Comparison of CO-dependent H2 production with strong promoters in Thermococcus onnurineus NA1
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To overproduce biotechnologically valuable products, the expression level of target genes has been modulated by using strong promoters. In a hyperthermophilic archaeon Thermococcus onnurineus NA1, two promoters, P TN0413 and P TN0157 , which drive expression of the genes encoding the S-layer protein and glutamate dehydrogenase were inserted in front of a gene cluster encoding a carbon monoxide dehydrogenase, a hydrogenase and a Na+/H+ antiporter. Two promoters exhibited strong activity by increasing the transcription and translation levels of the gene cluster in the mutant strains by 2.5- to 49-folds and 1.4- to 3.3-folds, respectively, than the native promoter in the wild-type strain. While KS0413 with P TN0413 promoter exhibited 2.7 to 4.7 times higher transcript level than KS0157 with P TN0157 promoter, the levels of proteins were a little different between them. The biomass concentrations and H2 production rates of two mutants were 2- to 3-fold higher than those of the wild-type strain in a bioreactor where CO was supplied at a flow rate of 120 ml min−1. Two mutants showed differential response to the higher CO flow rate, 240 ml min−1, in terms of growth pattern and product formation, indicating two promoters were regulated by culture conditions. The results demonstrate that not only promoter strength but also product-forming conditions should be considered in promoter engineering.
KeywordsStrong promoter Hyperthermophilic archaeon Carbon monoxide H2 production
This work was supported by the KIOST in-house program, the Marine and Extreme Genome Research Centre, and the Development of Biohydrogen Production Technology Using the Hyperthermophilic Archaea Program of the Ministry of Oceans and Fisheries in the Republic of South Korea.
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