Herbaceous plants as part of biological filter for aquaponics system

Aquaponics is a recirculating aquaculture system (RAS), where plants and aquatic animals are grown using the same water. In these systems, plants act as part of biological filters. The cultivation of O. basilicum, Menta x piperita and M. spicata is commonly integrated to the production of O. niloticus in aquaponics. The aim of this study was to evaluate the ability of these herbs as part of biological filters for tilapia intensive production in aquaponics. Various physicochemical parameters were evaluated as water quality indicators. N and P content in the different elements of the system were also measured. Results showed that for tilapia growing the three herbaceous evaluated could be used as part of the biological filters in aquaponics, because they remove significant concentration in nitrogen compounds and phosphates; however, there were no differences among species. There was a positive relationship between the time and the levels of NH₄ and therefore NO₃^? in the water. The pH, temperature and dissolved oxygen were kept at appropriate ranges for tilapia. The electrical conductivity and total dissolved solids were in suitable levels for growing herbaceous, which adapted to flooded substrates, with water constantly moving and high concentration of dissolved oxygen. A key parameter to consider is the oxygen concentration in water when herbaceous is used in aquaponics, due to the high input of this element for these species need, especially basil. Tilapia largely incorporated N and P entering the system.     

Use of planted biofilters in integrated recirculating aquaculture‐hydroponics systems in the Mekong Delta,Vietnam

The feasibility of using planted biofilters for purification of recirculated aquaculture water in the Mekong Delta of Vietnam was assessed. The plant trenches were able to clean tilapia aquaculture water and to maintain good water quality in the fish tanks without renewal of the water. NH₄‐N was removed efficiently in the plant trenches, particularly in the trenches with Canna glauca L., probably because of plant uptake and nitrification–denitrification. Plant uptake constituted 6% of N and 7% of P in the input feed. Approximately 1.0 m³ of water was needed per kg of fish produced, and 370, 97 and 2842 g fresh aboveground biomass of Ipomoea aquatica Forssk., Lactuca sativa L. and C. glauca, respectively, were produced. The leafy vegetables provide some extra income besides fish products, whereas C. glauca provides nice flowers and contributes to a significant nutrient removal with annual uptake rates of 725 kg N and 234 kg P ha^?1 year^?1. This research demonstrates that integrated recirculating aquaculture‐hydroponics (aquaponics) systems provide significant water savings and nutrient recycling as compared with traditional fish ponds.     

Phytase-producing bacteria in the digestive tracts of some freshwater fish

Isolation and enumeration of phytase‐producing bacterial flora in the foregut and hindgut regions of the gastrointestinal tracts of 10 culturable freshwater teleosts of different feeding habits, namely rohu (Labeo rohita), catla (Catla catla), mrigal (Cirrhinus mrigala), bata (Labeo bata), kalbasu (Labeo calbasu), Nile tilapia (Oreochromis niloticus), climbing perch (Anabas testudineus), common carp (Cyprinus carpio), silver carp (Hypophthalmichthys molitrix) and grass carp (Ctenopharyngodon idella), have been carried out. Microbial culture of the gut mucosa on selected nutrient media following the enrichment culture technique was performed for bacterial isolation. The bacterial isolates were screened on the basis of their enzyme‐producing ability. The bacterial population on the tryptone soya agar (TSA) plate was maximum in the hindgut region of bata, followed by mrigal and minimum in the foregut region of Nile tilapia. In modified phytase screening medium (MPSM), phytase‐producing strains were recorded at higher densities in the foregut region of mrigal and grass carp and minimum in the foregut region of bata. In case of the hindgut, maximum phytase‐producing strains were present in grass carp and mrigal and minimum in rohu. In general, in MPSM, the bacterial population was lower in the hindgut region of all the 10 species of fish examined. The phytase‐producing ability of the selected 31 strains (16 from the foregut and 15 from the hindgut region) was determined by clearing zones on phytate‐containing plates. Among these isolates, 22 strains (12 from the foregut and 10 from the hindgut region) were selected as potent phytase producers according to a quantitative enzyme assay. The highest phytase activity was observed in the bacterial strains LF1 and LH1 isolated from the fore and the hindgut regions of rohu respectively. Both the strains were identified as Bacillus licheniformis on the basis of phenotypic characteristics as well as 16S rDNA sequence analysis.     

