Expression of glf sub(Z.m.) ncreases D-mannitol formation in whole cell biotransformation with resting cells of Corynebacterium glutamicum

• Published in: Applied microbiology and biotechnology Vol. 76; no. 3; pp. 545 - 552
• Main Authors: Baeumchen, Carsten, Bringer-Meyer, Stephanie
• Format: Journal Article
• Language: English
• Published: 01.09.2007
• Subjects: Corynebacterium glutamicum; Leuconostoc pseudomesenteroides; Mycobacterium vaccae; Zymomonas mobilis
• ISSN: 0175-7598
• DOI: 10.1007/s00253-007-0987-8

A recombinant oxidation/reduction cycle for the conversion of D-fructose to D-mannitol was established in resting cells of Corynebacterium glutamicum. Whole cells were used as biocatalysts, supplied with 250 mM sodium formate and 500 mM D-fructose at pH 6.5. The mannitol dehydrogenase gene (mdh) from Leuconostoc pseudomesenteroides was overexpressed in strain C. glutamicum ATCC 13032. To ensure sufficient cofactor [nicotinamide adenine dinucleotide (reduced form, NADH)] supply, the fdh gene encoding formate dehydrogenase from Mycobacterium vaccae N10 was coexpressed. The recombinant C. glutamicum cells produced D-mannitol at a constant production rate of 0.22 g (g cdw) super(-1) h super(-1). Expression of the glucose/fructose facilitator gene glf from Zymomonas mobilis in C. glutamicum led to a 5.5-fold increased productivity of 1.25 g (g cdw) super(-1) h super(-1), yielding 87 g l super(-1) D-mannitol from 93.7 g l super(-1) D-fructose. Determination of intracellular NAD(H) concentration during biotransformation showed a constant NAD(H) pool size and a NADH/NAD super(+) ratio of approximately 1. In repetitive fed-batch biotransformation, 285 g l super(-1 )iD-mannitol over a time period of 96 h with an average productivity of 1.0 g (g cdw) super(-1) h super(-1) was formed. These results show that C. glutamicum is a favorable biocatalyst for long-term biotransformation with resting cells.