Lactobacillus casei is a type of probiotic bacterium commonly found in the human intestinal tract and mouth. It is widely used in probiotic products and fermented foods, such as yogurts and cheeses, for its health benefits. It aids digestion and can help bolster the immune system.

The name describes the structure of the molecule:

• Lactobacillus is a genus of bacteria that are part of the lactobacilli family. They are known for their ability to convert sugars into lactic acid, a process that makes them crucial in milk fermentation and other food fermentations.
• casei comes from "caseus", the Latin word for "cheese" (1). This indicates that Lactobacillus casei is particularly useful in the fermentation of dairy products, as well as having beneficial applications for human health.

Industrial Production Process

• Strain selection. The process begins with the selection of a pure strain of Lactobacillus casei that exhibits optimal characteristics for use in food fermentation.
• Culture medium preparation. A specific culture medium is prepared, enriched with essential nutrients such as peptones, meat extracts, and lactose, to support optimal bacterial growth.
• Fermentation. The selected strain is inoculated into sterile fermenters where fermentation takes place under controlled conditions of temperature (generally between 30°C and 37°C), pH, and anaerobiosis.
• Growth monitoring. Bacterial growth is continuously monitored to ensure optimal conditions and prevent contamination.
• Bacteria harvesting. Once fermentation is complete and the desired cell count is achieved, the bacteria are harvested via centrifugation.
• Stabilization. The bacteria can be stabilized through lyophilization or freezing processes to preserve vitality and facilitate transport and storage.
• Formulation. The final product can be formulated as a dry or frozen starter culture, ready to be used in the production of dairy products and other fermented foods.
• Quality control. Each batch produced undergoes rigorous quality control to ensure vitality, purity, and effectiveness in lactic fermentation.

What it is used for and where

Lactobacillus casei is a probiotic bacterium belonging to the lactobacilli group, widely used in dietary supplements and fermented dairy products such as yogurt and kefir. It is known for its benefits to gastrointestinal health and the immune system. Here are some of the main uses and benefits of Lactobacillus casei.

Digestive Health Support. It helps maintain a healthy balance of intestinal flora, improving digestion and contributing to the prevention of intestinal disorders such as diarrhea and irritable bowel syndrome.

Immune System Boost. It enhances the immune system (2), improving resistance to infections and reducing the duration of seasonal illnesses like the common cold.

Antioxidant Benefits. Lactobacillus casei may also play a role in enhancing antioxidant activity in the body, helping to combat oxidative stress (3).

Nutrient Absorption. It can improve the absorption of essential nutrients, thereby contributing to better overall nutritional status.

Prevention of Allergies and Inflammations. Studies suggest that Lactobacillus casei may help reduce the inflammatory response in individuals with food allergies.

Versatile Product. It is available in various forms, including probiotic supplements, yogurts, kefir, and other fermented foods, offering a wide range of options for its consumption.

References_____________________________________________________________________

(1) de Souza BMS, Borgonovi TF, Casarotti SN, Todorov SD, Penna ALB. Lactobacillus casei and Lactobacillus fermentum Strains Isolated from Mozzarella Cheese: Probiotic Potential, Safety, Acidifying Kinetic Parameters and Viability under Gastrointestinal Tract Conditions. Probiotics Antimicrob Proteins. 2019 Jun;11(2):382-396. doi: 10.1007/s12602-018-9406-y.

Abstract. The objective of this study was to evaluate the probiotic properties of Lactobacillus casei and Lactobacillus fermentum strains, as well as to select novel and safe strains for future development of functional fermented products. The in vitro auto-aggregation, co-aggregation, hydrophobicity, β-galactosidase production, survival to gastrointestinal tract (GIT), and antibiotic susceptibility were evaluated. The selected strains were additionally tested by the presence of genes encoding adhesion, aggregation and colonization, virulence factors, antibiotic resistance, and biogenic amine production, followed by the evaluation of acidifying kinetic parameters in milk, and survival of the strains under simulated GIT conditions during refrigerated storage of fermented milk. Most strains of both species showed high auto-aggregation; some strains showed co-aggregation ability with other lactic acid bacteria (LAB) and/or pathogens, and both species showed low hydrophobicity values. Seven L. casei and six L. fermentum strains produced β-galactosidase enzymes, and ten strains survived well the simulation of the GIT stressful conditions evaluated in vitro. All strains were resistant to vancomycin, and almost all the strains were resistant to kanamycin. L. casei SJRP38 and L. fermentum SJRP43 were distinguished among the other LAB strains by their higher probiotic potential. L. fermentum SJRP43 presented fewer genes related to virulence factors and antibiotic resistance and needed more time to reach the maximum acidification rate (Vmax). The other kinetic parameters were similar. Both strains survived well (> 8 log10 CFU/mL) to the GIT-simulated conditions when incorporated in fermented milk. Therefore, these strains presented promising properties for further applications in fermented functional products.

