Abstract
Liquid preparations of bdellovibrios are currently commercialized as water quality improvers to control bacterial pathogens in whiteleg shrimp Penaeus vannamei. However, the efficacy of these liquid preparations is significantly impaired due to a dramatic loss of viable cells during long-term room temperature storage. Thus, new formulations of bdellovibrios are greatly needed for high-stablility room-temperature storage. In the present study, the encapsulated powder of Bdellovibrio sp. strain F16 was prepared using spray drying with 20 g L−1 gelatin as the coating material under a spray flow of 750 L h−1, a feed rate of 12 mL min−1, and an air inlet temperature of 140 °C. It was found to have a cell density of 5.4 × 107 PFU g−1 and to have spherical microparticles with a wrinkled surface and a diameter of 3 μm to 12 μm. In addition, the encapsulated Bdellovibrio powder presented good storage stability with its cell density still remaining at 3.5 × 107 PFU g−1 after 120 days of room-temperature storage; it was safe for freshwater-farmed whiteleg shrimp with an LD50 over 1200 mg L−1, and it exhibited significant antibacterial and protective effects at 0.8 mg L−1 against shrimp-pathogenic vibrios. To our knowledge, this is the first report on a promising Bdellovibrio powder against shrimp vibrios with high stable room-temperature storage.
Highlights
The whiteleg shrimp Penaeus vannamei is one of the most important farming shrimp species around the world and is extensively cultivated in Central and South America, USA, East and South East Asia, Middle East, and Africa [1]
Infections caused by Vibrio parahaemolyticus, Vibrio cholerae, and Vibrio vulnificus have resulted in significant economic losses in shrimp farming regions [3,4,5]
Bdellovibrio sp. strain F16 cells could be well encapsulated by spray drying with 20 g L−1 of gelatin under spray flows of 650 to 750 L h−1, feed rates of 8–12 mL min−1, and an air inlet temperature of 140 ◦C (Figure 1)
Summary
The whiteleg shrimp Penaeus vannamei is one of the most important farming shrimp species around the world and is extensively cultivated in Central and South America, USA, East and South East Asia, Middle East, and Africa [1]. Vibriosis has become a major challenge in shrimp aquaculture because of the lack of effective and safe control agents [2]. Infections caused by Vibrio parahaemolyticus, Vibrio cholerae, and Vibrio vulnificus have resulted in significant economic losses in shrimp farming regions [3,4,5]. New agents to control vibriosis are needed for the sustainable development of the shrimp farming industry. The liquid preparations of bdellovibrios that are used in shrimp aquaculture are commercialized as water quality improvers and are widely available on the market [8]. The efficacy of these commercial liquid preparations has been significantly impaired as a result of the massive loss of viable cells during long-term room temperature storage [9]. Effective strategies should be adopted to enhance the stability of viable cells during storage at room temperature
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