Simmi Tomer, Priyanka Sharma, Nagesh Sonale
ICAR-Central Avian Research Institute, Izatnagar, Bareilly-243122 (Uttar Pradesh)
Probiotics, defined as living microorganisms that confer health benefits when administered in adequate amounts, have been utilized since the advent of agricultural revolution and animal domestication. The earliest identified probiotic, Lactobacillus bulgaricus, was discovered in 1905 by microbiologist Stamen Grigorov in Bulgarian yogurt. This discovery laid the foundation for the hypothesis proposed by Nobel laureate Elie Metchnikoff in 1907, which suggested the beneficial effects of probiotics on health.
In poultry, probiotics offer numerous advantages, including enhancing intestinal health, improving growth performance, and combating bacterial diseases such as Necrotic Enteritis (NE) (Kadam et al., 2024). Recent studies, including those by Shweta (2024), highlight the efficacy of probiotic supplementation, particularly with Bacillus subtilis, in improving feed conversion ratio (FCR), reducing NE lesion scores, and modulating gut microbiota to enrich beneficial bacteria like Streptococcus and Faecalibacterium. Probiotics also play a crucial role in maintaining poultry health by boosting immunity and promoting sustainable practices. They can replace antibiotics, helping to address concerns about antibiotic resistance in both animals and humans. Their benefits are attributed to mechanisms such as competitive exclusion of pathogens, production of antibacterial substances, and immune modulation, making them valuable additions to poultry diets for enhanced performance and overall well-being.
Benefits of Probiotics in Poultry:
- Promotes Gut Symbiosis: Probiotics support the optimal development of gut microbiota, fostering a balanced and healthy microbial community in the digestive system, which enhances overall gut function and health.
- Prevents Dysbiosis: They help prevent dysbiosis, particularly following antibiotic treatments, by restoring and maintaining a balanced microbial environment, reducing the risk of gastrointestinal imbalances and associated disorders.
- Enhances Weight Gain and Productivity: Probiotic supplementation leads to improved weight gain, better feed conversion ratios (FCR), and overall enhanced productivity across various poultry species, contributing to more efficient and profitable poultry farming.
- Reduces Chick Mortality: By competitively excluding pathogenic bacteria such as E. coli, probiotics help lower chick mortality rates, improving overall flock survival and health.
- Improves Feed Digestibility: Probiotics produce beneficial enzymes such as amylase, protease, and B-mannanase (e.g., Bacillus licheniformis), which enhance feed digestibility and nutrient absorption, leading to better growth and performance.
- Systemic Effects: Probiotics can influence systemic health by producing neurochemicals such as serotonin, GABA, and cortisol, which may impact stress levels and overall well-being in poultry.
- No Withdrawal Period: Probiotics have a zero-withdrawal period and can be administered throughout the host’s lifecycle, providing continuous benefits without concerns about residue or discontinuation before harvesting.
- Boosts Immunity: They enhance the immune system by stimulating phagocytosis and increasing antibody responses, thereby improving the bird’s ability to fight infections and maintain overall health.
Need for encapsulation:
Encapsulation of probiotics in poultry farming is essential for enhancing their effectiveness and stability. Probiotic bacteria face several stressors after consumption that can compromise their viability before reaching the gastrointestinal tract. Key factors affecting probiotics include the acidic pH of the stomach, emulsifying action of bile salts, osmotic stress, heat stress during production, oxidative stress during storage, and host immune responses. Additionally, environmental stresses such as light, humidity, and other conditions during storage and transport can further reduce probiotic efficacy. Encapsulation provides a protective barrier that shields probiotics from these harsh conditions, preserving their viability and ensuring their targeted delivery to the gut. This method helps maintain the probiotics’ effectiveness in improving intestinal health, nutrient absorption, and overall growth performance. Furthermore, encapsulation extends the shelf life and stability of probiotic products, making them more reliable and efficient in poultry feed formulations. Thus, encapsulation is crucial for safeguarding probiotics against various stressors and optimizing their benefits in poultry farming.
