Microbial α-amylase: A biomolecular overview

Recent developments in enzymatic preparation, physicochemical properties, bioactivity, and application of resistant starch type III from staple food grains

Resistant starch (RS) was classified into five types and referred to the starch that cannot be digested and absorbed by the small intestine of healthy human beings. Among them, RS3 has received a lot of attention from researchers because of its good functional properties and greater application prospects. Meanwhile, the enzymatic method is widely used in the preparation of RS3 because of its high efficiency and environmental protection. α-Amylase and pullulanase as the main enzymes can effectively improve the yield of RS3. The physical properties of RS3 have an excellent potential for application in improving food crispness, texture and producing low glycemic index (GI) foods. It is more valuable because it has biological activities such as inducing apoptosis in tumor cells, lowering intestinal pH, and regulating blood glucose, etc. This paper summarized the current research progress of RS3 from different staple food grains, including current applications of enzymes commonly used in the preparation of RS3, physical properties and biological activities of RS3, and the application of RS3 in different areas to provide a theoretical basis for future research on RS3 as well as further development and applications based on the market requirement.

Saccharide mapping as an extraordinary method on characterization and identification of plant and fungi polysaccharides: A review

Saccharide mapping was a promising scheme to unveil the mystery of polysaccharide structure by analysis of the fragments generated from polysaccharide decomposition process. However, saccharide mapping was not widely applied in the polysaccharide analysis for lacking of systematic introduction. In this review, a detailed description of the establishment process of saccharide mapping, the pros and cons of downstream technologies, an overview of the application of saccharide mapping, and practical strategies were summarized. With the updating of the available downstream technologies, saccharide mapping had been expanding its scope of application to various kinds of polysaccharides. The process of saccharide mapping analysis included polysaccharides degradation and hydrolysates analysis, and the degradation process was no longer limited to acid hydrolysis. Some downstream technologies were convenient for rapid qualitative analysis, while others could achieve quantitative analysis. For the more detailed structure information could be provided by saccharide mapping, it was possible to improve the quality control of polysaccharides during preparation and application. This review filled the blank of basic information about saccharide mapping and was helpful for the establishment of a professional workflow for the saccharide mapping application to promote the deep study of polysaccharide structure.

Exploring a novel GH13_5 α-amylase from Jeotgalibacillus malaysiensis D5T for raw starch hydrolysis

α-Amylase plays a crucial role in the industrial degradation of starch. The genus Jeotgalibacillus of the underexplored marine bacteria family Caryophanaceae has not been investigated in terms of α-amylase production. Herein, we report the comprehensive analysis of an α-amylase (AmyJM) from Jeotgalibacillus malaysiensis D5T (= DSM28777T = KCTC33550T). Protein phylogenetic analysis indicated that AmyJM belongs to glycoside hydrolase family 13 subfamily 5 (GH13_5) and exhibits low sequence identity with known α-amylases, with its closest counterpart being the GH13_5 α-amylase from Bacillus sp. KSM-K38 (51.05% identity). Purified AmyJM (molecular mass of 70 kDa) is stable at a pH range of 5.5-9.0 and optimally active at pH 7.5. The optimum temperature for AmyJM is 40 °C, where the enzyme is reasonably stable at this temperature. Similar to other α-amylases, the presence of CaCl2 enhanced both the activity and stability of AmyJM. AmyJM exhibited activity toward raw and gelatinized forms of starches and related α-glucans, generating a mixture of reducing sugars, such as glucose, maltose, maltotriose, maltotetraose, and maltopentaose. In raw starch hydrolysis, AmyJM exhibited its highest efficiency (51.10% degradation) in hydrolyzing raw wheat starch after 3-h incubation at 40 °C. Under the same conditions, AmyJM also hydrolyzed tapioca, sago, potato, rice, and corn raw starches, yielding 16.01-30.05%. These findings highlight the potential of AmyJM as a biocatalyst for the saccharification of raw starches, particularly those derived from wheat.

