ITS-seq
54 Swabs were taken from biofilms in filling halls of breweries, collected in sterile tubes and shipped on ice to the Netherlands. Biofilm samples were still cold upon arrival. Samples were resuspended in 100 to 300 l of 0.9 percent NaCl, depending on the size of the sample, by vigorously vortexing. A set of 20 samples from this survey was used for meta-barcoding analysis at BaseClear (www.baseclear.com) using Next Generation Sequencing of the internal transcribed spacer region (ITS). The ITS target region of the samples was amplified using Phusion HF PCR mastermix (www.thermofisher.com) and the primer pair TCGTCGGCAGCGTCAGATGTGTATAAGA GACAGGCATCGATGAAGAACGCAGC / GTCTCGTGGGCTCGGAGATGTGTATAAGAGAC AGTCCTCCGCTTATTGATATGC. PCR amplification was performed according to the following program: 98 C 30 sec, 25 cycles of 98 C 10 sec, 55 C 30 sec, 72 C 30 sec, followed by 72 C for 5 min and hold at 4 C. Barcodes and adapter sequences were added to the amplicons, after which they were purified, normalised, pooled and used for sequencing