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Production, characterization and food application of lactic acid bacteria-derived exopolysaccharides with health-promoting benefits
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Os exopolissacáridos (EPS) produzidos por bactérias do ácido láctico (BAL) são polímeros multifuncionais que têm atraído uma atenção crescente devido à sua dupla função nos sistemas alimentares e na saúde humana. Apesar da grande diversidade de EPS derivados das BAL, a investigação sistemática que relaciona as suas características estruturais com as propriedades tecno-funcionais e promotoras de saúde, permanece escassa.
Esta tese de doutoramento teve como objetivo estudar os EPS produzidos por estirpes de BAL selecionadas, combinando uma revisão do estado da arte com estudos experimentais. O trabalho foi estruturado em torno de três objetivos principais: (i) fazer uma revisão bibliográfica sobre a diversidade estrutural, biossíntese e propriedades funcionais dos EPS produzidos por BAL, com ênfase na sua aplicação nos alimentos e na saúde; (ii) caracterizar o EPS produzido pela estirpe Leuconostoc mesenteroides SJC113 (isolada do queijo de São Jorge) e avaliar suas propriedades tecnológicas e funcionais, bem como investigar os efeitos benéficos (como prebiótico) para a saúde humana (iii) caracterizar as estirpes produtoras de EPS de Streptococcus thermophilus isoladas do leite de cabra, ao nível tecnológico e segurança, com especial relevo à caracterização do EPS da estirpe GM4.
Uma extensa revisão de literatura foi conduzida apresentando os últimos avanços dos EPS produzidos pelas LAB, incluindo: (i) a estrutura, biossíntese e propriedades dos EPS; (ii) os métodos mais recentes utilizados na sua caracterização; (iii) a aplicação do EPS nos laticínios e em alimentos com baixo teor de gordura; e (iv) os efeitos do EPS na promoção da saúde, incluindo atividades prebióticas, antioxidantes e redutoras de colesterol.
O primeiro estudo experimental abordou o EPS produzido pela estirpe Ln. mesenteroides SJC113. A caracterização estrutural confirmou ser um homopolissacárido do tipo dextrano, resistente à hidrólise pela dextranase e de elevado peso molecular. Este EPS apresentou propriedades antioxidantes e de ligação ao colesterol, enquanto a estirpe exibiu atividade de β-galactosidase e resistência às condições gastrointestinais. A avaliação de segurança demonstrou a ausência de genes de virulência e suscetibilidade a antibióticos. Quando aplicados no queijo fresco sem gordura, o EPS melhorou a capacidade de retenção de água e as propriedades reológicas e sensoriais, confirmando o seu papel como substituto natural de gordura.
O segundo estudo investigou os potenciais efeitos promotores de saúde do EPS produzido por esta estirpe. Estudos in vitro demonstraram a sua capacidade em promover o crescimento de BAL probióticas, aumentar a adesão à mucina e modular positivamente a composição da microbiota intestinal. A capacidade antioxidante e as propriedades de redução do colesterol reforçaram a sua funcionalidade como um componente bioativo. Estes resultados apontam para a natureza prebiótica deste EPS e a sua potencial função na modulação da microbiota intestinal e na saúde cardiovascular.
O terceiro estudo caracterizou quatro estirpes de S. thermophilus produtoras de EPS (GM1-GM4), isoladas de leite de cabra, para avaliar seu potencial para uso em produtos lácteos funcionais. A segurança de GM4 foi confirmada por testes de atividade hemolítica, DNase e gelatinase, e pela presença de genes de virulência e resistência a antibióticos. A estirpe GM4 exibiu alta atividade da β-galactosidase e seu potencial probiótico foi confirmado pela elevada capacidade de autoagregação e coagregação com patógenos como Escherichia coli, Listeria monocytogenes e Staphylococcus aureus. Os EPS purificados foram identificados como heteropolissacáridos compostos essencialmente por glucose e manose, com alta resistência à dextranase e atividade antioxidante. A estirpe GM4 destacou-se pela sua segurança, sendo tecnologicamente versátil e funcional, produzindo EPS com propriedades bioativas, sendo por isso uma forte candidata para incorporação em alimentos funcionais.