Bottom-up approach to explore alpha-amylase assisted membrane remodelling

Soluble alpha-amylases play an important role in the catabolism of polysaccharides. In this work, we show that the malt α -amylase can interact with the lipid membrane and further alter its mechanical properties. Vesicle fluctuation spectroscopy is used for quantitative measurement of the membrane bending rigidity of phosphatidylcholines lipid vesicles from the shape fluctuation based on the whole contour of Giant Unilamellar Vesicles (GUVs). The bending rigidity of the 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine lipid vesicles in water increases significantly with the presence of 0.14 micromolar alpha-amylase (AA) in the exterior solution. It appears that the enzyme present in the external solution interacts with the outer layer of the bilayer membrane, leading to an asymmetry of the solution on either side of the bilayer membrane and altering its elasticity. At AA concentration of 1.5 micromolars and above, changes in the morphology of the GUV membrane are observed. The interaction between AA in the external solution and the external leaflet causes the bilayer membrane to curve spontaneously, leading to the formation of outbuds, giving a positive spontaneous curvature of C0 ≤ 0.05 μm-1 at ≈ 1 mg / ml of the AA concentration. We validate and characterize its concentration-dependent role in stabilizing the membrane curvature. Our findings indicate that the involvement of the enzyme, depending on the concentration, can have a considerable effect on the mechanical characteristics of the membrane.

Recent advances in the synthesis and medicinal perspective of pyrazole-based α-amylase inhibitors as antidiabetic agents

Diabetes is a serious health threat across the globe, claiming millions of lives worldwide. Among the various strategies employed, inhibition of α-amylase is a therapeutic protocol for the management of Type 2 diabetes mellitus. α-Amylase is a crucial enzyme involved in the breakdown of dietary starch into simpler units. However, the clinically used α-amylase inhibitors have various drawbacks. Therefore, design and development of novel α-amylase inhibitors have gained significant attention. The pyrazole motif has been identified as a versatile scaffold in medicinal chemistry, and recent studies have led to the identification of various pyrazole-based α-amylase inhibitors. This review compiles therapeutic implications of pyrazole-appended α-amylase inhibitors; their synthesis, biological activities, structure-activity relationships and molecular docking studies are discussed.

Exploring the partial degradation of polysaccharides: Structure, mechanism, bioactivities, and perspectives

Polysaccharides are promising biomolecules with lowtoxicity and diverse bioactivities in food processing and clinical drug development. However, an essential prerequisite for their applications is the fine structure characterization. Due to the complexity of polysaccharide structure, partial degradation is a powerful tool for fine structure analysis, which can effectively provide valid information on the structure of backbone and branching glycosidic fragments of complex polysaccharides. This review aims to conclude current methods of partial degradation employed for polysaccharide structural characterization, discuss the molecular mechanisms, and describe the molecular structure and solution properties of degraded polysaccharides. In addition, the effects of polysaccharide degradation on the conformational relationships between the molecular structure and bioactivities, such as antioxidant, antitumor, and immunomodulatory activities, are also discussed. Finally, we summarize the prospects and current challenges for the partial degradation of polysaccharides. This review will be of great value for the scientific elucidation of polysaccharide fine structures and potential applications.

Metaproteomic investigation of enzyme profile in daqu used for the production of Nongxiangxing baijiu

Enzymes and microbiota in daqu are essential for the brewing of Nongxiangxing baijiu. Uncover the key enzymes and functional strains in daqu is beneficial to improve the flavor and quality of Nongxiangxing baijiu. In this study, metaproteome technology was employed to determine the enzyme profiles in Nongxiangxing daqu, and strains with high saccharification activity were screened and identified. 933 proteins were identified in daqu, of which 463 belonged to enzymes, including 140 oxidoreductases, 98 transferases, 91 hydrolases, 49 ligases, 41 lyases and 27 isomerases, and hydrolase is the enzyme with the highest abundance in baijiu brewing. Among hydrolases, a total of 36 carbohydrate metabolism-related enzymes (CMEs) were identified, and 12 of them were key enzymes related to glycoside hydrolysis. Four major glycoside hydrolysis enzymes glucoamylase (EC 3.2.1.3), glucan 1,4-alpha-glucosidase (EC 3.2.1.3), glucanase (EC 3.2.1.-) and β-glucosidase (EC 3.2.1.21) were revealed, and their sources were Byssochlamys spectabilis, Lichtheimia ramosa and Thermoascus aurantiacus, respectively. Then, strains Aspergillus A2, A3, A7, Lichtheimia L1, L4, L5, and Saccharomycopsis S2, S4, S6 with high saccharifying enzyme-producing capacity were screened through culture-dependent approach. Resents presented in this study can further reveal the enzyme profiles and identify the main functional strains in daqu, which can provide theoretical support for the brewing of Nongxiangxing baijiu.

