Koushik Ghosh | The University of Burdwan (original) (raw)

Papers by Koushik Ghosh

Animals

The effects of Bacillus spp. (7 Log CFU g−1 feed) and fructooligosaccharide (FOS, 1%) as function... more The effects of Bacillus spp. (7 Log CFU g−1 feed) and fructooligosaccharide (FOS, 1%) as functional feed additives, either alone or in combination, were evaluated in a study on rohu, Labeo rohita fingerlings. The fish were fed different diets for 90 days, including a control diet and diets supplemented with FOS, B. licheniformis, B. methylotrophicus or synbiotic formulations of these. The results showed that the combination of B. licheniformis and FOS significantly improved weight gain, feed utilisation and protease activity compared to the other groups. Overall, the groups supplemented with probiotics and synbiotics (B. licheniformis + FOS or B. methylotrophicus + FOS) showed improvements in haematology, serum biochemistry and immune parameters compared to the control group. After 90 days of experimental feeding, the fish were challenged with pathogenic Aeromonas hydrophila, and data on haematology, immunity and stress parameters were collected. The results indicated that the appli...

International Journal of Aquaculture, 2017

The present study aimed at evaluation of gut associated bacteria and yeasts in Nile tilapia (Oreo... more 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.

Acta Ichthyologica et Piscatoria, 2016

Background. Although, presence of tannase-producing and/or tannin tolerant gut bacteria has been ... more Background. Although, presence of tannase-producing and/or tannin tolerant gut bacteria has been documented in ruminants and non-ruminant herbivores, the topic is rarely addressed in fi sh. The present study aimed at enumeration of autochthonous tannase-producing bacteria in the gut of freshwater teleosts. Materials and methods. This study covered seven freshwater teleost fi sh species: rohu, Labeo rohita

Journal of Applied Ichthyology, 2014

ABSTRACT Extracellular enzyme-producing yeasts might be involved in the supplementation of enzyme... more ABSTRACT Extracellular enzyme-producing yeasts might be involved in the supplementation of enzymes within the gastrointestinal tract of fish. The present study was intended to detect yeasts in the intestine of three Indian major carps (Labeo rohita, Catla catla, Cirrhinus mrigala), three exotic carps (Hypophthalmichthys molitrix, Ctenopharyngodon idella, Cyprinus carpio), as well as Nile tilapia (Oreochromis niloticus), and to identify the most promising extracellular enzyme-producing (e.g. amylase, protease, lipase, cellulase, xylanase and phytase) yeast strains by 18S rDNA sequence analysis. Selected for qualitative enzyme assay were 121 yeast strains, from which 28 were further studied for quantitative enzyme assay. The strain CMH6A isolated from C. mrigala exhibited the best extracellular enzyme activities except for amylase and cellulase. The strain ONF19B isolated from O. niloticus was noted as the best extracellular enzyme producer among the strains that produced all of the extracellular enzymes studied. Sequencing of the 18S rDNA fragment followed by nucleotide blast in the National Centre for Biotechnology Information (NCBI) GenBank revealed that strains CMH6A and ONF19B were similar to Pichia kudriavzevii (Accession no. KF479403) and Candida rugosa (Accession no. KF479404), respectively. The test of antagonism (in vitro) revealed that the isolated yeasts could not affect the growth of the autochthonous gut bacteria. This might indicate likely co-existence of autochthonous yeasts and bacteria in the fish gut. Further research is necessary to explore the possibilities of utilizing the extracellular enzyme-producing yeasts detected in the present study for commercial aquaculture.

