[1] Tech Univ Carolo Wilhelmina Braunschweig, Inst Microbiol, D-38106 Braunschweig, Germany
[2] Univ Kent, Prot Sci Grp, Dept Biosci, Canterbury CT2 7NJ, Kent, England
[3] Tech Univ Carolo Wilhelmina Braunschweig, Inst Biochem Engn, D-38106 Braunschweig, Germany