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Data of Thesis

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Author: Ronaldo Leal Carneiro

Title: Optimization of cultivation of Microcystis aeruginosa and Cylindrospermopsis raciborkii (Cyanobacteria) for production of microcystin-LR and cylindrospermopsin standards.

Year: 2005.    Full text (in Portuguese)

Abstract

Hepatotoxinas microcystin-LR and cylindrospermopsin produced by cyanobacteria have already been associated with cases of animal and human intoxication. The Brazilian Ministry of Health adopts as the acceptable maximum level 1 μg/L of microcystins in water for human consumption and recommends 15 μg/L of cylindrospermopsin. Additionally, drinking water for public provisioning must been monitored for the presence of cianotoxinas. This study aimed to collaborate with the establishment of optimized conditions for production of these two cianotoxinas to allow the possibility of the national production of microcystin-LR and cylindrospermopsin standards, which is crucial for water quality control process. We studied the variation on microcystin-LR synthesis, by a strain of Microcystis aeruginosa (NPJB-1) and in the cylindrospermopsin synthesis, by a strain of Cylindrospermopsis raciborskii (CYP 011K) in batch cultures submitted to different irradiance levels. Growth rate and physiological conditions of each strain were determined by daily cell counting, chlorophyll a concentration (extraction with methanol 100%), intracellular and extracellular carbohydrates concentration (using the phenol sulfuric acid method). The production of these two toxins was quantified in the exponential and stationary growth phases by specific HPLC techniques using UV detection and photodiiodearray detector. The best conditions for growth and microcystin-LR production in 106 cells of strain NPJB-1 (M.aeruginosa) were found in the cultures maintained under 100 μmoles fótons.m-2.s-1. The age of culture influenced in the cellular microcystin-LR concentration. The content was higher in the exponential phase and it decreased in the stationary phase. There was a direct relationship between chlorophyll a synthesis and microcystin-LR production by this strain. According to these results, the most favorable culture conditions for production of microcystin-LR standards by NPJB-1 strain are 100 μmoles fótons.m-2.s-1 for five days of cultivation. The highest growth rate of CYP 011K (C. raciborskii) strain was found in the cultures maintained under of 100 μmoles fótons.m-2.s-1. A viii .s-in the middle of exponential growth phase as well as in the end of culture period. According to these results, the most favorable culture conditions for production of cylindrospermopsin standards are 40 μmoles fótons.m-.s-for twelve days of cultivation. decrease of the length of C. raciborskii filaments was observed at the end of exponential growth phase for the cultures submitted to the highest light treatments (60 and 100 μmoles fótons.m-2.s-1). The highest cylindrospermopsin production in 106 cells of C. Raciborskii was observed in the cultures submitted to 40 μmoles fótons.m-21 21

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