Porphyridium cruentum A-408 and Planktothrix A-404 retain their capacity to produce biotechnologically exploitable metabolites after cryopreservation

Abstract

Long-term phenotypic and genotypic stability is a fundamental prerequisite for the successful biotechnological exploitation of any micro-organism, as without stable starter cultures productivity can not be guaranteed. In this study two biotechnological algal production strains; Porphyridium cruentum A-408, which produces zeaxanthin, and Planktothrix A-404, which produces a potent cytotoxin, were successfully cryopreserved using a two step protocol (cooling to −40 ∘C prior to plunging into liquid nitrogen). Post-thaw viability levels of 114 ± 27% were obtained for P. cruentum A-408 and 67 ± 18% for Planktothrix A-404. Unchanged productivity levels of Zeaxanthin and beta-carotene (77% and 12% of total carotenoids respectively) were obtained in batches of P. cruentum A-408 produced from standard (serial transfer) and utilizing post-thaw (ex-cryopreserved) inocula. In addition, cytotoxin production by Planktothrix A-404 was not influenced by the origin of the inoculum, with standard (serial transfer) and post-thaw (ex-cryopreserved) inocula giving high levels of activity.