| Summary: | 碩士 === 國立臺灣大學 === 動物科學技術學研究所 === 99 === The objective of this study was to develop a low-cost medium to cultivate potentially probiotic lactic acid bacteria (LAB) with antibacterial, antibiotic-tolerant and immunoregulatory activities and formulated these LAB using freeze-drying as commercial feed additives.
In the first part of study, eighteen LAB strains, isolated from pig feces, chicken intestine and feces, were evaluated their antibacterial activities (Escherichia coli BCRC 10450, Staphylococcus aureus BCRC 10451 and Salmonella typhimurium BCRC 10747), antibiotic susceptibilities and immune-modulating effect (interleukin-6 (IL-6)). Results indicated that four lactobacilli including Lactobacillus johnsonii 2-1A, Lb. mucosae x-4w-1, Lb. johnsonii x-1d-2 and Lb. mucosae 4-2B showed better functional properties than the other strains. These four strains were selected for the next study.
In the second part of study, we formulated the low-cost culture media for the above selected LAB. The response surface methodology and sequential quadratic programming methods were used to optimize the best formula to gain maximum populations of LAB. Results indicated that the cell counts of four LAB strains could reach to 9.14, 9.27, 8.76 and 8.99 log CFU/mL after a 16-hour incubation with the new media, respectively. The cell counts obtained from verification experiments were not significantly different to those from RSM-based prediction (P > 0.05). In addition, the cost of these new media was reduced to below 1% when compared with the price of MRS broth.
The effects of freeze-drying and alginate encapsulation on the survival of probiotic lactobacilli were also evaluated. After 8 weeks of storage at 4°C, the viabilities of the tested LAB strains remained high in the freeze-dried powders. The freeze-dried powders containing LAB were used in subsequent feeding trail. The 21-day pre-weaning piglets were fed with Lb. mucosae x-4w-1 and Lb. johnsonii x-1d-2 isolated from porcine and investigated the effect of LAB feeding on the piglet’s growth performance, fecal microflora and serum immunoglobulin level. It was only showed that the serum IgG concentration of piglet increased after 3 weeks of feeding.
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