGI a model for the complete depolymerization of the polysaccharide was generated. Briefly, the enzyme consortium that degraded the GalA-Rha backbone included three rhamnogalacturonan lyases and four glycoside hydrolases; two GH105 4,5unsaturated rhamnogalacturonase, a rhamnosidase and an RGI-specific galacturonosidase. The kinetic parameters of the lyases and GH105 enzymes revealed distinct but complementary specificities. The short galactan side chains remaining after endo-galactanase attack were removed by three -galactosidases. The model is completed by the identification of an esterase that was shown to play an important role in the capacity of the lyases and glycoside hydrolases to access the RGI backbone. Whole cell assays showed that significant RGI degradation occurred on the bacterial surface and unsaturated tetrasaccharides induced the expression of the RGI degrading enzymes. The data presented in this thesis underpins the use of CBMs in the industrial utilization of integral cell wall polysaccharides, while the data presented for pectin degradation by a prominent gut bacterium identifies opportunities for developing novel functional foods

PROTECTING PRIVATE PROPERTY IN CHINA - WHOSE PROPERTY?

The importance of protecting private property in China has now ascended to the same level as that of safeguarding public assets which has traditionally been a top priority for socialist nations. This article will firstly and heavily expound on the rationale behind the availability and at certain times the marginalisation of protecting private property de jure and de facto during some momentous stages in modern Chinese history. It will then touch on a lingering problem relevant to today’s Chinese society arising from the drainage of state assets, a phenomenon having occurred in the transformation process of China’s economic regimes over the most recent decades. It finally argues that while protecting the right to lawful private property is not a matter in dispute, pursuing the protection of private property shall in no way lead to the weakening of sticking to the core value of justice and egalitarianism, a key to ensuring a sound socialist institution

Nonlinear Aeroelasticity and Active Control of Airfoils Subjected to Gusts

In this thesis, the coupling effects of structural nonlinearities and a gust input on the aeroelastic behaviour of an airfoil are studied, and an adaptive controller which is effective for suppressing limit-cycle oscillations (LCOs) is designed. The dynamics of the airfoil are approximated via two- (pitch and plunge) and three-degree-of-freedom (pitch, plunge and flap) models. Different types of structural nonlinearities, such as free-play and hysteresis are considered in the modelling. The nonlinear dynamics is analyzed based on time history, power spectral density (PSD), phase-plane, and Poincar\'{e} section plots, along with the estimation of the dominant Lyapunov exponent for the chaotic-like motion. It is found that free-play and hysteresis nonlinearities may considerably reduce the critical flow velocity compared to the linear system. The dynamic responses of the nonlinear system to sharp-edged and 1-cosine gust profiles are obtained at different flow velocities and compared to those of the system with no gust input. In addition, basin of attraction is plotted to show the stability boundary of the system subjected to a sharp-edged gust with various amplitudes. It is discussed that as the gust becomes stronger, the likelihood of the occurrence of LCO increases. Based on the nonlinear model with a control surface, the suppression of LCO is studied. Without uncertainties, a PD controller together with a partial feedback linearized controller can effectively alleviate oscillations due to gusts and structural nonlinearities. Considering some uncertain structural parameters, an adaptive controller with estimation parameter update law is further designed to stabilize the system. A Lyapunov function is constructed and utilized to prove the stability of the system

Eliminating Privileges Enjoyed by Foreign Investors in China: Rationality and Ramifications Under a Unified Tax Code

The enterprise income tax law in China has for a long time been characterized by the co-existence of two tax codes applied to foreign investment enterprises and indigenous enterprises respectively. Tax privileges granted to foreign investors give rise to the inequality of tax treatment among enterprises in the country. Under the newly released Enterprise Income Tax Law, a unified tax code is to be applied to all enterprises alike, and tax impetus is no longer reserved for foreign investors. This is a move towards developing a platform on which all enterprises in China can compete equally in terms of taxation. A way forward is contemplated over integrating current laws on foreign investment enterprises into the general domain of the commercial law regime, in order that those mutually exclusive legal regulations presently applied to foreign investment enterprises and their local counterparts can eventually be unified in the same way as in the field of taxation

Contemplating privatisation of China's rural land ownership

Associate Professor Xiaoyang Zhang summarises the debate over the pros and cons of privatising rural land ownership in China, setting out the arguments for and against privatisation and outlining the Chinese government’s position