Administration of Probiotics in the Water in Finfish Aquaculture Systems: A Review

Harnessing biotechnology for penicillin production: Opportunities and environmental considerations

Since the discovery of antibiotics, penicillin has remained the top choice in clinical medicine. With continuous advancements in biotechnology, penicillin production has become cost-effective and efficient. Genetic engineering techniques have been employed to enhance biosynthetic pathways, leading to the production of new penicillin derivatives with improved properties and increased efficacy against antibiotic-resistant pathogens. Advances in bioreactor design, media formulation, and process optimization have contributed to higher yields, reduced production costs, and increased penicillin accessibility. While biotechnological advances have clearly benefited the global production of this life-saving drug, they have also created challenges in terms of waste management. Production fermentation broths from industries contain residual antibiotics, by-products, and other contaminants that pose direct environmental threats, while increased global consumption intensifies the risk of antimicrobial resistance in both the environment and living organisms. The current geographical and spatial distribution of antibiotic and penicillin consumption dramatically reveals a worldwide threat. These challenges are being addressed through the development of novel waste management techniques. Efforts are aimed at both upstream and downstream processing of antibiotic and penicillin production to minimize costs and improve yield efficiency while lowering the overall environmental impact. Yield optimization using artificial intelligence (AI), along with biological and chemical treatment of waste, is also being explored to reduce adverse impacts. The implementation of strict regulatory frameworks and guidelines is also essential to ensure proper management and disposal of penicillin production waste. This review is novel because it explores the key remaining challenges in antibiotic development, the scope of machine learning tools such as Quantitative Structure-Activity Relationship (QSAR) in modern biotechnology-driven production, improved waste management for antibiotics, discovering alternative path to reducing antibiotic use in agriculture through alternative meat production, addressing current practices, and offering effective recommendations.

The mitigating effects and mechanisms of Bacillus cereus on chronic cadmium poisoning in Litopenaeus vannamei based on histopathological, transcriptomic, and metabolomic analyses

Shrimp are non-negligible victims of cadmium (Cd) contamination, and there is still a lack of strategies for mitigating Cd toxicity in shrimp. Bacillus cereus, with its significant heavy metal (HM) tolerance and chelating effects, is a representative beneficial bacterium to be investigated for mitigating the toxicity of Cd exposure. This study revealed the effects and potential mechanisms of B. cereus in mitigating chronic Cd toxicity in shrimp by analyzing growth performance, hepatopancreatic Cd accumulation, pathology, as well as comprehensive hepatopancreatic transcriptomics and metabolomics in Litopenaeus vannamei. The results showed that shrimp's growth inhibition, hepatopancreatic Cd accumulation and physiological structure damage in B. cereus+chronic Cd group were effectively alleviated compared with the chronic Cd treatment group. The pathways related to amino acid metabolism, glycolipid metabolism, immune response, and antioxidant stress were significantly activated in the B. cereus+chronic Cd group, including glycolysis, pentose phosphate pathway, oxidative phosphorylation, biosynthesis of amino acids, and biosynthesis of unsaturated fatty acids pathways. The key differentially expressed genes (e.g., macrophage migration inhibitory factor, glycine cleavage system H protein, glycine dehydrogenase, phosphoglucomutase-2, asparaginase, ATP synthase subunit, cytochrome c, and 4-hydroxyphenylpyruvate dioxygenase) and metabolites (e.g., L-leucine, D-ribose, gluconic acid, 6-Phosphogluconic acid, sedoheptulose 7-phosphate, 1-Kestose, glyceric acid, arachidic acid, prostaglandins, 12-Keto-tetrahydro-leukotriene B4, and gamma-glutamylcysteine) associated with the above pathways were significantly altered. This study demonstrated that B. cereus is an effective mitigator for the treatment of chronic Cd poisoning in shrimp. B. cereus may play a role in alleviating the toxicity of Cd by enhancing the antioxidant performance, immune defense ability, metabolic stability, and energy demand regulation of shrimp. The study provides reference materials for the study of B. cereus in alleviating Cd toxicity of shrimp and broadens the application of probiotics in treating HM toxicity.

The regulatory effects of water probiotic supplementation on the blood physiology, reproductive performance, and its related genes in Red Tilapia (Oreochromis niloticus X O. mossambicus)

Probiotics are becoming increasingly popular as eco-friendly alternatives in aquaculture. However, there is limited research on their impacts on the reproductive efficiency of Red Tilapia (Oreochromis niloticus x O. mossambicus) broodstock. Therefore, this experiment aimed to explore the combined effects of selective probiotics Bacillus subtilis and B. licheniformis (BSL; 1:1) added to water on blood hematology, serum metabolites, gonadal histology, reproductive performance, and reproductive associated genes in Red Tilapia broodstock. Tilapia broodfish weighing 140-160 g were stocked in four treatment groups: control (T0), and the other three groups were added different levels of BSL to the water as follows: T1 (0.01 g/m3), T2 (0.02 g/m3), and T3 (0.03 g/m3), respectively. Results indicate that BSL administration significantly improved RBCs, hemoglobin, hematocrit, MCH, and MCHC, with the highest improvement seen in the T3 group (P < 0.05). BSL added to the fish water significantly enhanced serum protein fractions (total protein, albumin, and globulins), while AST, ALT, ALP, creatinine, uric acid, and glucose were significantly diminished in a dose-dependent way (P < 0.05). Adding 0.02-0.03 g/ m3 of BSL resulted in higher antioxidant status (superoxide dismutase and catalase) compared to other groups (P < 0.05). Testosterone levels were higher in T3 than in other groups (P < 0.05). All female hormones (LH, FSH, estradiol, and progesterone) were substantially augmented by the addition of BSL. Additionally, the BSL groups exhibited higher GSI, HSI, VSI (male only), egg diameter (mm), mean number of fry/fish, and mean fry weight (g) compared to the control group (P < 0.05). Expression of reproductive-associated genes (vasa, nanos1a, nanos2, dnd1, pum1, AMH, and vtg) were significantly up-regulated in the gonads of fish in the 0.03 g/m3 treatment. The histological gonadal structure exhibited that BSL improved gonad maturation in both genders of Tilapia fish. Overall, adding a mixture of B. subtilis and B. licheniformis (0.03 g/m3 water) can accelerate reproductive performance in Red Tilapia through up-regulation of reproductive genes and enhance the health profile.

Assessment of Encapsulated Probiotic Lactococcus lactis A12 Viability Using an In Vitro Digestion Model for Tilapia

Probiotics face harsh conditions during their transit through the gastrointestinal tract (GIT) of fish because of low-pH environments and intestine fluid. Therefore, the evaluation of probiotic viability under simulated gastrointestinal conditions is an important step to consider for probiotic supplementation in fish feed prior to in vivo trials. Therefore, this study aimed to evaluate the effect of stomach and intestinal simulated conditions on the viability of encapsulated Lactococcus lactis A12 using an in vitro digestion model for tilapia. A Box Behnken design was used to evaluate the potential effect of three factors, namely stomach pH, residence time in the stomach, and enzyme quantity, on the viability of encapsulated Lactococcus lactis A12. As the main results, low pH (4.00), long residence time (4 h), and enzyme quantity (2.68 U of total protease activity) led to lower final cell counts after the phases of the stomach and intestine. Encapsulated probiotic bacteria showed higher viability (p < 0.05) and antibacterial activity (p < 0.05) against the pathogen Streptococcus agalactiae than non-encapsulated bacteria. The results suggest that L. lactis A12 survives in GIT conditions and that the proposed in vitro model could be used to explore the viability of probiotic bacteria intended for fish feed supplementation.

