Cloning, characterization and expression of sesquiterpene synthase genes involved in the production of agarwood aromatic compounds in microbial system

Abstract

Aquilaria malaccensis or locally known as karas, is a tropical woody tree that is capable of producing agarwood which is valued for its aromatic properties. Agarwood is widely used as incense in rituals and in cosmetics especially in perfumery industry. Generally, natural plant extracts containing fragrances (inclusive of agarwood essential oil) are expensive and scarce in nature. It is therefore hypothesized that metabolic engineering could overcome this problem by enabling the transfer of the secondary metabolites biosynthetic pathway either partially or completely from the origin into host such as bacteria to produce the target compounds at desired titres. Hence, this study was carried out to profile the volatiles in agarwood, to determine the olfactory active compounds, to isolate the particular sesquiterpene synthase genes responsible for its aroma and finally to produce the aromatic compounds in Escherichia coli using metabolic engineering approach. The hydrodistillation derived essential oil of agarwood from this study was found to be of abundance in sesquiterpene and aromatic compounds (80.61% in total), similar to the results from solid phase micro extraction (SPME) that yields 86.94 %. Among the major sesquiterpene constituent in the essential oil includes α-cadinol (19.40 %) and 10-epi-γ-eudesmol (13.39 %) whereas α-humulene (13.33 %), α-copaene (12.49 %), and δ-guaiene (10.41 %) predominates in the SPME extract.