Acta Ichthyologica et Piscatoria, 2015

Background. Exoenzyme-producing gut microbiota and their likely use as probionts have been widely... more Background. Exoenzyme-producing gut microbiota and their likely use as probionts have been widely investigated in major carps. However, reports on exoenzyme-producing capacity together with inhibition of fi sh pathogens are scarce. The presently reported study aimed at characterization of novel probionts from the gastro-intestinal (GI) tract of an Indian major carp-catla, Catla catla (Hamilton, 1822) depending upon extracellular enzyme-production, antagonism against Aeromonas spp., growth in fi sh mucus, bile tolerance, and bio-safety to the target fi sh. Materials and methods. GI tracts were divided into proximal and distal parts, homogenized, and plated onto selective media plates following enrichment culture technique. Exoenzyme-producing isolates were selected through qualitative and quantitative assay of 6 enzymes. Inhibition of Aeromonas spp. was tested through 'cross-streaking' and 'double-layer' method. Tolerance to GI condition was determined by growth in sterilized fi sh mucus and exposure to bile juice. Bio-safety evaluation was done by intra-peritoneal injection of live candidate probiotics and co-culture with autochthonous gut bacteria. Further, 16S rDNA fragments from the putative probiotics were sequenced, edited, analysed, identifi ed, and deposited to the GenBank. Results. Seventeen potent isolates were primarily selected through the ability of producing extracellular enzymes, viz., amylase, protease, lipase, cellulase, phytase, and xylanase. Further study portraying antagonism against Aeromonas salmonicida, A. hydrophila, and A. veronii led to select the strains CCH1A and CCH1Ph as putative probiotics. Both the strains were competent to grow in intestinal mucus and could resist diluted bile juice (9% and 10.5%, respectively). The isolates did not produce any disease symptom or mortality in Catla catla fi ngerlings during the 21 day trial and were competent to grow with other autochthonous isolates. On the basis of phenotypic characteristics and 16S rDNA sequence analysis, the strains CCH1A and CCHIPh were identifi ed as Bacillus aerius (KF623288) and Bacillus sonorensis (KF623289), respectively. Conclusion. Exoenzyme-producing gut bacteria may inhibit the growth of pathogenic Aeromonas spp. and tolerate gastrointestinal condition. Further research is inevitable to explore their potentialities in aquaculture.

Research in Veterinary Science, 2016

The study explored antagonistic activity of the cellular components of potential probiotic bacter... more The study explored antagonistic activity of the cellular components of potential probiotic bacteria from mrigal (Cirrhinus mrigala) against fish pathogens with a basic insight of the chemical nature of the antagonistic compound. Totally 208 autochthonous gut bacteria were isolated, of which 22 strains revealed antagonism towards ≥2 of the six common fish pathogens. Zones of inhibition (halo diameter) were presented as score and the four most promising strains were selected as putative probiotics based on the cumulative score assigned. Further, evaluation of different cellular components exhibited bactericidal activity against the fish pathogens. Verification of other probiotic properties revealed that each of the selected strains produced diverse extra-cellular enzymes. The selected strains grew better in intestinal mucus than skin mucus, were resistant to diluted bile juice (2-20%) and safe for the target fish. The extracellular product used as crude bacteriocin revealed thermostability (up to 90°C) and activity over wide pH range (4-9). Partial loss of activity through treatment with proteinase-K and trypsin indicated proteinaceous nature of the antibacterial compound produced by the probiotic strains. 16S rRNA partial gene sequencing revealed that the four strains CM1FG7, CM1HG5, CM3FG19 and CM3HG10 were similar to Bacillus stratosphericus (KM277362), Bacillus aerophilus (KM277363), Bacillus licheniformis (KM277364) and Solibacillus silvestris (KM277365), respectively.

