Isolation and identification of Pantoea agglomerans from the inflated bag with dried hop pellets stored under a modified atmosphere.

Abstract

Isolation, characterization and identification of possible microbial contaminant(s) in the inflated foil bag containing hop pellets packed and stored in a modified atmosphere. Package gas of the inflated foil bag containing hop pellets was analysed by gas chromatography. Compared with the reference modified atmosphere, containing about 16vol.% of CO2 , the inflated bag atmosphere contained 53vol.% CO2 , suggesting possible microbial contamination. Therefore, several standard and mineral media, with added hop pellets or hop infusion, were used for cultivation at different temperatures under an anaerobic atmosphere. Cultivation in mineral medium with hop pellets yielded a bacterial isolate that was identified by MALDI-TOF mass spectrometry and verified by partial 16S rRNA gene analysis as Pantoea agglomerans, a known plant epiphyte. A novel strain of P. agglomerans (designed as DBM 3696) was found to be suspicious of causing inflation of the foil bag containing dried hop pellets packed in modified atmosphere. This study suggests that P. agglomerans, probably hop epiphyte, could cause sporadic inflation of bags with hop pellets packed in modified atmosphere causing logistical problems during bags transport.