Engineering S. cerevisiae for alkane biosynthesis from aldehyde decarbonylase precursor

• Main Author: Hazarki Yaohari
• Other Authors: Chang Wook, Matthew
• Format: Theses and Dissertations
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Chemical engineering::Biochemical engineering
• Online Access: https://hdl.handle.net/10356/59378
• Institution: Nanyang Technological University

Aldehyde decarbonylase (AD) catalyzes the conversion of aldehyde to alkane. ADs are naturally present in plants, insect or cyanobacteria. Cyanobacterial aldehyde decarbonylase (cAD) is a member of ferritin-like di-iron enzymes that catalyzes the conversion of aldehydes to alkanes and formate in the presence of a reducing system. This cAD enzyme can be utilized to generate a biofuel-producing platform by engineering biological systems to exploit this pathway for alkane synthesis from fatty acyl precursors. This study reports the expression, purification and characterization of two cADs that have not been studied, i.e. cADs from Anabaena variabilis ATCC 29413 (AD1) and Arthrospira platensis str. Paraca (AD2). Both genes which were cloned into Saccharomyces cerevisiae exhibit soluble expression and were subsequently extracted in its native form using a mild detergent, Tween 20, for in vitro characterization. AD1 showed activity towards dodecanal substrate with KM = 3.5±2.9 μM and kcat = 1.4±0.1/h under the phenazine methosulfate (PMS)/NADH reducing system. AD2 has a KM and kcat of 5.0±2.2 μM and 0.9±0.1/min, respectively. When NADH was replaced with NADPH, an electron donor that is abundant inside the cell, the efficiency of the cADs towards dodecanal substrate was compromised, though NADPH can still support the reaction. The activity of a few other decarbonylases from cyanobacteria and insect in vivo were also investigated. The ADs from Synechococcus elongatus (AD3) and Musca domestica (cytochrome P450 decarbonylase CYP4G2-CPR) were successfully cloned into S. cerevisiae and recombinantly expressed. In vivo conversion of a range of exogenous aldehydes fed to the cells expressing these decarbonylases did not yield alkanes. Further investigations involving protein and pathway engineering to improve decarbonylase activity are underway to address this challenge.