Journal of microbiology, biotechnology and food sciences, 2015

Present study was aimed at isolation of autochthonous chitinase-producing bacteria from the gastr... more Present study was aimed at isolation of autochthonous chitinase-producing bacteria from the gastrointestinal tracts of 3 Indian Major Carps (Labeo rohita, Catla catla, Cirrhinus mrigala) and 3 exotic carps (Hypophthalmichthys molitrix, Ctenopharyngodon idella, Cyprinus carpio). Altogether, 119 bacteria were isolated from both the proximal and distal intestine and screened for chitinolytic activity. On the basis of chitin hydrolysis zone, 63 isolates were primarily selected for chitinase production, from which 34 potent strains were further studied for quantitative enzyme assay. Amongst them, the strains HMH1 and CMF2 exhibited potent chitinolytic activity and were identified as Bacillus pumilus (KF454036) and Bacillus flexus (KF454035), respectively by 16S rRNA partial gene sequence analysis. Optimization of various fermentation parameters (e.g., temperature, pH, inoculums size, surfactant, colloidal chitin concentration, incubation time, carbon sources, organic and inorganic nitrog...

Acta Ichthyologica et Piscatoria, 2004

Background. Because of the advancement of multiple spawning of carps, the importance of a quality... more Background. Because of the advancement of multiple spawning of carps, the importance of a quality larval diet is increasing day by day. The larval fish do not have the necessary enzyme or the amount of digestive enzymes to digest feed at optimum level. Therefore, fermentation of feed ingredients and/or formulated diets by bacterial enzymes to produce simpler forms of nutrients may be beneficial for them. Materials and methods. Five isocaloric (4.38 kcal•g-1) and isonitrogenous (35% crude protein approximately) experimental diets (D1-D5) containing 32% fish meal, 34% mustard oil cake, 30% rice bran, and 2% cod liver oil, were fermented in vitro with Bacillus circulans cells (at the rate of 10 8 bacterial cells per g) at 37°C for 1-5 day duration (1 day: D1, 2 days: D2, 3days: D3, 4 days: D4, and 5 days: D5). The bacterial strain [extracellular enzyme producer Bacillus circulans (Lr 1.1)] used for fermentation was isolated from the intestine of rohu, Labeo rohita fingerlings. The reference diet (RD), containing same ingredients, was not fermented with bacterial cells. Rohu spawn (av. wt. 0.35 ± 0.01 mg) were fed ad libitum for 21 days in the laboratory condition at 30 minutes interval starting from 0900 h to 1600 h. Results. Fermentation of diets resulted in an increase in crude protein and free amino acid contents and decrease in crude fibre content. Diets D4 and D5 resulted in best growth and survival (98% and 98.33%, respectively) of rohu spawn compared to those fed with the reference diet (RD) and other experimental groups. A significant positive correlation was obtained between RNA : DNA ratio and specific growth rate (SGR) of 18 dietary groups (6 groups in triplicate). Conclusion. Fermentation of feed ingredients may be practiced as a tool for starter diet formulation to obtain better growth and survival of rohu spawn. The enzymeproducing strain, Bacillus circulans could be used to ferment diets for 4 to 5 days to increase the bioavailability of nutrients.

Aquaculture Research, 2014

Probiotic potential of the autochthonous bacteria in catla, Catla catla has been evaluated throug... more Probiotic potential of the autochthonous bacteria in catla, Catla catla has been evaluated through determination of antagonistic activity (in vitro) of the cellular components of gut bacteria against seven fish pathogens. Altogether 208 strains were isolated, inhibitory activity of the isolates was evaluated through cross-streaking and 16 primarily selected antagonistic strains were confirmed using the double-layer method. Four bacteria that showed antagonism against ≥4 pathogens were selected as putative probiotics. The intracellular, extracellular, whole-cell and heat-killed cell components exhibited bactericidal activity against the pathogens. In addition, the selected strains were capable of producing different extracellular enzymes, competent to grow in intestinal mucus and could tolerate diluted bile juice. Analysis of 16SrRNA partial gene sequence revealed that both the strains CC1FG2 and CC1FG4 were Bacillus methylotrophicus (KF559344 and KF559345), while the isolates CC1HG5 and CC2HG7 were Bacillus subtilis subsp. spizizenii (KF559346) and Enterobacter hormaechei (KF559347) respectively. Bio-safety evaluation through intra-peritoneal injection of the isolates did not induce any pathological signs or mortalities in C. catla. The study confirmed probiotic properties of autochthonous gut bacteria in C. catla and demonstrated potential for using them as biocontrol agents. However, in vivo studies are essential to explore their efficacy in the commercial aquaculture.

