Culture dependent and independent genomic identification of Alicyclobacillus species in contaminated commercial fruit juices.

Alicyclobacillus is a genus of thermo-acidophilic, endospore-forming, bacteria species which occasionally cause spoilage of heat-processed fruit juices by producing guaiacol taint. In this study, Alicyclobacillus contamination of commercial fruit juices in West Africa was investigated using culture-dependent and -independent approaches. Firstly, a total of 225 fruit juice products from Ghana (n = 39) and Nigeria (n = 186) were enriched with yeast-starch-glucose (YSG) broth (pH 3.7) following heat shock at 80 °C for 10 min. Alicyclobacillus was detected in 11.6% (26) of samples. Isolates were identified to the genus taxonomic level by genus-specific PCR which targeted the squalene-hopene-cyclase (shc) gene followed by analysis of the almost-complete 16S ribosomal RNA (rRNA) gene sequences that identified 16 Alicyclobacillus acidoterrestris, 7 Alicyclobacillus acidocaldarius and 3 Alicyclobacillus genomic species 1 (Alicyclobacillus sp. 1). Whole-genome fingerprinting using PCR-RAPD primers Ba-10, F-61 and F-64 grouped the 16 A. acidoterrestris isolates into two genetic clusters. Furthermore, high performance liquid chromatographic (HPLC) analyses revealed the activity of vanillic-acid decarboxylase (vdc) in all A. acidoterrestris isolates due to guaiacol production from vanillic-acid. Lastly, species-specific PCR-DGGE targeting the 16S rRNA gene clearly discriminated between the guaiacol-producing A. acidoterrestris and the non-spoilage A. acidocaldarius group. Information provided by this study is fundamental to the development of effective strategies for the improvement of quality and shelf-life of processed tropical fruit juices in W. Africa.