Pressurized liquid extraction of toxins from cyanobacterial cells

Abstract

The suitability of pressurized liquid extraction (PLE) of cyanotoxins from cells was investigated. The stability of cyanotoxins (MCYST-RR, MCYST-LR, and anatoxin-a) was evaluated at nine combinations of pressure and temperature (7,10, and 14 MPa and 60°C, 80°C and 100°C) using 75% (v/v) methanol in water (MeOH) as solvent. Additional experiments investigated the stability of cyanotoxins when water was used as solvent (at a pressure of 14 MPa and a temperature of 40°C, 50°C, 60°C, 80°C, or 100°C). Results using 75% MeOH showed that the MCYST-RR and MCYST-LR were stable under the tested pressures up to 80°C. At 100°C MCYST recovery decreased by 10% to 17%. When water was used as the solvent, no differences in recovery were observed for MCYST-LR, whereas for MCYST-RR, maximum recovery was obtained at 60°C, and degradation occurred at 100°C. In contrast, anatoxin-a was labile under all experimental conditions; the best recoveries (ca. 50%) were obtained at 60°C at the three pressures using 75% MeOH. However, only 17%-23% recovery was obtained with water extraction at all temperatures. The extraction of MCYST-LR and variants from cells (Microcystis aeruginosa, UTCC299) was studied using two solvents, 75% MeOH and 100% water, at 14 MPa and 60°C and 100°C. PLE extracts were compared with extracts obtained with 75% MeOH and ultrasonication. Complete extraction was achieved in both solvents in one 5-min cycle (at 100°C). Although lower recovery was obtained using PLE (79%-105%), shorter extraction time and automation are advantageous over ultrasonication. © 2005 Wiley Periodicals, Inc.