The Effects of Dietary Yeast Culture or Short‐chain Fructo‐oligosaccharides on the Intestinal Autochthonous Bacterial Communities in Juvenile Hybrid Tilapia,Oreochromis niloticus♀×Oreochromis aureus♂

The effects of dietary yeast culture (YC) or short‐chain fructo‐oligosaccharides (FOS) on intestinal autochthonous bacterial communities in juvenile hybrid tilapia, Oreochromis niloticus♀×Oreochromis aureus♂ were studied by 16S rDNA denaturing gradient gel electrophoresis (DGGE). Ninety Tilapias in tanks (10 fish per tank) were randomly and equally divided into three groups. At the end of an 8‐wk feeding period of CK (the control treatment), YC (3 g/kg), or FOS (1 g/kg), autochthonous gut bacteria were analyzed in intestinal samples of all fish in each tank of a recirculating aquaculture system. The clear differences in the banding patterns indicated the obvious effects of dietary prebiotics on intestinal communities in hybrid tilapia. Higher variation was detected within the dietary YC group. This difference might be due to the effects of certain immune‐stimulating agents in YC on the immunity response of hybrid tilapia. It was concluded that dietary prebiotics, YC, and FOS obviously affected the intestinal bacterial community in hybrid tilapia with different patterns for different kinds.     

Intestinal bacterial flora of Mediterranean gilthead sea bream (Sparus aurata Linnaeus) as a novel source of natural surface active compounds

Microbial communities play different functions in the digestive tract of fish and represent a source of bioactive compounds. This study was aimed to detect the presence of biosurfactant (BS)‐producing bacteria in the intestine of gilthead sea bream (Sparus aurata L.) to select strains candidate for biotechnological applications in aquaculture. A total of 100 bacterial strains were isolated from the guts of three groups of fish and analysed by different qualitative screening tests and the tensiometric analysis. BSs were extracted, characterized by thin‐layer chromatography (TLC) and their antibacterial activity against bacterial pathogens of interest in aquaculture was determined. A total of 17 out of 100 strains, affiliated to the genera Pseudomonas (11 isolates), Acinetobacter (1 isolate), Sphingomonas (4 isolates) and Aeromonas (1 isolate), displayed a stable emulsion production with the E₂₄ index from 0% to 44%, a surface tension reduction from 8.3 to 30 mN/m and 11 of them exhibited antibacterial activity against fish pathogens. The TLC analysis indicated that the intestinal BSs consisted of compounds ascribed to the class of glycolipids–rhamnolipids. This is the first study reporting on the isolation and selection of BS‐producing bacteria from fish gut, a natural novel source of surface active compounds with potential biotechnological applications in aquaculture.     

Identification of conditions underlying production of geosmin and 2-methylisoborneol in a recirculating system

Geosmin and 2-methylisoborneol (MIB) are semi-volatile terpenoid compounds produced as secondary metabolites by benthic and planktonic cyanobacteria, several genera of fungi, and various actinomycetes. These off-flavor compounds pose a heavy economic burden in the aquaculture industry rendering fish unmarketable unless purified by purging with large quantities of clean water. In the present study, the presence of off-flavor compounds was examined in a recirculating aquaculture system (RAS) for tilapia culture. In this zero-discharge system, where water from the fish basins is recirculated through parallel aerobic (drum filter and a trickling filter) and anaerobic treatment loops (sedimentation/digestion basin), concentrations of geosmin and, in particular, MIB were highest in the aerobic treatment loop. Lowest concentrations were detected in the anaerobic treatment loop. This latter finding pointed toward a possible reduction of these compounds in this basin. Two bacterial strains of the streptomycetes family were isolated from the aerobic, organic-rich, drum filter and the nitrifying trickling filter. In vitro tests with these isolates, closely related to Streptomyces roseoflavus and Streptomyces thermocarboxydus, revealed that MIB production exceeded geosmin production under all conditions tested and was significantly higher under aerobic than under anoxic conditions. Under the latter conditions, with nitrate as an electron donor, the S. roseoflavus-like isolate was capable of denitrification. Based on the results obtained in this study, it was concluded that aerobic, organic-rich conditions stimulate the growth of actinomycetes and subsequent production of geosmin and MIB in the system. The observed reduction of these compounds in the anaerobic water treatment component may serve in designing treatment steps aimed at alleviating the problem of geosmin and MIB accumulation in recirculating systems.     

