Abstract
Nodularin (NOD) is greatly produced by Nodularia spumigena and released into the environment when toxic cyanobacterial blooms happened in natural water body, which is seriously harmful to human and animals. The promising bacterial strain of Sphingopyxis sp. USTB-05 was found to have an ability in biodegrading NOD. Initially, 11.6 mg/L of NOD could be completely eliminated within 72 h by whole cells of USTB-05, and within 36 h by its crude enzymes (CEs) of 570 mg/L, respectively. During the enzymatic biodegradation process of NOD, two products were observed on the profiles of HPLC. Based on the analysis of m/z ratios of NOD and its two products on a rapid-resolution liquid chromatogram-mass spectrum (RRLC-MS), we suggested that at least two enzymes of USTB-05 participated in biodegrading NOD. The first enzyme hydrolyzed Arg-Adda peptide bond of cyclic NOD and converted it to linear NOD as the first product. The second enzyme was found to cut off the target peptide bond between Adda and Glu of linearized NOD, and Adda was produced as a second and dead-end product. This finding is very important in both basic research and the application of USTB-05 on the removal of NOD from a water environment.
Highlights
There is a drastically increasing trend for the breakout of harmful cyanobacterial blooms in recent decades, posing a serious threat to the natural ecological system
The results indicate that crude enzymes (CEs) of USTB-05 enzymatic activity to catalyze NOD
The number of bacterial species reported to be capable of degrading NOD is very limited [16,17,32] and less information was avaiable on NOD, it was frequently found in natural water body
Summary
There is a drastically increasing trend for the breakout of harmful cyanobacterial blooms in recent decades, posing a serious threat to the natural ecological system. One of the biggest hazards of cyanobacterial blooms is to produce and to release various kinds of microalgal toxins, in which toxic cyclic peptides, such as microcystins (MCs) and nodularin (NOD), are most frequently detected all over the world [1]. Nodularia spumigena, which is usually found in brackish water, such as the Baltic Sea [2], Lakes. The nodularin variants (L-Har2) produced in freshwater have been reported [6]. NOD shows a potent acute hepatotoxicity and tumor-promoting activity in domestic animals and humans by inhibition of the eukaryotic proteins phosphatase 1 and 2A [7]. The incidents of animal poisoning and human health problems resulted from toxic blooms of Nodularin spumigena have been well documented [5,10,11,12]
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