International Journal of Aquatic Biology, 2015

Sesame oil cake (SSC) was bio-processed through solid state fermentation (SSF) under optimized co... more Sesame oil cake (SSC) was bio-processed through solid state fermentation (SSF) under optimized conditions by a phytase-producing fish gut bacterium, Bacillus subtilis subsp. subtilis (JX292128). SSF significantly reduced anti-nutritional factors (e.g., phytic acid, tannins and trypsin inhibitor) and crude ﬁbre, while enhanced free amino acids, fatty acids and different minerals. Phytase production (39.72 ± 1.06 U/g) during SSF was also recorded. Along with a fish meal based reference diet (RD), 8 isonitrogenous (36% crude protein) and isocaloric (4.60 kcal g -1 ) experimental diets incorporating raw (R1-R4) and SSF processed (F1-F4) SSC(20%, 30%, 40% and 50%, w/w) were fed to rohu, Labeo rohita fingerlings (mean weight 3.28 ± 0.15 g) in triplicate treatments for 70 days. In general, growth and feed utilization efficiencies in fish fed diets containing SSF-processed SSC were superior to the groups fed diets containing raw SSC. The diet F3 (40% fermented SSC) showed significantly ( P ...

Fermentation Technology, 2016

Cellulose and hemicellulose (xylan) are the most common Non-Starch Polysaccharides (NSPs) present... more Cellulose and hemicellulose (xylan) are the most common Non-Starch Polysaccharides (NSPs) present in plant ingredients that exhibit anti-nutritional effect. Degradation of cellulose and xylan has been investigated under solidstate fermentation (SSF) using oil-cakes, viz., groundnut oil-cake (GOC), mustard oil-cake (MOC), sunflower oilcake (SOC), sesame oil-cake (SeOC) and linseed oil-cake (LOC) as substrates. Finally LOC was considered in the present study as it contained maximum amount of cellulose (17.51 ± 0.87 g 100 g-1) and xylan (13.02 ± 0.66 g 100 g-1). Bio-processing of LOC was carried out through SSF in two different combinations utilizing efficient cellulaseand xylanase-producing strains, Bacillus pumilus KF640221 (Set-I) and Bacillus tequilensis KF640219 (Set-II), isolated previously from the proximal intestines of rohu, Labeo rohita and silver carp, Hypophthalmichthys molitrix, respectively. Analysis of the fermentation sets revealed that B. pumilus KF640221 in Set-I was most effective in reducing the cellulose and xylan contents of LOC. Besides, SSF under optimized conditions caused considerable increase in crude protein, crude lipid, total free amino acids and total free fatty acids along with reduction in the contents of other anti-nutritional factors, e.g., crude fiber, tannins, phytic acid and trypsin inhibitor. High performance liquid chromatography (HPLC) analysis of raw and fermented LOC of Set-I indicated that concentrations of methionine, histidine, tryptophan, phenylalanine, threonine were increased considerably. Further research is inevitable to explore the possibilities for utilization of SSF-processed LOC to set up a strategy for sustainable utilization of low cost oil-cakes as animal feed ingredients.

Journal of Fisheries, 2016

The present study was carried out to screen autochthonous gut bacteria in freshwater air breathin... more The present study was carried out to screen autochthonous gut bacteria in freshwater air breathing walking catfish, Clarias batrachus Linnaeus. Altogether, 100 extracellular enzyme-producing bacteria were isolated from the foregut (FG) and hindgut (HG) regions. Data were presented as log viable counts g-1 gut (LVC). The occurrence of heterotrophic bacterial population was higher in the FG region (LVC = 8.25) than the HG (LVC= 7.3). Similarly, proteolytic, amylolytic and lipolytic bacteria in FG outnumbered (LVC=7.25, 6.77 and 5.23 respectively) the HG (LVC=6.38, 5.58 and 4.04 respectively). However, occurrence of cellulolytic bacteria in both, FG and HG was less (LVC=2.1 and 1.34 respectively) in comparison to the other extracellular enzyme-producing bacteria. Out of the 100 bacterial isolates, 22 isolates were primarily selected through qualitative assay of extracellular enzyme activities. Among them, 3 promising isolates were chosen as potent extracellular enzyme producers on the ...