High Production of Maltooligosaccharides in the Starch Liquefaction Process: A Study on the Hyperthermophilic Mechanism of α-Amylase

The efficient production of high-value-added bioproducts from starchy substances requires α-amylases with hyperthermophilic properties for industrial starch liquefaction. In this study, two hyperthermophilic α-amylases with significant differences in thermostability, PfAmy and TeAmy, were comparatively studied through structural analysis, domain swapping, and site-directed mutagenesis, finding that three residues, His152, Cys166, and His168, located in domain B were the main contributors to hyperthermostability. The effects of these three residues were strongly synergistic, causing the optimum temperature for the mutant K152H/A166C/E168H of TeAmy to shift to 95-100 °C and stabilize at 90 °C without Ca²⁺. Compared to PfAmy and TeAmy, the mutant K152H/A166C/E168H, respectively, exhibited 1.7- and 2.5-times higher starch hydrolysis activity at 105 °C and pH 5.5 (10411 ± 70 U/mg) and released 1.1- and 1.7-times more maltooligosaccharides from 1% starch. This work has interpreted the hyperthermophilic mechanism of α-amylase and thereby providing a potential candidate for the efficient industrial conversion of starch to bioproducts.

Improving thermostability of Bacillus amyloliquefaciens alpha-amylase by multipoint mutations

The medium-temperature alpha-amylase of Bacillus amyloliquefaciens is widely used in the food and washing process. Enhancing the thermostability of alpha-amylases and investigating the mechanism of stability are important for enzyme industry development. The optimal temperature and pH of the wild-type BAA and mutant MuBAA (D28E/V118A/S187D/K370 N) were all 60 °C and 6.0, respectively. The mutant MuBAA showed better thermostability at 50 °C and 60 °C, with a specific activity of 206.61 U/mg, which was 99.1% greater than that of the wild-type. By analyzing predicted structures, the improving thermostability of the mutant MuBAA was mainly related to enhanced stabilization of a loop region in domain B via more calcium-binding sites and intramolecular interactions around Asp187. Furthermore, additional intramolecular interactions around sites 28 and 370 in domain A were also beneficial for improving thermostability. Additionally, the decrease of steric hindrance at the active cavity increased the specific activity of the mutant MuBAA. Improving the thermostability of BAA has theoretical reference values for the modification of alpha-amylases.

Isolation and Screening of High-Yielding α-Amylase Mutants of Bacillus subtilis by Heavy Ion Mutagenesis

To improve fermentative production of α-amylase, heavy-ion mutagenesis technology was used to irradiate Bacillus subtilis (B. subtilis) to obtain the high yielding mutants in this study. After continuous cultivation for 12 generations, eight mutants exhibited positive mutation rate with greater H/C. The α-amylase production was stable and obviously exceeded that by the parent strain, which shows that the mutants have a good genetic stability. Among the mutants, the α-amylase activity of B. subtilis KC-180-2 was 72.26 U·mL^-1, which was 82.34% higher than that of the original strain. After optimization of fermentation conditions and media, the α-amylase activity of B. subtilis KC-180-2 reached a maximum of 156.83 U·mL^-1 at 36 h in a bioreactor. In addition, the optimized fermentation temperature of B. subtilis KC-180-2 was increased to 49℃, indicating B. subtilis KC-180-2 possesses high-temperature resistance, which has great application prospects for industrial fermentation for α-amylase production.

Repurposing CRISPR RNA-guided integrases system for one-step, efficient genomic integration of ultra-long DNA sequences

Genomic integration techniques offer opportunities for generation of engineered microorganisms with improved or even entirely new functions but are currently limited by inability for efficient insertion of long genetic payloads due to multiplexing. Herein, using Shewanella oneidensis MR-1 as a model, we developed an optimized CRISPR-associated transposase from cyanobacteria Scytonema hofmanni (ShCAST system), which enables programmable, RNA-guided transposition of ultra-long DNA sequences (30 kb) onto bacterial chromosomes at ∼100% efficiency in a single orientation. In this system, a crRNA (CRISPR RNA) was used to target multicopy loci like insertion-sequence elements or combining I-SceI endonuclease, thereby allowing efficient single-step multiplexed or iterative DNA insertions. The engineered strain exhibited drastically improved substrate diversity and extracellular electron transfer ability, verifying the success of this system. Our work greatly expands the application range and flexibility of genetic engineering techniques and may be readily extended to other bacteria for better controlling various microbial processes.

