مجله علوم و صنایع غذایی ایران

مجله علوم و صنایع غذایی ایران

جداسازی و شناسایی Pseudomonas protegens از شیرخام و تحلیل مولکولی - پروتئومیکی آن در ژله‌ای شدن شیر پس‌چرخ استریل

نوع مقاله : مقاله پژوهشی

نویسندگان
1 گروه علوم و صنایع غذایی، دانشگاه علوم کشاورزی و منابع طبیعی گرگان،
2 گروه علوم و صنایع غذایی، دانشگاه علوم کشاورزی و منابع طبیعی گرگان- ایران
3 مرکز تحقیقات بیماری‌های عفونی و گرمسیری دانشگاه علوم پزشکی اصفهان- ایران
4 دانشگاه اصفهان-ایران
چکیده
مطالعه حاضر، مکانیزم‌های مولکولی و عملکردی ژله‌ای شدن شیر استریل شده با اتوکلاو را با تمرکز بر فعالیت Pseudomonas protegens و سایر گونه‌های سایکروتروف بررسی کرد. شیر خام جمع‌آوری‌شده از دامداری‌های اصفهان از نظر حضور گونه‌های Pseudomonas غربالگری شد و سویه P. protegens KSM1 برای تحلیل دقیق انتخاب گردید. نتایج PCR نشان داد هیچ ایزوله‌ای حامل ژن AprX با اندازه ۸۹۰ جفت‌باز نیست و تحلیل ORF نیز تنها وجود ORFهای کوتاه‌تر از 171 جفت‌باز را تأیید کرد. تنوع ژنتیکی ۳۰ ایزوله با RAPD- PCR و پرایمر XD5 ارزیابی شد و ضریب شباهت 79/0 تا 00/1 و واگرایی تا ۴۳٪ به‌دست آمد؛ به‌طوری‌که P. aeruginosa در یک خوشه منسجم قرار گرفت، اما P. protegens، P. koreensis، P. putida و P. fluorescens در شاخه‌های جداگانه توزیع شدند. بررسی SDS-PAGE نشان داد، نمونه‌های تلقیح‌شده تخریب شدید کازئین را تجربه کردند و وجود باند شاخص ۴۵–۵۰ کیلودالتن، بیانگر فعالیت آلکالین پروتئاز باکتریایی است. میزان پروتئولیز در نمونه‌های تلقیح‌شده به‌طور معنی‌داری به‌ویژه بین روزهای ۳ تا ۱۰ افزایش یافت (p≤0.05). در حالی که نمونه‌های شاهد تغییرات اندکی داشتند. این داده‌ها نشان می‌دهد پروتئازهای باکتریایی عامل اصلی تخریب پروتئین طی نگهداری هستند. در میان ایزوله‌ها، P. protegens KSM1 مدل مناسبی برای مطالعه مکانیسم‌های فساد پروتئینی و توسعه راهبردهای پیشگیری از ژله‌ای شدن شیر فرادما محسوب می‌شود.
کلیدواژه‌ها
موضوعات

عنوان مقاله English

Isolation and Identification of Pseudomonas protegens from raw milk and its Molecular–Proteomic Analysis in Gelation of Sterilized Skim Milk

نویسندگان English

Meysam Salehi 1
Morteza Khomeiri 2
Soodabe Rostami 3
Alireza Sadeghi Mahoonak 1
Ali Moayedi 1
Majid Moghaddam 4
1 Department of Food Science and Technology, Gorgan University of Agricultural Sciences and Natural Resources
2 Department of Food Science and Technology, Gorgan University of Agricultural Sciences and Natural Resources
3 Research Center for Infectious and Tropical Diseases, Isfahan University of Medical Sciences, Isfahan, Iran
4 University of Isfahan, Isfahan-Iran
چکیده English

The present study investigated the molecular mechanisms and functional aspects of proteolytic gelation in autoclave-sterilized milk, focusing on Pseudomonas protegens and other psychrotrophic species. Raw milk collected from dairy farms in Isfahan was screened for the presence of Pseudomonas species, and the strain P. protegens KSM1 was selected for detailed analysis. PCR results showed that none of the isolates carried the AprX gene of 890 bp, and ORF analysis confirmed the presence of only short ORFs (<171 bp). The genetic diversity of 30 isolates was evaluated using RAPD-PCR with the XD5 primer, revealing similarity coefficients ranging from 0.79 to 1.00 and divergence up to 43%; P. aeruginosa formed a compact cluster, whereas P. protegens, P. koreensis, P. putida, and P. fluorescens were distributed across separate branches. SDS-PAGE analysis indicated that inoculated samples experienced severe casein degradation, and the presence of a marker band at 45–50 kDa indicated bacterial alkaline protease activity. Proteolysis in inoculated samples increased significantly, particularly between days 3 and 10 (p≤0.05), while control samples showed minimal changes. These findings demonstrate that bacterial proteases are the main contributors to protein degradation during storage. Among the isolates, P. protegens KSM1 represents a suitable model for studying protein spoilage mechanisms and developing strategies to prevent gelation in UHT milk.

کلیدواژه‌ها English

UHT milk
Pseudomonas protegens
gellation
SDS-PAGE
RAPD-PCR
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