No conjunto, esta tese demonstrou que os EPS derivados de BAL são moléculas multifuncionais que associam a inovação tecnológica e promoção da saúde. Ao combinar estudos estruturais, funcionais e orientados para a aplicação, ela fornece novas perceções sobre o papel duplo dos EPS como agentes estruturais e ingredientes bioativos nos alimentos. Essas descobertas contribuem para o desenvolvimento de alimentos funcionais “clean label” e destacam o potencial das estirpes de BAL como uma fonte de biomoléculas com benefícios para a saúde.
ABSTRACT: Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) are multifunctional carbohydrate polymers that have attracted increasing attention due to their dual role in food systems and human health. Despite the wide diversity of LAB-derived EPS, systematic research connecting their structural features to both techno-functional and health-promoting properties remains scarce. This PhD thesis aimed to advance the understanding of LAB-derived EPS by combining a broad review of the state of the art with original experimental studies on selected EPS-producing strains. The work was structured around four main objectives: (i) to review the structural diversity, biosynthetic pathways, and functional roles of LAB-produced EPS with emphasis on their application in food and health; (ii) to characterize the EPS produced by Leuconostoc mesenteroides SJC113 (isolated from São Jorge cheese) and evaluate its technological and functional properties, including the beneficial effects (as a prebiotic) on human health; and (iv) to screen goat milk-derived Streptococcus thermophilus strains for EPS production and safety, leading to the selection and characterization of the EPS from strain GM4. An extensive literature review was conducted to summarize the latest advances in LAB-derived EPS, including: (i) the structure, biosynthesis, and properties of EPS; (ii) modern methods for their characterization; (iii) their application in improving the quality of dairy and low-fat food products; and (iv) their documented health-promoting effects, including prebiotic, antioxidant, and cholesterol-lowering activities. The first experimental work focused on EPS produced by Ln. mesenteroides SJC113. Structural characterization confirmed a dextran-type homopolysaccharide resistant to dextranase hydrolysis and of high molecular weight. Functional assays revealed antioxidant and cholesterol-binding properties, while the strain itself exhibited β-galactosidase activity and tolerance to gastrointestinal conditions. Safety assessment demonstrated the absence of virulence genes and appropriate antibiotic susceptibility. When applied in fat-free fresh cheese, the EPS improved water-holding capacity, rheology, and sensory perception, validating its role as a natural fat replacer. The second study investigated the potential health-promoting effects of the dextran-type EPS. In vitro experiments demonstrated its ability to support the growth of probiotic LAB, enhance mucin adhesion, and positively modulate fecal microbiota composition. Antioxidant capacity and cholesterol-lowering properties further supported its functionality as a bioactive dietary component. These results underline the prebiotic nature of dextran-type EPS and their potential role in gut microbiota modulation and cardiovascular health. The third study characterized four exopolysaccharide (EPS)-producing S. thermophilus strains (GM1-GM4), isolated from goat milk, to evaluate their potential for use in functional dairy products. Safety of GM4 was confirmed by testing for hemolytic, DNase, and gelatinase activities, and by screening for virulence and antibiotic resistance genes. Strain GM4 exhibited a high β-galactosidase activity and its probiotic potential was emphasized by a high auto-aggregation capacity and co-aggregation with pathogens like Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus. The purified EPS from GM4 was identified as a heteropolysaccharide composed primarily of glucose and mannose with high dextranase resistance and antioxidant activity. GM4 emerged as a safe, technologically versatile, and functional strain, with its EPS possessing bioactive properties, making it a strong candidate for incorporation into functional foods. Altogether, this thesis demonstrates that LAB-derived EPS are multifunctional molecules bridging technological innovation and health promotion. By combining structural, functional, and application-oriented studies, it provides new insights into the dual role of EPS as natural food structuring agents and bioactive ingredients. These findings contribute to the development of clean-label, functional foods and highlight the potential of LAB strains as a source of health-supporting biomolecules.
