Effects of Temperature, Growth Media, and Photoperiod on Growth and Toxin Production of Azadinium spinosum.

Jane Kilcoyne,Bernd Krock,Urban Tillmann,Amy Mccoy,Stephen Burrell

doi:10.3390/md17090489

Abstract

Azaspiracids (AZAs) are microalgal toxins that can accumulate in shellfish and lead to human intoxications. To facilitate their study and subsequent biomonitoring, purification from microalgae rather than shellfish is preferable; however, challenges remain with respect to maximizing toxin yields. The impacts of temperature, growth media, and photoperiod on cell densities and toxin production in Azadinium spinosum were investigated. Final cell densities were similar at 10 and 18 °C, while toxin cell quotas were higher (~3.5-fold) at 10 °C. A comparison of culture media showed higher cell densities and AZA cell quotas (2.5–5-fold) in f10k compared to f/2 and L1 media. Photoperiod also showed differences, with lower cell densities in the 8:16 L:D treatment, while toxin cell quotas were similar for 12:12 and 8:16 L:D treatments but slightly lower for the 16:8 L:D treatment. AZA1, -2, and -33 were detected during the exponential phase, while some known and new AZAs were only detected once the stationary phase was reached. These compounds were additionally detected in field water samples during an AZA event.

Highlights

Since the first identification and characterisation of azaspiracid-1 (AZA1) in 1998 [1], following the consumption of contaminated shellfish that led to a poisoning incident in 1995, more than 60 additional analogues have been reported [2,3,4,5,6,7]
The results indicate that toxin cell quotas increased after this change in temperature, with an increase in toxin levels occurring after ~56 days, suggesting that a low temperature stress can enhance toxin cell quotas
This study provides some useful information on maximizing toxin cell quotas and yields for the purposes of large scale culturing and isolation of AZAs, and it provides valuable information on changes in toxin profiles over the various growth phases

Summary

Introduction

Since the first identification and characterisation of azaspiracid-1 (AZA1) in 1998 [1], following the consumption of contaminated shellfish that led to a poisoning incident in 1995, more than 60 additional analogues have been reported [2,3,4,5,6,7]. The AZAs have a global distribution, but to date they have been most problematic for the Irish shellfish industry with blooms of A. spinosum occurring annually on the west coast of Ireland, resulting in frequent shellfish farm closures [9]. 26 AZAs have been identified in A. spinosum, A. poporum, A. dexteroporum, and Amphidoma languida strains [7]. Many of the other AZAs identified are shellfish metabolites [5], while some have been reported as artefacts [12,13]

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Conclusion