碩士 / 國立屏東科技大學 / 水產養殖系所 / 98 / The purpose of this study was to isolate and identify a beneyicial bacterium, Bacillus subtilis E20, from natto (fermented soybeans), and incorporate it into shrimp (L. vannamei) feed to promote shrimp (L. vannamei) growth performance. A protease-producing bacterium, E20, isolated from natto was identified as B. subtilis by an API 50 CHB kit and the 16S rDNA sequence. B. subtilis E20 was able to grow at a broad range of temperatures (10–50℃), pH values (5–10), and NaCl levels (0–9%). The best culture conditions for B. subtilis E20 to produce the protease were 40℃, a pH of 6–8 and 0% NaCl. No shrimp (L. vannamei) died after being injected with B. subtilis E20 [up to 109 colony-forming units (cfu) per shrimp]. The analysis of bacterial growth inhibitory showed that B. subtilis E20 has an ability to supress the growth of Aeromonas hydrophila. B. subtilis E20 was incorporated in diets at the levels of 0 (control), 106, 107, and 108 cfu/ kg) for shrimp (L. vannamei) grow-out culture, and results showed that after feeding on B. subtilis E20-containing diets (108 cfu/kg) of diet), shrimp (L. vannamei) had excellent growth performance and production compared to the control because protease activities in the digestive tract were improved by B. subtilis E20. According the results of PCR and real-time PCR analysis, positive result was recorded in intestine of shrimp (L. vannamei) fed with B. subtilis E20 containing diets, and the concentration of B. subtilis E20 in shrimp (L. vannamei) intestine was significant increased at the 14 days of feeding. It is suggested that B. subtilis E20 is able to survivial and colon in shrimp (L. vannamei) intestine. In order to understand the effect of storage on the quality of B. subtilis E20 containing diets, the experimental diets was placed at 4℃ and room temperature for 2 months. The results showed that the concentration of B. subtilis E20 was not statistical decreased in all experimental diets, but the contaminated bacteria in diets was increased as the increase of storage time. However, the time of contaminated bacteria occurring in B. subtilis E20 containing diets was significant postponed compared to control diet. In conclusion, Bacillus subtilis E20 isolated from natto is a great protease producer and is able to improve shrimp (L. vannamei) growth performance through increasing the digestibility of food. Results suggest that B. subtilis E20 is a potential candidate for use as a probiotic to improve shrimp (L. vannamei) growth performance, and consequently reduce feed costs.
| Identifer | oai:union.ndltd.org:TW/098NPUS5086006 |
| Date | January 2010 |
| Creators | Pei Lin Ho, 何珮琳 |
| Contributors | Chun Hung Liu, 劉俊宏 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 79 |
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