Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
In order to determine the reason for loss of vacuum in canned food, obligately anaerobic, spore forming thermophilic organisms were isolated from shelf-stable canned food containing vegetables, noodles and potatoes as main ingredients. Thermophilic bacteria from 44 canned food samples that had been stored under anaerobic conditions at 37 °C for at least 7 days were isolated. In addition, organic fertilizer used for the cultivation of some of the foods’ ingredients was examined and anaerobic, thermophilic bacteria could also be isolated from this source. Identification of bacterial strains was carried out by partial and complete 16S-rRNA-gene sequencing. Some of the obtained gene sequences showed a high level of similarity to existing 16S-rRNA gene sequences towards strains of the genera Thermoanaerobacter, Thermoanaerobium and Thermoanaerobacterium respectively, which have not yet been reported to be of importance as food spoilers. In the course of identification of these thermophilic bacteria we developed genera specific PCR-based approaches for detecting isolates belonging to the genera Thermoanaeroacterium and Thermoanaerobacter. Direct capturing of free DNA from contaminated samples using oligonucleotides coupled with paramagentic beads allowed the reduction of the detection time to six hours with a lower limit of 104 cells/mL.Da bi se odredio uzrok nestanka vakuuma u limenkama konzervirane hrane, obligatni anaerobi, termofilni organizmi koji stvaraju spore, izolirani su iz hrane u limenkama s glavnim sastojcima: povrće, rezanci i krumpir. Izolirane su termofilne bakterije iz 44 uzorka limenki uskladištenih pod anaerobnim uvjetima pri 37 °C barem 7 dana. Osim toga, ispitana su organska gnojiva upotrijebljena za uzgoj navedenog povrća pa su i iz tog izvora izolirane anaerobne termofilne bakterije. Identifikacija bakterijskih sojeva provedena je djelomičnim i potpunim sekvencioniranjem 16S-rRNA gena. Neke od dobivenih genskih sekvencija pokazale su visoki stupanj sličnosti s postojećim sekvencijama 16S-rRNA gena sojeva rodova Thermoanaerobacter, Thermoanaerobium i Thermoanaerobacterium. Do sada još nije bila ustanovljena važnost tih sojeva kao onečišćavača hrane. Tijekom identifikacije navedenih termofilnih bakterija autori su razvili genetički specifičan pristup utemeljen na PCR za određivanje izolata koji pripadaju rodovima Thermoanaerobacterium i Thermoanaerobacter.
Izravno vezanje slobodne DNA iz onečišćenih uzoraka, koristeći oligonukleotide povezane s paramagnetskim zrncima omogućilo je smanjenje vremena detekcije na 6 sati s donjom granicom od 104 stanica/mL