Microbially-derived cocktail of carbohydrases as an anti-biofouling agents: a 'green approach'

Enzymes, also known as biocatalysts, display vital properties like high substrate specificity, an eco-friendly nature, low energy inputs, and cost-effectiveness. Among their numerous known applications, enzymes that can target biofilms or their components are increasingly being investigated for their anti-biofouling action, particularly in healthcare, food manufacturing units and environmental applications. Enzymes can target biofilms at different levels like during the attachment of microorganisms, formation of exopolymeric substances (EPS), and their disruption thereafter. In this regard, a consortium of carbohydrases that can target heterogeneous polysaccharides present in the EPS matrix may provide an effective alternative to conventional chemical anti-biofouling methods. Further, for complete annihilation of biofilms, enzymes can be used alone or in conjunction with other antimicrobial agents. Enzymes hold the promise to replace the conventional methods with greener, more economical, and more efficient alternatives. The present article explores the potential and future perspectives of using carbohydrases as effective anti-biofilm agents.

Structural and functional adaptation in extremophilic microbial α-amylases

Maintaining stable native conformation of a protein under a given ecological condition is the prerequisite for survival of organisms. Extremophilic bacteria and archaea have evolved to adapt under extreme conditions of temperature, pH, salt, and pressure. Molecular adaptations of proteins under these conditions are essential for their survival. These organisms have the capability to maintain stable, native conformations of proteins under extreme conditions. The enzymes produced by the extremophiles are also known as extremozyme, which are used in several industries. Stability and functionality of extremozymes under varying temperature, pH, and solvent conditions are the most desirable requirement of industry. α-Amylase is one of the most important enzymes used in food, pharmaceutical, textile, and detergent industries. This enzyme is produced by diverse microorganisms including various extremophiles. Therefore, understanding its stability is important from fundamental as well as an applied point of view. Each class of extremophiles has a distinctive set of dominant non-covalent interactions which are important for their stability. Static information obtained by comparative analysis of amino acid sequence and atomic resolution structure provides information on the prevalence of particular amino acids or a group of non-covalent interactions. Protein folding studies give the information about thermodynamic and kinetic stability in order to understand dynamic aspect of molecular adaptations. In this review, we have summarized information on amino acid sequence, structure, stability, and adaptability of α-amylases from different classes of extremophiles.

Nanobiocatalyst consisting of immobilized α-amylase on montmorillonite exhibiting enhanced enzymatic performance based on the allosteric effect

Enzyme immobilization on nanostructured substrates is an emerging method for the efficient development of nanobiocatalysts to enhance enzymatic performance. In this study, a novel α-amylase nanobiocatalytic system was constructed based on the allosteric activation of the enzyme and its immobilization on a natural nanostructured mineral montmorillonite. The strategy of allosteric modulation and immobilization, equipped the immobilized α-amylase with higher catalytic activity and greater stability (compared to those of free α-amylase) over a broad range of pH values (4.5-9.0) and temperatures (30-80 °C). Kinetic experiments revealed that although the immobilized α-amylase possessed a considerably lower affinity for its substrate, its catalytic activity was higher than that of free α-amylase, likely owing to allosteric modulation. Thus, this study demonstrates a convenient and environmentally benign immobilization strategy to construct a nanobiocatalytic α-amylase system that exploits the phenomenon of allosteric activation of the enzyme and lays the foundation for further industrial applications.

Complete genome sequence of Lactobacillus plantarum SK156, a candidate vehicle for mucosal vaccine delivery

Lactobacillus plantarum SK156 was isolated from traditional Korean food. The genome of SK156 strain consists of a circular chromosome (3,231,383 bp) with guanine (G) + cytosine (C) content of 44.56%. Among the predicted 2,991 protein-coding genes, the genome included genes encoding for α-amylase, which hydrolyzes α-bonds of polysaccharides. Genomic sequencing of L. plantarum SK156 will give information on the mechanism involved in the enzymatic degradation of polysaccharides and its application for improving feed efficiency.

