International Journal of Aquaculture, 2017, Vol.7, No.23, 143-158
143
Research Article Open Access
Evaluation of Gut Associated Extracellular Enzyme-producing and Pathogen
Inhibitory Microbial Community as Potential Probiotics in Nile Tilapia,
Oreochromis niloticus
Koushik Ghosh , Sudeshna Banerjee, Urmi Mustafi Moon, Hassan Ahmad Khan, Dipanjan Dutta
Aquaculture Laboratory, Department of Zoology, The University of Burdwan, Golapbag, Burdwan 713 104, West Bengal, India
Corresponding author Email
International Journal of Aquaculture, 2017, Vol. 7, No.23 doi
Received: 09 Nov., 2017
Accepted: 19 Dec., 2017
Published: 29 Dec., 2017
Copyright © 2017
Ghosh et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article
:
Ghosh K., Banerjee S., Moon U.M., Khan H.A., and Dutta D., 2017, Evaluation of gut associated extracellular enzyme-producing and pathogen inhibitory
microbial community as potential probiotics in Nile Tilapia,
Oreochromis niloticus
, International Journal of Aquaculture, 7(23): 143-158 (doi:
Abstract
The present study aimed at evaluation of gut associated bacteria and yeasts in Nile tilapia (
Oreochromis niloticus
) as
novel probiotics depending on extracellular digestive (amylase, protease and lipase) and degradation (cellulase, phytase, and xylanase)
enzymes-producing ability, pathogen inhibition and bio-safety. The gastrointestinal (GI) tracts were taken out, separated into
proximal and distal segments, homogenized, and enrichment culture was done on selective media plates for isolation of bacteria.
Yeasts were isolated on yeast extract-peptone-dextreose media supplemented with antibiotics (150 mg L
-1
). Both, bacteria and yeasts
were detected in the GI tracts of Nile tilapia. Diverse enzyme-producing microbial populations were higher in the distal segment than
the proximal segment. Ten out of 97 bacteria and 5 out of 32 yeast strains were primarily selected. The bacterium ONF1P and the
yeast strain ONF7.1C were noticed as the efficient exo-enzyme producing strains. Both the isolates were antagonistic against
≥
2
tested fish pathogens. Both the strains were tolerant to diluted bile juice, capable to grow in fish mucus (intestinal) and compatible
with previously isolated autochthonous fish gut bacteria. The isolates didn’t induce any pathological lesions or mortality in
O.
niloticus
fingerlings. The strains ONF1P and ONF7.1C were identified as
Bacillus
licheniformis
(KT362744) and
Pichia kudriavzevii
(KT582009), respectively, through 16S /18S rRNA gene fragment analyses. Extracellular enzyme-producing gut bacteria and yeast
may restrain the growth of some fish pathogens and tolerate conditions within the GI tract. Further research should be directed to
determine their in vivo effects on growth and disease resistance in
O. niloticus
.
Keywords
Nile tilapia;
Bacillus
;
Pichia
; Antagonism; Co-culture; Probiotics
1 Background
Tilapia, the second most common farmed fish in the world, is native to Africa and the Middle East (FAO, 2017).
Ease of spawning (multiple spawner), efficient feed conversion, tolerance to adverse environmental conditions,
resistance to disease, rapid growth rate and acceptability to the consumers made it a candidate species for culture
(El-Saidy and Gaber, 2005). At present, many tropical and subtropical countries have focused on tilapia-culture to
maximize aquaculture production (Lin et al., 2008). Tilapia has established a secure position in a number of water
impoundments of India. At present,
O. niloticus
contributes more than 80% of tilapia aquaculture production
globally and its performance in the ponds and reservoirs of India is much better than
O. mossambicus
. Production
of tilapia is expanding in India following government approved responsible aquaculture. Exports of frozen tilapia
augmented from 1133 tonnes in 2013 to 7738 tonnes in 2014 during the period of January-September (FAO,
2015). The rapid growth in the tilapia culture industry has led to the emergence of a number of pathogens e.g.,
Aeromonas
spp.,
Streptococcus
spp.,
Flexibacter
spp. In consequence of high stocking density, intensive fish
production often results in poor water quality explicating reduced growth and increased disease. Besides causing
environmental hazards (Martinez, 2009), the excessive and inappropriate use of antibiotics has resulted in
emergence of resistant strains that could be pathogenic in nature (Nomoto, 2005). Therefore, alternative ways of
combating diseases need to be developed. Application of probiotics is suggested to be an environment-friendly
method to improve nutrient utilization and combat pathogens in aquaculture (Vaseeharan and Ramasamy, 2003;
Zheng et al., 2011; Sorroza et al., 2012).
