{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,12]],"date-time":"2026-08-12T14:40:01Z","timestamp":1786545601994,"version":"build-2736575974"},"reference-count":43,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,5,20]],"date-time":"2025-05-20T00:00:00Z","timestamp":1747699200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012428","name":"Central Public-interest Scientific Institution Basal Research Fund, CAFS","doi-asserted-by":"publisher","award":["2023TD71"],"award-info":[{"award-number":["2023TD71"]}],"id":[{"id":"10.13039\/501100012428","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Proteolytic enzymes, which play a crucial role in peptide bond cleavage, are widely applied in various industries. In this study, protease-producing bacteria were isolated and characterized from marine sediments collected from the Yellow Sea, China. Comprehensive screening and 16S rDNA sequencing identified a promising G4 strain as Bacillus atrophaeus. Following meticulous optimization of fermentation conditions and medium composition via response surface methodology, protease production using strain G4 was significantly enhanced by 64%, achieving a yield of 3258 U\/mL. The G4 protease exhibited optimal activity at 50 \u00b0C and pH 7.5, demonstrating moderate thermal stability with 52% residual activity after 30-min incubation at 50 \u00b0C\u2014characteristics typical of an alkaline protease. Notably, the enzyme retained over 79% activity across a broad pH range (6\u201311) and exhibited excellent salt tolerance, maintaining over 50% activity in a saturated NaCl solution. Inhibition by phenylmethylsulfonyl fluoride, a serine protease inhibitor, confirmed its classification as a serine protease. The enzyme\u2019s potential in generating bioactive peptides was further demonstrated through hydrolysis of sheep (Ovis aries) placenta, resulting in a hydrolysate with notable antioxidant properties. The hydrolysate exhibited a 64% superoxide anion scavenging activity, surpassing that of reduced glutathione. These findings expand the current understanding of Bacillus\u00a0atrophaeus G4 proteases and provide a foundation for innovative sheep placenta utilization with potential industrial applications.<\/jats:p>","DOI":"10.3390\/molecules30102217","type":"journal-article","created":{"date-parts":[[2025,5,20]],"date-time":"2025-05-20T04:48:18Z","timestamp":1747716498000},"page":"2217","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Screening and Characterization of Marine Bacillus atrophaeus G4 Protease and Its Application in the Enzymatic Hydrolysis of Sheep (Ovis aries) Placenta for the Preparation of Antioxidant Peptides"],"prefix":"10.3390","volume":"30","author":[{"given":"Wei","family":"Wang","sequence":"first","affiliation":[{"name":"Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guoqing","family":"Peng","sequence":"additional","affiliation":[{"name":"Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jingjing","family":"Sun","sequence":"additional","affiliation":[{"name":"Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chengcheng","family":"Jiang","sequence":"additional","affiliation":[{"name":"Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7634-7567","authenticated-orcid":false,"given":"Jianhua","family":"Hao","sequence":"additional","affiliation":[{"name":"Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China"},{"name":"Jiangsu Collaborative Innovation Center for Exploitation and Utilization of Marine Biological Resource, Lianyungang 222005, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiu","family":"Zhang","sequence":"additional","affiliation":[{"name":"Ningxia Key Laboratory for the Development and Application of Microbial Resources in Extreme Environments, College of Biological Science and Engineering, North Minzu University, Yinchuan 750021, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,5,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"678","DOI":"10.1007\/s00343-021-0441-2","article-title":"Screening and characterization of proteases produced by deep-sea cold seep bacteria","volume":"40","author":"Guo","year":"2021","journal-title":"J. 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