What is the independent variable(s)? Dependent variable? What is the control? What is the purpose of sanitizing the apple prior to inoculating it with plantarum and L. monocytogenes? Why must this work be done in a biological safety cabinet? **Objective:** To determine the efficacy of *Lactobacillus plantarum* on the reduction of *L. monocytogenes* on Granny Smith apples stored at 4°C and 20°C for seven and five days, respectively.**Methods:** Prior to inoculation, the surface of the apples was washed for 15 seconds in running deionized water, sprayed with 5 ml of 70% ethanol, and air-dried for 30 minutes under a biological safety cabinet. The sanitized apples were sliced using a sterile stainless-steel apple slicer. The weight of the apple slices was approximately 12 ± 3 g. The flesh of the apple slices was spot inoculated with 20 µL of either the pathogen or 0.1% sterile peptone water. Treated apple slices were air-dried at 20°C in the biological safety cabinet for approximately 45 minutes. Afterwards, 200 µL of either *Lb. plantarum* was spot-inoculated on the flesh of the apple slices. Treated apple slices were air-dried at room temperature in the biological safety cabinet for approximately 1.5 hours. The treated apple slices were then placed in Whirl-Pak® bags and stored at 4°C and 20°C for seven and five days, respectively. Samples were diluted with 0.1% peptone water, homogenized in a stomacher at 200 rpm for one minute, serially diluted, and plated on the appropriate media. *Lb. plantarum* and *L. monocytogenes* were enumerated using de Man, Rogosa, and Sharpe (MRS) and modified Oxford agar (MOX) agar.**Results:**The graph is a line chart that displays the mean population (log CFU/g) of *L. monocytogenes* over storage days, with treatments at 4°C and 20°C in the presence and absence of *Lb. plantarum*. There are four lines, denoting different conditions:- □ *L. monocytogenes*, 4°C- ■ *L. monocytogenes*, 20°C- ○ *L. monocytogenes*/*Lb. plantarum*, 4°C- ● *L. monocytogenes*/*Lb. plantarum*, 20°CThe x-axis represents the storage day (0, 1, 3,

Lactobacillus bacteria are found in rich carbohydrates containing products like milk, cheese, yogurt, fermented milk products and fermented beverages (example- wine and Cider) Lactobacillus Bacteria are a part of microbial flora in human blody. They are found in gastrointestinal system, urinary system and genital system. Lactobacillus Bacteria are present in human intestines, they protect the gut by preventing colonization of pathogen in gut. They are also present in vagina, they maintain the low vaginal pH by producing lactic acid. Lactobacillus are gram positive, rod shaped Bacteria. Interesting features of lactobacillus Bacteria are Lactobacillus convert sugars/carbohydrates into lactic acid through anaerobic Fermentation. Lactobacillus have a symbiotic/ mutualistic relationship with human , human provides them with food and shelter and in turn they protect human gut from pathogen.1. An independent variable can be directly controlled by the observer or experimenter. Storage day under the growth of Lb. plantarum is the independent variable of the experiment. 2. Dpendant variable is the output of the experiment. Here, CFU of L.monocytogenes. 3. Negative control is the sample pretreated with sterile peptone instead Lb. plantarum. 4. Apple must be sanitized prior to the inoculation inorder to avoid contamination (growth of unwanted bacteria/fungi) which influence the experimental result. 5. BSL is a ventilated enclosure ensure protection to the experimenter from aerosols arising from the handling of potentially hazardous micro-organisms like L.movnocytogenes. HEPA filter continuously discharge the airflow to the atmosphere.