Yong-Chang Seo

Enhancement of Lipid Extraction from Marine Microalga, Scenedesmus Associated with High-Pressure Homogenization Process

Marine microalga, Scenedesmus sp., which is known to be suitable for biodiesel production because of its high lipid content, was subjected to the conventional Folch method of lipid extraction combined with high-pressure homogenization pretreatment process at 1200 psi and 35°C. Algal lipid yield was about 24.9% through this process, whereas only 19.8% lipid can be obtained by following a conventional lipid extraction procedure using the solvent, chloroformu2009:u2009methanol (2u2009:u20091, v/v). Present approach requires 30 min process time and a moderate working temperature of 35°C as compared to the conventional extraction method which usually requires >5 hrs and 65°C temperature. It was found that this combined extraction process followed second-order reaction kinetics, which means most of the cellular lipids were extracted during initial periods of extraction, mostly within 30 min. In contrast, during the conventional extraction process, the cellular lipids were slowly and continuously extracted for >5 hrs by following first-order kinetics. Confocal and scanning electron microscopy revealed altered texture of algal biomass pretreated with high-pressure homogenization. These results clearly demonstrate that the Folch method coupled with high-pressure homogenization pretreatment can easily destruct the rigid cell walls of microalgae and release the intact lipids, with minimized extraction time and temperature, both of which are essential for maintaining good quality of the lipids for biodiesel production.

Enhanced Antimicrobial Activity of Nisin-Loaded Liposomal Nanoparticles against Foodborne Pathogens

This study was designed to evaluate the prolonged antimicrobial stability of nisin-loaded liposome (LipoN) nanoparticles against Listeria monocytogenes and Staphylococcus aureus. The sizes of bare liposomes and LipoN were uniformly distributed between 114 and 125 nm. The nanoparticles were homogeneously dispersed in water with less than 0.2 of polydispersity index. The zeta potential value of LipoN was +17.1 mV due to the positive charged nisin, attaining 70% of loading efficiency. The minimum inhibitory concentration of LipoN against L. monocytogenes and S. aureus was 320 international unit/mL. The LipoN significantly enhanced the antimicrobial stability in brain heart infusion agar compared to free nisin. The numbers of L. monocytogenes and S. aureus exposed to LipoN were effectively reduced by more than 6 log colony-forming unit/mL after 48 and 72 h of incubation, respectively. These results provide useful information for the development of antimicrobial delivery system to improve food safety.

Enhancement of Whitening Effects of Lithospermum erythrorhizon Extracts by Ultra High Pressure

In this study, whitening activity of Lithospermum erythrorhizon extracts were investigated according to several extraction processes: water extraction at (WE100) and (WE60), 70% ethyl alcohol extraction (EE) and ultra high pressure extraction (HPE) at 500 MPa for 30 minutes at . The extracts from ultra high pressure extraction showed the highest tyrosinase inhibition and melanogenesis inhibition activities as 52% and 79.5%, respectively, in adding than others extraction processes. HPE extracts also showed the strong reducing power as 3.19 that absorbance at 450 mm. The contents of polyphenol in WE100, we measured as in adding . Extracts have a high total flavonoid contents by HPE as at . We can conclude that better whitening activity of extracts from high pressure extraction was due to high antioxidant activities which could be extracted by higher polyphenol and flavonoid contents in HPE than others.