Ph. D., Huazhong Agricultural University

   

Office:     311B Life Sciences Building

Phone:   1-419-372-4645

Email:     zxu@bgsu.edu

   

Research:

Microbial genetics; biotechnology

   

Personal Page: http://personal.bgsu.edu/~zxu/

Research Interests:

Microorganisms represent the major portion of biomass on Earth with enormous diversity in morphology, genetics, and metabolism, which implies huge application potentials. We are interested in using genetic, biochemical, and photochemical approaches to develop microbial systems that can be applied to environmental processes, such as remediation of hazardous substances, development of detection or monitoring systems, and production of high value products from agricultural or industrial by-products or wastes. Currently, we are focusing on the following projects:

1. Genetic engineering of the surface layer (S-layer) protein RsaA of Caulobacter crescentus for heavy metal retrieval. Caulobacter crescentus is a harmless dimorphic bacterium widely found in aquatic environments. In common with many other prokaryotic organisms, Caulobacter cells are coated with an orderly structured S-layer, which is composed of identical subunits of protein or glycoprotein. Because of their external location and crystalline arrangement, S-layer proteins become ideal carriers to display foreign peptides on the surface of a host cell, allowing us to build remediation bioreactors with heavy metal removal capacity or to fabricate nano-scale constructs for photodegradation of organic pollutants.

2. Site-directed mutagenesis of bacterial sensory rhodopsin for wanted optical properties. In Anabaena (Nostoc) sp. PCC7120, the light sensory rhodopsin ASR is responsible for sensing green light and activating a cascade of light-sensitive reactions in the cell body. In this project, we aim to generate ASR mutants that can absorb light at different wavelengths. The application of the results can be foreseen in a variety of aspects, such as development of molecular light switches in nanotechnology and light-induced gene expression in biotechnology. This project is in collaboration with Dr. Massimo Olivucci at the BGSU Department of Chemistry.

3. Genetic modification of cellulases to improve the enzyme catalytic efficiency, thermostability, and substrate specificity or stereoselectivity. Due to global energy crisis, developing renewable forms of energy like hydro, solar and bio-energy has become increasingly important. Energy from biomass has a promising future because it ensures self-reliance through the use of local resources with simple technologies and less production hazards. This project aims to utilize genetic tools to facilitate the hydrolysis of cellulose, which becomes useful as a food and energy source once it is broken down into soluble cellobiose (β-1,4 glucose dimer) and glucose.

Selected Publications:

Patel J, Zhang Q, McKay RML, Vincent R, Xu Z. 2009. Genetic engineering of Caulobacter crescentus for removal of cadmium from water. Applied Biochemistry and Biotechnology. DOI 10.1007/s12010-009-8540-0.

Zhang Q, Sun M, Xu Z, Yu Z. 2007. Cloning and characterization of pBMB9741, a native plasmid of Bacillus thuringiensis subsp. kurstaki strain YBT-1520. Current Microbiology. 55: 302-7.

Dutton R.J., Z. Xu and J.W. Gober. 2005. Linking structural assembly to gene expression: a novel mechanism for regulating the activity of a σ54 transcription factor. Molecular Microbiology. 58 (3): 743-757.

Xu Z., B. Yao, M. Sun and Z Yu. 2004. Protection of mice infected with Plasmodium berghei by Bacillus thuringiensis crystal proteins. Parasitology Research, 92(1): 53-57.

Xu Z., A. Mulchandani and W. Chen. 2003. Detection of benzene, toluene, ethyl benzene and xylenes (BTEX) using toluene dioxygenase-peroxidase coupling reactions. Biotechnology Progress. 19: 1812-1815.

Lee S.Y., J.H. Choi and Z. Xu. 2003. Microbial cell surface display. Trends in Biotechnology, 12(1): 45-52.

Xu Z., W. Bae, A. Mulchandani, R.K. Mehra and W. Chen. 2002. Heavy metal removal by novel CBD-EC20 sorbents immobilized on cellulose. Biomacromolecules, 3:462-465.

Lee S.Y., Z. Xu, and J.H. Choi. 2001. Expression vectors encoding Escherichia coli OmpC as a cell surface anchoring motif. US Patent: US 6: 274,345.

Xu Z., S.Y. Lee and Z. Yu. 1999. Physiological characteristics of recombinant E. coli cells displaying poly-His peptides. Biotechnology Letters, 21: 1091-1094.

Xu Z., and S.Y. Lee. 1999. Display of polyhistidine peptides on the Escherichia coli cell surface by using outer membrane protein C as an anchoring motif. Applied and Environmental Microbiology, 65: 5142-5147.