Responses of growth performance, immunity, disease resistance of shrimp and microbiota in Penaeus vannamei culture system to Bacillus subtilis BSXE-1601 administration: Dietary supplementation versus water addition

This study evaluated the effects of Bacillus subtilis BSXE-1601, applied either as dietary supplementation or water addition, on growth performance, immune responses, disease resistance of Penaeus vannamei, and microbiota in shrimp gut and rearing water. During the 42-day feeding experiment, shrimp were fed with basal diet (CO and BW group), basal diet supplemented with live strain BSXE-1601 at the dose of 1 × 109 CFU kg-1 feed (BD group) and 15 mg kg-1 florfenicol (FL group), and basal diet with strain BSXE-1601 added to water at the concentration of 1 × 107 CFU L-1 every five days (BW group). Results showed that dietary supplementation of strain BSXE-1601 significantly promoted growth performance of shrimp, both in the diet and water, enhanced disease resistance against Vibrio parahaemolyticus (P < 0.05). The BD and BW groups exhibited significant increases in acid phosphatase, alkaline phosphatase, lysozyme, peroxidase, superoxide dismutase activities, phenonoloxidase content in the serum of shrimp compared to the control (P < 0.05). Meanwhile, the expression of immune-related genes proPO, LZM, SOD, LGBP, HSP70, Imd, Toll, Relish, TOR, 4E-BP, eIF4E1α, eIF4E2 were significantly up-regulated compared to the control (P < 0.05). When added in rearing water, strain BSXE-1601 induced greater immune responses in shrimp than the dietary supplement (P < 0.05). Chao1 and Shannon indices of microbiota in rearing water were significantly lower in BD group than in the control. The microbiota in rearing water were significantly altered in BD, BW and FL groups compared to the control, while no significant impacts were observed on the microbiota of shrimp gut. When supplemented into the feed, strain BSXE-1601 obviously reduced the number of nodes, edges, modules in the ecological network of rearing water. The results suggested that dietary supplementation of BSXE-1601 could be more suitable than water addition in the practice of shrimp rearing when growth performance, non-specific immunity, disease resistance against V. parahaemolyticus in shrimp were collectively considered.

Probiotics for Aquaculture: Hope, Truth, and Reality

The use of microorganisms as beneficial crops for human and animal health has been studied for decades, and these microorganisms have been in practical use for quite some time. Nowadays, in addition to well-known examples of beneficial properties of lactic acid bacteria, bifidobacteria, selected Bacillus spp., and yeasts, there are several other bacteria considered next-generation probiotics that have been proposed to improve host health. Aquaculture is a rapidly growing area that provides sustainable proteins for consumption by humans and other animals. Thus, there is a need to develop new technologies for the production practices associated with cleaner and environment-friendly approaches. It is a well-known fact that proper selection of the optimal probiotics for use in aquaculture is an essential step to ensure effectiveness and safety. In this critical review, we discuss the evaluation of host-specific probiotics in aquaculture, challenges in using probiotics in aquaculture, methods to improve the survival of probiotics under different environmental conditions, technological approach to improving storage, and delivery along with possible negative consequences of using probiotics in aquaculture. A critical analysis of the identified challenges for the use of beneficial microbes in aquaculture will help in sustainable aquafarming, leading to improved agricultural practices with a clear aim to increase protein production.

Diversity, distribution, and bioprospecting potentials of carotenogenic yeast from mangrove ecosystem

Microbial production of carotenoids has gained significant interest for its cost-effectiveness and sustainable nature. This study focuses on 47 red-pigmented yeasts isolated from sediments and plant parts of 13 species of mangrove trees. The relative abundance and distribution of these yeasts varied with plant species and plant parts. The highest number of red yeasts was associated with the mangrove plant Avicennia officinalis (32%). Notably, the leaves harbored the highest percentage (45%) of carotenogenic yeasts, and definite compartmentalization of these yeast species was noticed in mangrove plant parts. All the isolates were molecularly identified and they belonged to the genera of Rhodotorula, Rhodosporidiobolus, and Cryptococcus. The diversity of the pigmented yeasts isolated from A. officinalis was found to be the greatest. Among these strains, Rhodotorula mucilaginosa PV 8 was identified as the most potent producer of carotenoid pigment. Under optimized conditions of physical parameters - 28 °C, pH 5, and 15% salinity led to biomass production of 9.2 ± 0.12 g/L DCW and a pigment yield of 194.78 µg/g. The pigment produced by PV 8 was identified as β-carotene by thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FT-IR). This β-carotene demonstrated strong antioxidant activity. Moreover, the carotenoid displayed promising antibacterial activity against multidrug-resistant organisms, including Aeromonas sp. and Vibrio sp. In vitro studies revealed the probiotic traits of PV 8. The cytotoxicity of R. mucilaginosa PV 8 was assessed in the invertebrate model Artemia salina and the survival rate showed that it was non-toxic. Furthermore, the β-carotene from PV 8 demonstrated the ability to transfer its vibrant color to various food products, maintaining color stability even under varied conditions. This research underscores the potential of R. mucilaginosa PV 8, as a versatile and valuable resource for the production of carotenoids.

Supplementation of Bacillus subtilis and Lactobacillus casei to increase growth performance and immune system of catfish (Clarias gariepinus) due to Aeromonas hydrophila infection

Background and Aim

Catfish has a high economic value and is popular among consumers. To ensure well-stocked catfish stocks, good fisheries management must also be ensured. The high demand for catfish must be supplemented by preventive measures against pathogenic bacterial infections using probiotics with high potential for Lactobacillus casei and Bacillus subtilis. The aim of this study was to determine the effect of probiotic supplementation consisting of a combination of L. casei and B. subtilis probiotics on the growth, immune system, water quality, proximate value of feed, and body composition of catfish infected with Aeromonas hydrophila.

Materials and Methods

This study used a completely randomized study with eight treatments and three replications. The manipulated factor was the probiotic concentration [0% (A), 0.5% (B), 10% (C), and 15% (D)] in groups of catfish infected and uninfected with A. hydrophila. Combination of B. subtilis, and L. casei that were used in a 1:1 ratio of 108 colony forming unit/mL. The study lasted for 42 days. On the 35th day, A. hydrophila was infected by intramuscular injection into fish. The Statistical Package for the Social Sciences (SPSS) software version 23.0 (IBM SPSS Statistics) was used to analyze data on growth, immune system, and water quality.

Results

Providing probiotics in feed can increase the nutritional value of feed based on proximate test results. There were significant differences in average daily gain (ADG), feed conversion ratio (FCR), and survival rate (SR) parameters in the group of catfish infected with A. hydrophila (p > 0.05); however, there were no significant differences in final body weight, specific growth rate (SGR), and percentage weight gain. Interleukin-1β (IL-1β) levels were significantly different between treatments C and D. The tumor necrosis factor (TNF) α parameters were significantly different between treatments A and C, whereas the phagocytic activity of treatment A was significantly different from that of treatment D. There was a significant difference (p > 0.05) in the growth parameters of SGR, ADG, and FCR in the group of fish that were not infected with A. hydrophila, with the best treatment being a probiotic concentration of 15%, but there was no significant difference in the SR parameters. IL-1β and TNF-α levels significantly differed between E and E0 (15% probiotics) but were not significantly different in terms of phagocytosis parameters.

Conclusion

Based on the results of this study, it can be concluded that using a combination of probiotics L. casei and B. subtilis can improve the growth, immune system, water quality, proximate value of feed, and body composition of catfish infected with A. hydrophila.

Synbiotic Agents and Their Active Components for Sustainable Aquaculture: Concepts, Action Mechanisms, and Applications

Aquaculture is a fast-emerging food-producing sector in which fishery production plays an imperative socio-economic role, providing ample resources and tremendous potential worldwide. However, aquatic animals are exposed to the deterioration of the ecological environment and infection outbreaks, which represent significant issues nowadays. One of the reasons for these threats is the excessive use of antibiotics and synthetic drugs that have harmful impacts on the aquatic atmosphere. It is not surprising that functional and nature-based feed ingredients such as probiotics, prebiotics, postbiotics, and synbiotics have been developed as natural alternatives to sustain a healthy microbial environment in aquaculture. These functional feed additives possess several beneficial characteristics, including gut microbiota modulation, immune response reinforcement, resistance to pathogenic organisms, improved growth performance, and enhanced feed utilization in aquatic animals. Nevertheless, their mechanisms in modulating the immune system and gut microbiota in aquatic animals are largely unclear. This review discusses basic and current research advancements to fill research gaps and promote effective and healthy aquaculture production.

