Aims: To isolate and identify a benefic bacterium, Bacillus subtilis E20, from natto (fermented soybeans), and incorporate it into shrimp feed to promote shrimp growth performance. Methods and Results: 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°C), pH values (5-10), and NaCl levels (0-9%). The best culture conditions for B. subtilis E20 to produce the protease were 40°C, a pH of 6-8 and 0% NaCl. No shrimp died after being injected with B. subtilis E20 [up to 10 9 colony-forming units (CFU) per shrimp]. Bacillus subtilis E20 was incorporated in diets at the levels of 0 (control), 10 6 , 10 7 , and 10 8 CFU kg )1 for shrimp grow-out culture, and results showed that after feeding on B. subtilis E20-containing diets (10 8 CFU kg )1 of diet), shrimp had excellent growth performance and production compared to the control because protease activities in the digestive tract were improved by B. subtilis E20. Conclusions: Bacillus subtilis E20 isolated from natto is a great protease producer and is able to improve shrimp growth performance through increasing the digestibility of food. Significance and Impact of the Study: Results suggest that B. subtilis E20 is a potential candidate for use as a probiotic to improve shrimp growth performance, and consequently reduce feed costs.
To produce a thermostable and neutral phytase (phy) of Bacillus subtilis E20 in Escherichia coli HMS174 and evaluate its efficiency in improving growth performance. The phy C of B. subtilis E20 was expressed in E. coli HMS 174, and then the 42‐kDa recombinant phy C was purified by Ni‐NAT and analysed by SDS–PAGE. The recombinant phy C had optimal ranges of pH of 6 ~ 7 and temperature of 50 ~ 60 °C. A thermostability analysis showed that the enzyme is a thermostable phytase, and around 33% of residual activity was detected after being incubated at 90 ~ 100 °C for 10 min. The recombinant phy C‐pretreated soybean meal for feed preparation improved white shrimp, Litopenaeus vannamei, growth and feed efficiency. Overall, the neutral and thermostable phy C is suitable for aquafeed, and it is able to improve the nutritional utilization, resulting in enhanced shrimp growth and reduced feed costs.
Using appropriate experimental design and modeling approach is important for predicting fruit yield of strawberry (Fragaria virginiana Mill.). A field study with Taoyuen 3 (T3) strawberry, a hybrid of Fragaria virginiana and Fragaria chiloensis (L.) Mill., was conducted at Taitung County, Taiwan, using a central composite design (CCD) to optimize its fruit yield. Response surface methodology (RSM), based on a three‐variable and five‐level CCD, was employed to obtain an optimal combination of porphyritic andesite (X1: 20 g kg−1), arbuscular mycorrhizal fungi (X2: 9 g kg−1), and soil pH levels (X3: 6.5) for predicting yields and maximum fruit productivity (10.3 g fruit−1). The data obtained in this study were fitted to a second‐order polynomial using multiple regression analysis. The observed data were in close agreement with the predicted value (two‐tailed independent t test with p = 0.923) based on the model. Our data indicate that RSM is a reliable approach to develop a model for predicting the fruit yields of the T3 strawberry in net houses.
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