Hydrolysis of nicosulfuron under acidic environment caused by oxalate secretion of a novel Penicillium oxalicum strain YC-WM1

Abstract

A novel Penicillium oxalicum strain YC-WM1, isolated from activated sludge, was found to be capable of completely degrading 100 mg/L of nicosulfuron within six days when incubated in GSM at 33 °C. Nicosulfuron degradation rates were affected by GSM initial pH, nicosulfuron initial concentration, glucose initial concentration, and carbon source. After inoculation, the medium pH was decreased from 7.0 to 4.5 within one day and remained at around 3.5 during the next few days, in which nicosulfuron degraded quickly. Besides, 100 mg/L of nicosulfuron were completely degraded in GSM medium at pH of 3.5 without incubation after 4 days. So, nicosulfuron degradation by YC-WM1 may be acidolysis. Based on HPLC analysis, GSM medium acidification was due to oxalate accumulation instead of lactic acid and oxalate, which was influenced by different carbon sources and had no relationship to nicosulfuron initial concentration. Furthermore, nicosulfuron broke into aminopyrimidine and pyridylsulfonamide as final products and could not be used as nitrogen source and mycelium didn’t increase in GSM medium. Metabolomics results further showed that nicosulfuron degradation was not detected in intracellular. Therefore, oxalate secretion in GSM medium by strain YC-WM1 led to nicosulfuron acidolysis.

Pathway and kinetics of malachite green biodegradation by Pseudomonas veronii

“…All other reagents used were of analytical grade. The microbial community was enriched using modified mineral salt medium (MSM) modified with glucose (1.0 g/L) and supplemented with 20 µL trace element solution 25 . LB (Difco), tryptic soy agar medium (TSA, Difco), and tryptic soy broth (TSB, Difco) were used to isolate degradative strains.…”

Nicosulfuron Degradation by an Ascomycete Fungus Isolated From Submerged Alnus Leaf Litter

“…Chemical hydrolysis of the sulfonylurea linkage has been described as the main abiotic degradation process (Sarmah and Sabadie, 2002), its rate being greater as pH of the medium decreases (Berger and Wolfe, 1996). This phenomenon was also observed for Penicillium oxalicum YC-WM1 where nicosulfuron degradation was due to medium acidification resulting from oxalate secretion by the fungal strain (Feng et al, 2017). Two degradation products are usually formed: 2-amino-4,6-dimethoxypyrimidine (ADMP) and 2-(aminosulfonyl)- N,N -dimethyl-3-pyridinecarboxamide (ASDM), the latter being able to cyclize at basic pH (Sarmah and Sabadie, 2002).…”

“…Our results showed that P. cucumerina AR1 can also be used to reduce nicosulfuron contamination since we demonstrated that (i) it was tolerant to nicosulfuron in contrast to what was described for other fungal species (Karpouzas et al, 2014) and (ii) it was able to degrade the nicosulfuron herbicide both in planktonic (Figure 2) and in biofilm conditions with various simple and complex carbon sources (glucose, leaf or wood; Figure 7). Regarding the literature, this is the first time that a leaf-associated fungal strain able to degrade nicosulfuron has been isolated in freshwater, the other ones being isolated from agricultural soil or sludge (Yang et al, 2008; Zhang et al, 2011, 2012; Lu et al, 2012; Song et al, 2013; Zhao et al, 2015a,b, 2018; Wang et al, 2016; Carles et al, 2017a; Feng et al, 2017; Zhou et al, 2017).…”

“…Our results showed that the herbicide dissipation was mainly due to biodegradation since the pH values of the medium of all the cultures remained around neutrality (ranging from 6.1 to 6.7) at the end of the experiment, contrarily to what was observed with Penicillium oxalicum YC-WM1 fungal strain. In this last case, nicosulfuron was degraded by hydrolysis resulting from the acidification of the medium (Feng et al, 2017).…”

“…J5-2 (Zhang et al, 2011), Alcaligenes faecalis ZWS11 (Zhao et al, 2015a), Klebsiella sp. Y1 (Wang et al, 2016), Serratia marcescens N80 (Zhang et al, 2012), Pseudomonas fluorescens SG-1 (Carles et al, 2017a) and Pseudomonas nitroreducens strain NSA02 (Zhao et al, 2018)], and three fungal [ Talaromyces flavus LZM1 (Song et al, 2013), Aspergillus niger YF1 (Yang et al, 2008; Lu et al, 2012) and Penicillium oxalicum YC-WM1 (Feng et al, 2017)] nicosulfuron-degrading strains have been described in the literature. In most cases, the metabolites identified were ADMP and ASDM, suggesting similar degradation pathways.…”