| Summary: | 碩士 === 國立宜蘭大學 === 食品科學系碩士班 === 101 === Nisin and hydrolyzed chitosan (HC) are natural antibacterial materials; these antibacterial materials effectively suppressed Gram-positive and Gram-negative microbacteria, respectively. Nevertheless, high-dosage and narrow antibacterial targets were the problems for treatment by single antibacterial substance. In this study, bacterial cellulose (BC) with fine fiber network was applied as the carrier. Water-soluble CMC was applied to be the coating layer. These materials were prepared which was investigated the composite antibacterial effect by controlled-release nisin and HC to lessen the antibacterial substance dosage. At 37oC environment, the minimum inhibitory concentration (MIC) of 12 hours hydrolyzed HC against G() Escherichia coli and G(+) Staphylococcus aureus were 100 and 400 μg/mL, while nisin against E. coli and S. aureus were 6 and 150 IU, respectively. At 12oC environment, the MIC of nisin and HC against E. coli were 25 IU and 50 μg/mL while against S. aureus were 0.87 IU and 400 μg/mL, respectively. It revealed that the MIC of nisin and HC at 12oC were lower than those at 37oC. The controlled-release of nisin and HC by simultaneously adding nisin contained BC (NBC) and HC contained BC (CBC) offered desirable composite antibacterial ability than that in N-CBC and bi-layer BC (BLBC) system in microbial broth medium at 12oC. The simultaneous adding of NBC and CBC possessed a desirable antibacterial ability against both S. aureus and E. coli at low dosage for 12.5 IU nisin in NBC and 62.5 g HC in CBC, respectively. The low concentration of nisin significantly inhibited the S. aureus growth in 12oC milk, however, high concentration of nisin (600 IU) or HC (500 g/mL) was required to inhibit the E. coli growth. Since directly adding high concentration of HC, higher than 500 g/mL, caused protein aggregation in the milk, gradual release of HC from CBC resolved such problem. For low temperature environment, simultaneous addition of NBC (300 IU nisin) and low dosage of HC (62.5 g in CBC) in 12oC milk is enough to offer composite antibacterial ability against S. aureus by hurdle effect while no apparent hurdle inhibition effect against E. coli.
|
|---|
