## 2 Materials and Methods
### Culture Preparation and Enumeration  
The _L. brevis_, CCC B1300, Molson strain was obtained from the MICB 421 culture collection at the University of British Columbia Department of Microbiology and Immunology, as referred by [PERSON], [PERSON], and [PERSON] [22]. The strain was grown in De Man, Rogosa, and Sharpe (MRS) broth (Sigma, Toronto, ON, Canada) and incubated in a sealed bottle at 30 \({}^{\circ}\)C overnight (first incubation). The incubated strain was streaked on MRS agar plates and incubated inside an anaerobic jar with CO\({}_{2}\) generators (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) for 48 h at 30 \({}^{\circ}\)C. The incubated MRS agar plates were stored at 4 \({}^{\circ}\)C as a backup.  
The strain was acclimatized to each beer style to achieve a more realistic simulation of the contaminating strain within the breweries. Acclimatization induced the expression of _horA_ genes that have been associated with the strain's hop resistance capability [4]. The acclimatization procedure was adopted from [PERSON] et al. [23]. An aliquot (1 mL) of the incubated unacclimatized _L. brevis_ MRS broth was pipetted into 100 mL of sterilized 85:15 medium containing 85% beer and 15% MRS broth. Inoculated acclimatization mediums were incubated in a sealed media bottle for 48 h at 30 \({}^{\circ}\)C. BA and CA acclimatized strains were each streaked into three MRS agar plates and incubated inside an anaerobic jar with CO\({}_{2}\) generators (Becton, Dickinson and Company, Franklin Lakes, NJ, USA) for 48 h at 30 \({}^{\circ}\)C. The agar plates were stored at 4 \({}^{\circ}\)C until needed.  
Sterilized MRS broth (100 mL) was inoculated with 4-5 colonies of acclimatized strain using a sterile loop. The inoculated MRS broth (10 mL) was incubated overnight at 30 \({}^{\circ}\)C in a pre-autoclaved 1L media bottle with a stirring magnet and partially wrapped with aluminum foil with only the volume indicator lines exposed. The top lids of two 473 mL cans of beer, corresponding to the acclimatized strain, were flamed, and the contents were aseptically and slowly poured in at an angle to avoid excessive foaming. Another layer of aluminum foil was loosely wrapped around the 1 L bottle. The sample was homogenized  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Filter**} & \multicolumn{4}{c}{**Residence Time (min)**} \\ \cline{2-5}  & **5** & **2.5** & **0.5** & **0.25** \\ \hline \multicolumn{5}{c}{Fluence (J/cm\({}^{2}\)) 1  } \\ \hline No filter & 16.75 & 8.37 & 1.67 & 0.84 \\ \hline Clear filter & 8.93 & 4.46 & 0.89 & 0.45 \\ \hline Bronze-tinted filter & 1.32 & 0.66 & 0.13 & 0.07 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Accumulated fluence (J/cm\({}^{2}\)) for different treatments imparted on the two types of beer in this study.  
on a magnetic stir plate for 1 min. The estimated total volume of 956 mL was used for one treatment.  
Untreated and treated samples were serially diluted in test tubes of 9 mL sterile 0.1% peptone water until 10\({}^{-6}\) dilution was reached and then plated in triplicate on 3M LAB Petrifilms (Petrifilms). Loaded Petrifilms were incubated for 48-72 h at 30 \({}^{\circ}\)C. Colonies in Petrifilms with 30-300 CFU were enumerated. Petrifilms were used due to their convenience and accuracy. [PERSON] et al. [24] showed no significant differences in bacterial counts enumerated by Petrifilms and MRS agar medium.