Utilisation of probiotics for disease management in giant freshwater prawn (Macrobrachium rosenbergii): Administration methods, antagonistic effects and immune response

The giant freshwater prawn (Macrobrachium rosenbergii) is a high-yielding prawn variety well-received worldwide due to its ability to adapt to freshwater culture systems. Macrobrachium rosenbergii is an alternative to shrimp typically obtained from marine and brackish aquaculture systems. However, the use of intensive culture systems can lead to disease outbreaks, particularly in larval and post-larval stages, caused by pathogenic agents such as viruses, bacteria, fungi, yeasts and protozoans. White tail disease (viral), white spot syndrome (viral) and bacterial necrosis are examples of economically significant diseases. Given the increasing antibiotic resistance of disease-causing microorganisms, probiotics have emerged as promising alternatives for disease control. Probiotics are live active microbes that are introduced into a target host in an adequate number or dose to promote its health. In the present paper, we first discuss the diseases that occur in M. rosenbergii production, followed by an in-depth discussion on probiotics. We elaborate on the common methods of probiotics administration and explain the beneficial health effects of probiotics as immunity enhancers. Moreover, we discuss the antagonistic effects of probiotics on pathogenic microorganisms. Altogether, this paper provides a comprehensive overview of disease control in M. rosenbergii aquaculture through the use of probiotics, which could enhance the sustainability of prawn culture.

Probiotic Supplementation as an Emerging Alternative to Chemical Therapeutics in Finfish Aquaculture: a Review

Aquaculture is a promising food sector to fulfil nutritional requirements of growing human population. Live weight aquaculture production reached up to 114.5 million tonnes in 2018 and it is further expected to grow by 32% by year 2030. Among total aquaculture production, major product harvested is finfish and its contribution has reached 46% in recent years. Frequent outbreaks of infectious diseases create obstacle in finfish production, result in economic losses to the farmers and threaten the sustainability of aquaculture industry itself. In spite of following the best management practices, the use of antibiotics, chemotherapeutics and phytochemicals often become the method of choice in finfish culture. Among these, phytochemicals have shown lesser effect in animal welfare while antibiotics and other chemotherapeutics have led to negative consequences like emergence of drug-resistant bacteria, and accumulation of residues in host and culture system, resulting in quality degradation of aqua products. Making use of probiotics as viable alternative has paved a way for sustainable aquaculture and minimise the use of antibiotics and other chemotherapeutics that pose adverse effect on host and culture system. This review paper elucidates the knowledge about antibiotics and other chemicals, compilation of probiotics and their effects on health status of finfish as well as overall culture environment. Besides, concoction of probiotics and prebiotics for simultaneous application has also been discussed briefly.

Current Status of Probiotics in European Sea Bass Aquaculture as One Important Mediterranean and Atlantic Commercial Species: A Review

European sea bass production has increased in recent decades. This increase is associated with an annually rising demand for sea bass, which encourages the aquaculture industries to increase their production to meet that demand. However, this intensification has repercussions on the animals, causing stress that is usually accompanied by dysbiosis, low feed-conversion rates, and immunodepression, among other factors. Therefore, the appearance of pathogenic diseases is common in these industries after immunodepression. Seeking to enhance animal welfare, researchers have focused on alternative approaches such as probiotic application. The use of probiotics in European sea bass production is presented as an ecological, safe, and viable alternative in addition to enhancing different host parameters such as growth performance, feed utilization, immunity, disease resistance, and fish survival against different pathogens through inclusion in fish diets through vectors and/or in water columns. Accordingly, the aim of this review is to present recent research findings on the application of probiotics in European sea bass aquaculture and their effect on growth performance, microbial diversity, enzyme production, immunity, disease resistance, and survival in order to help future research.

Functional properties of lactic acid bacteria isolated from Tilapia (Oreochromis niloticus) in Ivory Coast

BACKGROUND

Probiotics have recently been applied in aquaculture as eco-friendly alternatives to antibiotics to improve fish health, simultaneously with the increase of production parameters. The present study aimed to investigate the functional potential of lactic acid bacteria (LAB) isolated from the gut of Tilapia (Oreochromis niloticus) originating from the aquaculture farm of Oceanologic Research Center in Ivory Coast.

RESULTS

Twelve LAB strains were identified by 16 S rDNA gene sequence homology analysis belonging to two genera Pediococcus (P. acidilactici and P. pentosaceus) and Lactobacillus (L. plantarum) with a predominance of P. acidilactici. Several aspects including functional, storage, and safety characteristics were taken into consideration in the selection process of the native LAB isolates as potential probiotics. All LAB isolates showed high antagonistic activity against bacterial pathogens like Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis, and Staphylococcus aureus. In addition, the LAB isolates exhibited different degrees of cell surface hydrophobicity in the presence of hexane, xylene, and chloroform as solvents and a good ability to form biofilm. The strong antioxidant activity expressed through the DPPH scavenging capacity of LAB intact cells and their cell-free supernatants was detected. LAB strains survived between 34.18% and 49.9% when exposed to low pH (1.5) and pepsin for 3 h. In presence of 0.3% bile salts, the growth rate ranged from 0.92 to 21.46%. Antibiotic susceptibility pattern of LAB isolates showed sensitivity or intermediate resistance to amoxicillin, cephalothin, chloramphenicol, imipenem, kanamycin, penicillin, rifampicin, streptomycin, tetracycline and resistance to oxacillin, gentamicin, and ciprofloxacin. No significant difference in antibiotic susceptibility pattern was observed between P. acidilactici and P. pentosaceus strains. The non-hemolytic activity was detected. Following the analysis of the enzyme profile, the ability of LAB isolates to produce either lipase or β-galactosidase or both enzymes was highlighted. Furthermore, the efficacy of cryoprotective agents was proved to be isolate-dependent, with LAB isolates having a high affinity for D-sorbitol and sucrose.

CONCLUSION

The explored LAB strains inhibited the growth of pathogens and survived after exposure to simulated gastrointestinal tract conditions. The safety and preservative properties are desirable attributes of these new probiotic strains hence recommended for future food and feed applications.

Whole genome sequence analysis enabled affirmation of the probiotic potential of marine sporulater Bacillus amyloliquefaciens BTSS3 isolated from Centroscyllium fabricii

Probiotics are microorganisms when administered in adequate amounts, confer health benefits on the host. Many probiotics find application in various industries however, probiotic bacteria linked to marine environments are less explored.Although Bifidobacteria, Lactobacilli, and Streptococcus thermophilus are the most frequently used probiotics, Bacillus spp. have acquired much acceptance in human functional foods due to their increased tolerance and enduring competence in harsh environments like the gastrointestinal (GI) tract. In this study, the 4 Mbp genome sequence of Bacillus amyloliquefaciens strain BTSS3, a marine spore former isolated from deep-sea shark Centroscyllium fabricii, with antimicrobial and probiotic properties was sequenced, assembled, and annotated. Analysis revealed the presence of numerous genes presenting probiotic traits like production of vitamins, secondary metabolites, amino acids, secretory proteins, enzymes and other proteins that allow survival in GI tract as well as adhesion to intestinal mucosa. Adhesion by colonization in the gut was studied in vivo in zebrafish (Danio rerio) using FITC labelled B.amyloliquefaciens BTSS3. Preliminary study revealed the ability of the marine Bacillus to attach to the intestinal mucosa of the fish gut. The genomic data and the in vivo experiment affirms that this marine spore former is a promising probiotic candidate with potential biotechnological applications.

