RESUMO
Manipulation of multiple genes is a common experience in metabolic engineering and synthetic biology studies. Chromosome integration of multiple genes in one single position is always performed, however, there is so far no study on the integration of multiple genes separately in various positions (here in after referred to as "scattered integration") and its effect on fine-tuning of cellular metabolism. In this study, scattered integration of the xylose assimilation genes PsXR, PsXDH and ScXK was investigated in Saccharomyces cerevisiae, and transcription analysis of these genes as well as their enzyme activities were compared with those observed when the genes were integrated into one single site (defined as "tandem integration" here). Not only notable differences in transcription levels and enzyme activities were observed when the genes were integrated by the two strategies, but also change of the cofactor preference of PsXR gene was validated. Xylose fermentation was further studied with the strains developed with these strategies, and elevated xylose utilization rate was obtained in the scattered integration strain. These results proved that by positioning multiple genes on different chromosomes, fine-tuning of cellular metabolism could be achieved in recombinant S. cerevisiae.
Assuntos
Aldeído Redutase/genética , D-Xilulose Redutase/genética , Engenharia Metabólica/métodos , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Xilose/metabolismo , Aldeído Redutase/biossíntese , Cromossomos Fúngicos/genética , D-Xilulose Redutase/biossíntese , Eletroporação , Fermentação , Fosfotransferases (Aceptor do Grupo Álcool)/biossíntese , Pichia/enzimologia , Pichia/genética , Saccharomyces cerevisiae/enzimologiaRESUMO
The influence of zirconia polymorphs on methanol adsorption was investigated by FTIR technique. One terminal and two types of bridged methoxyl were formed on the am-ZrO2 and t-ZrO2 samples, while another tribridged methoxyl species was detected on the m-ZrO2 sample. During the formation of methoxyl, bridged hydroxyl species on the am-ZrO2 and m-ZrO2 was more active, while the terminal one on the t-ZrO2 sample was more active. The methoxyl was oxygenated by surface oxygen ions to be formate and further to be carbonate on the m-ZrO2 and am-ZrO2 samples. But for t-ZrO2, methoxyl could be directly oxygenated to be carbonate at RT, which implied that the surface oxygen ions on t-ZrO2 were more active than those on the two other samples.
