Biotransformation of Isobutyraldehyde to Isobutanol by an Engineered Escherichia coli Strain

Abstract

Introduction: Biotransformation process has been used in various industries due to its ability to produce valuable chemicals and address environmental concerns. Propylene hydroformylation is a process in which n-butyraldehyde and isobutyraldehyde are produced. N-butyraldehyde is a high valuable chemical with many industrial applications, while isobutyraldehyde produced as a by-product is an environmental pollutant. This study offers a biotechnological approach for conversion of isobutyraldehyde into a high-value substance. An engineered strain of Escherichia coli was developed by genomic insertion of alcohol-dehydrogenase gene (adhA) from Lactococcus lactis which can convert isobutyraldehyde into isobutanol. Materials and Methods: The adhA gene was engineered to substitute some of its amino acids to result in a more efficient enzyme. Engineered gene was synthesized and introduced into E. coli genome to develop recombinant E. coli EG-296 strain. In addition, by using the Qualiteck-4 software, 16 well-defined experiments (L16 Orthogonal array) with two levels of seven variable parameters were used to optimize the process efficiency. Results: The findings of this study revealed that the E. coli strain EG-296 is capable of converting isobutyraldehyde into isobutanol. The optimization results showed that optimum medium composition for the highest isobutanol production were 10 g/L glucose or glycerol as carbon source, 10 g/L NH4CL as nitrogen source, mid-log of inoculum age, and 1% inoculum volume in 25ml medium. After optimization, 560 mg/L isobutanol was produced from 600 mg/L isobutyraldehyde with 91% yield. Conclusions: Recombinant E. coli strain with a relatively optimum medium can be used to remove isobutyraldehyde in refineries or other industries producing this chemical as a by-product.