Highly stable and versatile α-amylase from Anoxybacillus vranjensis ST4 suitable for various applications

α-Amylase from the thermophilic bacterial strain Anoxybacillus vranjensis ST4 (AVA) was cloned into the pMALc5HisEk expression vector and successfully expressed and purified from the Escherichia coli ER2523 host strain. AVA belongs to the GH13_5 subfamily of glycoside hydrolases and has 7 conserved sequence regions (CSRs) distributed in three distinct domains (A, B, C). In addition, there is a starch binding domain (SBD) from the CBM20 family of carbohydrate binding modules (CBMs). AVA is a monomer of 66 kDa that achieves maximum activity at 60-80 °C and is active and stable over a wide pH range (4.0-9.0). AVA retained 50 % of its activity after 31 h of incubation at 60 °C and was resistant to a large number of denaturing agents. It hydrolyzed starch granules very efficiently, releasing maltose, maltotriose and maltopentaose as the main products. The hydrolysis rates of raw corn, wheat, horseradish, and potato starch, at a concentration of 10 %, were 87.8, 85.9, 93.0, and 58 %, respectively, at pH 8.5 over a 3 h period. This study showed that the high level of expression as well as the properties of this highly stable and versatile enzyme show all the prerequisites for successful application in industry.

The genus Anoxybacillus: an emerging and versatile source of valuable biotechnological products

Thermophilic and alkaliphilic microorganisms are unique organisms that possess remarkable survival strategies, enabling them to thrive on a diverse range of substrates. Anoxybacillus, a genus of thermophilic and alkaliphilic bacteria, encompasses 24 species and 2 subspecies. In recent years, extensive research has unveiled the diverse array of thermostable enzymes within this relatively new genus, holding significant potential for industrial and environmental applications. The biomass of Anoxybacillus has demonstrated promising results in bioremediation techniques, while the recently discovered metabolites have exhibited potential in medicinal experiments. This review aims to provide an overview of the key experimental findings related to the biotechnological applications utilizing bacteria from the Anoxybacillus genus.

Anoxybacillus: an overview of a versatile genus with recent biotechnological applications

The Bacillaceae family members are considered to be a good source of microbial factories for biotechnological processes. In contrast to Bacillus and Geobacillus, Anoxybacillus, which would be thermophilic and spore-forming group of bacteria, is a relatively new genus firstly proposed in the year of 2000. The development of thermostable microbial enzymes, waste management and bioremediation processes would be a crucial parameter in the industrial sectors. There has been increasing interest in Anoxybacillus strains for biotechnological applications. Therefore, various Anoxybacillus strains isolated from different habitats have been explored and identified for biotechnological and industrial purposes such as enzyme production, bioremediation and biodegradation of toxic compounds. Certain strains have ability to produce exopolysaccharides possessing biological activities including antimicrobial, antioxidant and anticancer. This current review provides past and recent discoveries regarding Anoxybacillus strains and their potential biotechnological applications in enzyme industry, environmental processes and medicine.

Unraveling the Genomic Potential of the Thermophilic Bacterium Anoxybacillus flavithermus from an Antarctic Geothermal Environment

Antarctica is a mosaic of extremes. It harbors active polar volcanoes, such as Deception Island, a marine stratovolcano having notable temperature gradients over very short distances, with the temperature reaching up to 100 °C near the fumaroles and subzero temperatures being noted in the glaciers. From the sediments of Deception Island, we isolated representatives of the genus Anoxybacillus, a widely spread genus that is mainly encountered in thermophilic environments. However, the phylogeny of this genus and its adaptive mechanisms in the geothermal sites of cold environments remain unknown. To the best of our knowledge, this is the first study to unravel the genomic features and provide insights into the phylogenomics and metabolic potential of members of the genus Anoxybacillus inhabiting the Antarctic thermophilic ecosystem. Here, we report the genome sequencing data of seven A. flavithermus strains isolated from two geothermal sites on Deception Island, Antarctic Peninsula. Their genomes were approximately 3.0 Mb in size, had a G + C ratio of 42%, and were predicted to encode 3500 proteins on average. We observed that the strains were phylogenomically closest to each other (Average Nucleotide Identity (ANI) > 98%) and to A. flavithermus (ANI 95%). In silico genomic analysis revealed 15 resistance and metabolic islands, as well as genes related to genome stabilization, DNA repair systems against UV radiation threats, temperature adaptation, heat- and cold-shock proteins (Csps), and resistance to alkaline conditions. Remarkably, glycosyl hydrolase enzyme-encoding genes, secondary metabolites, and prophage sequences were predicted, revealing metabolic and cellular capabilities for potential biotechnological applications.