A Novel Digestive α-Amylase from Blue Crab (Portunus segnis) Viscera: Purification, Biochemical Characterization and Application for the Improvement of Antioxidant Potential of Oat Flour

This study reports on the purification and characterization of a digestive α-amylase from blue crab (Portunussegnis) viscera designated Blue Crab Amylase (BCA). The enzyme was purified to homogeneity by ultrafiltration, Sephadex G-100 gel filtration and Sepharose mono Q anion exchange chromatography, with the final purification fold of 424.02, specific activity of 1390.8 U mg⁻¹ and 27.8% recovery. BCA, showing a molecular weight of approximately 45 kDa, possesses desirable biotechnological features, such as optimal temperature of 50 °C, interesting thermal stability which is enhanced in the presence of starch, high stability towards surfactants (Tween 20, Tween 80 and Triton X-100), high specific activity, quite high storage and broad pH range stability. The enzyme displayed Km and Vmax values, of 7.5 ± 0.25 mg mL⁻¹ and 2000 ± 23 μmol min⁻¹ mg⁻¹ for potato starch, respectively. It hydrolyzed various carbohydrates and produced maltose, maltotriose and maltotetraose as the major end products of starch hydrolysis. In addition, the purified enzyme was successfully utilized for the improvement of the antioxidant potential of oat flour, which could be extended to other cereals. Interestingly, besides its suitability for application in different industrial sectors, especially food industries, the biochemical properties of BCA from the blue crab viscera provide novel features with other marine-derived enzymes and better understanding of the biodegradability of carbohydrates in marine environments, particularly in invasive alien crustaceans.

Microbial lipases and their industrial applications: a comprehensive review

Lipases are very versatile enzymes, and produced the attention of the several industrial processes. Lipase can be achieved from several sources, animal, vegetable, and microbiological. The uses of microbial lipase market is estimated to be USD 425.0 Million in 2018 and it is projected to reach USD 590.2 Million by 2023, growing at a CAGR of 6.8% from 2018. Microbial lipases (EC 3.1.1.3) catalyze the hydrolysis of long chain triglycerides. The microbial origins of lipase enzymes are logically dynamic and proficient also have an extensive range of industrial uses with the manufacturing of altered molecules. The unique lipase (triacylglycerol acyl hydrolase) enzymes catalyzed the hydrolysis, esterification and alcoholysis reactions. Immobilization has made the use of microbial lipases accomplish its best performance and hence suitable for several reactions and need to enhance aroma to the immobilization processes. Immobilized enzymes depend on the immobilization technique and the carrier type. The choice of the carrier concerns usually the biocompatibility, chemical and thermal stability, and insolubility under reaction conditions, capability of easy rejuvenation and reusability, as well as cost proficiency. Bacillus spp., Achromobacter spp., Alcaligenes spp., Arthrobacter spp., Pseudomonos spp., of bacteria and Penicillium spp., Fusarium spp., Aspergillus spp., of fungi are screened large scale for lipase production. Lipases as multipurpose biological catalyst has given a favorable vision in meeting the needs for several industries such as biodiesel, foods and drinks, leather, textile, detergents, pharmaceuticals and medicals. This review represents a discussion on microbial sources of lipases, immobilization methods increased productivity at market profitability and reduce logistical liability on the environment and user.

Identification and characterization of novel thermostable α-amylase from Geobacillus sp. GS33

In this study, the heterologous expression and biochemical characterization of a thermostable α-amylase from Geobacillus sp. GS33 was investigated. The recombinant α-amylase was overexpressed in Escherichia coli BL21 (λDE) and purified via anion exchange and size-exclusion chromatography. The purified α-amylase had a molecular weight of about 60 kDa, and was active in a broad range of pH 3-10 and temperature (40-90 °C) with maximum activity at pH 7-8 and 60 °C. The enzyme retained 50% residual activity at 65 °C, but only 20% at 85 °C after 16 h. At pH 9 and pH 7, the residual activity at 65 °C was 50% and 30%, respectively. The enzyme was remarkably activated by Co²⁺, Ca²⁺, Mg²⁺, PMSF, DTT, and Triton X-100, but partially inhibited by Cu²⁺, methanol, hexane, ethanol, acetone, SDS, and Tween 20. A molecular phylogeny analysis showed that the enzyme's amino acid sequence had the closest connection with an α-amylase from Geobacillus thermoleovorans subsp. stromboliensis nov. 3D-structure-based amino acid sequence alignments revealed that the three catalytic residues (D217, E246, D314) and the four Ca²⁺ ion coordination residues (N143, E177, D186, H221) were conserved in α-amylase from Geobacillus sp. GS33. The temperature stability and neutral pH optimum suggest that the enzyme may be useful for industrial applications.

