In summary metagenome sequencing of paddy soil was performed

In summary, metagenome sequencing of paddy soil was performed with 55.68 Gb sequences, and subsequent data mining was performed for functional profiles and metabolic pathways. Several GH family proteins, such as amylases, cellulases, xylanases, and galactosidases, were explored in the paddy soil metagenome, and they have the potential to be applied in various industrial fields. To demonstrate the functional property of the assembly ORFs, a putative gene encoding α-galactosidase, namely GalR, was successfully synthesized using its optimal igf1r and overexpressed in E. coli. The alkaliphilic GalR was characterized in detail. The strategy of the metagenomic sequencing–based gene identification can not only discover various novel genes but also save time compared with screening DNA libraries.
Acknowledgments This work was supported by the Ministry of Science and Technology, Taiwan (Grant 102-2313-B-157-003-MY3), the Doctor Startup Fund Project of Xiamen Medical College (K2016-31), Fujian, China, and the Innovation and Development Center of Sustainable Agriculture from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education (MOE) in Taiwan.
Introduction Lactase (EC 3.2.1.108) is an enzyme typical for human and other mammals. It is located in the small intestine and responsible mainly for digestion of lactose – one of the essential disaccharides in the food industry (Pokrzywnicka & Koncki, 2018). Unfortunately, for about 70% of the world human population genetically programmed reduction in lactase activity during adulthood occurs, causing a digestive disorder – so-called lactose intolerance (Corgneau, et al., 2017). This digestive discomfort contributes to the decline in consumption of dairy products, which have a beneficial effect on one’s health, mainly due to their high calcium content and the positive influence on probiotic bacteria. Two main symptom-reducing strategies for people suffering from lactose intolerance is the consumption of lactose-free food or the use of exogenous enzyme dietary supplements (Corgneau et al., 2017). However, due to its presence mainly in mammals small intestines (“BRENDA - Information on EC 3.2.1.108 - lactase,”), the isolation and purification of lactase required for both these strategies are rather expensive, thus not utilized in the large-scale food industry. Fortunately, β–galactosidase (GAL [EC 3.2.1.23], also imprecisely known as lactase) is more widely distributed in nature. This lysosomal hydrolase naturally occurs in many bacteria, fungi, plant and animal cells (Husain, 2010). It has awider than human lactase spectrum of biocatalytic activity. It acts on hydrolysis of terminal non-reducing β–D–galactose residues of many types of compounds. Due to its lactase-like activity, GAL is widely applied in the food and pharmaceutical industry for the production of lactose hydrolyzed milk, low-lactose dairy products as well as dietary supplements for lactose intolerance treatment (Husain, 2010). β-galactosidase such as many other enzymes occurs in various isoforms which properties, specificity and structure significantly differ on the origin of an enzyme. They might differ in molecular weight, amino-acid chain length, the location of the active site, pH and thermal optimum and stability (Harju, Kallioinen, & Tossavainen, 2012). Proper evaluation of their activity and the optimal condition is essential from the biochemical point of view because it allows finding the potential applications. Nowadays there are at least, ten of known commercially available sources of GAL mainly from microbes: fungi (from Kluyveromyces yeasts and Aspergillus mold), bacterial (aerobic Bacillus and Lactobacillus, as well as anaerobic Streptococcus thermophilus and Escherichia Coli) (Harju, Kallioinen, & Tossavainen, 2012). The enzyme isolated from Kluyveromyces lactis, with pH optimum 6.5–7, is widely applied in the dairy industry in the process of lactose-free products manufacturing (Mlichová & Rosenberg, 2006). GAL from Aspergillus Oryzae, with pH optimum 3-5, is most useful for the hydrolysis of lactose present in acidic products such as whey, (Husain, 2010) it is also used in dietary supplements and pharmaceutical formulations (Mlichová & Rosenberg, 2006). Moreover, β-galactosidase is very important for the proper functioning of the human body. Deficiency of this enzyme in human cells leads to lysosomal storage disorders such as GM1 gangliosidosis and Morquio B disease (Kwapiszewski, Szczudlowska, Kwapiszewska, Chudy, & Brzozka, 2014). Unlike the lactose intolerance, these are sporadic medical conditions that have a devastating impact on the brain and skeletal systems and the measuring enzyme activity is crucial for accurate diagnosis of those diseases (Kwapiszewski, Kwapiszewska, Kutter, & Brzozka, 2015).