Inhibiton and Staphylococcus aureus Cell Membrane Leakage by Papaya Latex.

Abstract

Dangke is a traditional milk curd product, made by coagulation of milk using fresh papaya latex. This product is usually kept at room temperature until consumption and it can lasting until 24 hours. Dried papaya latex in dangke production was considered not only as coagulant but also act as antibacterial agent. In this study, the antibacterial activity of dried papaya latex toward S. aureus was determined by direct contact in broth media and dangke. Fresh papaya latex was dried using vacuum oven at 50-55 for 22 hours. As much as 0.0277 g/100 mL in concentration of dried papaya latex could reduce approximately 1 log CFU/mL of S. aureus and 0.0011 g/100 mL of papain showed inhibition effect instead of reducing effect against S. aureus in broth after 24 hours. Dried papaya latex and papain also showed ability to inhibit S. aureus growth in dangke within 24 hours storage at room temperature. The antibacterial activity of non-proteolytic compound of papaya latex, i.e ethanolic extract of papaya latex was determined by macrodilution method, resulted in the MIC90 of 8 mg/mL. Antibacterial agent could inhibit bacterial growth by some mechanisms, one of them is cell membrane damage, protein synthesize and DNA synthesize disruption. Papaya latex which contains proteolytic enzyme as bioactive compound was considered can cause the cell membrane leakage. The antibacterial activity toward cell membrane caused the leakage of 260 nm absorbing material from cell. In this study, the cell membrane leakage after exposure was detected by measuring the optical density of bacterial supernatant at 260 nm. The result showed that exposure to increasing antibacterial concentration resulted in increasing of optical density of S. aureus supernatant, indicating that the antibacterial caused the S. aureus membrane leakage. Imaging by fluorescence microscopy showed that S. aureus exposure to antibacterial caused the membrane leakage thus gave Propidium Iodide (PI) chance to penetrate onto the cell, which indicated by the changing of fluorescence color from green fluorescence to red fluorescence.