Administration of microencapsulated Enterococcus faecium ABRIINW.N7 with fructo-oligosaccharides and fenugreek on the mortality of tilapia challenged with Streptococcus agalactiae

We investigated the probiotic potential of a microencapsulated Enterococcus faecium ABRIINW.N7 for control of Streptococcus agalactiae infection in hybrid (Oreochromis niloticus × Oreochromis mossambicus) red tilapia. A two-phase experiment approach was completed in which E. faecium bacteria were propagated, from which a culture was isolated, identified using molecular techniques, and microencapsulated to produce a stable commercial fructooligosaccharide (FOS) and fenugreek (Fk) product of optimal concentration. The FOS and Fk products were assessed in a 90-days in vivo challenge study, in which red hybrid tilapia were allocated to one of five treatments: (1) No Streptococcus agalactiae (Sa) challenge (CON); (2) Sa challenge only (CON+); (3) Sa challenge in a free cell (Free Cell); (4) Sa challenge with 0.8% (w/v) Alginate; (5) Microencapsulated FOS and Fk. In vitro results showed high encapsulation efficiency (≥98.6 ± 0.7%) and acceptable viability of probiotic bacteria within the simulated fish digestive system and high stability of viable cells in all gel formulations (34 < SR% <63). In vivo challenges demonstrated that the FOS and Fk products could be used to control S. agalactiae infection in tilapia fish and represented a novel investigation using microencapsulation E. faecium as a probiotic diet for tilapia fish to control S. agalactiae infection and to lower fish mortality. It is recommended that local herbal gums such as 0.2% Persian gum and 0.4% Fk in combination with 0.8% alginate (Formulation 7) can be used as a suitable scaffold and an ideal matrix for the encapsulation of probiotics. These herbal gums as prebiotics are capable of promoting the growth of probiotic cells in the food environment and digestive tract.

Herbal hydrogel-based encapsulated Enterococcus faecium ABRIINW.N7 improves the resistance of red hybrid tilapia against Streptococcus iniae

AIMS

The streptococcal disease has been associated with serious mortality and significant global economic loss in the tilapia farming industry. The overall goal of this work was to test herbal hydrogels based on encapsulated Enterococcus faecium ABRIINW.N7 for potential probiotic anti-microbial activity against Streptococcus iniae in red hybrid tilapia.

METHODS AND RESULTS

Abnormal behaviour, clinical signs, postinjection survival and histopathology (kidney, liver, eye and brain) were measured. Cumulative mortality of CON⁺ , free cells, ALG and treatments (F1-F7) was 30, 24, 22, 19, 17, 17, 16, 14, 14 and 12 out of 30 fish and the survival rates for E. faecium ABRIINW.N7 microencapsulated in an alginate-BS blend with 0·5, 1, 1·5, 2, 2·5 and 3% fenugreek were 43, 43, 47, 53, 53 and 60%, respectively. After the incorporation of fenugreek with the alginate-BS blend, there was an 8-21% increase in probiotic cell viability. Furthermore, the survival rate for the alginate-BS blend with 2·5 and 3% fenugreek (F6 and F7) was significantly (P ≤ 0·05) higher than other blends. The highest encapsulation efficiency, viability in gastrointestinal conditions and during storage time and excellent antipathogenicity against S. iniae were observed in alginate-BS +3% fenugreek formulation (F7).

CONCLUSIONS

It is recommended that probiotic strains like E. faecium ABRIINW.N7 in combination with local herbal gums, such as BS and fenugreek plus alginate, can be used as a suitable scaffold and an ideal matrix for the encapsulation of probiotics.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study proposes models connecting process parameters, matrix structure and functionality.