Aquaculture Reports, 2015

De-oiled groundnut oil cake (GOC) was bio-processed through solid state fermentation (SSF) for 15... more De-oiled groundnut oil cake (GOC) was bio-processed through solid state fermentation (SSF) for 15 days at 34 ± 1 • C by a tannase producing yeast, Pichia kudriavzevii (GU939629) isolated from the gut of a freshwater carp, Cirrhinus cirrhosus. SSF of GOC was effective in significantly (P < 0.05) reducing crude fibre content and antinutritional factors (e.g., tannin, phytic acid and trypsin inhibitor), whereas enhancing crude protein, lipid, ash, total free amino acids and fatty acids. Bio-processing revealed significant increase in the levels of argenine, histidine, isoleusine, lysine, methyonine and threonine in the GOC. Eight isonitrogenous (37.5%) and isocaloric (18.8 kJ g −1) experimental diets were prepared incorporating raw (R1-R4) and fermented (F1-F4) GOC at 20%, 30%, 40% and 50% levels by weight replacing fishmeal and other feed ingredients into a fishmeal-based reference diet (RD) and fed to rohu, Labeo rohita, fingerlings (initial weight 3.24 ± 0.11 g) for 80 days. In general, diets with SSF-processed GOC produced significantly better performance than the raw GOC in terms of growth, feed utilization, nutrient digestibility, carcass composition and digestive enzyme activity. Rohu fingerlings fed the diet F3 containing 40% fermented GOC resulted in best performance in terms of weight gain (final weight 7.08 ± 0.06 g), specific growth rate (% day −1), protein efficiency ratio and apparent net protein utilization. Highest protein (14.93 ± 0.51%) and lipid deposition in the carcass were also recorded in the group of fish reared on diet F3. In comparison to the FM based reference diet, the present study explored the possibility of replacing 45-55% of FM through incorporation of 40-50% (w/w) SSF-processed GOC in the diets for rohu fingerlings.

