β-galactosidase Production by Aspergillus niger ATCC 9142 Using Inexpensive Substrates in Solid-State Fermentation: Optimization by Orthogonal Arrays Design

Genome-wide identification and comparative in-silico characterization of β-galactosidase (GH-35) in ascomycetes and its role in germ tube development of Aspergillus fumigatus via RNA-seq analysis

β-galactosidase (Lactase), an enzyme belonging to the glycoside hydrolase family causing the hydrolysis and trans-glycosylation of β-D-galactosides, has a vital role in dairy industries. The current investigation emphasizes on in-silico identification and comparative analysis of different fungal lactases present in Aspergillus fumigatus, Aspergillus oryzae, Botrytis cinerea, and Fusarium fujikuroi. Prediction of motifs and domains, chromosomal positioning, gene structure, gene ontology, sub-cellular localization and protein modeling were performed using different bioinformatics tools to have an insight into the structural and functional characteristics of β-galactosidases. Evolutionary and homology relationships were established by phylogenetic and synteny analyses. A total of 14 β-gal genes (GH-35) were identified in these species. Identified lactases, having 5 domains, were predicted to be stable, acidic, non-polar and extracellularly localized with roles in polysaccharide catabolic process. Results showed variable exonic/intronic ratios of the gene structures which were randomly positioned on chromosomes. Moreover, synteny blocks and close evolutionary relationships were observed between Aspergillus fumigatus and Aspergillus oryzae. Structural insights allowed the prediction of best protein models based on the higher ERRAT and Q-MEAN values. And RNA-sequencing analysis, performed on A. fumigatus, elucidated the role of β-gal in germ tube development. This study would pave the way for efficient fungal lactase production as it identified β-gal genes and predicted their various features and also it would provide a road-way to further the understanding of A. fumigatus pathogenicity via the expression insights of β-gal in germ tube development.

A Novel Thermal-Activated β-Galactosidase from Bacillus aryabhattai GEL-09 for Lactose Hydrolysis in Milk

β-Galactosidase has been greatly used in the dairy industry. This study investigated a novel thermostable β-galactosidase (lacZBa) from Bacillus aryabhattai GEL-09 and evaluated the hydrolytic performance of this enzyme. Firstly, the lacZBa-encoding gene was cloned and overexpressed in Escherichia coli BL21(DE3). Phylogenetic analyses revealed that lacZBa belonged to the glycoside hydrolase family 42. Using SDS-PAGE, we determined that the molecular weight of lacZBa was ~75 kDa. Purified lacZBa exhibited a maximum activity at 45 °C, pH 6.0, and could be activated following incubation at 45 °C for several minutes. The half-life of lacZBa at 45 °C and 50 °C was 264 h and 36 h, respectively. While Co²⁺, Mn²⁺, Zn²⁺, Fe²⁺, Mg²⁺, and Ca²⁺ enhanced enzymatic activity, Cu²⁺ and ethylenediaminetetraacetic acid inhibited enzymatic activity. Moreover, lacZBa could hydrolyze lactose and oNPG with K_m values of 85.09 and 14.38 mM. Molecular docking results revealed that lacZBa efficiently recognized and catalyzed lactose. Additionally, the hydrolysis of lactose by lacZBa was studied in lactose solution and commercial milk. Lactose was completely hydrolyzed within 4 h with 8 U/mL of lacZBa at 45 °C. These results suggested that lacZBa identified in this study has potential applications in the dairy industry.

β-Galactosidase-Producing Isolates in Mucoromycota: Screening, Enzyme Production, and Applications for Functional Oligosaccharide Synthesis

β-Galactosidases of Mucoromycota are rarely studied, although this group of filamentous fungi is an excellent source of many industrial enzymes. In this study, 99 isolates from the genera Lichtheimia, Mortierella, Mucor, Rhizomucor, Rhizopus and Umbelopsis, were screened for their β-galactosidase activity using a chromogenic agar approach. Ten isolates from the best producers were selected, and the activity was further investigated in submerged (SmF) and solid-state (SSF) fermentation systems containing lactose and/or wheat bran substrates as enzyme production inducers. Wheat bran proved to be efficient for the enzyme production under both SmF and SSF conditions, giving maximum specific activity yields from 32 to 12,064 U/mg protein and from 783 to 22,720 U/mg protein, respectively. Oligosaccharide synthesis tests revealed the suitability of crude β-galactosidases from Lichtheimia ramosa Szeged Microbiological Collection (SZMC) 11360 and Rhizomucor pusillus SZMC 11025 to catalyze transgalactosylation reactions. In addition, the crude enzyme extracts had transfructosylation activity, resulting in the formation of fructo-oligosaccharide molecules in a sucrose-containing environment. The maximal oligosaccharide concentration varied between 0.0158 and 2.236 g/L depending on the crude enzyme and the initial material. Some oligosaccharide-enriched mixtures supported the growth of probiotics, indicating the potential of the studied enzyme extracts in future prebiotic synthesis processes.

A New β-Galactosidase from the Antarctic Bacterium Alteromonas sp. ANT48 and Its Potential in Formation of Prebiotic Galacto-Oligosaccharides

As an important medical enzyme, β-galactosidases catalyze transgalactosylation to form prebiotic Galacto-Oligosaccharides (GOS) that assist in improving the effect of intestinal flora on human health. In this study, a new glycoside hydrolase family 2 (GH2) β-galactosidase-encoding gene, galA, was cloned from the Antarctic bacterium Alteromonas sp. ANT48 and expressed in Escherichia coli. The recombinant β-galactosidase GalA was optimal at pH 7.0 and stable at pH 6.6–7.0, which are conditions suitable for the dairy environment. Meanwhile, GalA showed most activity at 50 °C and retained more than 80% of its initial activity below 40 °C, which makes this enzyme stable in normal conditions. Molecular docking with lactose suggested that GalA could efficiently recognize and catalyze lactose substrates. Furthermore, GalA efficiently catalyzed lactose degradation and transgalactosylation of GOS in milk. A total of 90.6% of the lactose in milk could be hydrolyzed within 15 min at 40 °C, and the GOS yield reached 30.9%. These properties make GalA a good candidate for further applications.

Sources of β-galactosidase and its applications in food industry

The enzyme β-galactosidases have been isolated from various sources such as bacteria, fungi, yeast, vegetables, and recombinant sources. This enzyme holds importance due to its wide applications in food industries to manufacture lactose-hydrolyzed products for lactose-intolerant people and the formation of glycosylated products. Absorption of undigested lactose in small intestine requires the activity of this enzyme; hence, the deficiency of this enzyme leads to lactose intolerance. Lactose intolerance affects around 70% of world's adult population, while the prevalence rate of lactose intolerance is 60% in Pakistan. β-Galactosidases are not only used to manufacture lactose-free products but also employed to treat whey, and used in prebiotics. This review focuses on various sources of β-galactosidase and highlights the importance of β-galactosidases in food industries.