Application and mode of action of the poly-U+03B2-hydroxybutyrate (PHB) in Penaeus culture

In this PhD research, the mechanisms of action of the bacterial storage compound poly-U+03B2-hydroxybutyrate (PHB) and its application in penaeid shrimp were explored. The supplementation of crystalline PHB (98 % poly-U+03B2-hydroxybutyrate - 2 % poly-U+03B2-hydroxyvalerate) at 1 g L-1 via Artemia in a short term enrichment strategy significantly increased the survival and overall performance of postlarval tiger shrimp Penaeus monodon. Co-supplying with lipid emulsion rich in highly unsaturated fatty acids (HUFAs) at 0.3 g L-1 did not add to these effects (Chapter 2). Dietary PHB supplemented at 100 mg L-1 for 48 h significantly increased the total lipid contents from 6.5 ± 0.2 % on dry weight (DW) in starved Artemia to 8.3 ± 0.5 % and 9.3 ± 0.7 % on DW in Artemia supplied with crystalline and amorphous PHB, respectively (Chapter 3). In a carbon isotope tracer study, it was found that PHB offered in a natural matrix to postlarval whiteleg shrimp Litopenaeus vannamei was not used as building block but probably rather as energy source (Chapter 4). A completely new approach to use PHB in penaeid shrimp culture, namely the use of PHB-based bioplastics as substratum in penaeid culture systems, was explored in Chapter 5. The survival of postlarval tiger shrimp provided with PHB substratum made out of PHB type DP9002 (Metabolix GmbH, Köln, Germany) was 88.7 ± 3.4 % and this was significantly higher as compared to postlarvae provided conventional substratum consisting of polyvinylchloride (PVC) pipes (67.3 ± 6.5 %). In a separate experiment, provision of PHB substratum made out of PHB type P209 (Biomer, Krailling, Germany) to postlarval whiteleg shrimp (106 ± 52 mg) also resulted in significantly higher survival of 83.6 ± 3.4 % as compared to 73.9 ± 3.0 % for postlarvae provided with PVC substratum. Additional tests conducted to evaluate the effects of PHB substratum on the water quality resulted in a trend towards higher total ammonia-nitrogen (TAN) conversion from an initial concentration of 1.75 ± 0.0 mg L-1 to 0.35 mg ± 0.04 mg L-1 after 72 h while using no substratum and PVC substratum led to TAN concentrations of 1.28 ± 0.06 mg L-1 and 1.23 ± 0.10 mg L-1, respectively. Overall, the findings obtained in this PhD research have pointed out the important contributions of the bacterial storage compound PHB in improving the survival and overall performance of penaeid shrimp. Future studies are needed to determine whether PHB particles, once ingested and digested in the gut of penaeid shrimp, are degraded into the U+03B2-HB monomer and to determine whether this product could affect gut-associated microbial biota. Further study is also needed to evaluate the mechanisms behind the total ammonia-nitrogen removal capacity of PHB when offered as artificial substratum. Finally, strategies to lower costs of PHB are foreseen to be essential in order to render PHB more useful in the future.

ISBN:9789059899445

Jaar van publicatie:2016

Toegankelijkheid:Open