Isolation and screening of Bacillus sp. producing protease and evaluation of the effects of pH and temperature on enzyme activity
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Abstract
This study aimed to isolate and screen protease-producing Bacillus spp. from bread-processing wastewater collected in Can Tho City and to evaluate the effects of temperature and pH on protease activity. A total of 18 bacterial isolates were obtained, of which 16 were identified as members of the genus Bacillus based on morphological and biochemical characteristics. All isolates exhibited proteolytic activity, with hydrolysis zone diameters ranging from 12.00 to 17.10 mm and protease activities of 0.21 – 0.55 U/mL. The highest protease activities were recorded in isolates StNK1.1 (0.55 U/mL) and StCR3.3 (0.52 U/mL). Temperature affected both protein hydrolysis and protease activity, with optimal values observed between 40 and 45°C. Isolate StCR3.3 exhibited the largest hydrolysis zone (23.50 mm) and the highest protease activity (1.45 U/mL) at 45°C. Protease activity remained high within the pH range of 6 – 8. Based on 16S rRNA gene sequence analysis, isolate StCR3.3 was identified as a member of the genus Bacillus, indicating its potential for protease production and the biological treatment of protein-rich wastewater.
Tóm tắt
Nghiên cứu được thực hiện nhằm phân lập và tuyển chọn các dòng Bacillus spp. sinh protease từ nước thải sản xuất bánh mì tại thành phố Cần Thơ; đồng thời, việc khảo sát ảnh hưởng của nhiệt độ và pH cũng đã được tiến hành. Kết quả phân lập được 18 dòng vi khuẩn, trong đó 16 dòng được xác định thuộc chi Bacillus dựa trên đặc điểm hình thái và sinh hóa. Tất cả các dòng đều có khả năng phân giải với đường kính từ 12,33 đến 17,10 mm và hoạt độ protease đạt 0,21 – 0,55 U/mL cao nhất ở dòng StNK1.1 là 0,55 U/mL và StCR3.3 là 0,52 U/mL. Nhiệt độ ảnh hưởng đến khả năng phân giải protein và hoạt tính protease, với giá trị cao nhất được ghi nhận trong khoảng 40 – 45°C. Dòng StCR3.3 đạt đường kính vòng phân giải (23,50 mm) và hoạt tính protease cao nhất (1,45 U/mL) tại 45°C. Hoạt tính enzyme giảm duy trì ở mức cao trong khoảng pH 6 – 8. Kết quả định danh bằng gen 16S rRNA xác định dòng StCR3.3 thuộc chi Bacillus, cho thấy tiềm năng ứng dụng trong sản xuất và xử lý nước thải giàu protein.
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