Probiotics, Postbiotics and Synbiotics
The term functional food encompasses a wide range of products – from yoghurt enriched with probiotic bacteria to bread fortified with prebiotic fibres. Within this domain, three interconnected concepts have refined our understanding of how microbial metabolites influence host health.
Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. Our research focuses on LAB strains isolated from traditional Bangladeshi fermented foods and beverages, including borhani, laban, mattha and sugarcane juice. These strains are systematically evaluated for their ability to survive gastrointestinal transit, adhere to intestinal epithelium, antagonise pathogens, and produce bioactive metabolites.
Postbiotics are non‑viable microbial cells or their metabolic products – exopolysaccharides (EPS), short‑chain fatty acids, antimicrobial peptides – that confer health benefits without requiring live microorganisms. This emerging category offers advantages in terms of stability, safety and ease of formulation, particularly for products where maintaining probiotic viability is challenging. Our lab has extensively characterised EPS from Limosilactobacillus fermentum LAB‑1, demonstrating potent antioxidant, antimicrobial, antibiofilm, anti‑inflammatory and emulsifying activities.
Synbiotics are combinations of probiotics and prebiotics (substrates that selectively stimulate beneficial microbes). By pairing our best probiotic LAB with prebiotic carbohydrates or purified EPS, we aim to enhance the survival and activity of the probiotic during storage and after ingestion, while providing additional health benefits through the prebiotic component. Together, these categories allow for flexible, science‑based design of health‑promoting foods.
Traditional Fermented Foods as Functional Food Platforms
Bangladesh possesses a rich and diverse repertoire of traditional fermented foods that have been consumed for generations. Dairy‑based products include yogurt, laban, ghee and mattha. Plant‑based ferments include panta bhat (fermented rice) and vegetable pickles. Fermented beverages range from borhani and sugarcane juice to date palm sap. These foods are naturally fermented by indigenous LAB communities, which produce a complex array of bioactive compounds during fermentation.
Our lab has systematically isolated LAB from these sources and demonstrated that many strains possess probiotic properties, antimicrobial activity, antioxidant capacity and EPS production. These autochthonous strains are well‑adapted to local substrates and fermentation conditions, making them ideal candidates for developing functional foods that are both culturally acceptable and technologically robust.
Harnessing Lactic Acid Bacteria for Functional Food Development
The core of our functional foods research is the selection and application of autochthonous LAB strains that are both safe and technologically suitable. We evaluate strains across multiple criteria: acid and bile tolerance to survive gastrointestinal transit, adhesion properties to transiently colonise the gut, antagonism against foodborne pathogens to improve safety, and production of functional metabolites such as EPS, bacteriocins, vitamins and enzymes.
From laban, a traditional fermented milk product, we isolated Pediococcus pentosaceus L1 and Streptococcus thermophilus L3, both of which demonstrated excellent coagulation properties and EPS production, making them ideal candidates for developing functional yoghurt and cheese products. These strains also exhibited tolerance to low pH and bile salts, along with notable antioxidant capacity.
From sugarcane juice, we obtained multifunctional LAB strains that not only survive gut‑like stress but also reduce microbial loads in perishable foods, acting as natural biopreservatives. The potential of LAB as natural preservatives has been increasingly recognised, as they can inhibit spoilage and pathogenic bacteria through the production of organic acids, bacteriocins and other antimicrobial compounds, reducing the need for synthetic additives while enhancing food safety.
From mattha, a yogurt‑based beverage, Streptococcus thermophilus M2 showed rapid milk coagulation, strong adhesion properties and significant antioxidant activity, positioning it as a promising starter culture for functional dairy products. This strain also demonstrated favourable safety profiles and technological attributes suitable for industrial application.
Exopolysaccharides as Postbiotic Ingredients
Exopolysaccharides (EPS) represent one of the most important postbiotic metabolite classes produced by LAB. These long‑chain carbohydrate polymers are secreted by bacteria into their surrounding environment and exhibit remarkable physicochemical and bioactive properties. Our lab has extensively characterised EPS from Limosilactobacillus fermentum LAB‑1, demonstrating that it possesses potent antioxidant activity, broad‑spectrum antimicrobial effects against both Gram‑positive and Gram‑negative pathogens, significant inhibition of biofilm formation, notable anti‑inflammatory properties, and good emulsification capacity.
Such multifunctional EPS can be incorporated directly into functional foods as natural thickeners, stabilisers or bioactive additives that benefit the consumer without requiring live bacteria. Importantly, EPS can also function as prebiotic fibres that selectively stimulate the growth of other beneficial gut microbes, creating synergistic loops within a single product. This dual functionality – acting as both a direct postbiotic and an indirect prebiotic – positions EPS as a uniquely versatile ingredient for next‑generation functional food formulations.
Synbiotics: Combining Probiotics with Prebiotic Substrates
We are actively developing synbiotic formulations by pairing our best probiotic LAB with prebiotic carbohydrates – inulin, oligofructose, or crude extracts from local plants – and with purified EPS from the same or complementary strains. The goal is twofold: to enhance the survival and metabolic activity of the probiotic during storage and after ingestion, and to provide additional health benefits through the prebiotic component itself.
Preliminary in vitro studies suggest that such synbiotic combinations improve the adhesion of LAB to intestinal mucus and increase short‑chain fatty acid production, key metabolites that support gut barrier integrity and immune function. Synbiotics represent a rapidly advancing area of functional food research, with growing evidence that carefully designed combinations can outperform either component alone in maintaining or restoring a balanced microbial ecosystem.
Bioenrichment: Enhancing Nutritional Value
Functional foods are not only about disease prevention – they can also correct nutritional deficiencies, a critical concern in many populations. Our research includes the development of bioenriched functional foods by fermenting staple ingredients with LAB that synthesise vitamins (B‑group, K), essential amino acids, or minerals in more bioavailable forms. For instance, fermentation of rice or lentils with selected LAB can increase the content of folate and riboflavin while reducing anti‑nutrients such as phytate.
This approach directly addresses malnutrition in vulnerable populations using culturally acceptable, low‑cost foods. By improving the nutritional quality of staple foods through targeted fermentation, we aim to provide sustainable solutions for food security and public health, particularly in resource‑limited settings where dietary diversity may be restricted.
Translating Discovery into Application
Our functional foods research is structured to move from fundamental understanding to practical implementation. The pipeline begins with the isolation and molecular characterisation of LAB from traditional ferments, followed by systematic in vitro evaluation of probiotic, safety and technological properties. Strains that meet these criteria proceed to small‑scale fermentation trials, where we optimise growth conditions, substrate composition and processing parameters. Finally, prototype products are developed and evaluated for stability, sensory acceptability and functional efficacy.
This integrated approach ensures that our research remains grounded in local food systems while adhering to international standards for probiotic and functional food development. The ultimate goal is to generate evidence‑based, scalable solutions that can be adopted by small‑scale producers and larger food manufacturers alike, contributing to both public health and economic development.
