Identification and assessment of the effects of yeast decarboxylases expressed in Escherichia coli for producing higher alcohols.

AIMS: To contribute to the improvement of methods for the regulation and production of higher alcohols using micro-organisms, we assessed the yields achieved using 10 decarboxylase genes from three different yeast species (Saccharomyces cerevisiae, Candida tropicalis and Pichia pastoris) by cloning them into vectors and overexpressing them in Escherichia coli hosts of different genotypes. Genes that produced the greatest yields in higher alcohol production were further assessed for the catalytic effects of the decarboxylase enzymes in the different E. coli hosts.

METHODS AND RESULTS: A major metabolic pathway is structured via overexpressing a series of five genes, to detect the effect of decarboxylase on the production of higher alcohols. Results suggested that these genes can facilitate production of specific types of higher alcohols by diverse types of E. coli. We also showed that they play direct roles in the metabolic pathways that lead to production of higher alcohols in E. coli. The gene ARO10 from S. cerevisiae produced the highest yields for producing isobutanol and isopentanol in the host JM109. Significant differences were found in the types of higher alcohols and yields produced within the same host, for the genes PAD1, GAD1, SPE1 from S. cerevisiae. Similar results were observed for the genes ODC1 and gadB from Candida tropicalis and P. pastoris, respectively.

CONCLUSIONS: Investigation of these genes for identification of the key enzymatic steps or regulatory pathways involved in the Ehrlich metabolic network to produce higher alcohols is paramount for producing biofuels. The selected genes are promising targets for the development of improved production strains.

SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first published assessment of the effects of decarboxylases from different yeast species that were expressed in E. coli, for the production of higher alcohols. Our results provide guidance for future studies about the use of yeast enzymes for transforming or constructing a new metabolic pathway utilizing E. coli for the production of target higher alcohols.