Fig:1. Probiotic Microcapsule
What is probiotic micro-encapsulation:
It can be defined as a technology for coating solid, liquid or gaseous ingredients (probiotic bacteria in this case) with an encapsulating material to form micro sized capsules (2-5000 micrometre in size. The polymer acts as a protective film, isolating and protecting the core material of interest. On exposure to specific stimulus, this wall membrane dissolves itself facilitating the release of core material at the appropriate place and time for effective utilization. The active agent that is encapsulated is referred to as core material, the active agent, internal phase, or payload phase. The material that is used for encapsulating is called as coating, membrane, shell, carrier material, wall material, external phase or matrix. In general, there are two forms of encapsulates viz., reservoir type; and matrix type (Fig. 1). In reservoir type, the active agent is surrounded by an inert diffusion barrier. It is also called single-core or mono-core or core-shell type. In matrix type, the active agent is dispersed or dissolved in an inert polymer.
Biomaterials for Encapsulation:
Macromolecules which are in direct contact and act with biological systems are referred to as biomaterials. For probiotic encapsulation such biomaterials are utilised where these act as protective coating against the stressors mentioned above. Carbohydrate like dextrose, starch, cellulose, chitosan, gums like gum Arabic, alginate, carrageenan and proteins like gelatine, albumin, gluten and casein are potential encapsulants. For instance, Calcium alginate is preferred material for encapsulation of Lactobacillus bacteria, due to ease of handling, non-toxic nature, low cost, high porosity and tolerance to salts. These biomaterials must fulfil following criteria to be utilised as encapsulating agents:
1.Non-reactive with the core (probiotic bacteria)
2.Maintain core integrity
3.Non –toxic
4.Economical
5. Accessible
6.Semipermeable
Fig 2. Biomaterials
Methods of probiotic encapsulation:
1.Extrusion Technology:
Extrusion is one of the widely used encapsulation technologies for encapsulating the probiotic microorganisms (sometimes prebiotics are added) in hydrocolloid gel matrices. This process is also called as prilling and is simple, low cost and has high retention of encapsulated probiotics because of gentle conditions. It consists of a pipette, a vibrating nozzle, a syringe, a spraying nozzle, atomizing disk or jet cutter. Mostly carrageenan and alginate biopolymer solutions are used to protect the probiotics from external harsh stresses during storage. The probiotic microorganisms are mixed with hydrocolloid solution to form a suspension then extruded through syringe. The formed suspension of probiotics and hydrocolloid solution are then subjected to settle in the hardening solutions. The hardening solution consists of divalent cations (magnesium or calcium). Many factors like the distance between the needle and the hardening solution, needle diameter, surface tension of the hardening solution, type of cations used in hardening solution are responsible for the size and shape of the extruded beads. This technology produces beads with 2 to 5 mm diameters. The effect of extrusion on Lactobacillus acidophillus has been studied by Shinde et al (2014). There is less damage to probiotic cells resulting in high viability and that the process can be scaled up for industrial manufacturing are the main advantages of this process (Burgain et al., 2011). Encapsulation yield of multi-strain bacteria by extrusion method was 83% (Alisha et al., 2022) The extrusion method is frequently utilized to create particles from mixtures that contain alginates and other natural polysaccharides that can prolong the survival of encapsulated cells under storage and simulated gastric and enteric environments (Rodrigues et al., 2020). There are few disadvantages also associated with the extrusion technology which are of the size of the beads are large for several applications, limited application, less survivability during storage and less encapsulating efficiency.
Fig 3. Process of extrusion Technology
2. Compression Coating:
It contains dried bacteria powder, pellet or core tablet surrounded by a compressing coating material. The dried bacterial powder is compressed into a core tablet which is then encapsulated with a suitable coating material by further compression. Sureteric Hydroxypropyl methylcellulose Phtalate (HPMCP), Pectin, sodium alginate, hydroxypropyl cellulose (HPC) and guar gum are used as compression coating materials (Semde et al., 1999). These coating materials form a viscous gel layer when exposed to dissolution fluid around the core material. HPC showed better rigidity compared with other coating materials. However, sodium alginate is an ideal coat- ing material and is widely used in food industries. Various authors had studied the effect of compression coating on different probiotic bacteria (Riaz & Masud, 2013). The stabilization of lyophilized probiotic bacteria during storage was significantly improved using com- pression coating with gel forming polymers. The polymer coating mate- rial and the parameters of the compression coating has significant effect in probiotic viability because high pressure applied during compression coating may reduce the viability of the cells. The compression pressure during the process should be maintained below 90 MPa unless the cell viability decreases linearly as the pressure increases. The compression coated bacteria up to 60 MPa have 10 times higher stability than the free cell containing powders after 30 days of storage at 25 °C (Chan & Zhang, 2002). The main disadvantages of this process are that it requires a specialized tablet making machine, size of the final product is high, tablet core cannot tolerate organic solvents or water.
