Gıda Tuzlarında Halotolerant Bakterilerin İncelenmesi

Abstract

Bu çalışmada, Fransa, Almanya, İngiltere, Pakistan, Türkiye, İsviçre, Avusturya’dan toplanan 25 gıda tuz örneğinin nem içeriği, kül içeriği, pH değerleri, toplam bakteri sayısı ve toplam halotolerant bakteri sayısı incelenmiştir. Gıda tuz örneklerinden tuza toleranslı saf bakteriler izole edilmiştir ve bu izolatların fenotipik özellikleri incelenmiştir. Tuza toleranslı bakterilerin gelişmesi üzerine farklı tuz, farklı pH değerleri ve farklı sıcaklık değerlerinin etkisi araştırılmıştır. Tuzların nem içeriği, kül içeriği ve pH değerleri sırasıyla %2.3-3.7, %95-97, 6.37-9.94 olarak bulunmuştur. Yüz on sekiz tuza toleranslı bakteri 17 tuz örneğinden izole edilmiştir. Tüm izolatlar çomak şeklindeydi. Yüz otuz bir izolat hareketli olmasına rağmen, yedi izolat hareketsizdi. Toplam olarak 118 izolat ve 20 izolat sırasıyla Gram-pozitif ve Gram-negatif olarak bulunmuştur. Tüm izolatlar hem NaCl yokluğunda hem de %10 NaCl varlığında; pH 5, 7, 9’da; 24°C ve 37°C’de gelişmiştir. Sekiz izolatın gelişimi 4°C’de de saptanmıştır. Yirmi iki izolat %20 NaCl konsantrasyonunda gelişti. İzolatların 86’sı farklı pigmentasyon gösterdi. İzolatların tamamı, 83’ü, 84’ü, 48’i, 92’si ve 100’ü sırasıyla katalaz, oksidaz, proteaz, lipaz, amilaz ve kazeinaz pozitif olarak saptanmıştır. Altmış izolat peptondan amonyak üretmiştir. Sonuç olarak, tuz örneklerinin nem içeriği çok düşük olmasına rağmen, tuz örneklerinin %80’i bakteri (1-58 KOB/g) ve %68’i tuza toleranslı bakteri (1-40 KOB/g) içerdi. Tuza toleranslı bakterilerin %57’si endospor oluşturdu ve tuza toleranslı bakterilerin %14’ü endotoksin içerdi. Bu nedenle, gıdaların bozulmasını ve insanlarda gıda kaynaklı hastalıkları önlemek için gıda tuzu numunelerindeki bu mikroorganizmaların etkili sterilizasyon yöntemleri kullanılarak tuzdan uzaklaştırılması gerekmektedir.

Keywords

• Halotolerant bakteriler
• gıda tuzları
• biyokimyasal testler
• enzimatik aktiviteler
• fenotipik karakteristikler

A Detailed Study on Halotolerant Bacteria Isolated from Food Salts Collected from Different Countries

Abstract

Twenty-five food salts, collected from seven-country, were examined for moisture contents and ash contents, pH values, total numbers of bacteria, and total numbers of bacteria halotolerant bacteria. The growth and biochemical reactions of halotolerant bacteria at different NaCl concentrations, pH, and temperature values were investigated. The efficacy of dry-heat sterilization and high-pressure steam sterilization for the inactivation of bacteria was examined using six food salts. Moisture contents, ash contents, and pH values of salts were respectively found as 2.3-3.7%, 95-97%, and 6.37-9.94. Total numbers of bacteria and halotolerant bacteria were detected as between 1-58 CFU/g and 1-40 CFU/g on Modified Nutrient Agar media, respectively. While bacteria were found in twenty salt samples, halotolerant bacteria were detected in seventeen samples. One hundred thirty- eight rod-shaped halotolerant bacteria were isolated from seventeen samples. One hundred eighteen and twenty isolates were found Gram-positive and Gram-negative, respectively. While 131 isolates were motile, seven isolates were observed as non-motile. All isolates grew in both absence of NaCl and presence of 10% NaCl, pH 5, 7, and 9, 24°C, and 37°C. Eighty-six isolates showed different pigmentations. Ammonia production was detected at sixty isolates. Catalase, oxidase, protease, lipase, amylase, caseinase were produced by 138, 83, 84, 48, 92, 100 isolates, respectively. Fifty-seven percent of halotolerant bacteria formed endospores. All bacteria in six salts were killed using both dry-heat sterilization (175oC for 2 hours) and high-pressure steam sterilization (121oC for 30 minutes). In conclusion, we suggest using dry-heat sterilization or high-pressure steam sterilization to kill Gram-negative halotolerant bacteria containing endotoxin and Gram-positive halotolerant bacteria with endospores in food salts to prevent food spoilage and foodborne diseases in humans.

Keywords

• Halotolerant bacteria
• food salt
• biochemical tests
• enzymatic activities
• phenotypic characteristics
• sterilization of food salts

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