Pulsed electric field permeabilization and extraction of phycoerythrin from Porphyridium cruentum

This paper assesses the extraction of beta-phycoerythrin (BPE) into aqueous media by the application of pulsed electric field treatments (PEF) to the fresh biomass of Porphyridium cruentum. An increase in electric field strength from 2 to 10 kV/cm, or a prolongation of treatment time increased electroporation and inactivation of P. cruentum in the range investigated (2-10 kV/cm; 30-150 mu s). A perfect agreement between fraction of dead cells and fraction of electroporated cells was observed when more than 20% of the cells were inactivated. Even after 48 h of incubation, BPE was not detected in the extraction medium containing untreated cells of P. cruentum: thus, an intact cytoplasmic membrane prevented the exit of BPE. After 24 h of extraction, the entire BPE content (32 mg/g d.w.) was released after treating P. cruentum cells at 8 or 10 kV/cm for 150 mu s. However, BPE was not released immediately after the PEF treatment, thereby requiring, in most cases, a lag time of over 6 h until the compound could be detected in the extraction medium. This behavior indicates that BPE extraction requires not only the diffusion of the compound across the cell membrane, but also the dissociation of the compound from the cell structures. In this sense, it is hypothesized that P. cruentum autolysis triggering by PEF could be the main cause involved in the effectivity of these treatments in BPE extraction. An improved grasp of the kinetics and the mechanism of the enzymes participating in microalgae autolysis, and of the autolysis trigger by PEF, will allow this process to be developed at an industrial scale.