Optimization of cellulase-assisted hydrodistillation for Homalomena occulta essential oil: A response surface methodology approach

Species belonging to the genus Homalomena naturally grow in tropical climates, particularly in areas with high humidity, such as the tropical forests of Vietnam. Essential oils extracted from plants in this genus are currently considered to be expensive. This study focused on the rhizome essential oil of Homalomena occulta (Lour.) Schott., collected in Gia Lai province, and aimed to optimize the extraction process through cellulase-assisted hydrodistillation. Using response surface methodology (RSM) with a central composite design (CCD), the study evaluated the effects of three factors—pH level, enzyme concentration, and incubation time—on the extraction yield. The optimal conditions identified were a cellulase concentration of 0.25 % at a pH of 3.5 for an incubation period of 5 h. Under these conditions, there was a three-fold increase in yield (0.321 ± 0.016 %) compared to the control (0.100 ± 0.011 %). When comparing essential oil samples extracted without cellulase to those extracted using cellulase under optimal conditions, it was evident that the oils obtained from cellulase-treated materials had a higher yield without compromising quality. The organoleptic and physical properties remained largely unchanged; the essential oil retained a transparent, pale yellow color and a sweet, fresh aroma. However, the sample from the cellulase-treated material had a stronger woody scent. The physical properties demonstrated minimal variation, with specific gravities of 0.877 ± 0.0026 g/cm³ and 0.888 ± 0.0016 g/cm³ , respectively. The refractive indices were 1.4671 ± 0.00020 and 1.4680 ± 0.00046, while the optical rotation angles changed insignificantly (-10.388 ± 0.3506 vs. −9.271 ± 0.1851). The essential oil from Homalomena remains rich in natural aromatic compounds, including linalool and various oxygenated compounds such as terpinene-4-ol, α-terpineol, epi-α-muurol, and α-cadionol, all of which have biological value and potential applications.