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.
Highlights
Nicosulfuron, a member of the sulfonylurea herbicides used to control broad-leaved weeds and sedge weeds in corn, rice, citrus, vines, and potatoes field, was introduced into China and became the utmost frequently used herbicide on account of its high herbicidal activity at low application rates[1]
A 561 bp internal transcribed spacer (ITS) fragment of YC-WM1 was sequenced and phylogenetic analysis (Fig. 1, ITS fragment was offered in supplementary file) was performed based on the ITS sequences which revealed that YC-WM1 was closely related to Penicillium oxalicum (100%)
According to its morphological characteristics and phylogenetic analysis, YC-WM1 was identified as a Penicillium oxalicum strain
Summary
Nicosulfuron, a member of the sulfonylurea herbicides used to control broad-leaved weeds and sedge weeds in corn, rice, citrus, vines, and potatoes field, was introduced into China and became the utmost frequently used herbicide on account of its high herbicidal activity at low application rates[1]. Sulfonylurea herbicides in natural environment can be removed via chemical hydrolysis[3,4,5], microbial metabolism[6,7,8], and photocatalytic degradation[9,10,11,12,13,14,15,16,17,18]. Song et al isolated a fungal strain LZM1 from activated sludge with the capability of degrading nicosulfuron, which may be used in bioremediation of nicosulfuron-contaminated environments. Several sulfonylurea herbicide-degrading strains, such as Serratia sp. The objective of this study was to isolate a new microorganism species capable of efficiently degrading nicosulfuron. We described the isolation, identification and degradation characteristics of Penicillium oxalicum sp. YC-WM1 exhibited the highest nicosulfuron degradation efficiency compared to the other reported strains
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