Roles of water quality and disinfectant application on inactivation of fish pathogenic Streptococcus agalactiae with povidone iodine,quaternary ammonium compounds and glutaraldehyde

Streptococcosis is an important bacterial disease in Nile tilapia causing severe economic losses to tilapia aquaculture worldwide. The effects of water quality (low‐ [LS] and high‐level [HS] soiling, to mimic clean or dirty surface conditions and temperatures) and disinfectant application (diluted concentrations and exposure time) were characterized on the inactivation of Streptococcus agalactiae isolated from diseased tilapia. Five isolates were tested against three commercial disinfectant products with the main ingredients being povidone iodine (Anidine 100?; AD), benzalkonium chloride (Better BKC 80%?; BKC 80), and a mixture of quaternary ammonium compounds and glutaraldehyde (Chloraldehyde?; CR). CR demonstrated highest efficacy to S. agalactiae inactivation, followed by BKC 80 and AD, respectively. Higher‐level soiling, low temperature, diluted concentrations and short exposure time all decreased the disinfectant efficacy. CR and BKC 80 provided more than 5‐log inactivation at 1‐min exposure at 20°C under HS conditions, and also with ten‐fold‐diluted concentrations at 60‐min exposure time at 30°C. However, AD required 10‐min exposure to effectively remove bacteria under LS conditions at 30°C. The results could facilitate aquaculture management planning that leads to operating cost reductions and improvements in biosecurity.     

Response of Bacterial Biofilms in Recirculating Aquaculture Systems to Various Sanitizers

ABSTRACT

Pathogenic microorganisms may be incorporated into biofilms found in aquaculture systems, causing recurring exposure to potential disease agents. Aerobic plate counts, the presence of Enterobacteriaceae, and the presence of Escherichia coli, modified to express a green fluorescent protein (GFP E. coli), was used to evaluate the effectiveness of various sanitizers in decreasing bacterial incorporation into newly generated biofilms in recirculating aquaculture systems. Disks of Buna-N rubber, polyvinyl chloride (PVC), chlorinated PVC, glass, fiberglass, and stainless steel were placed in aquariums stocked with Nile tilapia, Oreochromis niloticus. The effectiveness of water, an alkaline cleanser, sodium hypochlorite, a quaternary ammonium compound, or peracetic acid as a sanitizer was evaluated on each substrate by enumerating total plate counts, GFP E. coli, and Enterobacteriaceae. Sodium hypochlorite and peracetic acid were the most effective sanitizers, with an overall percentage reduction of GFP E. coli of approximately 2 logs₁₀. The quaternary ammonium compound was moderately effective, 1 log₁₀, against the target organisms. Water demonstrated a 2 log₁₀ reduction of the total plate count, suggesting that some mechanical cleaning was achieved. The type of material used as substrate for the biofilm had no significant (P?>?0.05) effect on the effectiveness of the sanitizers.     

Exploring economic and legal barriers to commercial aquaponics in the EU through the lens of the UK and policy proposals to address them

Aquaponics is a food production system which connects recirculating aquaculture (fish) to hydroponics (plants) systems. Although aquaponics has the potential to improve soil conditions by reducing erosion and nutrient loss and has been shown to reduce food production related carbon emissions by up to 73%, few commercial aquaponics projects in the EU and UK have been successful. Key barriers to commercial success are insufficient initial investment, an uncertain and complex regulatory environment, and the lack of projects operating on a large scale able to demonstrate profitability. In this paper, we use the UK as a case study to discuss the legal and economic barriers to the success of commercial aquaponics in the EU. We also propose three policies: (1) making aquaponics eligible for the new system of Environmental Land Management grants; (2) making aquaponics eligible for organic certification; and (3) clarifying and streamlining the aquaponics licence application process. The UK’s departure from the EU presents a unique opportunity to review agricultural regulations and subsidies, which in turn could provide evidence that similar reforms are needed in the EU.