ABSTRACT: Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) are multifunctional carbohydrate polymers that have attracted increasing attention due to their dual role in food systems and human health. Despite the wide diversity of LAB-derived EPS, systematic research connecting their structural features to both techno-functional and health-promoting properties remains scarce. This PhD thesis aimed to advance the understanding of LAB-derived EPS by combining a broad review of the state of the art with original experimental studies on selected EPS-producing strains. The work was structured around four main objectives: (i) to review the structural diversity, biosynthetic pathways, and functional roles of LAB-produced EPS with emphasis on their application in food and health; (ii) to characterize the EPS produced by Leuconostoc mesenteroides SJC113 (isolated from São Jorge cheese) and evaluate its technological and functional properties, including the beneficial effects (as a prebiotic) on human health; and (iv) to screen goat milk-derived Streptococcus thermophilus strains for EPS production and safety, leading to the selection and characterization of the EPS from strain GM4. An extensive literature review was conducted to summarize the latest advances in LAB-derived EPS, including: (i) the structure, biosynthesis, and properties of EPS; (ii) modern methods for their characterization; (iii) their application in improving the quality of dairy and low-fat food products; and (iv) their documented health-promoting effects, including prebiotic, antioxidant, and cholesterol-lowering activities. The first experimental work focused on EPS produced by Ln. mesenteroides SJC113. Structural characterization confirmed a dextran-type homopolysaccharide resistant to dextranase hydrolysis and of high molecular weight. Functional assays revealed antioxidant and cholesterol-binding properties, while the strain itself exhibited β-galactosidase activity and tolerance to gastrointestinal conditions. Safety assessment demonstrated the absence of virulence genes and appropriate antibiotic susceptibility. When applied in fat-free fresh cheese, the EPS improved water-holding capacity, rheology, and sensory perception, validating its role as a natural fat replacer. The second study investigated the potential health-promoting effects of the dextran-type EPS. In vitro experiments demonstrated its ability to support the growth of probiotic LAB, enhance mucin adhesion, and positively modulate fecal microbiota composition. Antioxidant capacity and cholesterol-lowering properties further supported its functionality as a bioactive dietary component. These results underline the prebiotic nature of dextran-type EPS and their potential role in gut microbiota modulation and cardiovascular health. The third study characterized four exopolysaccharide (EPS)-producing S. thermophilus strains (GM1-GM4), isolated from goat milk, to evaluate their potential for use in functional dairy products. Safety of GM4 was confirmed by testing for hemolytic, DNase, and gelatinase activities, and by screening for virulence and antibiotic resistance genes. Strain GM4 exhibited a high β-galactosidase activity and its probiotic potential was emphasized by a high auto-aggregation capacity and co-aggregation with pathogens like Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus. The purified EPS from GM4 was identified as a heteropolysaccharide composed primarily of glucose and mannose with high dextranase resistance and antioxidant activity. GM4 emerged as a safe, technologically versatile, and functional strain, with its EPS possessing bioactive properties, making it a strong candidate for incorporation into functional foods. Altogether, this thesis demonstrates that LAB-derived EPS are multifunctional molecules bridging technological innovation and health promotion. By combining structural, functional, and application-oriented studies, it provides new insights into the dual role of EPS as natural food structuring agents and bioactive ingredients. These findings contribute to the development of clean-label, functional foods and highlight the potential of LAB strains as a source of health-supporting biomolecules.
Descrição
Tese de Doutoramento, Ciências Agrárias, 15 de maio de 2026, Universidade dos Açores.
Palavras-chave
Lactic acid bacteria Exopolysaccharides Food application Health-promoting benefits
Contexto Educativo
Citação
JURÁŠkOVÁ, Dominika. (2025). Production, characterization and food application of lactic acid bacteria-derived exopolysaccharides with health-promoting benefits. Angra do Heroísmo: Universidade dos Açores, 2025. 168 p. Tese de Doutoramento em Ciências Agrárias. Disponível em http://hdl.handle.net/10400.3/9016