Biofilm Formation of Listeria Monocytogenes on Plastic Surface as Affected by Temperature and pH Level

Ng, Poh Yun (2018) Biofilm Formation of Listeria Monocytogenes on Plastic Surface as Affected by Temperature and pH Level. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Listeria monocytogenes is one of the main causes of foodborne illness called listeriosis that could be found in food industry. Biofilm formation of L. monocytogenes could protect them against the environmental stress and disinfection, but it could be affected by the surrounding conditions include temperature and pH level. In this project was study on the effect of temperature at 7 and 37˚C with pH level of 6 and 7 on biofilm formation of L. monocytogenes on plastic surface. Biofilm formation was measured and percentage of cell affinity was used to determine cell surface changes. The attachment kinetic of L. monocytogenes was carry out under different conditions at different time point. The highest biofilm formation for pH 7, 37˚Cwas 9.08 ±0.02 log CFU/cm2 and for pH6, 37˚C was 10.69 ± 0.00 log CFU/cm2 at time 72 hour; while for pH7, 7˚C was 8.09 ± 0.05 log CFU/cm2 and for pH6, 7˚C was 8.46 ±0.01 log CFU/cm2 at time 168 hour. The modified Gompertz equation was used to estimate the attachment kinetics parameters. For pH6, 37˚C shown the highest C value 6.45 ± 0.03 log CFU/cm2 and shortest time, m to reach the formation rate, k compare to other conditions. C is total amount of biofilm that formed after first hour (log CFU/ cm2). Value m is time required to reach the maximum biofilm formation rate (h) and k is formation rate at time m (1/h). Besides, pH6, 37˚C had shown the highest percentage cell affinity 86.25% ± 2.17(Chloroform), 37.08% ± 1.91(Ethyl acetate) and 10.83% ± 1.91 (Hexadecane) compare to others.