Diversity and enzymatic activity of Polish beehive products microbiota, and characterization of a novel β-galactosidase from Paenibacillus sp. 8.

Microbial enzymes are widely used in many industries, and beehive products are an abundant source of microorganisms. In this study, bacteria, yeasts, and filamentous fungi were isolated from Polish honey and bee bread samples and were investigated as enzyme producers. The best producers of glycoside hydrolases were Paenibacillus spp., whereas Micrococcus spp. showed high proteolytic and lipolytic activity. The β-galactosidase-encoding bgaP gene from Paenibacillus sp. 8 was cloned and expressed in Escherichia coli. BgaP, a hexameric protein with a molecular mass of 466 kDa, was optimally active at pH 6.6-7.0 and 40 °C, and maintained 18% of its maximum activity at 10 °C. β-Galactosidase was strongly inhibited by galactose, moderately by glucose, and slightly by fructose; therefore, it hydrolyzed lactulose much more efficiently than lactose. The efficiency of lactose digestion by BgaP was increased to almost 80% by the L-arabinose isomerase-catalyzed bioconversion of galactose to tagatose. These features make BgaP β-galactosidase a potential candidate for application in lactulose detection and in the production of health-promoting sweeteners. Furthermore, the cell-free extract of Paenibacillus sp. 8 hydrolyzed lactose in milk and synthesized galactooligosaccharides at 10 °C, indicating the presence of β-galactosidase other than BgaP in bacterial cells, justifying further research.