Characterization of a halotolerant GH2 family β-galactosidase GalM from Microvirga sp. strain MC18

A description of Joostella sp. strain CR20 with potential biotechnological applications

The underexplored halophilic genus Joostella within the Flavobacteriaceae family consists of only two species, both of which have received little attention for their potential biotechnological applications. In this study, we report the isolation and characterisation of a novel halophilic bacterium, strain CR20, using a genomic approach to investigate its biotechnological potential. Analysis of the 16S rRNA gene revealed that strain CR20 shares 97.5% and 96.2% sequence similarity with Joostella marina DSM 19592 T and Joostella atrarenae M1-2 T, respectively. Strain CR20 exhibited average nucleotide identity and digital DNA-DNA hybridisation values of 76.8-79.1% and 20.8-22.8%, respectively, with Joostella spp., which fall below the species delineation thresholds. Additionally, strain CR20 demonstrated average amino acid identity and percentage of conserved proteins values of 81.3-84.0% and 71.7-75.3%, respectively, with Joostella spp., above the genus delineation thresholds. Meanwhile, the average amino acid identity and percentage of conserved proteins values of strain CR20 against Galbibacter spp. are 73.9-80.0% and 61.3-72.3%, respectively, also above the genus delineation thresholds. These findings indicated strain CR20 has a close relationship with both genera. Chemotaxonomic analysis of strain CR20 identified predominant fatty acids, including iso-C17:0 3OH (25.3%), iso-C15:0 (14%), and C16:1 ω6c/C16:1 ω7c (12.2%). The assembled genome comprises 62 contigs, with a size of approximately 3,168,727 bp and a G + C content of 35.1%. Among 2,804 predicted genes, 2,559 were classified into 25 COG functional groups. A total of 68 genes with potential industrial applications were identified, including 1 β-mannanase, 2 β-xylosidases, 1 polysaccharide deacetylase, 4 other hemicellulases, 6 β-glucosidases, 25 proteases, and 29 phosphate-solubilising enzymes. Hydrolytic assays confirmed that strain CR20 produces these enzymes extracellularly. These findings highlight strain CR20 has potential for industrial applications.

Protein Engineering of a Novel β-Galactosidase from Thermus scotoductus for Efficient Synthesis of Lacto-N-Neotetraose from Chitin Powder

A novel β-galactosidase (TsGal48) from Thermus scotoductus was cloned, and the enzyme was biochemically characterized. TsGal48 catalyzed the synthesis of lacto-N-neotetraose (LNnT) from lactose via the transglycosylation reaction with a maximal yield of 20%, which is the highest yield for the synthesis of LNnT so far. To further improve the yield of LNnT, TsGal48 was successfully engineered by directed evolution and site-saturation mutagenesis. A mutated β-galactosidase (mTsGal48) was selected and characterized. mTsGal48 produced LNnT with a yield of 27.7 g/L, which is 1.4-fold higher than that of TsGal48 (19.7 g/L). Then, a developed strategy for LNnT synthesis from chitin powder was provided in a 30 L bioreactor. The reaction process included chitin powder hydrolysis, lacto-N-triose II (LNT2) synthesis, and LNnT synthesis. The reaction time was reduced from 44 to 17 h in chitin powder hydrolysis and LNT2 synthesis. The content of LNnT was up to 25 g/L in the multienzyme system. The green and efficient route may be suitable for large-scale production of LNnT from chitin powder.

A Review on the Various Sources of β-Galactosidase and Its Lactose Hydrolysis Property

β-Galactosidase is a glycoside hydrolase enzyme that possesses both hydrolytic and transgalactosylation properties and has several benefits and advantages in the food and dairy industries. The catalytic process of β-galactosidase involves the transfer of a sugar residue from a glycosyl donor to an acceptor via a double-displacement mechanism. Hydrolysis prevails when water acts as an acceptor, resulting in the production of lactose-free products. Transgalactosylation prevails when lactose acts as an acceptor, resulting in the production of prebiotic oligosaccharides. β-Galactosidase is also obtained from many sources including bacteria, yeast, fungi, plants, and animals. However, depending on the origin of the β-galactosidase, the monomer composition and their bonds may differ, thereby influencing their properties and prebiotic efficacy. Thus, the increasing demand for prebiotics in the food industry and the search for new oligosaccharides have compelled researchers to search for novel sources of β-galactosidase with diverse properties. In this review, we discuss the properties, catalytic mechanisms, various sources and lactose hydrolysis properties of β-galactosidase.