Sustainable Ornamental Fish Aquaculture: The Implication of Microbial Feed Additives

Ornamental fish trade represents an important economic sector with an export turnover that reached approximately 5 billion US dollars in 2018. Despite its high economic importance, this sector does not receive much attention. Ornamental fish husbandry still faces many challenges and losses caused by transport stress and handling and outbreak of diseases are still to be improved. This review will provide insights on ornamental fish diseases along with the measures used to avoid or limit their onset. Moreover, this review will discuss the role of different natural and sustainable microbial feed additives, particularly probiotics, prebiotics, and synbiotics on the health, reduction in transport stress, growth, and reproduction of farmed ornamental fish. Most importantly, this review aims to fill the informational gaps existing in advanced and sustainable practices in the ornamental fish production.

Bacillus subtilis KM0 Impacts gut Microbiota Profile and Transcription of Genes Related to Transcellular Transport in Zebrafish (Danio rerio)

It is known that probiotic microorganisms play important roles in the composition of the intestinal microbiota. Also, probiotics can affect the paracellular and transcellular transport mechanisms performed by intestinal cells. The aim of this work was to evaluate the effect of the potential probiotic Bacillus subtilis KM0 on the profile of the gut microbiota and transcription of genes related to intestinal transport of zebrafish (Danio rerio). Zebrafish was exposed by immersion to B. subtilis KM0 for 48 h, and the intestines were collected for metataxonomic analysis and transcription of genes related to transcellular and paracellular transports. Although exposure to B. subtilis changed the intestinal microbiota profile of zebrafish, the diversity indices were not altered. A decrease in the number of genera of potentially pathogenic bacteria (Flavobacterium, Plesiomonas, and Pseudomonas) and downregulation in transcription of transcellular transport genes (cubn and amn) were observed. B. subtilis KM0 strain had the expected probiotic effect, by interfering with the proliferation of potentially pathogenic bacteria and decreasing the transcription of genes codifying for signals involved with a mechanism that can be used for invasion by pathogens. The present study demonstrated that, even with a short-term exposure, a bacterium with probiotic potential such as the KM0 strain of B. subtilis can modify the profile of the host's intestinal microbiota, with an impact on the regulation of intestinal genes related to mechanisms that can be used for invasion by pathogenic bacteria.

The role of probiotics in vannamei shrimp aquaculture performance – A review

Vannamei shrimp (Litopenaeus vannamei) is an important food commodity of economic benefit due to its high price, low susceptibility to disease, and popularity for consumption. These advantages have led many farmers to cultivate vannamei shrimp. Efforts are underway to improve the aquaculture performance of this species, including the use of probiotics, which are non-pathogenic bacteria that aid in digestion and help fight disease. Probiotics are usually obtained from the intestines of vannamei shrimp or the culture environment. They are low-cost, non-pathogenic, and largely non-toxic source of antibiotics and are able to synthesize various metabolites that have antibacterial functions and applications. Research on probiotic use has primarily been focused on increasing vannamei shrimp aquaculture production. Bacterial species, such as Lactobacillus or Nitrobacter, can be administered orally, by injection, or as a supplement in aquaculture water. Probiotics help to improve survival rate, water quality, immunity, and disease resistance through space competition with disease-causing bacteria, such as Vibrio spp. An increased number of probiotic bacteria suppresses the growth and presence of pathogenic bacteria, which lowers disease susceptibility. In addition, probiotic bacteria also aid digestion by breaking down complex compounds into simpler substances that the body can absorb more easily. This mechanism improves growth performance in terms of weight, length, and feed conversion ratio. This review aimed to provide information regarding contribution of probiotic to improve vannamei shrimp production in aquaculture. Keywords: application, bacteria, farm, microbiome, shrimp.

Micro-/bio-/nano-/syn-encapsulations and co-treatments of bioactive microbial feed supplementation in augmenting finfish health and aquaculture nutrition: a review

Finfish and fish products are globally the most acknowledged health-promoting foods. The rising incidence of pathogenic and disease outbreaks have had a sizeable impact on aquaculture. Microbial supplementation of food in the form of probiotics, prebiotics, and their controlled release combinations (=co-encapsulations) as 'synbiotics' is noted for its significant biotherapeutic and health benefits. Supplementation of probiotic microbial feed additives in the fish diet claims to improve fish health by modulation of resident intestinal microbiota and by introducing healthy microbiota procured from an exogenous source, capable of combating pathogens, improving nutrient uptake, assimilation, growth as well as survival. Prebiotics are selectively digestible substrates beneficially used by host gut microbes to enhance probiotic effects. Formulating a fish diet with augmented probiotics and prebiotic microbial bio-supplements can ensure a sustainable alternative for establishing fish health in a naturally susceptible aquaculture scenario. Micro-encapsulation, co-encapsulation, and nano-encapsulation are novel strategies of biotechnical interventions in functional feeds for finfish. These aim to improve probiotic persistence, survivability, and efficacy in commercial formulations during probiotic transit through the host-gut environment. This review discusses the importance of co-treatment and encapsulation strategies for improving probiotic and prebiotic potential in aquafeed formulations, reliably improving finfish health and nutritional returns from aquaculture, and, consequently, for consumers.

Genomic features of Pseudomonas sp. RGM2144 correlates with increased survival of rainbow trout infected by Flavobacterium psychrophilum

This study evaluated the probiotic potential of the biofilm formed by the strain Pseudomonas sp. RGM2144 on rainbow trout survival. When challenged with the fish pathogen Flavobacterium psychrophilum, Pseudomonas sp. RGM2144 increased rainbow trout survival to 92.7 ± 1.2% (control: 35.3 ± 9.5%, p < .0001). The draft genome of Pseudomonas sp. RGM2144 is 6.8 Mbp long, with a completeness 100% and a contamination of 0.4%. The genome contains 6122 protein-coding genes of which 3564 (~60%) have known functions. The genome and phylogeny indicate that Pseudomonas sp. RGM2144 is a new species in the Pseudomonas genus, with few virulence factors, plasmids, and genes associated with antimicrobial resistance, suggesting a non-pathogenic bacterium with protective potential. In addition, the genome encodes for 11 secondary metabolite biosynthetic gene clusters that could be involved in the inhibition of F. psychrophilum. We suggest that Pseudomonas sp. RGM2144 may be applied as a probiotic in salmonid fish farming.

In Vitro Assessment of Yeasts Strains with Probiotic Attributes for Aquaculture Use

This study aimed to investigate in vitro the probiotic potential of three yeasts strains (BB06, OBT05, and MT07) isolated from agro-food natural sources. Screening was performed, including several functional, technological, and safety aspects of the yeast strains, in comparison to a reference Saccharomyces boulardii, to identify the ones with suitable probiotic attributes in aquaculture. The yeast strains were identified by 5.8S rDNA-ITS region sequencing as Metschnikowia pulcherrima OBT05, Saccharomyces cerevisiae BB06, and Torulaspora delbrueckii MT07. All yeast strains were tolerant to different temperatures, sodium chloride concentrations, and wide pH ranges. S. cerevisiae BB06 showed a strong and broad antagonistic activity. Moreover, the S. cerevisiae strain exhibited a high auto-aggregation ability (92.08 ± 1.49%) and good surface hydrophobicity to hexane as a solvent (53.43%). All of the yeast strains have excellent antioxidant properties (>55%). The high survival rate in the gastrointestinal tract (GIT) can promote yeast isolates as probiotics. All yeast strains presented a resistance pattern to the antibacterial antibiotics. Non-hemolytic activity was detected. Furthermore, freeze-drying with cryoprotective agents maintained a high survival rate of yeast strains, in the range of 74.95−97.85%. According to the results obtained, the S. cerevisiae BB06 strain was found to have valuable probiotic traits.

