Apr , 2022, Volume : 3 Article : 8
Application of Paraprobiotic in Feed to Boost Fish Immunity
Author : Chetan Kumar Garg, Saiprasad Bhusare, Nisha Chuphal and Khemraj Bunkar
ABSTRACT
The use of uncontrolled chemicals or antibiotics in aquaculture to treat or prevent disease negatively affects environmental and consumer health. Currently, researchers and governments are encouraging farmers to use natural immunostimulants instead of harmful chemicals. Probiotics are the most widely used immunostimulants for disease prevention, but they have several drawbacks. Therefore, the concept of paraprobiotic arose to address the problem of viable probiotics, which provide growth and immunological benefits similar as probiotics. Several findings establish that feeding paraprobiotic to fish and shellfish for boost their immunity is safe and eco-friendly.
Keywords: Aquaculture, Fish feed, Immunity, Paraprobiotic
The demand for fish and fish-based food products has been consistently growing with the ever-increasing human population. Intensification and expansion of aquaculture has been practiced during the past two decades to meet the growing fish demand. The intensification of aquaculture stresses fish and weakens their immune systems, resulting in massive financial losses due to disease outbreaks. Antibiotics and chemotherapeutics have long been used in aquaculture to control diseases, but their use has negative consequences for both the fish and the environment. Researchers are progressively focusing on using natural immuno-stimulators as a substitute for chemical and antibiotics (Garg et al., 2020). Several studies have proven that probiotics are an effective way to control infectious diseases in aquaculture.
Probiotics are defined as "live microorganisms that confer health benefits on the host when administered in adequate amounts." Despite the numerous advantages of employing live beneficial microorganisms in aquaculture, there are also some drawbacks, such as probiotic species survivability in products/feed, different colonization patterns and durability in the gut and the risk of horizontal gene transfer acquiring virulence genes from harmful bacteria (Adams, 2010). According to earlier studies, even non-viable/dead microbes benefit the host similarly to their viable counterparts, and these non-viable microbes are referred to as paraprobiotic.
Paraprobiotic
The non-viable beneficial microorganisms are known as paraprobiotic and defined as "non-viable microbial cells (intact or broken) or crude cell extracts (i.e., with complicated chemical composition) that offer a health benefit to the human or animal consumer when delivered (orally or topically) in adequate amounts." Ghost probiotics, dead probiotics, inactivated probiotics and non-viable probiotics are all terms used to describe paraprobiotic. The distinction between paraprobiotics and probiotics is that paraprobiotics are non-viable beneficial microbes, whereas probiotics are live or viable beneficial microbes (Taverniti and Guglielmetti, 2011).
The use of paraprobiotic in the feed could offer various advantages over probiotics:
1) Probiotics are used in feed as live form that interacts with other feed components, which can directly affect feed shelf life, but paraprobiotics have little or no interaction with feed or feed components.
2) The use of paraprobiotics facilitates feed thermal processing because they can be added before thermal processes, which may not alter their health-promoting activities.
3) The use of paraprobiotic in feed is easy because they can be mixed with other feed supplements.
4) In addition, paraprobiotic can be easily stored, handled and transported as they do not require cold storage and have a longer shelf life.
Mechanism
A. Enhancement of growth and feed utilization
The presence of paraprobiotic in the gastrointestinal tract of fish may increase the abundance of beneficial indigenous microbes that stimulate the secretion of digestive enzymes, which aid in the digestion and absorption of nutrients. It has been shown that paraprobiotic can modify the morphological structure of gut, such as the length and surface area of the microvillus and number of goblet cells, promoting nutrient digestion and absorption thereby improving fish growth performance and nutrient utilization (Tran et al., 2022).
B. Immunostimulation
Paraprobiotics enhance the immunity of animals by modulating humoral and cellular immune responses. The intestinal barrier is the primary defense mechanism employed to maintain gut integrity and protect the organism from the environment. Paraprobiotics have the ability to adhere to intestinal cells by stimulating the mucosal immune system and inhibiting the colonization of pathogenic bacteria in the gastrointestinal tract, thereby reducing the risk of disease (Choudhury and Kamilya, 2019). Due to the presence of bioactive substances such as peptidoglycan, bacteriocin, lipopolysaccharides, teichoic acid, microbial nucleic acids, flagellin, etc., paraprobiotic exhibit antibacterial, antiviral, anti-inflammatory and anti-allergic effects in fish (Fig. 1) (de Almada et al., 2016).
Methods for inactivation of viable probiotic microorganisms
Paraprobiotic can be made by inactivating viable probiotic microorganisms through various methods. Thermal inactivation, high-intensity ultrasound, ultraviolet (UV) irradiation, ionizing radiation and high-pressure technique are the most commonly employed methods for paraprobiotic production (de Almada et al., 2016).
1. Thermal inactivation
• It is the most common and widely used method of inactivation of microorganisms.
• High temperatures alter cell structure, causing membrane disruption, nutrition and ion loss, ribosome aggregation, DNA filament rupture, inactivation of essential enzymes, and protein coagulation.
• Different thermal conditions (temperature and time) ranging from 60-121°C for 5 to 60 minutes can be used to produce inactivate microorganisms.
2. High-pressure technique
• The inactivation of microorganisms can also be achieved by using high hydrostatic pressure, which causes membrane rupture due to shear stress.
• In this process, a fluid (water) is employed as a medium to transfer the pressure with pressure between 100 to 1200 MPa.
