Effect of temperature on microcystin-LR removal and lysis activity on <i>Microcystis aeruginosa</i> (cyanobacteria) by an indigenous bacterium belonging to the genus <i>Achromobacter</i>

Abstract

<i>Microcystis</i> is a frequent cyanobacterium bloom-forming with cosmopolitan distribution which can produce a hepatotoxin group called microcystins (MCs). These MCs are resistant to the traditional processes employed in the water treatment plants and they are often detected after conventional treatments. Because of this, the bio-removal studies have obtained a great interest in the last decades. In this work, a bacterial strain namely LG1 with the ability to remove microcystin-LR (MC-LR) under laboratory conditions was isolated from Rio de la Plata River and it was identified as <i>Achromobacter</i> spp. This ubiquitous bacterium was able to remove 79.5% MC-LR in 7 days with average removal time of 3.33 ± 0.08, 3.06 ± 0.05, and 2.77 ± 0.05 days at 28, 32, and 36 ± 1 °C, being higher at high temperature (36 °C) with an activation energy = 16.79 ± 1.99 kJ mol⁻¹. LG1 grew better at higher temperature (from 28 to 36 ± 1 °C) increasing the specific growth rate (μ) and reducing 2-fold the lag phase duration (LPD) without significant differences (p > 0.05) between maximum population density (MPD). In addition, LG1 showed a lysis activity on two <i>M. aeruginosa</i> native strains in 7 days measured as chlorophyll a (Chl-a) concentration. The lysis activity increased around 2-fold when increasing the temperature from 28 to 36 ± 1 °C. This is the first report of an indigenous bacterium belonging to the genus<i>Achromobacter</i> spp. isolated from the Rio de la Plata River with the capacity to remove MC-LR and lysis activity on <i>M. aeruginosa</i>.