Preparation and assessment of cross-linked enzyme aggregates (CLEAs) of β-galactosidase from Lactobacillus leichmannii 313

•CLEA of crude β-galactosidases from LL 313, is reported for the first time.•CLEAs had higher storage stabilities (60–90% after 14 days) than free enzyme.•Optimum conditions for preparing ASF-CLEA were identified via RSM.•Free enzyme (Km = 4.08), differed from ASF-CLEA (Km = 4.95), but Vmax were same.•ASF-CLEA hydrolysed lactose (∼33%) and synthesized GOS (∼10% yield).