     

Bacterial community of pond's water,sediment and in the guts of tilapia (Oreochromis niloticus) juveniles characterized by fluorescent in situ hybridization technique

Information about bacterial community structure and functioning in fish farming ponds remains scarce, mainly due to methodological difficulties in counting and identifying uncultured bacteria. The main objective of this study was to evaluate the degree of similarity between the bacterial community of the digestive tract of tilapia (Oreochromis niloticus) juveniles and that of the test pond's water and sediment, using the Fluorescent In Situ Hybridization (FISH) technique. Samples of water, sediment and gut content of 30 tilapia juveniles from a single nursery ground were collected in January 2010. Potentially probiotic and pathogenic bacteria of the species Bacillus, Lactobacillus brevis, Lactobacillus collinoides, Lactobacillus coryniformis, Lactobacillus farciminis, Vibrio and Pseudomonas fluorescens were found in different samples using specific fluorescent probes. The similarity between bacterial community environments and gastrointestinal tracts was determined using the Morisita‐Horn index. The fish guts presented higher abundances of Pseudomonas fluorescens, Bacillus, Lactobacillus brevis and Lactobacillus collinoides. The bacterial community composition of tilapia gastrointestinal tract was more similar to the water than the sediment of the pond. The results of this study showed that the FISH technique can be easily used for monitoring of probiotics and pathogen detection in aquaculture systems.     

Efficacy of florfenicol for control of mortality associated with Francisella noatunensis subsp. orientalis in Nile tilapia,Oreochromis niloticus (L.)

Francisella noatunensis subsp. orientalis (Fno) (syn. F. asiatica) is an emergent Gram‐negative facultative intracellular bacterium. Although it is considered one of the most pathogenic bacteria in fish, there are no commercially available treatments or vaccines. The objective of this project was to determine the most efficacious concentration of florfenicol (FFC) [10, 15 or 20 mg FFC kg^?1 body weight (bw) per days for 10 days] administered in feed to control experimentally induced infections of Fno in Nile tilapia, Oreochromis niloticus (L.), reared in a recirculating aquaculture system. The cumulative mortality of fish that received 0, 10, 15 or 20 mg FFC kg^?1 bw per day was 60, 37, 14 and 16%, respectively. Francisella noatunensis subsp. orientalis genome equivalents were detected in water from all challenged groups with slight reduction in the concentration in the florfenicol‐treated groups 4 days after treatment. The mean LOG of CFU Fno mg^?1 spleen was 3–5 and was present in all challenged groups at necropsy 11 days after treatment (21 days after challenge). Results show that florfenicol administered at doses of 15 and 20 mg FFC kg^?1 bw per days for 10 days significantly reduced mortality associated with francisellosis in Nile tilapia.     

Incidence of class 1 integron and other antibiotic resistance determinants in Aeromonas spp. from rainbow trout farms in Australia

There is limited information on antibiotic resistance determinants present in bacteria of aquaculture origin in Australia. The presence of integron and other resistance determinants was investigated in 90 Aeromonas isolates derived from nine freshwater trout farms in Victoria (Australia). Polymerase chain reaction was carried out for the detection of integrase genes Int1, Int2 and Int3, gene cassette array, integron‐associated aadA, sul1 and qac1 genes, streptomycin resistance genes strA‐strB, β‐lactamase resistance genes bla_TEM and bla_SHV, and tetracycline resistance genes tetA‐E and tetM. Clonal analysis was performed by pulsed‐field gel electrophoresis (PFGE). Class 1 integrons were detected in 28/90 (31%) and class 2 and class 3 in none of the strains, aadA gene in 19/27 (70%) streptomycin‐resistant strains, sul1 in 13/15 (86.7%) sulphonamide‐resistant strains and qac1 gene in 8/28 (28.6%) integron‐bearing strains. Five strains from two different farms carried gene cassettes of 1000 bp each containing the aadA2 gene and PFGE analysis revealed genetic relatedness. tetC was detected in all and tetA in 9/18 (50%) tetracycline‐resistant strains. The strA‐strB, bla_TEM or bla_SHV genes were not detected in any of the strains. Aeromonas spp. carrying integrons and other resistance genes are present in farm‐raised fish and sediments even though no antibiotics were licensed for use in Australian aquaculture at the time of the study.     