(2) Huynh DT, Chathuranga WAG, Chathuranga K, Lee JS, Kim CJ. Mucosal Administration of Lactobacillus casei Surface-Displayed HA1 Induces Protective Immune Responses against Avian Influenza A Virus in Mice. J Microbiol Biotechnol. 2024 Mar 28;34(3):735-745. doi: 10.4014/jmb.2307.07040.

Abstract. Avian influenza is a serious threat to both public health and the poultry industry worldwide. This respiratory virus can be combated by eliciting robust immune responses at the site of infection through mucosal immunization. Recombinant probiotics, specifically lactic acid bacteria, are safe and effective carriers for mucosal vaccines. In this study, we engineered recombinant fusion protein by fusing the hemagglutinin 1 (HA1) subunit of the A/Aquatic bird/Korea/W81/2005 (H5N2) with the Bacillus subtilis poly γ-glutamic acid synthetase A (pgsA) at the surface of Lactobacillus casei (pgsA-HA1/L. casei). Using subcellular fractionation and flow cytometry we confirmed the surface localization of this fusion protein. Mucosal administration of pgsA-HA1/L. casei in mice resulted in significant levels of HA1-specific serum IgG, mucosal IgA and neutralizing antibodies against the H5N2 virus. Additionally, pgsA-HA1/L. casei-induced systemic and local cell-mediated immune responses specific to HA1, as evidenced by an increased number of IFN-γ and IL-4 secreting cells in the spleens and higher levels of IL-4 in the local lymphocyte supernatants. Finally, mice inoculated with pgsA-HA1/L. casei were protected against a 10LD50 dose of the homologous mouse-adapted H5N2 virus. These results suggest that mucosal immunization with L. casei displaying HA1 on its surface could be a potential strategy for developing a mucosal vaccine against other H5 subtype viruses.

(3) Wang J, Zhu Z, Tian S, Fu H, Leng X, Chen L. Dietary Lactobacillus casei K17 Improves Lipid Metabolism, Antioxidant Response, and Fillet Quality of Micropterus salmoides. Animals (Basel). 2021 Aug 31;11(9):2564. doi: 10.3390/ani11092564. 

Abstract. We previously demonstrated that Lactobacillus casei K17, isolated from Korean kimchi, has high antioxidant levels in vitro and in vivo. However, its effect on Micropterus salmoides is unknown. In this study, we investigated the impact of L. casei K17 supplementation on the lipid metabolism, antioxidant response, liver histology, and fillet quality of M. salmoides. We randomly assigned 450 M. salmoides (33.0 ± 0.5 g) to six diet groups for 69 days. The diets were as follows: 0.85% normal saline; 10% skim milk powder; 1 × 108 CFU/g live L. casei K17 (LB); 1 × 108 live L. casei K17 protected by skim milk powder (MB); 1 × 108 dead L. casei K17 (DB); and L. casei K17 fermentation supernatant. MB significantly improved the crude protein, total collagen, alkaline-insoluble collagen, fiber numbers, hardness, chewiness, and gumminess of M. salmoides fillets (p < 0.05). LB significantly improved crude protein and fiber numbers (p < 0.05). Furthermore, dietary supplementation with LB, MB, and DB maintained normal liver histology, preserved liver function, and increased hepatic and hemal antioxidant status by enhancing antioxidant enzyme activities. Meanwhile, the three diets also promoted lipid metabolism by increasing HDL-C effectiveness and reducing total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels in serum and liver tissues, indicating that dietary supplementation with DB, LB, and MB had hypolipidemic effects on M. salmoides. MB and LB significantly improved fillet quality and LB, MB, and DB improved hemal and hepatic lipid metabolism and antioxidant response and reduced reactive oxygen species production, protecting M. salmoides hepatic cells from injury.