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Biotechnology and Bioprocess Engineering
Vol. 20 (1), 2015, Pages: 79-90

Characterization of a thermophilic hemoglobin-degrading protease from Streptomyces rutgersensis SCSIO 11720 and its application in antibacterial peptides production

Jian Yang, Jie Li, Yunfeng Hu, Lizhen Li, Lijuan Long, Fazuo Wang, Si Zhang

CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, RNAM Center for Marine Microbiology, Guangdong Key Laboratory of Marine Materia Medica, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510-301, China.


High value utilization of byproduct of slaughterhouses is regarded as beneficial to both economy and environment. A hemoglobin degrading protease PA720 was purified from fermentation broth of a Porites lutea associated strain Streptomyces rutgersensis SCSIO 11720 (SCSIO 11720) and exhibited maximal activity at 70°C, pH 10.5. The isolated strain was identified by genotypic method and 16 s RNA gene sequence was deposited in GenBank under accession No. KC414842. The enzyme exhibited excellent thermostability since it was stable at 70°C with t 1/2 value of 1,386.3 min. Kinetic and thermodynamic study showed the activation energy (Ea), ΔG * (free energy), ΔH * (enthalpy) and ΔS* (entropy) for protease deactivation were 62.71 kJ/mol, 74.26 kJ/mol, 59.86 kJ/mol, and −41.97 J/mol/K, respectively. Highest specific activity of protease PA720 was observed when using casein (9,953 U/mg) and hemoglobin (9,854 U/mg) as substrates. Hemoglobin hydrolysate prepared by protease PA720 showed significant antibacterial activity towards Escherichia coli, Staphylococcus aureus and Bacillus subtilis, indicating this protease could be used as an instrumental enzyme for production of hemoglobin-based antibacterial peptides. Based on partial amino acid sequences of the enzyme PA720, the full gene encoding this protease was obtained by degenerate primer PCR and has been deposited in GenBank under accession No. KC414842. The deduced amino acid sequence exhibits homology with other microbial thermophilic proteases in subtilisin family.

Keywords: hemoglobin protease, thermophilic enzyme, enzyme purification, antibacterial peptides, Streptomyces isolation and identification.

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