Ethanol from rice byproduct using amylases secreted by Rhizopus microsporus var. oligosporus. Enzyme partial purification and characterization

A three-stage bioethanol bioprocess was developed. Firstly, amylases were obtained from Rhizopus microsporus var. oligosporus using wheat bran in solid-state fermentation. Secondly, amylases hydrolyzed a rice byproduct to make a glucose-rich solution, and this sugar was finally metabolized by Saccharomyces cerevisiae to produce bioethanol. Besides, the secreted enzymes were also partially purified and characterized. The amylase activity (AA) in the crude extract was 358 U/g substrate, and the partially purified enzyme showed the best activity in the 4.0-5.5 pH range. A wide pH stability range (3.5-8.5) was confirmed. The amylase was thermostable up to 60 °C. The ion Mn⁺² (10 mM) improved by 60% the AA. There was a 54.9% yield in the conversion of rice residues into reducing sugars in 10 h. The glucose-rich solution was undergone fermentation by S. cerevisiae and showed high ethanol efficiency, 95.8% of the theoretical value. These results suggested a promising technology for bioethanol production.

A detailed in silico analysis of the amylolytic family GH126 and its possible relatedness to family GH76

The glycoside hydrolase (GH) family 126 was established based on the X-ray structure determination of the amylolytic enzyme CPF_2247 from Clostridium perfringens genome. Its original identification as a putative carbohydrate-active enzyme was based on its low, yet significant sequence identity to members of the family GH8, which are inverting endo-β-1,4-glucanases. As the family GH8 forms the clan GH-M with GH48, the CPF_2247 protein also exhibits similarities with members of the family GH48. The original screening of the CPF_2247 on carbohydrate substrates demonstrated its activity on glycogen and amylose, thus classifying this protein as an "α-amylase". It should be pointed out, however, there are apparent inconsistencies concerning the exact enzyme specificity of the "amylase" CPF_2247, since it exhibits both the endo- and exo-fashion of action. The family GH126 currently counts ~1000 amino acid sequences solely from Bacteria; all belonging to the phylum Firmicutes. The present study delivers the first detailed bioinformatics study of 117 selected amino acid sequences from the family GH126, featuring the insightful sequence-structure comparison with the aim to define seven conserved sequence regions and elucidate the evolutionary relationships within the family. In addition, a comparative structural analysis of the GH126 members with representatives of other GH families adopting the same (α/α)₆-barrel catalytic domain fold indicates the possible sharing a catalytic residue between the families GH126 and GH76.

Functional study of C-terminal domain of the thermoacidophilic raw starch-hydrolyzing α-amylase Gt-amy

Since the thermoacidophilic raw-starch hydrolyzing α-amylase Gt-amy can effectively hydrolyze corn starch under starch liquefaction conditions, it has potential for many industrial applications. To identify the raw starch-binding domain of Gt-amy, a C-terminal domain (CTD)-truncated mutant (Gt-amy-T) was constructed, and its enzymatic properties were compared with Gt-amy. In comparison to CTD of Gt-amy, which could effectively bind corn starch, the Gt-amy-T could not bind to and hydrolyze corn starch under similar conditions. In addition, Gt-amy-T showed significantly lower thermal activity and thermal stability. Using soluble starch as the substrate, the k _cat of Gt-amy-T at 80 °C was approximately 77.9% of that of Gt-amy. The half-life of Gt-amy at 80 °C was 3 h, while that of Gt-amy-T was 2 h. These results reveal that the CTD plays a vital role in raw starch binding and degradation by Gt-amy and helps Gt-amy maintain thermal activity and stability.

Low molecular weight alkaline thermostable α-amylase from Geobacillus sp. nov

Industrial demands for enzymes that are stable in a broad range of conditions are increasing. Such enzymes, one of which is α-amylase, could be produced by extremophiles. This study reports a thermostable α-amylase produced by a newly isolated Geobacillus sp. nov. from a geothermal area. The phylogenetic analysis of the 16S rRNA gene showed that the isolate formed a separate branch with 95% homology to Geobacillus sp. After precipitation using ammonium sulphate followed by ion-exchange chromatography, the enzyme produced a specific activity of 25.1 (U/mg) with a purity of 6.5-fold of the crude extract. The molecular weight of the enzyme was approximately 12.2 kDa. The optimum activity was observed at 75 °C and pH 8. The activity increased in the presence of Ba²⁺ and Fe²⁺ but decreased in the presence of K⁺ and Mg²⁺. Ca²⁺ and Mn²⁺ increased the activity slightly. The activity completely diminished with the addition of Cu²⁺. EDTA and PMSF also sharply reduced enzyme activity. Although the stability was moderate, the low molecular weight could be an important feature for its future applications.

