ENVIRONMENTAL BIOTECHNOLOGY Poly-ß-hydroxybutyrate content and dose of the bacterial carrier for Artemia enrichment determine the performance of giant freshwater prawn larvae Truong Quoc Thai & Mathieu Wille & Linsey Garcia-Gonzalez & Patrick Sorgeloos & Peter Bossier & Peter De Schryver Received: 6 December 2013 /Revised: 7 January 2014 /Accepted: 10 January 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract The beneficial effects of poly-β-hydroxybutyrate (PHB) for aquaculture animals have been shown in several studies. The strategy of applying PHB contained in a bacterial carrier has, however, hardly been considered. The effect of administering PHB-accumulated Alcaligenes eutrophus H16 containing 10 or 80 % PHB on dry weight, named A10 and A80, respectively, through the live feed Artemia was investigat- ed on the culture performance of larvae of the giant freshwater prawn (Macrobrachium rosenbergii ). Feeding larvae with Artemia nauplii enriched in a medium containing 100 and 1,000 mg L -1 A80 significantly increased the survival with about 15 % and the development of the larvae with a larval stage index of about 1 as compared to feeding non-enriched Artemia . The survival of the larvae also significantly increased with about 35 % in case of a challenge with Vibrio harveyi . The efficiency of these treatments was equal to a control treatment of Artemia enriched in an 800 mg L -1 PHB powder suspension, while Artemia enriched in 10 mg L -1 A80, 100 mg L -1 A10, and 1,000 mg L -1 A10 did not bring similar effects. From our results, it can be concluded that PHB supplemented in a bacterial carrier (i.e., amorphous PHB) can increase the larviculture effi- ciency of giant freshwater prawn similar to supplementation of PHB in powdered form (i.e., crystalline PHB). When the level of PHB in the bacterial carrier is high, similar beneficial effects can be achieved as crystalline PHB, but at a lower live food enrichment concentration expressed on PHB basis. Keywords Amorphous . Poly-ß-hydroxybutyrate . Macrobrachium rosenbergii . Survival . Growth . Disease resistance Introduction The occurrence of bacterial infections is a major obstacle in the development of giant freshwater prawn (Macrobrachium rosenbergii ) production (Sung et al. 2000; Kennedy et al. 2006; Shailender et al. 2012). In larviculture, mass mortality of larvae as well as infections in post-larvae have especially been imputed to opportunistic pathogens (Nhan et al. 2010a). Vibrio spp. have been isolated at several occasions from af- fected M. rosenbergii larvae and are considered the main causative agents of disease outbreaks in the larviculture of M. rosenbergii (Alavandi et al. 2004; Jayaprakash et al. 2006). Besides maintaining optimal environmental conditions in prawn hatcheries, antibiotics have been used as a popular method to control bacterial pathogens. However, the prophy- lactic use of antibiotics can result in multiple resistances in several pathogens (Teo et al. 2000; 2002), leading to ineffec- tive treatment and an increased risk of resistance transfer to animal and human pathogens (Defoirdt et al. 2007a; Das et al. 2009; Liu et al. 2010). Therefore, new microbial control techniques should be developed to make M. rosenbergii cul- ture more sustainable. Short-chain fatty acids (SCFAs) seem good candidates to be used in an alternative strategy as they have been shown to possess bacteriostatic and bactericidal activity depending on the concentration of application (Defoirdt et al. 2009). The mechanism for inhibition of pathogenic growth is based on the T. Q. Thai : M. Wille : P. Sorgeloos : P. Bossier : P. De Schryver (*) Laboratory of Aquaculture and Artemia Reference Center, Ghent University, Rozier 44, 9000 Ghent, Belgium e-mail: peter.deschryver@ugent.be T. Q. Thai Research Institute for Aquaculture, No. 3, 33 Dang Tat, Nha Trang City, Vietnam L. Garcia-Gonzalez VITO, Boeretang 200, 2400 Mol, Belgium Appl Microbiol Biotechnol DOI 10.1007/s00253-014-5536-7