Identification, characterization and hydrolase producing performance of thermophilic bacteria: geothermal hot springs in the Eastern and Southeastern Anatolia Regions of Turkey

In the last two decades, researchers have increasingly focused on the rich microorganism-based diversity of natural hot spring sources to explore the benefits of thermophiles in industrial and biotechnological fields. Within the scope of this study, a total of 83 thermophilic Bacilli strains were isolated from 7 different geothermal hot springs (at temperatures ranging between 40 and 85 °C) located in the Eastern and Southeastern Anatolia Regions of Turkey. The physiological, morphological, biochemical and molecular properties of the isolates were determined. As a result of the 16S rRNA gene sequence analysis, 5 different species (Bacillus licheniformis, Bacillus sp., Bacillus subtilis, Geobacillus kaustophilus, and Weizmannia coagulans,) were identified. B. licheniformis and B. subtilis were the most frequently encountered species among those obtained from the researched hot spring sources. Phylogenetic analysis was conducted to evaluate the phylogenetic relationships of the isolated species. The results showed that there was no significant difference between the groups and the bacteria in terms of the locations or optimum temperatures of the isolates. The bacterial isolates were screened for amylase, cellulase, lipase and protease hydrolytic enzyme activities. The hydrolytic enzyme production potentials among the isolates were identified in 68 (82%) isolates for amylase, 34 (41%) for cellulase, 69 (83%) for lipase and 73 (88%) for protease. All isolates were found to have at least one or more extracellular enzyme activities. Additionally, it was determined that 27 of the existing isolates (32.8%) were able to produce all of the aforementioned hydrolytic enzymes.

Introduction of novel thermostable α-amylases from genus Anoxybacillus and proposing to group the Bacillaceae related α-amylases under five individual GH13 subfamilies

Among the thermophilic Bacillaceae family members, α-amylase production of 15 bacilli from genus Anoxybacillus was investigated, some of which are biotechnologically important. These Anoxybacillus α-amylase genes displayed ≥ 91.0% sequence similarities to Anoxybacillus enzymes (ASKA, ADTA and GSX-BL), but relatively lower similarities to Geobacillus (≤ 69.4% to GTA, Gt-amyII), and Bacillus aquimaris (≤ 61.3% to BaqA) amylases, all formerly proposed only in a Glycoside Hydrolase 13 (GH13) subfamily. The phylogenetic analyses of 63 bacilli-originated protein sequences among 93 α-amylases revealed the overall relationships within Bacillaceae amylolytic enzymes. All bacilli α-amylases formed 5 clades different from 15 predefined GH13 subfamilies. Their phylogenetic findings, taxonomic relationships, temperature requirements, and comparisonal structural analyses (including their CSR-I-VII regions, 12 sugar- and 4 calcium-binding sites, presence or absence of the complete catalytic machinery, and their currently unassigned status in a valid GH13 subfamiliy) revealed that these five GH13 α-amylase clades related to familly share some common characteristics, but also display differentiative features from each other and the preclassified ones. Based on these findings, we proposed to divide Bacillaceae related GH13 subfamilies into 5 individual groups: the novel a2 subfamily clustered around α-amylase B2M1-A (Anoxybacillus sp.), the a1, a3 and a4 subfamilies (including the representatives E184aa-A (Anoxybacillus sp.), ATA (Anoxybacillus tepidamans), and BaqA,) all of which were composed from the division of the previously grouped single subfamily around α-amylase BaqA, and the undefinite subfamily formerly defined as xy including Bacillus megaterium NL3.