Preparation and characterization of resistant starch type III from enzymatically hydrolyzed maize flour

Polysaccharides including resistant starch are categorized as dietary fiber and are used as an important prebiotic. Similar to soluble fibers, resistant starch also has a number of physiological effects that have been shown to be beneficial for health. Starch hydrolyzing enzymes, most importantly amylases, play essential roles in the production of resistant starch. This study aimed to develop α-amylase-treated maize flour with slow digestibility and unique physicochemical characteristics compared to native maize flour. In the current study, resistant starch type III from maize flour was prepared using α-amylase obtained from indigenously isolated Bacillus licheniformis. The α-amylase gene from B. licheniformis was amplified and cloned into the pET-24(a) vector, expressed in E. coli BL21 (DE3) cells and purified by metal ion affinity chromatography. The purified enzyme enhanced the yield of resistant starch 16-fold in maize flour. Scanning electron microscopy revealed that the granular structure of maize flour was disrupted into a dense network with irregular structure, and X-ray diffractograms confirmed the transformation from an amorphous to a crystalline structure upon α-amylase treatment. Thermogravimetric analysis revealed increased amylose content of α-amylase-treated maize flour. Moreover, α-amylase-treated maize flour resulted in a significant enhancement of the desired properties of maize flour, such as resistant starch content, amylose, milk absorption capacity, and iodine and fatty acid complexing ability, and a reduction in swelling power, water binding, oil absorption capacity, and in vitro digestibility compared to untreated maize flour. Resistant starch type III showed low digestibility and increased complexing ability with iodine and fatty acid and therefore could be a safe and beneficial alternative as a coating material for the delivery of active, sensitive ingredients to the colon.

Purification and characterization of a novel wild-type α-amylase from Antarctic sea ice bacterium Pseudoalteromonas sp. M175

A novel wild-type α-amylase named wtAmy175 from Pseudoalteromonas sp. M175 strain was purified through ammonium sulphate precipitation, DEAE cellulose, and Sephadex G-75 sequentially (25.83-fold, 7.67%-yield) for biochemical characterization. SDS-PAGE and zymographic activity staining of purified enzyme showed a single band with a predicted molecular mass of about 61 kDa. The optimum temperature and pH for enzyme activity were 30 °C and 7.5, respectively. Additionally, the enzyme exhibited high activity and remarkable stability in 0-10 mM SDS. The values of K_m and V_max for soluble starch as substrate were 2.47 mg/ml and 0.103 mg/ml/min, respectively. Analysis of hydrolysis products of soluble starch and maltooligosaccharides showed that wtAmy175 cleaved the interior and the terminal α-1,4-glycosidic linkage in starch, and had transglycosylation activity. The result of fluorescence spectroscopy showed that wtAmy175 had strong binding affinity with soluble starch. In brief, this study discovered the first wild-type α-amylase so far with several distinctive properties of cold activity, SDS-resistance, and the mixed activity of α-amylase and α-glucosidase, suggesting that wtAmy175 possess high adaptive capability to endure harsh industrial conditions and would be an excellent candidate in detergent and textile industries.

Heterologous expression, purification, immobilization and characterization of recombinant α-amylase AmyLa from Laceyella sp. DS3

AmyLa α-amylase gene from Laceyella sp. DS3 was heterologously expressed in E. coli BL21. E. coli BL21 maximally expressed AmyLa after 4 h of adding 0.02 mM IPTG at 37 °C. The recombinant AmyLa α-amylase was purified 2.19-fold through gel filtration and ion exchange chromatography. We immobilized the purified recombinant AmyLa α-amylase on four carriers; chitosan had the best efficiency. The recombinant free and the immobilized AmyLa α-amylase showed optimum activity in the pH ranges of 6.0-7.0 and 4.0-7.0, respectively and possessed an optimum temperature of 55 °C. The free enzyme had activation energy, Km, and Vmax of 291.5 kJ, 1.5 mg/ml, and 6.06 mg/min, respectively. The immobilized enzyme had activation energy, Km, and Vmax of 309.74 kJ, 6.67 mg/ml, and 50 mg/min, respectively. The immobilized enzyme was calcium-independent and insensitive (relative to the free enzyme) to metals. It could also be reused for seven cycles.