Growth Performance, Survival, Blood Chemistry, and Immune Gene Expression of Channel Catfish (Ictalurus punctatus) Fed Probiotic-Supplemented Diets

The channel catfish (Ictalurus punctatus) farming industry is the largest and one of the oldest aquaculture industries in the United States. Despite being an established industry, production issues stemming from disease outbreaks remain problematic for producers. Supplementing fish diets with probiotics to enhance the immune system and growth potential is one approach to mitigating disease. Although considerable laboratory data demonstrate efficacy, these results do not always translate to natural modes of disease transmission. Hence, the present work was conducted in the laboratory but incorporated flow-through water from large catfish pond production systems, allowing for natural exposure to pathogens. Two feeding trials were conducted in an 18-tank aquaria system housing two different sizes, 34.8 ± 12.5 g and 0.36 ± 0.03 g, of channel catfish. Channel catfish in the first trial were fed three experimental diets over six weeks. Commercial diets were top-coated with two selected spore-forming Bacillus spp. probiotics, Bacillus velezensis AP193 (1 × 106 CFU g−1) and BiOWiSH (3.6 × 104 CFU g−1), or a basal diet that contained no dietary additive. In the second eight-week trial, diets were top-coated with BiOWiSH at three concentrations (1.8, 3.6, and 7.3 × 104 CFU g−1), along with one basal diet (no probiotic). At the completion of these studies, growth performance, survival, hematocrit, blood chemistry, and immune expression of interleukin 1β (il1β), tumor necrosis factor-alpha (tnf-α), interleukin-8 (il8), transforming-growth factor β1 (tgf-β1), and toll-like receptor 9 (tlr9) were evaluated using qPCR. Trial results revealed no differences (p > 0.05) among treatments concerning growth, survival, or hematological parameters. For immune gene expression, interesting trends were discerned, with substantial downregulation observed in B. velezensis AP193-fed fish for il1β, tnf-α, and tlr9 expression within splenic tissue, compared to that of the basal and BiOWiSH diets (p < 0.05). However, the results were not statistically significant for anterior kidney tissue in the first trial. In the second trial, varied levels of probiotic inclusion revealed no significant impact of BiOWiSH’s products on the expression of il1β, tnf-α, il8, and tgf-β1 in both spleen and kidney tissue at any rate of probiotic inclusion (p > 0.05). Based on these findings, more research on utilizing probiotics in flow-through systems with natural infection conditions is crucial to ensure consistency from a controlled laboratory scale to real-world practices.

Probiotic effects of Pseudoalteromonas ruthenica: Antibacterial, immune stimulation and modulation of gut microbiota composition

This study aimed to characterise and evaluate the probiotic properties of a newly isolated marine bacterium, strain S6031. The isolated strain was identified as Pseudoalteromonas ruthenica. In vivo experiments were conducted with P. ruthenica-immersed larvae and P. ruthenica-enriched Artemia fed to adult zebrafish. Disease tolerance of larval zebrafish against Edwardsiella piscicida was demonstrated by 66.34% cumulative per cent survival (CPS) in the P. ruthenica-exposed group, which was higher than the CPS of the control (46.67%) at 72 h post challenge (hpc). Heat-stressed larvae had 55% CPS in the P. ruthenica-immersed group, while the control had 30% CPS at 60 hpc. Immune-stress response gene transcripts (muc5.1, muc5.2, muc5.3, alpi2, alpi3, hsp70, and hsp90a) were induced, while pro-inflammatory genes (tnfα, il1b, and il6) were downregulated in P. ruthenica-immersed larvae compared to the control. This trend was confirmed by low pro-inflammatory and high stress-responsive protein expression levels in P. ruthenica-exposed larvae. Adult zebrafish had higher CPS (27.2%) in the P. ruthenica-fed group than the control (9.52%) upon E. piscicida challenge, suggesting increased disease tolerance. Histological analysis demonstrated modulation of goblet cell density and average villus height in the P. ruthenica-supplemented group. Metagenomics analysis clearly indicated modulation of alpha diversity indices and the relative abundance of Proteobacteria in the P. ruthenica-supplemented zebrafish gut. Furthermore, increased Firmicutes colonisation and reduced Bacteroidetes abundance in the gut were observed upon P. ruthenica supplementation. Additionally, this study confirmed the concentration-dependent increase of colony dispersion and macrophage uptake upon mucin treatment. In summary, P. ruthenica possesses remarkable functional properties as a probiotic that enhances host defence against diseases and thermal stress.

Adipose Fin as a Natural “Optical Window” for Implantation of Fluorescent Sensors into Salmonid Fish

Simple Summary

Novel optical sensors require implantation into the most transparent organs in order to ensure the most reliable and rapid monitoring of animal health. Widely farmed salmonid fish, such as rainbow trout, have highly translucent adipose fin, which we tested here and showed its high potential as the implantation site for the fluorescent sensors. The filamentous sensors were convenient to inject into the fin, and their optical signal was easily detectable using a simple hand-held device even without immobilization of the fish. Responsiveness of the sensors inside the adipose fin to bodily changes was shown under induced acidosis of fish fluids. The obtained results characterize adipose fin as the favorable site for implantation of optical sensors into salmonids for real-time tracking animal physiological status in basic research and aquaculture.

Abstract

Implantable optical sensors are emerging tools that have the potential to enable constant real-time monitoring of various internal physiological parameters. Such a possibility will open new horizons for health control not only in medicine, but also in animal husbandry, including aquaculture. In this study, we analyze different organs of commonly farmed rainbow trout (Oncorhynchus mykiss) as implantation sites for fluorescent sensors and propose the adipose fin, lacking an endoskeleton, as the optimal choice. The fin is highly translucent due to significantly thinner dermis, which makes the detectable fluorescence of an implanted sensor operating at the visible light range by more than an order of magnitude higher relative to the skin. Compared to the proximal parts of ray fins, the adipose fin provides easy implantation and visualization of the sensor. Finally, we tested fluorescent pH sensors inside the adipose fin and demonstrated the possibility of acquiring their signal with a simple hand-held device and without fish anesthesia. All these features will most likely make the adipose fin the main “window” into the internal physiological processes of salmonid fish with the help of implantable optical sensors.

Improvement the Hatchery Seed Production Strategy on Embryonic Development and Larval Growth Performance and Development stages of Green Tiger Prawn, Penaeus semisulcatus Using Environmental Aspects

This investigation aimed to improve the hatchery seed production strategy in terms of chronologies of embryonic and larval development as well as hatching, growth and survival rates, and rearing water quality of green tiger prawn, Penaeus semisulcatus by the integration effects of different water temperatures (23 °C, 26 °C, 29 °C, 32 °C) and probiotic as water additives. The best and shortest chronologies of embryonic development stages were in favor of 32 °C with probiotic. The best hatching rate was in favor of 29 °C with probiotics. The fastest larval development and greatest larval growth as total length until PL1 stage was promoted by 32 °C with probiotic but the best survival rate was recorded at 26 °C with probiotic followed by 29 °C with probiotic treatment. During larval development, the lowest value of NH4–N was recorded under the effect of 26 °C and probiotic. Therefore, probiotics as water additives at 29 and 32 °C water temperatures have a beneficial impact on the hatchery seed production strategy and quality of P. semisulcatus. Our findings could apply to rearing larvae in shrimp hatchery to decrease the chronology of embryonic and larval development, while increase the hatching rate, growth performance, and survival rates as well as improving the water quality.

Improvement of aquaculture water quality by mixed Bacillus and its effects on microbial community structure

Microbial remediation, especially the application of probiotics, has recently gained popularity in improving water quality and maintaining aquatic animal health. The efficacy and mechanism of mixed Bacillus for improvement of water quality and its effects on aquatic microbial community structure remain unknown. To elucidate these issues, we applied two groups of mixed Bacillus (Bacillus megaterium and Bacillus subtilis (A0 + BS) and Bacillus megaterium and Bacillus coagulans (A0 + BC)) to the aquaculture system of Crucian carp. Our results showed that the improvement effect of mixed Bacillus A0 + BS on water quality was better than that of A0 + BC, and the NH₄⁺-N, NO₂^--N, NO₃^--N, and total phosphorus (TP) concentrations were reduced by 46.3%, 76.3%, 35.6%, and 80.3%, respectively. In addition, both groups of mixed Bacillus increased the diversity of the bacterial community and decreased the diversity of the fungal community. Microbial community analysis showed that mixed Bacillus A0 + BS increased the relative abundance of bacteria related with nitrogen and phosphorus removal, such as Proteobacteria, Actinobacteria, Comamonas, and Stenotrophomonas, but decreased the relative abundance of pathogenic bacteria (Acinetobacter and Pseudomonas) and fungi (Epicoccum and Fusarium). Redundancy analysis showed that NH₄⁺-N, NO₂^--N, and TP were the primary environmental factors affecting the microbial community in aquaculture water. PICRUST analysis indicated that all functional pathways in the A0 + BS group were richer than those in other groups. These results indicated that mixed Bacillus A0 + BS addition produced good results in reducing nitrogenous and phosphorus compounds and shaped a favorable microbial community structure to further improve water quality.

