Isolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer
Bioconversion (e.g. anaerobic fermentation and compost) is the common recycling method of waste activated sludge (WAS) and its hydrolysis, as the rate-limiting step of fermentation, could be accelerated by protease. However, the commercial protease was unstable in a sludge environment, which increas...
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IWA Publishing
2021
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oai:doaj.org-article:15057c9100bf4b43921690bcd830081f2021-11-06T11:07:36ZIsolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer0273-12231996-973210.2166/wst.2021.167https://doaj.org/article/15057c9100bf4b43921690bcd830081f2021-06-01T00:00:00Zhttp://wst.iwaponline.com/content/83/11/2700https://doaj.org/toc/0273-1223https://doaj.org/toc/1996-9732Bioconversion (e.g. anaerobic fermentation and compost) is the common recycling method of waste activated sludge (WAS) and its hydrolysis, as the rate-limiting step of fermentation, could be accelerated by protease. However, the commercial protease was unstable in a sludge environment, which increased the cost. An endogenous alkaline protease stable in sludge environment was screened in this study and its suitability for treating the sludge was analyzed. The optimal production medium was determined by Response Surface Methodology as starch 20 g/L, KH2PO4 4 g/L, MgSO4·7H2O 1 g/L, sodium carboxy-methyl-cellulose 4 g/L, casein 4 g/L and initial pH 11.3, which elevated the yield of protease by up to 15 times (713.46 U/mL) compared with the basal medium. The obtained protease was active and stable at 35 °C–50 °C and pH 7.0–11.0. Furthermore, it was highly tolerant to sludge environment and maintained high efficiency of sludge hydrolysis for a long time. Thus, the obtained protease significantly hydrolyzed WAS and improved its bioavailability. Overall, this work provided a new insight for enzymatic treatment of WAS by isolating the endogenous and stable protease in a sludge environment, which would promote the resource utilization of WAS by further bioconversion. HIGHLIGHTS A novel protease-producing bacterium was isolated from the sludge.; The screened protease was highly tolerant to the sludge environment.; Treatment of the sludge by the screened protease elevated its bioavailability.; The screened protease was a promising biocatalyst for sludge treatment.;Jie HouWenbin LiuWanrong HuJing ChenJinqiong WangPanyu LiYonghong LiIWA Publishingarticleendogenous alkaline proteaseprocess optimizationsludge hydrolysisstability assessmentwaste activated sludgeEnvironmental technology. Sanitary engineeringTD1-1066ENWater Science and Technology, Vol 83, Iss 11, Pp 2700-2713 (2021) |
| institution |
DOAJ |
| collection |
DOAJ |
| language |
EN |
| topic |
endogenous alkaline protease process optimization sludge hydrolysis stability assessment waste activated sludge Environmental technology. Sanitary engineering TD1-1066 |
| spellingShingle |
endogenous alkaline protease process optimization sludge hydrolysis stability assessment waste activated sludge Environmental technology. Sanitary engineering TD1-1066 Jie Hou Wenbin Liu Wanrong Hu Jing Chen Jinqiong Wang Panyu Li Yonghong Li Isolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer |
| description |
Bioconversion (e.g. anaerobic fermentation and compost) is the common recycling method of waste activated sludge (WAS) and its hydrolysis, as the rate-limiting step of fermentation, could be accelerated by protease. However, the commercial protease was unstable in a sludge environment, which increased the cost. An endogenous alkaline protease stable in sludge environment was screened in this study and its suitability for treating the sludge was analyzed. The optimal production medium was determined by Response Surface Methodology as starch 20 g/L, KH2PO4 4 g/L, MgSO4·7H2O 1 g/L, sodium carboxy-methyl-cellulose 4 g/L, casein 4 g/L and initial pH 11.3, which elevated the yield of protease by up to 15 times (713.46 U/mL) compared with the basal medium. The obtained protease was active and stable at 35 °C–50 °C and pH 7.0–11.0. Furthermore, it was highly tolerant to sludge environment and maintained high efficiency of sludge hydrolysis for a long time. Thus, the obtained protease significantly hydrolyzed WAS and improved its bioavailability. Overall, this work provided a new insight for enzymatic treatment of WAS by isolating the endogenous and stable protease in a sludge environment, which would promote the resource utilization of WAS by further bioconversion. HIGHLIGHTS
A novel protease-producing bacterium was isolated from the sludge.;
The screened protease was highly tolerant to the sludge environment.;
Treatment of the sludge by the screened protease elevated its bioavailability.;
The screened protease was a promising biocatalyst for sludge treatment.; |
| format |
article |
| author |
Jie Hou Wenbin Liu Wanrong Hu Jing Chen Jinqiong Wang Panyu Li Yonghong Li |
| author_facet |
Jie Hou Wenbin Liu Wanrong Hu Jing Chen Jinqiong Wang Panyu Li Yonghong Li |
| author_sort |
Jie Hou |
| title |
Isolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer |
| title_short |
Isolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer |
| title_full |
Isolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer |
| title_fullStr |
Isolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer |
| title_full_unstemmed |
Isolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer |
| title_sort |
isolation, production and optimization of endogenous alkaline protease from in-situ sludge and its evaluation as sludge hydrolysis enhancer |
| publisher |
IWA Publishing |
| publishDate |
2021 |
| url |
https://doaj.org/article/15057c9100bf4b43921690bcd830081f |
| work_keys_str_mv |
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| _version_ |
1718443715438051328 |