Identification and characterization of lipolytic bacteria from Thai fermented foods

Aims: Gram-positive spore forming rod-shaped bacteria from Thai fermented foods were isolated, identified and screened for lipolytic activity. Methodology and results: Bacterial strains were isolated from Thai fermented foods by the standard dilution technique using Tryptic soy agar. Seven isolates which belong to the genus Bacillus and one isolate which belongs to Paenibacillus were characterized based on their phenotypic characteristics and 16S rRNA gene sequence analyses. Isolates NM8-1 (Group 1), PR9-2 (Group 2), PR11-1 (Group 3), KM15-1 and SS49-4 (Group 4), SS48-5 (Group 5) and SS503 (Group 6), were closely related to Bacillus methylotropicus, B. pumilus, B. flexus, B. cereus, B. subtilis and B. anthracis, based on 99.90-100% similarities, respectively. Isolate NM45-3 (Group 7) was closely related to Paenibacillus pasadenensis based on 99.55% similarity. All the isolates were susceptible to amikacin, chloramphenicol, clindamycin, erythromycin, gentamicin, imipenem, kanamycin, levofoxacin, novobiocin, streptomycin, tetracycline and vancomycin. Their lipase production in nutrient broth with Tween 20, Tween 40, Tween 60 or Tween 80 ranged from 0.014±0.129 - 3.231±0.087 U/mL. Bacillus subtilis SS48-5 exhibited highest lipase production when cultured with Tween 80 at pH 7.5 for 24 h. The optimum lipase production of this strain was at 40 °C after incubated for 30 h. Conclusion, significance and impact of study: The characterization and evaluation of the lipolytic activity of Bacillus and Paenibacillus strains isolated from Thai fermented foods will be useful for the species diversity, food fermentation and the lipase production.

Variation and Characterization of Bacterial Communities Contaminating Two Saunas Operated at 64degrees C and 76degrees C

This study was performed to analyze 6 day-term variations in bacterial communities contaminating the floor of two dry saunas that were operated at 64degrees C (low temp) and 76degrees C (high temp). Bacteria were sampled daily from the saunas for 6 days from Monday to Saturday. Genomic DNA was isolated directly from bacteria-collected cotton swabs. The diversity of the bacterial communities collected from the saunas was analyzed using thermal gradient gel electrophoresis (TGGE). The total numbers of DNA bands separated by TGGE for bacteria collected from the low temp and high temp sauna were 20 and 18, respectively, during the 6 days. Seven of 20 bacteria in the low temp sauna and eight of 18 bacteria in the high temp sauna were detected more than three times over the 6 experimental days. Twelve of the 26 bacterial genera contaminating the saunas were cross detected. Bacteria belonging to the genera Moraxella and Acinetobacter were selectively detected in the low temp sauna, whereas those belonging to Aquaspirillum, Chromobacterium, Aquabacterium, Gulbenkiania, Pelomonas, and Aquitalea were selectively detected in the high temp sauna. Three species of bacteria contaminating both the low and high temp saunas were thermophile or thermoduric. The results indicate that the sauna-contaminating bacteria may have been transferred from outside the saunas by user traffic but did not inhabit the saunas.

Characterization of Bacterial Community Contaminating Floor of A Hot and Dry Sauna

The purpose of this study was to examine profile of bacteria contaminated in a dry sauna. Bacteria sampled from the floor of the dry sauna (75~80degrees C) were separated and identified by using a thermal gradient gel electrophoresis (TGGE) technique, and were cultivated using a defined medium at 50degrees C. Bacteria grown in the defined medium were identified based on 16S-rDNA sequence homology. The band number of DNA separated by TGGE was 15, indicating the species diversity of bacteria contaminating the dry sauna. Seven species of bacteria were successfully cultured on agar plate medium at 50degrees C, which represented a combination of thermophilic and thermoduric bacteria contaminating the dry sauna. The highest limit temperature for growth of the bacterial isolates was generally 50degrees C when cultivated in a defined medium, but was raised to 60degrees C when cultivated in a complex medium. Consequently, the bacteria grown at 50~60degrees C are thermoduric or thermophilic, but others may not be.