3. High-intensity ultrasound
• Viable microorganisms can also be inactivated with High-Intensity Ultrasound (HIUS)
• The physical forces generated by acoustic cavitation result in cell wall rupture, DNA and cell membranes damage that inactivates microorganisms.
4. Ultraviolet radiation
• While microbial cells are exposed to ultraviolet radiation, bacterial proteins are denaturing that inactivate the microbes.
• UV radiation with an electromagnetic spectrum of 200-400 nm can effectively inactivate a range of bacterial cells and spores.
5. Ionizing radiation
• Microorganisms are also inactivated by ionizing radiation (X-rays and gamma rays) by altering nucleic acids.
• Application of gamma-rays on microorganisms at doses of 2-10 kGy can inactivate the microorganisms.
6. Chemical treatment
• The inactivation of viable microorganisms can be done by applying chemical treatments.
• Formalin treatment at the rate of 1% (v/v) for 24 hours can help to neutralize the viability of microorganisms.
Paraprobiotic application in aquaculture
The use of probiotics in aquaculture is widely established, but the concept and application of paraprobiotics have not yet gained momentum. Paraprobiotics have been used in fish feed in many studies and have been reported to be as effective as viable microorganisms in promoting growth and improving the immune system. According to Wu et al. (2020), dietary supplementation of paraprobiotic (inactivated Rhodotorula minuta and Cetobacterium somerae) can boost the sturgeon growth and modulate the gut microbiota profile. Similarly, Dash et al. (2015) and Hien et al. (2021) reported that feeding of paraprobiotic (inactivate Lactobacillus plantarum) juvenile giant freshwater prawn and bighead catfish, respectively resulted in increased growth rate and improved immune response and disease resistance. Yassine et al. (2021) demonstrated that dietary heat-killed Lactobacillus plantarum improves growth rate, intestinal health, immune-related gene expression and resilience to a suboptimal water temperature of common carp.
Conclusion
From the available literature, it can be concluded that paraprobiotic can trigger immune responses of animals with the primary mechanism being stimulation of the host`s innate or non-specific immune system. Thermal inactivation, high-intensity ultrasound, UV irradiation, ionizing radiation and high-pressure methods can be used for paraprobiotic production. Paraprobiotic can improve the gut beneficial microbiota profile and non-specific immune response of fish and shellfish, strengthening their immunity. In addition, the use of paraprobiotic in aquaculture is a safe and eco-friendly approach to disease prevention.
References
Adams, C. A. (2010). The probiotic paradox: live and dead cells are biological response modifiers. Nutrition research reviews, 23(1), 37-46.
Taverniti, V., & Guglielmetti, S. (2011). The immunomodulatory properties of probiotic microorganisms beyond their viability (ghost probiotics: proposal of paraprobiotic concept). Genes & nutrition, 6(3), 261-274.
Tran, N. T., Yang, W., Nguyen, X. T., Zhang, M., Ma, H., Zheng, H., Zhang, Y., Chan, K. G., & Li, S. (2022). Application of heat-killed probiotics in aquaculture. Aquaculture, 548, 737700.
Choudhury, T. G., & Kamilya, D. (2019). Paraprobiotics: An aquaculture perspective. Reviews in Aquaculture, 11(4), 1258-1270.
de Almada, C. N., Almada, C. N., Martinez, R. C., & Sant`Ana, A. S. (2016). Paraprobiotics: Evidences on their ability to modify biological responses, inactivation methods and perspectives on their application in foods. Trends in Food Science & Technology, 58, 96-114.
Garg, C. K., Sahu, N. P., Maiti, M. K., Shamna, N., Deo, A. D., & Sardar, P. (2020). Dietary Houttuynia cordata leaf extract and meal enhances the immunity and expression of immune genes in Labeo rohita (Hamilton, 1822). Aquaculture Research, 52(1), 381-394.
Dash, G., Raman, R. P., Prasad, K. P., Makesh, M., Pradeep, M. A., & Sen, S. (2015). Evaluation of paraprobiotic applicability of Lactobacillus plantarum in improving the immune response and disease protection in giant freshwater prawn, Macrobrachium rosenbergii (de Man, 1879). Fish & Shellfish Immunology, 43(1), 167-174.
Hien, T. T. T., Hoa, T. T. T., Liem, P. T., Onoda, S., & Duc, P. M. (2021). Effects of dietary supplementation of heat-killed Lactobacillus plantarum L-137 on growth performance and immune response of bighead catfish (Clarias macrocephalus). Aquaculture Reports, 20, 100741.
Wu, X., Teame, T., Hao, Q., Ding, Q., Liu, H., Ran, C., Yang, Y., Zhang, Y., Zhou, Z., Duan, M., & Zhang, Z. (2020). Use of a paraprobiotic and postbiotic feed supplement (HWF™) improves the growth performance, composition and function of gut microbiota in hybrid sturgeon (Acipenser baerii x Acipenser schrenckii). Fish & Shellfish Immunology, 104, 36-45.
Yassine, T., Khalafalla, M. M., Mamdouh, M., Elbialy, Z. I., Salah, A. S., Ahmedou, A., Mamoon, A., El-Shehawi, A. M., Van Doan, H., & Dawood, M. A. (2021). The enhancement of the growth rate, intestinal health, expression of immune-related genes, and resistance against suboptimal water temperature in common carp (Cyprinus carpio) by dietary paraprobiotics. Aquaculture Reports, 20, 100729.
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