Evaluation of Tilapia Effluent with Ion Supplementation for Marine Shrimp Production in a Recirculating Aquaculture System

Reuse of fish effluent for the culture of marine shrimp, such as Pacific white shrimp, Litopenaeus vannamei, could provide an opportunity for the US shrimp farming industry to ease constraints (e.g., environmental concerns and high production costs) that have limited them in the past. In this study under laboratory‐scale conditions, the feasibility of culturing L. vannamei in effluents derived from a commercial facility raising tilapia in recirculating aquaculture systems (RAS), supplemented with various salt combinations, was compared to the shrimp’s survival and growth in well water supplemented with 17.6 (control) and 0.6 (freshwater treatment) g/L synthetic sea salt. Three independent trials were conducted in RAS in which survival and growth in the control, the freshwater treatment, and two effluent treatments were compared. Water quality during this study was within safe levels and no differences (P < 0.05) between treatments were observed for dissolved oxygen, nitrite, pH, total ammonia nitrogen, and temperature. However, average nitrate and orthophosphate levels were consistently more than an order of magnitude greater in the effluent treatments compared to the control and the freshwater treatments. Survival and growth of shrimp over 6‐wk periods did not vary significantly between the control and the freshwater treatments; however, shrimp tested in the tilapia effluents often exhibited significant effects (P < 0.05) depending on the salts added. In the low‐salinity waters, correlations (P < 0.05) were observed between Ca²⁺, Mg²⁺, Ca²⁺ and Mg²⁺, K⁺, Na⁺ : K⁺ and Ca²⁺ : K⁺, and shrimp survival and growth. The results of this study revealed that L. vannamei can be raised in tilapia effluent when supplemented with synthetic sea salt (0.6 g/L), CaO (50 mg/L Ca²⁺), and MgSO₄ (30 mg/L Mg²⁺).     

Vertical transmission and concurrent infection of multiple bacterial pathogens in naturally infected red tilapia (Oreochromis spp.)

Horizontal transmission of various bacterial pathogens in tilapia is well described, but there is scant information regarding their vertical transmission. This study aimed to determine the possibility of vertical transmission of two commonly reported bacterial pathogens (Francisella noatunensis subsp. orientalis and Shewanella putrefaciens) in natural stocks of red tilapia (Oreochromis spp.). Vertical transmission of these pathogens via gametes was evaluated using in vitro fertilization from 10 different families and analysing for the presence of bacteria in milt, unfertilized eggs, fertilized eggs and offspring at various ages (1‐day‐old larvae, 10‐day‐old fry and 30‐day‐old fingerlings), as well as water samples using colorimetric LAMP assay. The study revealed that both F. n. orientalis (6/10) and S. putrefaciens (4/10) was transmitted vertically to the fertilized eggs. Analysis of the water samples from different water sources (brood stock tanks, hatching chamber and larval rearing tanks) showed that both the pathogens were present in water samples with highest prevalence for F. n. orientalis followed by S. putrefaciens. Analyses for the presence of two pathogens in various organs (gonads, gill, liver, spleen, kidney and brain) of the healthy tilapia broodstock without any clinical symptoms of disease demonstrated they were carriers of S. putrefaciens and F. n. orientalis. This is the first documented evidence that vertical transmission via the broodstock of tilapia may also play an important role in transmitting these problematic pathogens to their progeny and underlines the necessity to modify the current disease management strategies in tilapia aquaculture.     

The autochthonous microbiota of the freshwater omnivores jundiá (Rhamdia quelen) and tilapia (Oreochromis niloticus) and the effect of dietary carbohydrates

Previous studies have shown that the gut microbiota of fish differs depending on host feeding habits and these populations may also be influenced by dietary ingredients. In this study, the bacterial populations of the intestinal tract of the opportunistic omnivore jundiá Rhamdia quelen and the typical omnivore tilapia Oreochromis niloticus were investigated in two experiments. In experiment I, the levels of amylolytic, cellulolytic, lipolytic, proteolytic and total culturable bacteria were compared in the proximal, mid and distal intestine using selective agar. Higher levels of amylolytic, cellulolytic, lipolytic, proteolytic and total culturable bacteria were observed in the tilapia than jundiá, in all intestinal regions. Jundiá contained higher levels of proteolytic bacteria and lipid digesting bacteria in the distal intestinal portion as compared with the mid intestine; both fish species also presented more amylolytic bacteria in the distal intestine. In experiment II, the amylolytic intestinal microbiota between the two species was compared after administration of diets containing different carbohydrate sources. Jundiá fed broken rice presented higher total culturable bacterial levels; however, dietary cassava bagasse and ground corn significantly elevated the population of amylolytic bacteria in tilapia (P > 0.05). PCR‐DGGE was also used to assess the bacterial communities in experiment II. A Cetobacterium spp. was detected in jundiá fed diets containing broken rice, and tilapia fed cassava bagasse, dextrin, broken rice and ground corn. Microbial differentiation was further demonstrated between jundiá and tilapia, because an uncultured bacterium was unique in tilapia and an uncultured spirochete was observed only in jundiá; the presence of these bacterial species was also influenced by dietary carbohydrate sources.     