Aquamimicry system: a sutiable strategy for shrimp aquaculture – a review

Shrimp culture is the most lucrative sector in aquaculture industry; however, for its sustainable development the environment conservation should be concerned. New developed technologies are required to achieve aquaculture to its sustainable goals. Among the different novel sustainable technologies, the biofloc technology (BFT) and more recently the aquamimicry system are considered as reliable methods in burgeoning development of shrimp culture. The establishment of the BFT needs a certain carbon to nitrogen (C: N) ratio so that heterotrophic bacteria able to utilize nitrogenous metabolites, and preserve the water quality in the standard ranges suitable for shrimp culture. In addition, the produced floc can be used as supplementary food for shrimp. On the other hand, the establishment of the aquamimicry system relies on organic carbon without providing a specific C: N ratio. In this system, a synergistic relationship between a prebiotic source, which usually consists of an oligosaccharide derived from the fermentation of a carbon source (e.g., rice bran), and a probiotic source such as Bacillus sp. can provide natural conditions by blooming phytoplankton and zooplankton organisms, especially copepods. These live foods can be used as complementary foods for shrimp. Furthermore, the proliferation of beneficial bacteria in the aquamimicry system can provide stable culture condition for growth and welfare of shrimp. Based on the findings of recent literature, using the aquamimicry system for shrimp production is a more sustainable, eco-friendly, and greener than the conventional systems.

Assessing the Influence of Dietary Pediococcus acidilactici Probiotic Supplementation in the Feed of European Sea Bass (Dicentrarchus labrax L.) (Linnaeus, 1758) on Farm Water Quality, Growth, Feed Utilization, Survival Rate, Body Composition, Blood Biochemical Parameters, and Intestinal Histology

The probiotics are being used as ecofriendly and bioremediation tools for developing sustainability to aquaculture. The present study was conducted to explore the practical capability of using dietary lactic acid bacteria (Pediococcus acidilactici) probiotics and see how its dose variation affected the water quality, growth performance, survival rate, body composition, blood biochemical parameters, and intestinal histology of European sea bass (Dicentrarchus labrax L.). A total of 120 fingerlings with an initial weight of $9\pm 0.2$  g were divided into four groups, each with three replicates. The feeding experiment lasted for 60 days. In addition to the control (without probiotics) (T0), fish were fed diets containing (T1) 2.0, (T2) 2.5, and (T3) 3.0 g of probiotics per kg of diet twice a day. When compared to the control, sea bass fed probiotic-supplemented diets had significantly higher growth parameters, fish body “crude lipid,” and villi height ( $p<0.05$ , $p<0.01$ , and $p<0.001$ ). The P. acidilactici probiotic treatments improved survival rate, feed conversion ratio, body composition, and blood biochemical markers, but not statistically significant ( $p>0.05$ ). Also, in regard to water quality, P. acidilactici drastically reduced ammonia and pH levels. In this experiment, fish fed with a dosage of 3.0 g of this commercial probiotic per kg of probiotics performed better. The study found that including probiotics in the diets of European sea bass improved growth, body composition, survival rate, blood biochemical markers, intestinal histology, and some water quality parameters.

Influence of probiotics on water quality in intensified Litopenaeus vannamei ponds under minimum-water exchange

The effects of two probiotics on NH₃ degradation, as well as the magnetic field (21.56 m tesla) on the germination and proliferation of Bacillus spores, were studied in-vitro. Additionally, the effect of these probiotics on water quality maintenance in Litopenaeus vannamei holding ponds was investigated. For 180 min, NH₃ degradation was assessed as follows: Set 1: ammonia-free tap water with NH₃; Probiotic A (5 × 10¹⁰ viable Bacillus spores/g) with NH₃; Probiotic B (multi spp. 2 × 10⁹ CFU/g) with NH₃; and Set 2: same as set 1 with 30 mg L⁻¹ OM. The magnetic field was tested on Probiotic A (3.5 × 10⁷ CFU) for 36 h in triplicate. In the presence of organic matter, both probiotics degrade NH₃. The viable Bacillus count increased within 6 h of being exposed to the magnetic field, reaching its peak after 36 h. Firstly, fifteen ponds (250,000 PL/acre) were investigated, then 360 water samples were collected from the same corresponding pond for 8 weeks, and subjected to T1: control; T2: Probiotic A (0.007 g/m³/2 weeks); T3: Probiotic B (0.03 g/m³/2 weeks). Both probiotics with TVC and NH₃ demonstrated a negative correlation, on the other hand, they showed a significant (P ≤ 0.01) improvement in DO and pH. Overall, both probiotics were able to degrade NH₃ and the magnetic field (21.56 m tesla) was efficient to improve the germination and proliferation of Bacillus spores in-vitro. Probiotics were also effective for reducing TVC and NH₃ levels by increasing dissolved oxygen and pH in pond water.

Probiotics Have the Potential to Significantly Mitigate the Environmental Impact of Freshwater Fish Farms

Probiotics for freshwater fish farming can be administered as single or multiple mixtures. The expected benefits of probiotics include disease prophylaxis, improved growth, and feed conversion parameters, such as the feed conversion rate (FCR) and specific growth rate (SGR). In the current work, we review the impact of probiotics on freshwater finfish aquaculture. Data were gathered from articles published during the last decade that examined the effects of probiotics on fish growth, FCR, and water quality in freshwater fishponds/tanks. While the expected benefits of probiotics are significant, the reviewed data indicate a range in the level of effects, with an average reduction in ammonia of 50.7%, SGR increase of 17.1%, and FCR decrease of 10.7%. Despite the variability in the reported benefits, probiotics appear to offer a practical solution for sustainable freshwater aquaculture. Disease prophylaxis with probiotics can reduce the need for antibiotics and maintain gut health and feed conversion. Considering that fish feed and waste are two significant parameters of the aquaculture ecological footprint, it can be argued that probiotics can contribute to reducing the environmental impact of aquaculture. In this direction, it would be beneficial if more researchers incorporated water quality parameters in future aquaculture research and protocols to minimize aquaculture’s environmental impact.

Water quality assessment of East Kolkata Wetland with a special focus on bioremediation by nitrifying bacteria

East Kolkata Wetlands (EKW) is designated as International Ramsar site and are the hotspot for large-scale wastewater aquaculture practices. However, the continued surveillance of physicochemical properties of water and application of an eco-friendly approach are essential to ensure safe aquaculture practices. In the present study, we assessed the seasonal variation in physicochemical parameters of water across EKW and investigated the role of nitrifying bacteria as probiotics. We statistically analyzed various physicochemical properties of water samples from EKW. Results of the statistical analysis indicated a significant variation in all the physicochemical parameters across the selected water bodies of EKW (p < 0.01). We isolated and enumerated Nitrosomonas sp. and Nitrobacter sp. and assessed their ability to degrade trichloroethylene (TCE). The role of Nitrosomonas sp. and Nitrobacter sp. were further investigated and established through a small-scale experiment. Two microbial isolates, NSW3 and NBW2, displayed superior TCE degradation ability at pH 5, and the application of these strains as probiotics were found to improve the quality of water and survival rate of fishes in the treated experimental tanks. Our findings suggest that the application of the above mixed bacterial cultures in aquaculture could be an effective and environment-friendly approach for safe and productive aquaculture operations.

