Genetic and functional characterization of a Limosilactobacillus fermentum strain with β-galactosidase activity, isolated from Chhurpi sample of Sikkim

Abstract

Milk sugar lactose is intolerant to a majority of the world’s population. The enzyme β-galactosidase has the potential to hydrolyze lactose into glucose and galactose. In this study, β-galactosidase enzyme-producing strain was screened from fermented food products, Chhurpi and curd, of the Sikkim Himalayas. A potential isolate exhibiting β-galactosidase activity was selected for comprehensive genomic and biochemical characterization. The genomic analysis determined that the selected isolate is a strain of Limosilactobacillus fermentum. The optimum β-galactosidase activity was recorded at a temperature of 40 °C and pH 7.0, with a specific activity of 2.46 + 0.70 U mg⁻¹. The presence of metal ions like K⁺, Ca²⁺, and Fe²⁺ favored enzymatic activity. The in-depth genomic analysis revealed the presence of two copies of β-galactosidase genes in L. fermentum C2C, presumably bestowing higher β-galactosidase activity as compared to other strains of L. fermentum. The genomic characterization established the absence of any genomic signature for antibiotic resistance, virulence, toxin, allergenicity, and pathogenicity, endorsing it to be a safe strain that can be used for the processing of milk samples. The L. fermentum C2C β-galactosidase was demonstrated to catalyze the hydrolysis of approximately 98 % lactose in milk in 12 h.