β‐Galactosidase: Insights into source variability, genetic engineering, immobilisation and diverse applications in food, industry and medicine.

β‐Galactosidases are crucial enzymes that hydrolyse oligosaccharides and polysaccharides with terminal β‐1,4‐glycosidic bonds. Though the traditional application of β‐Galactosidases has been to catalyse the breakdown of lactose in dairy products, its application extends beyond the production of lactose‐free products since variants capable of facilitating lactose condensation and exhibiting galactosyl transferase activity are extensively utilised for the synthesis of prebiotic galacto‐oligosaccharides. This review analyses β‐Galactosidase in multiple aspects, including sources, classification, characterisation, immobilisation, genetic engineering and applications in terms of whey treatment, biofuel production, production of lactose‐free dietary product, synthesis of galacto‐oligosaccharides and the early detection of cellular senescence and tumours. [ABSTRACT FROM AUTHOR]