Prevention and Control of Streptococcosis in Tilapia Culture: A Systematic Review

Tilapia culture is a very promising industry within the aquaculture sector. However, disease outbreaks have continued to threaten the industry, causing serious economic losses among the producers. Streptococcosis has become the major bacterial disease affecting tilapia production in most regions of the world. To combat the disease and minimize its economic impact on fish producers, numerous preventive and control measures have been developed and reported over the years. This paper aims to systematically review the measures that could be used to manage the disease outbreaks and maintain fish health based on previously published scientific studies. Although numerous measures currently available have been highlighted, it is far better for the producers to maximize the preventive measures for management to be economically feasible. Among the currently available preventive measures, the use of vaccines has been shown to have the most promise, while the use of herbs has been demonstrated to be a more sustainable and economically affordable control measure. However, there are still a number of important gaps in existing literature that require further investigation. Overall, significant progress has been made in preventing and controlling streptococcosis in tilapia although, no single effective measure has been identified. Therefore, a combination of these measures may provide a more effective result.

The Efficacy of Moina micrura Enriched with Probiotic Bacillus pocheonensis in Enhancing Survival and Disease Resistance of Red Hybrid Tilapia (Oreochromis spp.) Larvae

The administration of probiotics via live feeds, such as Artemia and rotifers, has gained significant attention. Moreover, indiscriminate use of antibiotics in conventional aquaculture practices in order to prevent or control disease outbreaks has resulted in the occurrence of residues and antimicrobial resistance. Thus, the application of eco-friendly feed additives, such as probiotics, as a safer alternative has received increasing attention in recent years. However, only minimal information on the administration of probiotics via freshwater cladoceran Moina micrura is available despite being commonly used for larval and post-larval feeding of freshwater crustaceans and fish. Thus, this study aimed to evaluate the application of Bacillus pocheonensis strain S2 administered via M. micrura to red hybrid tilapia (Oreochromis spp.) larvae. Bacillus pocheonensis that has been previously isolated from Spirulina sp. was subjected to preliminary in vitro evaluation of antagonistic properties. The agar well-diffusion assay revealed that this probiont could inhibit the growth of Streptococcus agalactiae and Aeromonas hydrophila. The size of inhibition zones ranged from 8.8 ± 0.2 to 18.2 ± 0.4 mm. Moina micrura was later used as a biological model in preliminary in vivo bacterial challenge assays to evaluate the efficacy of B. pocheonensis in protecting the host from diseases. Moina micrura was pre-enriched with B. pocheonensis at 104 and 106&nbsp;CFU&nbsp;mL-1 before S. agalactiae and A. hydrophila were introduced into the culture. The study revealed that B. pocheonensis at 104&nbsp;CFU&nbsp;mL-1 was able to significantly enhance the survival of M. micrura after being challenged with both pathogens (63 ± 3%) in comparison to the control group. The relative percentage survival (RPS) of M. micrura was highest (p < 0.05) when treated with B. pocheonensis at both concentrations 104 and 106&nbsp;CFU&nbsp;mL-1 (38.33) after being challenged against S. agalactiae. To assess the efficacy of B. pocheonensis in protecting red hybrid tilapia against streptococcosis, the larvae were fed with either unenriched (control) Moina or probiont-enriched Moina daily for 10 days. A significantly (p < 0.05) higher survival rate (77 ± 3%) was observed in larvae fed with probiont-enriched M. micrura compared to other treatments, and the RPS was recorded at 62.90. In addition, the S. agalactiae load was suppressed in larvae fed probiont-enriched M. micrura (6.84±0.39&nbsp;CFU&nbsp;mL-1) in comparison to the control group (7.78±0.09&nbsp;CFU&nbsp;mL-1), indicating that the probiont might have contributed to the improvement of tilapia health and survival. This study illustrated that M. micrura was suitable to be used as a vector for probiotics in freshwater fish larvae as an alternative to hazardous antibiotics for disease control.

The Effect of Two Dietary Protein Sources on Water Quality and the Aquatic Microbial Communities in Marron (Cherax cainii) Culture

Feeding freshwater crayfish species with different diets not only affects the water quality but also induces the abundance of various microbial communities in their digestive tracts. In this context, very limited research has been undertaken to understand the impacts of various protein incorporated aqua-diets on the characteristics of water and its microbial communities. In this study, we have critically analysed the water quality parameters including pH, dissolved oxygen, nitrate, nitrite, ammonia and phosphorus, as well as bacterial communities under marron (Cherax cainii) aquaculture, fed fishmeal (FM) and poultry by-product meal (PBM)-based diets for 60 days. The results unveiled that over the time, feeding has significant impacts on organic waste accumulation, especially ammonia, nitrate, nitrite and phosphate, while no effects were observed on pH and dissolved oxygen. Analysis of 16S rRNA sequence data of water sample indicated significant (P < 0.05) shift of microbial abundance in post-fed FM and PBM water with the evidence of microbial transmission from the gut of marron. Post-fed marron resulted in a significant correlation of Hafnia, Enterobacter, Candidatus Bacilloplasma and Aquitella with the quality and microbial population of water. The results of this study generated valuable knowledge database of microbes-water relationship for better health management practices and production of marron aquaculture fed with FM and PBM diets in under restricted feeding regime with the feeding ratios provided.

Isolation of Lactic Acid Bacteria from Intestine of Freshwater Fishes and Elucidation of Probiotic Potential for Aquaculture Application

Probiotics play significant roles in enhancing systemic immunity, improving intestinal balance and feed value, enhancing enzymatic digestion, and inhibiting pathogenic microorganisms of freshwater fish. Probiotics from an identical organism's gastrointestinal system promote effective colonization and provide greater benefits than other sources. This study aimed to evaluate the usefulness of probiotic bacteria isolated from the intestines of freshwater fishes for a dietary supplement of freshwater aquaculture. A total of 120 isolates were collected from freshwater fishes of Channa striata, Puntius filamentosus, Oreochromis mossambicus, Cirrhinus mrigala, and Rasbora daniconius. Seven of these isolates exhibited antagonistic activity against fish pathogens: Aeromonas hydrophila, Staphylococcus epidermidis, Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Pseudomonas aeruginosa. Using 16S rRNA gene sequencing analysis, the isolates were identified as Enterococcus sp., Lactococcus lactis, Weissella cibaria, and Limosilactobacillus fermentum. Of these tolerates, L. fermentum URLP18 isolated from C. mrigala exhibited high tolerance to low acidic (pH 2.0) and high bile salt (2%) concentrations, exhibiting a significant hydrophobicity and extracellular enzyme secretions like amylase, protease, and lipase. In vitro evaluations on intestinal mucus indicate that L. fermentum URLP18 have strong adherence capacity, and its survival rate increased after being administered to Artemia nauplii. The results suggest that L. fermentum URLP18 has high probiotic potential and is an effective dietary supplement for freshwater aquaculture.

Probiotic Shewanella putrefaciens (SpPdp11) as a Fish Health Modulator: A Review

Aquaculture is considered one of the largest food production sectors in the world. Probiotics have long been considered as a beneficial tool in this industry since these microorganisms improve the welfare of different fish species by modulating several physiological functions, such as metabolism, digestion, immune response, stress tolerance, and disease resistance, among others. SpPdp11, a probiotic isolated from the skin of healthy gilthead seabream, has been the center of attention in a good number of studies since its discovery. The purpose of this paper is to summarize, comment, and discuss the current knowledge related to the effects of SpPdp11 in two commercially important fish species in aquaculture (gilthead seabream and Senegalese sole). Furthermore, some considerations for future studies are also indicated.

