Microencapsulation of probiotics by multiple emulsion using protein– polysaccharide blends: seawater stability and viability for aquaculture
This study demonstrates that microencapsulating *L. acidophilus* and *L. plantarum* via double-emulsion spray drying using a WPI/GA/MD protein–polysaccharide blend at 10% total solids effectively preserves probiotic viability and seawater stability for six months, offering a robust, sustainable alternative to antibiotics in shrimp aquaculture.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the world of shrimp farming, the earliest days of a shrimp's life are a time of extreme vulnerability. Larvae are tiny, filter-feeding creatures that drift in the water column, relying on microscopic food to survive and grow. For decades, farmers have used antibiotics to keep these delicate animals healthy, but the overuse of these drugs has led to resistant bacteria and environmental damage. A growing number of scientists are looking for a natural alternative: probiotics. These are beneficial bacteria that, when fed to the shrimp, can boost their immune systems and fight off harmful pathogens. However, there is a catch. The bacteria used as probiotics are fragile. They are easily killed by the oxygen in the air, the heat of processing, and the saltiness of seawater. To be useful, these living cells must be protected, packaged, and delivered exactly when and where the shrimp need them.
This challenge led a team of researchers in Mexico to explore a method of hiding these sensitive bacteria inside microscopic protective shells. Their goal was to create a food source that would float in the seawater long enough for the shrimp larvae to find it, dissolve slowly to release the bacteria, and keep the bacteria alive through the harsh process of turning the mixture into a dry powder. The researchers focused on a specific technique called double emulsion, which works like a water-in-oil-in-water sandwich. Imagine a tiny drop of water containing the bacteria, surrounded by a layer of oil, which is then suspended in a larger body of water. This structure shields the bacteria from the outside world. To make this structure strong enough to survive, the team mixed proteins and plant-based sugars to form a protective wall around the droplets. They tested different recipes, varying the amounts of these ingredients to see which combination created the most stable and effective shield.
The team experimented with three different blends of wall materials. One mixture used whey protein, a common dairy protein, combined with two types of plant gums. Another used whey protein with a different set of gums and a starch-like substance called maltodextrin. The third relied on whey protein and maltodextrin alone. They created these mixtures at different concentrations, ranging from low to high solid content, and then subjected them to a spray-drying process. This step involves spraying the liquid mixture into a stream of hot air to instantly remove the water and create a fine powder. This is a critical moment for the bacteria, as the heat and rapid drying can easily kill them. The researchers needed to find a recipe that allowed the bacteria to survive this ordeal while still forming particles small enough for tiny shrimp larvae to eat.
After creating the powders, the scientists put them to the test in artificial seawater. They measured how long the particles stayed afloat and how quickly they dissolved. The results showed that the composition of the wall material mattered immensely. One specific blend, made of whey protein, gum arabic, and maltodextrin at a high concentration of solids, proved to be the clear winner. Microcapsules made from this recipe dissolved very slowly, losing less than five percent of their mass after four hours in the water. More importantly, they stayed floating for an impressive 1,000 minutes, far longer than the typical feeding window for shrimp larvae. This meant the probiotic food would remain available in the water column, waiting to be eaten, rather than sinking to the bottom where the larvae could not reach it. In contrast, other blends dissolved much faster or failed to stay buoyant.
The researchers also checked how many bacteria survived the journey from liquid to powder. While the heat of the spray dryer did kill a significant portion of the bacteria, about one-third of the original population remained alive in the best formulations. This survival rate is considered successful for this type of process. To ensure their counts were accurate, the team used two different methods: a traditional technique of growing the bacteria on a plate and a modern method using a special light that glows when it hits living cells. The two methods agreed almost perfectly, confirming that the bacteria were indeed alive and healthy. When stored in a cool environment for six months, the best formulations retained a high number of living bacteria, well above the level needed to be effective.
Using computer simulations to look further into the future, the team projected that these high-quality formulations would likely remain effective for even longer, potentially lasting well beyond the six-month mark tested. However, they were careful to note that this is a projection based on the data they have, and the true test will come when these powders are fed to live shrimp. The study did not involve feeding the shrimp yet; instead, it focused entirely on perfecting the physical shell and proving that the bacteria could survive the journey from the lab to the tank. By identifying the specific combination of ingredients that offers the best protection, buoyancy, and survival, the researchers have provided a solid foundation for the next step. They have created a candidate for a sustainable, antibiotic-free way to feed shrimp, one that keeps the delicate bacteria safe until they are ready to do their work in the water.
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