Fig 4. Process of Compression coating
3.Spray Drying:
It is a unique drying process in which continuous production of probiotic powder particles is possible followed by spraying liquid stock culture inside the drying chamber. The spray drying process is one of the hygienic, cheap, energy efficient and long-term preservation methods for encapsulating lactic acid and other probiotic cultures along with different carrier materials. The speed of drying and continuous production makes probiotic viable even after drying at higher temperatures (150–200°C). Research has been reported on spray drying of bacteria without loss of cell viability and activity (Prajapati et al., 1987). The encapsulated micro capsule size (0.2-5000 μm) and shape depends on the material and method of preparation of the sample (Balassa et al., 1971). Despite many advantages it also has some disadvantages like loss of viability of probiotic cells during high temperature drying inside the spray drying chamber. Protectants like trehalose, reconstituted skim mik, lactose, Calcium or Magnesium chloride, maltodextrin, inulin, chia seed and flax seed mucilage can be used against effect of heat on bacteria. Different protectants can be used together for better results like Lactose and Sodium Caseinate in 3:1 showed synergistic protection in drying of L.cremoris but less protection when used individually(Ghandi et al.,2012). Similarly, Lactobacillus rhanmosus showed a survival of 91.23% when chia seed mucilage was utilised as heat protectant and coating material (Mariela et al., 2020)
Fig 5: Mechanism of spray drying
4. Spray Chilling:
This technique is mainly based on the atomization of bioactive compounds already added to the carrier materials and cooled below melting point of matrix material. Lipid carriers like palm oil, beeswax, cocoa butter etc. are commonly used (melting point:32-42 0C)
5. Freeze Drying:
Freeze drying is the more convenient and commonly used drying technique for preserving probiotic bacteria. But the combination of freeze drying, and encapsulation is a new concept for encapsulating probiotics with the suitable carrier material. Freeze drying is the most convenient process for encapsulating the probiotic bacteria because it does not require any freezing conditions during the distribution of the product. But freeze-drying process is a more expensive (4 to 7 times than spray drying) and time-consuming process compared with other drying methods (Chávez & Ledeboer, 2007). The basic principle in freeze drying is sublimation i.e., transformation of solid phase to the gas (vapour) phase directly without reaching the liquid phase. Sublimation occurs when a molecule gains enough energy to break free from the molecules around it. The temperature and pressure of sublimation (vacuum sublimation) varies from -50 °C to -30 °C and 0.05 to 0.1 mBar, respectively. Ice crystal formation and stress condition by osmolarity in freezing causes damage to the cell membrane of probiotics. Therefore, various cryoprotectants like lactose, sorbitol, sucrose, trehalose, skim milk and milk protein are used for stabilizing and preserving the probiotic bacteria. For instance, encapsulation yield of Lactobacillus reuteri was 75.3% with sucrose as cryoprotectant and shelf life of 2 months at room temperature (Alisha et al., 2022).
Conclusion:
Probiotics significantly enhance poultry health by fostering gut symbiosis, improving growth performance, and mitigating bacterial diseases like Necrotic Enteritis. They offer substantial benefits, including boosting immunity, reducing chick mortality, and improving feed digestibility, all while providing a zero-withdrawal period for continuous use. To maintain probiotic viability amidst environmental stresses, encapsulation technologies such as extrusion, compression coating, spray drying, spray chilling, and freeze-drying are essential. Each method presents unique advantages and limitations concerning cost, complexity, and impact on probiotic survival. Given the poultry industry’s challenges—antimicrobial resistance, rising disease incidence, and escalating feed costs—the development of cost-effective and efficient encapsulation techniques is crucial. Microencapsulation stands out as a promising approach for producing species-specific, improved, and affordable probiotics. Ongoing research and innovation in this field are vital to enhancing poultry sustainability and productivity while addressing critical industry needs and supporting animal health