In vitro Evaluation of Antibacterial, Cytotoxic and Adherence Studies of Selected Commercial Probiotics

There is increasing scientific evidence and commercial interest for using probiotics for eliminating and handling of specific diseases. Probiotics can be evaluated for its role and performance against isolated pathogens from contaminating sources. The present work reports on invitro antimicrobial activity of commercial selected probiotics against pathogenic microbe Vibrio parahaemolyticus. The work also describes cytotoxic activities using MTT assay and adherence studies of selected probiotics. Results for the studies showed maximum zone of inhibition 13.66±0.46mm in probiotic enteroplus,12.33±0.93mm in lactobacillus (NCIM2056) and 10.66±0.93mm in Avant Bact. Cytotoxicity was expressed as IC50(µg/ml) values, observed on CaCO cell lines for different probiotics. Avant Bact showed a IC50 value of 104.7745, Lactobacillus (NCIM2056) a value of 58.13223 and Enteroplus a value of 50.09716. These values expressed different safety aspects of probiotics used for study. Finally the adherence study was done to check probiotic colonizing capacity. The probiotics showed varied adherence capacity against caco cell lines. Enteroplus has % adhesion of 10.25±0.74, Avant Bact. 7.25±0.82 and Lactobacillus (NCIM2056) 7.5±1.12. In conclusion antimicrobial results show importance of probiotics to be used against specific gastro intestinal diseases. Cytotoxicity determines safety aspects of probiotics and adherence study determines probiotic as a promising candidate for in vivo studies.

A continuously changing selective context on microbial communities associated with fish, from egg to fork

Fast increase of fish aquaculture production to meet consumer demands is accompanied by important ecological concerns such as disease outbreaks. Meanwhile, food waste is an important concern with fish products since they are highly perishable. Recent aquaculture and fish product microbiology, and more recently, microbiota research, paved the way to a highly integrated approach to understand complex relationships between host fish, product and their associated microbial communities at health/disease and preservation/spoilage frontiers. Microbial manipulation strategies are increasingly validated as promising tools either to replace or to complement traditional veterinary and preservation methods. In this review, we consider evolutionary forces driving fish microbiota assembly, in particular the changes in the selective context along the production chain. We summarize the current knowledge concerning factors governing assembly and dynamics of fish hosts and food microbial communities. Then, we discuss the current microbial community manipulation strategies from an evolutionary standpoint to provide a perspective on the potential for risks, conflict and opportunities. Finally, we conclude that to harness evolutionary forces in the development of sustainable microbiota manipulation applications in the fish industry, an integrated knowledge of the controlling abiotic and especially biotic factors is required.

Diversity of non-starter lactic acid bacteria in autochthonous dairy products from Western Balkan Countries - Technological and probiotic properties

The aim of this review was to summarize the data regarding diversity of non-starter lactic acid bacteria (NSLAB) isolated from various artisanal dairy products manufactured in Western Balkan Countries. The dairy products examined were manufactured from raw cow's, sheep's or goat's milk or mixed milk, in the traditional way without the addition of commercial starter cultures. Dairy products such as white brined cheese, fresh cheese, hard cheese, yogurt, sour cream and kajmak were sampled in the households of Serbia, Croatia, Slovenia, Bosnia and Herzegovina, Montenegro, and North Macedonia. It has been established that the diversity of lactic acid bacteria (LAB) from raw milk artisanal dairy products is extensive. In the reviewed literature, 28 LAB species and a large number of strains belonging to the Lactobacillus, Lactococcus, Enterococcus, Streptococcus, Pediococcus, Leuconostoc and Weissella genera were isolated from various dairy products. Over 3000 LAB strains were obtained and characterized for their technological and probiotic properties including: acidification and coagulation of milk, production of aromatic compounds, proteolytic activity, bacteriocins production and competitive exclusion of pathogens, production of exopolysaccharides, aggregation ability and immunomodulatory effect. Results show that many of the isolated NSLAB strains had one, two or more of the properties mentioned. The data presented emphasize the importance of artisanal products as a valuable source of NSLAB with unique technological and probiotic features important both as a base for scientific research as well as for designing novel starter cultures for functional dairy food.

The role of the gut microbiome in sustainable teleost aquaculture

As the most diverse vertebrate group and a major component of a growing global aquaculture industry, teleosts continue to attract significant scientific attention. The growth in global aquaculture, driven by declines in wild stocks, has provided additional empirical demand, and thus opportunities, to explore teleost diversity. Among key developments is the recent growth in microbiome exploration, facilitated by advances in high-throughput sequencing technologies. Here, we consider studies on teleost gut microbiomes in the context of sustainable aquaculture, which we have discussed in four themes: diet, immunity, artificial selection and closed-loop systems. We demonstrate the influence aquaculture has had on gut microbiome research, while also providing a road map for the main deterministic forces that influence the gut microbiome, with topical applications to aquaculture. Functional significance is considered within an aquaculture context with reference to impacts on nutrition and immunity. Finally, we identify key knowledge gaps, both methodological and conceptual, and propose promising applications of gut microbiome manipulation to aquaculture, and future priorities in microbiome research. These include insect-based feeds, vaccination, mechanism of pro- and prebiotics, artificial selection on the hologenome, in-water bacteriophages in recirculating aquaculture systems (RAS), physiochemical properties of water and dysbiosis as a biomarker.

Probiotics for cultured freshwater fish

Probiotic products are viewed as an alternative to the use of antibiotics in freshwater fishes farming. Probiotic organisms include bacteria, yeast, and filamentous fungi offering different benefits to fish including growth promotion, inhibition of pathogen colonisation, and improvement of nutrient digestion, water quality, and stress tolerance, as well as enhancement of reproduction. For these reasons, this review aims to identify the main trends in probiotic amendment in freshwater fishes. Strategies to incorporate the probiotic strains in the fish feed or pellets to allow optimal viability of the strains as they reach the fish gastrointestinal tract (GIT) are crucial in probiotic research and commercial applications for freshwater fish.

Oral vaccination of tilapia against Streptococcus agalactiae using Bacillus subtilis spores expressing Sip

Streptococcus agalactiae infections are becoming an increasing problem in aquaculture because of significant morbidity and mortality, which restricts the healthy development of tilapia aquaculture. To seek safe and effective prevention measures, a Bacillus subtilis GC5 surface displayed vaccine was prepared and applied orally in tilapia. The study first showed that recombinant spores can engraft in the tilapia intestine. Then, the effect of protection and the immune responses were evaluated. The results of ELISA showed that Sip-specific antibody in the sera of GC5-Sip-immunized fish can be detected after the first oral administration when compared to the phosphate buffer saline (PBS) control group, and the levels of specific IgM gradually strengthened with boosting, so does the specific antibody against bacteria, proving that humoral immunity was induced. Quantitative real-time PCR (qRT-PCR) results showed that the immune-related gene expression of the gut and spleen exhibited a different rising trend in the GC5-Sip group, revealing that innate immune response and local as well as systemic cellular immunity were induced. The outcome of fish immunized with GC5-Sip spores provided a relative percent survival (RPS) of 41.7% against S. agalactiae and GC5 group had an RPS of 24.2%, indicating that GC5-Sip was safe and effective in protecting tilapia against bacterial infection. Our study demonstrated that the oral administration of B. subtilis spores expressing Sip could cause an effective immune response and offer good resistance to bacterial infection. Our work may lead to the development of new ideas for immunoprophylaxis against S. agalactiae infection.

Gut Microbiota and Energy Homeostasis in Fish

The microorganisms within the intestinal tract (termed gut microbiota) have been shown to interact with the gut-brain axis, a bidirectional communication system between the gut and the brain mediated by hormonal, immune, and neural signals. Through these interactions, the microbiota might affect behaviors, including feeding behavior, digestive/absorptive processes (e.g., by modulating intestinal motility and the intestinal barrier), metabolism, as well as the immune response, with repercussions on the energy homeostasis and health of the host. To date, research in this field has mostly focused on mammals. Studies on non-mammalian models such as fish may provide novel insights into the specific mechanisms involved in the microbiota-brain-gut axis. This review describes our current knowledge on the possible effects of microbiota on feeding, digestive processes, growth, and energy homeostasis in fish, with emphasis on the influence of brain and gut hormones, environmental factors, and inter-specific differences.