1. Biological Systems Engineering Department; Virginia Tech; 304 Seitz Hall Blacksburg Virginia 24061 USA
2. Department of Biochemistry and Molecular Biology; University of Georgia; Athens GA 30602 USA
3. Tianjin Institute of Industrial Biotechnology; Chinese Academy of Sciences; 32 West 7th Avenue, Tianjin Airport Economic Area Tianjin 300308 P. R. China