Agricultural Reviews, 2015

ABSTRACT An element is considered as dietary essential when its absence or insufficiency in diet ... more ABSTRACT An element is considered as dietary essential when its absence or insufficiency in diet causes deficiency syndrome and supplementation in normal level brings back normal health. An organism can neither grow nor remain healthy without the element in question. The element should have a direct influence on the organism and involved in the metabolism. Effects of the essential elements cannot be wholly or partly replaced by any other elements. All forms of aquatic inhabitants require some inorganic elements in little or trace amounts for their normal growth and metabolism. Trace minerals do not exist only by themselves but in combination with others. Therefore too much of one element may lead to imbalances in others resulting in disease or adverse effect in metabolism. Factors such as diet, absorption ability, toxicities and drug-nutrient interactions may play a role in maintaining a balance of trace minerals in the animal body. In comparison to the farmed animals, the knowledge on dietary essentiality of minerals in fish is scarce being mainly restricted to iron, copper, manganese, zinc, iodine, selenium, cobalt and chromium as components of body fluids, co-factors in enzymatic reactions, structural units of non-enzymatic macromolecules, etc. Investigations in fish are comparatively complicated as both dietary intake and its uptake from availability in water have to be taken in account for determining the total mineral budgets. The importance of trace minerals as essential ingredients in diets, although in small quantities, is also evident in fish. Though requirements of trace minerals have been studied in some species, still research work needs to be intensified for other freshwater fish species. INTRODUCTION All terrestrial and aquatic organisms require inorganic elements or minerals for their normal life processes. Fishes have the ability to absorb inorganic elements from diets as well as from their external environment in both freshwater and marine water. Minerals, which comprise the ash of biological materials remaining after the organic substances have been completely burnt or oxidized in the body of all animals including fish, are known to be essential for cellular metabolism. Freiden, (1984) described that an element is considered essential when its deficient intake produces an impairment of function and when restoration of physiological levels of the element prevents or relieves the deficiency. Organisms can neither grow nor complete its life cycle without those inorganic elements. They should have a direct influence on the organisms and involved in the metabolism. Minerals, which are present in fairly large quantities in biological materials, are those of calcium, phosphorus, potassium, sodium, magnesium, etc. The principle minerals present in micro quantities (or trace levels) are iron, manganese, zinc, copper, cobalt, selenium, chromium and iodine (Lall, 1979). There are approx fifteen trace elements considered to be essential in animals. Among these the physiological role of a deficiency of chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium and zinc is well recognized (Lall, 1989). The main function of those essential elements in the body is formation of skeletal structure, colloidal systems maintenance (osmotic pressure, viscosity and diffusion) and regulation of acid-base equilibrium. They serve as an important component of hormones, enzymes and enzyme activators. Calcium and phosphorus are required for the formation of the skeletal structures of the body and scales. Sodium, potassium and chloride along with phosphates and bicarbonates maintain homeostasis and acid-base balance equilibrium. A fixed number of specific trace minerals viz., iron, manganese, copper and zinc are firmly associated with a specific protein in metalloenzymes, which produce a unique catalytic function.

Aquaculture is globally expanding into new directions. A constant goal of global aquaculture is t... more Aquaculture is globally expanding into new directions. A constant goal of global aquaculture is to maximize the effectiveness of production to optimize profitability. Intensification and commercialization of aquaculture production need to develop microbial control strategy. Conventional culture methods involve delivery of micronutrients as well as probiotics as feed supplements or direct use in the aquaculture. Providing probiotics directly to the aquaculture industry does not guarantee for its intake by fishes. Moreover, these conventional methods may not be conclusive as some of the bioactive compounds are not able to withstand feed processing temperature and thereby lose its activity. Cultivation of larval stages of different species involved in aquaculture is still largely dependent on live food. Normal growth and behaviour of fish juveniles are dependent on the quality of the diet provided to them. Since live feed is rich in proteins, carbohydrates and fats along with diverse t...

Medical and veterinary entomology, Jan 29, 2015

Two haemolytic bacterial strains of Bacillus pumilus (CU1A, CU1B) and one blood-utilizing strain ... more Two haemolytic bacterial strains of Bacillus pumilus (CU1A, CU1B) and one blood-utilizing strain of Bacillus licheniformis (CU2B) were isolated from relatively low numbers of field-collected females of Culicoides oxystoma and Culicoides peregrinus (Diptera: Ceratopogonidae). A total of 36 females, including 18 of each of C. oxystoma and C. peregrinus (consisting of one and a pool of eight blood-engorged specimens, and one and a pool of eight non-engorged specimens for each species), were tested. In C. oxystoma, all three strains of bacteria were isolated from the one non-engorged, the pool of non-engorged and the pool of blood-engorged females tested, but CU1A and CU2B were not found in the one blood-engorged female tested. In C. peregrinus, all three strains were present in the pool of blood-engorged females. However, the strain CU2B was not found in the pool of non-engorged females. In the one blood-engorged and one non-engorged female tested, CU1A and CU2B were detected. The bact...

