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- Studies with galacto-oligosaccharides and lactic acid bacteria for the valorization of food by-productsPublication . Martins, Gonçalo Nuno Gouveia; Castilho, Paula Cristina Machado Ferreira; Gómez-Zavaglia, AndreaFood wastes and by-products’ generation raises humanitarian, economic and environmental concerns. The UN’s 12th Sustainable Development Goal promotes waste reduction and co-products’ valorisation along the food production chain. Prebiotic sugars galacto-oligosaccharides (GOS) resist digestion in the upper gastrointestinal tract, being metabolized by beneficial gut bacteria, supporting their proliferation, and promoting consumers’ health. GOS show cryoprotective potential towards lactic acid bacteria during freezing, freeze-drying, and storage, by replacing water molecules and forming a glass like structure around the bacteria, preventing cell damage. α-GOS can be obtained from natural sources and β-GOS by enzymatic synthesis from lactose. Removal of glucose formed during the synthesis increases the mixture’s health benefits. For the valorisation of food by-products, α-GOS from chickpeas’ and lentils’ cooking wastewaters were used for growing and the stabilization of two food-grade Lactiplantibacillus plantarum strains, and β-GOS were produced by two β-galactosidases immobilized in halloysite nanotubes and purified by fermentation with surplus yeast from the Madeiran brewing industry. Chickpeas’ yielded the most α-GOS, while lentils’ water contained more GOS of higher degree of polymerization and fewer simple sugars. L. plantarum CIDCA 83114 grew in cooking water-containing media, similarly to the standard microbiological media that uses glucose as carbon source. After freezing, freeze-drying, and storage for 3 weeks at 37 °C, GOS wastewaters were the most successful cryoprotectants towards L. plantarum WCFS1 strain, outperforming reference materials (sucrose and fructo oligosaccharides). After the enzymatic synthesis and purification by fermentation in a repeated batch operation, both mixtures’ final composition consisted in 41 % β-GOS, with unreacted lactose and galactose present, but only 1 % glucose. Food industry’s by-products are valuable sources of bioactive compounds and materials. Legumes’ cooking waters support the growth and protection of food-grade bacteria, while surplus yeast can be used in β-GOS’ purification. These added-value products can circle back to the food industry, tackling waste management and environmental concerns, while improving consumers’ health by the production of prebiotics, and probiotics with increased shelf-life.