Authors

T. Maeda; G. Vardar; W. T. Self;T. K. Wood

Comments

Authors: contact us about adding a copy of your work at STARS@ucf.edu

Abbreviated Journal Title

BMC Biotechnol.

Keywords

DIAPHORASE SUBUNIT HOXU; BIDIRECTIONAL HYDROGENASE; GENE-EXPRESSION; RHODOPSEUDOMONAS-PALUSTRIS; ENTEROBACTER-AEROGENES; FUNCTIONAL-ANALYSIS; BIOFILM FORMATION; K-12; OPERON; TRANSCRIPTION; Biotechnology & Applied Microbiology

Abstract

Background: Molecular hydrogen is an environmentally- clean fuel and the reversible ( bidirectional) hydrogenase of the cyanobacterium Synechocystis sp. PCC 6803 as well as the native Escherichia coli hydrogenase 3 hold great promise for hydrogen generation. These enzymes perform the simple reaction 2H(+) + 2e-. H-2 ( g). Results: Hydrogen yields were enhanced up to 41- fold by cloning the bidirectional hydrogenase ( encoded by hoxEFUYH) from the cyanobacterium into E. coli. Using an optimized medium, E. coli cells expressing hoxEFUYH also produced twice as much hydrogen as the well- studied Enterobacter aerogenes HU- 101, and hydrogen gas bubbles are clearly visible from the cultures. Overexpression of HoxU alone ( small diaphorase subunit) accounts for 43% of the additional hydrogen produced by HoxEFUYH. In addition, hydrogen production in E. coli mutants with defects in the native formate hydrogenlyase system show that the cyanobacterial hydrogenase depends on both the native E. coli hydrogenase 3 as well as on its maturation proteins. Hydrogen absorption by cells expressing hoxEFUYH was up to 10 times lower than cells which lack the cloned cyanobacterial hydrogenase; hence, the enhanced hydrogen production in the presence of hoxEFUYH is due to inhibition of hydrogen uptake activity in E. coli. Hydrogen uptake by cells expressing hoxEFUYH was suppressed in three wild- type strains and in two hycE mutants but not in a double mutant defective in hydrogenase 1 and hydrogenase 2; hence, the active cyanobacterial locus suppresses hydrogen uptake by hydrogenase 1 and hydrogenase 2 but not by hydrogenase 3. Differential gene expression indicated that overexpression of HoxEFUYH does not alter expression of the native E. coli hydrogenase system; instead, biofilm- related genes are differentially regulated by expression of the cyanobacterial enzymes which resulted in 2- fold elevated biofilm formation. This appears to be the first enhanced hydrogen production by cloning a cyanobacterial enzyme into a heterologous host. Conclusion: Enhanced hydrogen production in E. coli cells expressing the cyanobacterial HoxEFUYH is by inhibiting hydrogen uptake of both hydrogenase 1 and hydrogenase 2.

Journal Title

Bmc Biotechnology

Volume

7

Publication Date

1-1-2007

Document Type

Article

Language

English

First Page

12

WOS Identifier

WOS:000247751100001

ISSN

1472-6750

Download

Share

COinS