TURKISH JOURNAL OF ZOOLOGY, 2014

Occurrence and distribution of enzyme-producing bacteria in the proximal (PI), middle (MI), and d... more Occurrence and distribution of enzyme-producing bacteria in the proximal (PI), middle (MI), and distal (DI) segments of the gastrointestinal tracts of 4 brackish water teleosts (Scatophagus argus, Terapon jarbua, Mystus gulio, and Etroplus suratensis) have been investigated. Data were presented as log viable counts g-1 intestine (LVC). The heterotrophic bacterial population had the highest occurrence in the DI regions of all fish species studied except M. gulio. Proteolytic and amylolytic bacteria had the highest occurrence in the DI of M. gulio (LVC = 5.50 and 5.93, respectively), while cellulolytic and lipolytic populations exhibited highest occurrences in the DI regions of T. jarbua (LVC = 6.33) and S. argus (LVC = 5.78), respectively. Out of the 81 bacterial isolates, the most promising 3 isolates were determined through quantitative enzyme assay and studied through 16S rRNA gene sequence analysis for identification. Both the strains SA2.2 isolated from S. argus and TJ2.3 isolated from T. jarbua showed high similarity to different strains of Brevibacillus parabrevis, while another strain, MG4.2, isolated from M. gulio, was similar to Bacillus licheniformis. The NCBI GenBank accession numbers of the 16S rRNA gene sequences for isolates SA2.2, TJ2.3, and MG4.2 were KF377322, KF377324, and KF377323, respectively. The present study might offer scope for further research to evaluate prospects for application of the gut-associated extracellular enzymeproducing bacteria in brackish water aquaculture.

Journal of Applied Ichthyology, 2012

ABSTRACT Tannins are the most abundant among the plant derived antinutrients that bind readily wi... more ABSTRACT Tannins are the most abundant among the plant derived antinutrients that bind readily with protein and other macromolecules to form indigestible complexes, thereby reducing nutritional value of the plant feedstuffs. Presence of tannase-producing gut microbiota in herbivorous animals has been suggested to overcome the antinutritional effects of tannins. However, this topic is less investigated in herbivorous/omnivorous fish species. The present study was undertaken to evaluate the presence of tannase-producing autochthonous microbiota in the gastrointestinal (GI) tracts of some culturable freshwater teleosts and to identify most promising tannase-producing strains by molecular methods. Isolation and enumeration of tannase-producing autochthonous microbiota have been carried out from the gut of 10 culturable freshwater teleosts, namely catla (Catla catla), silver carp (Hypophthalmichthys molitrix), rohu (Labeo rohita), grass carp (Ctenopharyngodon idella), mrigal (Cirrhinus mrigala), common carp (Cyprinus carpio), bata (Labeo bata), kalbasu (Labeo calbasu), tilapia (Oreochromis mossambicus), and Nile tilapia (Oreochromis niloticus). Culturable heterotrophic and tannase-producing microbial populations evaluated on tryptone soy agar and selective tannic acid agar media respectively revealed maximum in the hind guts of all the fish species studied. Out of 72 tannase producing colonies, 18 randomly selected isolates were maintained as pure cultures and evaluated quantitatively for tannase production. Among these, 4 most promising tannase producers were identified by 16S/26S rDNA sequencing following nucleotide blast and deposited to the National Centre for Biotechnology Information (NCBI) GenBank. The strain LR01 isolated from rohu was a bacterium, Enterobacter asburae (GenBank Accession No. GU939631). However, the strains CM02, OM01 and LR03 isolated from mrigal, tilapia and rohu were yeasts and identified as Pichia kudriavzevii (GenBank Accession No. GU939629), Candida tropicalis (GenBank Accession No. GU911469) and Candida parasilopsis (GenBank Accession No. GU939630) respectively. To the authors’ knowledge, present study is the first one reporting tannase producing autochthonous microbiota in the gut of freshwater teleosts. Tannin degrading microbiota detected in the present study may endow the fish with some ecological advantages by enabling them to overcome the anti-nutritional effects of plant tannins.

Acta Ichthyologica Et Piscatoria, 2010

The gut microbiota of marine and freshwater fish has been widely investigated during the last two... more The gut microbiota of marine and freshwater fish has been widely investigated during the last two decades (Cahill 1990,