Synthesis of oxo-fatty acid esters in a whole cell cascade reaction with engineered monooxygenase (P450 BM3) and dehydrogenase (cpADH5) variants

Hydroxyl or ketone functionalized fatty acid methyl esters are important compounds for production of pharmaceuticals, cosmetics or dietary supplements. For instance, 3-hydroxyhexanoate or its methyl ester is used in the synthesis of laulimalide which is an anticancer drug. Biocatalysis through enzymatic cascades has drawn attention for the development of more efficient, sustainable, and greener synthetic processes to produce complex valuable chemical compounds. Furthermore, whole cell catalysts which employs enzyme cascade offers important advantageous over classical chemical catalysis and enzyme based biotransformation such as; cofactor regeneration by the cell metabolism, omission of protein purification steps and increased enzymes. In this thesis, a whole cell catalyst which includes a P450 BM3 and cpADH5 coupled cascade reaction was developed for the synthesis of hydroxy- or keto- fatty acid methyl esters, which is a greener route for production. P450 BM3 monooxygenase from Bacillus subtilis and alcohol dehydrogenase from Candida parapsilosis (cpADH5) are powerful enzymes and have been used for the synthesis of many industrially relevant compounds. However, P450 BM3 and cpADH5 poorly accept fatty acid methyl esters and hydroxy-fatty acid methyl esters as substrate respectively. P450 BM3 and cpADH5 enzymes were engineered in order to enable the conversion of methyl hexanoate by P450 BM3 and methyl 3-hydroxyhexanoate by cpADH5. In chapter I, the directed evolution of P450 BM3 was performed by employing the KnowVolution approach. The P450 BM3 YE_M1_2 variant exhibited boosted performance toward methyl hexanoate. Initial oxidation rate of YE_M1_2 toward methyl hexanoate was determined to be 32 fold higher when compared to WT enzyme. Furthermore, 1.5 fold increased methyl 3-hydroxyhexanoate production was obtained with YE_M1_2 variant (YE_M1_2; 2.75 mM and WT; 1.8 mM). In addition, a second improved P450 BM3 variant named as YE_M3_1 showed 5.4 fold improved initial oxidation rate (YE_M3_1; 1085 min-1 and WT; 146 ...