Single and Dual Species Biofilm Formation by Listeria Monocytogenes and Staphylococcus Aureus and its Sensitivity to Homemade Sanitizer

See, Wen Wen (2019) Single and Dual Species Biofilm Formation by Listeria Monocytogenes and Staphylococcus Aureus and its Sensitivity to Homemade Sanitizer. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Listeria monocytogenes are easily migrated from biofilm on the surfaces of the equipment to foods in food industry. This project studied on the biofilm producing ability of single- and dualspecies on stainless steel coupons under four different treatments at different time point. The highest biofilm formation was formed under Treatment 1 has shown which is 8.34 ± 0.29 log CFU/cm2 at 7 hour with uncontaminated surface in Listeria suspension in 2 mg/mL of diluted chicken juice extract while Treatment 2 has shown 8.35 ± 0.04 log CFU/cm2 at 24 hour with uncontaminated surface in Listeria suspension in 50 mg/mL of diluted chicken juice extract. Treatment 3 has shown 8.42 ± 0.04 log CFU/cm2 at 7 hour with contaminated surface in Listeria suspension in 50 mg/mL diluted chicken juice extract and Treatment 4 has shown 8.71 ± 0.02 log CFU/cm2 at 24 hour with contaminated surface in Listeria and Staphylococcus suspension in 50 mg/mL diluted chicken juice extract. The modified Gompertz equation was used to determine the attachment kinetics parameters. Among four different treatments, Treatment 4 has shown the lowest C value 0.98 ± 0.002 log CFU/cm2 with longest time, m to reach the formation rate, k compare to other treatments. The efficiency of commercial sanitizer with 100% concentration at Treatment 1 has shown the greatest log reduction which was 7.95 ± 0.04 log CFU/cm2 with calcium carbonate as an active ingredient compare to homemade sanitizer at 24 hour. At 168 hour, Treatment 1 has shown the greatest log reduction which was 7.72 ± 0.10 log CFU/cm2 by using commercial sanitizer with calcium carbonate as an active ingredient at 100% concentration. Homemade sanitizer with natural ingredients has shown lower sensitivity at both time point 24 and 168 hours along the mature biofilms formation. Microscope observation by scanning electron microscope (SEM) has shown in this project was to reveal the attachment of Listeria monocytogenes on stainless steel surface at 24 hour and 168 hour, using chicken juice culture medium as a substrate. Keyword: Listeria monocytogenes, Staphylococcus aureus, stainless steel surface, sanitizer