Effect of turbidity on the ultraviolet disinfection performance in recirculating aquaculture systems with low water exchange

This research was carried out to study the effect of turbidity on the effectiveness of ultraviolet light (UVC) for removing heterotrophic bacteria (HB) from two commercial recirculating aquaculture systems (RAS). We developed a simple and straightforward UV disinfection model based on water turbidity to predict the cost‐effectiveness of disinfection. The UVC from RAS1 (12.8 m³, 80 L min^?1, indoor system) was tested at 9.2, 9.9, 16.3, 17.2, 23.1 and 28.2 nephelometric turbidity units (NTU) after 24 h of exposure. The RAS2 (140 m³, 1140 L min^?1, outdoor system) was tested at 8.0, 9.2, 11.0, 12.1, 16.0, 24.2, 27.0, 31.3 and 31.7 NTU after 72 h. An increase in turbidity in the water was achieved by rearing Oreochromis niloticus fish. The RAS1 achieved a maximum UV efficiency (89.8%≈1 Log) at 9.2 NTU after 24 h and RAS2 at 8.0 NTU (86.4%≈0.9 Log) after 72 h of exposure. For RAS1, the UVC removed 90% of HB in 24 h when the turbidity was <9.9 NTU. For RAS2, without restrictions on particle size and relatively high phytoplankton abundance, the UV was unlikely to be a cost‐effective way of removing HB at turbidity above 11.0 NTU.     

Use of live and dead probiotic cells in tilapia Oreochromis niloticus

ABSTRACT:   To investigate the effect of live and dead probiotic cells on the non-specific immune system of tilapia Oreochromis niloticus , probiotics were introduced by feeding either in the form of live or dead cells, or supplying live cells to the rearing water in a closed recirculating system. The probiotics treatment enhanced non-specific immune parameters such as lysozyme activity, migration of neutrophils and plasma bactericidal activity, resulting in improvement of resistance to Edwardsiella tarda infection. Especially, oral administration of live cells seemed to be more effective compared with other probiotic treatments such as oral administration of dead probiotic cells and supply of live probiotic cells to the rearing water. These results indicate that probiotics treatment is promising as an alternative method to antibiotics for disease prevention in aquaculture, and the viability of probiotic bacteria is a key factor to induce more potential effect of probiotics used for fish production.     

Antibiotic resistance in potentially bacteriocinogenic probiotic bacteria in aquaculture environments

Bacteriocin‐producing bacteria in aquaculture may prevent spreading of potentially pathogenic microorganisms, and could be used as an alternative to the empirical use of antimicrobial drugs, especially for prophylaxis. Bacteriocinogenic bacteria inoculated as probiotics should not carry undesirable traits, such as antibiotic resistance. This study aimed to find potentially bacteriocinogenic bacteria in an aquaculture system and evaluate their antimicrobial susceptibility patterns. Selective cultures for enterobacteria, non‐fermenting Gram‐negative rods and Gram‐positive cocci were obtained from water samples before bacterial isolation and biochemical identification. Overall, 160 representative strains were recovered and for 57 antagonism was observed against selected strains such as Staphylococcus aureus, with antagonism being expressed better on Brain Heart Infusion medium. After exclusion of interfering factors, bacteriocin or bacteriocin‐like substances were suggested to be related to the antagonism observed. Higher drug‐resistant rates were observed among potentially bacteriocinogenic bacteria for different antimicrobials of clinical relevance. Although antibiotic resistance is a global health problem and bacteriocins are attractive alternatives to classical antibiotic even to multiresistant bacteria, the data obtained suggest that bacteriocin‐producing bacteria may harbour resistance genes available for transference in different environments. From the ecological and biotechnological perspective, antimicrobial susceptibility tests must be always performed when prospecting potentially bacteriocinogenic bacteria as probiotic candidates in the environment.