Secretion of the recombination α-amylase in Escherichia coli and purification by the gram-positive enhancer matrix (GEM) particles

α-Amylases are important enzymes in industry. A recombinant α-amylase with a secretion signal peptide and an AcmA tag was expressed in Escherichia coli to improve the yield. The induction concentrations were optimized, and the temperature had a significant influence on soluble expression and secretion. A visible band could be obtained when the induction was conducted at 16 °C. The gram-positive enhancer matrix (GEM) particles could separate and purify the recombinant α-amylase with the AcmA tag, and no visible band could be seen in the culture even after the culture was concentrated ten times. The solution and concentration of the recombinant α-amylase could be adjusted by GEM particles. The recombinant untagged α-amylase was obtained after digestion. The α-amylase was characterized. The recombinant α-amylase was a thermophilic enzyme with a broad pH tolerance. In addition, the enzyme activity of the recombinant α-amylase was independent of Ca²⁺. The recombinant α-amylase contained the OmpA signal peptide and the AcmA tag and was expressed and purified quickly and easily.

AmyZ1: a novel α-amylase from marine bacterium Pontibacillus sp. ZY with high activity toward raw starches

BACKGROUND

Starch is an inexpensive and renewable raw material for numerous industrial applications. However, most starch-based products are not cost-efficient due to high-energy input needed in traditional enzymatic starch conversion processes. Therefore, α-amylase with high efficiency to directly hydrolyze high concentration raw starches at a relatively lower temperature will have a profound impact on the efficient application of starch.

RESULTS

A novel raw starch digesting α-amylase (named AmyZ1) was screened and cloned from a deep-sea bacterium Pontibacillus sp. ZY. Phylogenetic analysis showed that AmyZ1 was a member of subfamily 5 of glycoside hydrolase family 13. When expressed in Escherichia coli, the recombinant AmyZ1 showed high activity at pH 6.0-7.5 and 25-50 °C. Its optimal pH and temperature were 7.0 and 35 °C, respectively. Similar to most α-amylases, AmyZ1 activity was enhanced (2.4-fold) by 1.0 mM Ca²⁺. Its half-life time at 35 °C was also extended from about 10 min to 100 min. In comparison, AmyZ1 showed a broad substrate specificity toward raw starches, including those derived from rice, corn, and wheat. The specific activity of AmyZ1 towards raw rice starch was 12,621 ± 196 U/mg, much higher than other reported raw starch hydrolases. When used in raw starch hydrolyzing process, AmyZ1 hydrolyzed 52%, 47% and 38% of 30% (w/v) rice, corn, and wheat starch after 4 h incubation. It can also hydrolyze marine raw starch derived from Chlorella pyrenoidosa, resulting in 50.9 mg/g DW (dry weight of the biomass) of reducing sugars after 4 h incubation at 35 °C. Furthermore, when hydrolyzing raw corn starch using the combination of AmyZ1 and commercial glucoamylase, the hydrolysis rate reached 75% after 4.5 h reaction, notably higher than that obtained in existing starch-processing industries.

CONCLUSIONS

As a novel raw starch-digesting α-amylase with high specific activity, AmyZ1 efficiently hydrolyzed raw starches derived from both terrestrial and marine environments at near ambient temperature, suggesting its application potential in starch-based industrial processes.

Optimization and partial characterization of ca-independent α-amylase from Bacillus amyloliquefaciens BH1

Strain Bacillus amyloliquefaciens BH1 was evaluated for the generation of α-amylase. Culture conditions and medium components were optimized by a statistical approach for the optimal generation of α-amylase with response surface methodology (RSM) method. The Plackett-Burman (PB) design was executed to select the fermentation variables and Central composite design (CCD) for optimizing significant factors influencing production. The optimum levels for highest generation of α-amylase activity (198.26 ± 3.54 U/mL) were measured. A 1.69-fold improve generation was acquired in comparison with the non-optimized. Partial characterization of the α-amylase indicated optimal pH and temperature at 7.0 and 40 °C, respectively. Crude α-amylase maintained a constant pH range 5.0-8.0 and 30-70 °C. The α-amylase was independent of Ca²⁺, and the activity was inhibited by Fe³⁺, Co²⁺, Cu²⁺, and Hg²⁺. The thermo and pH stability of the α-amylase indicate its extensive application in the food and pharmaceutical industries.

Molecular Cloning and Characterization of a Novel α-Amylase from Antarctic Sea Ice Bacterium Pseudoalteromonas sp. M175 and Its Primary Application in Detergent

A novel cold-adapted and salt-tolerant α-amylase gene (amy175) from Antarctic sea ice bacterium Pseudoalteromonas sp. M175 was successfully cloned and expressed. The open reading frame (ORF) of amy175 had 1722 bp encoding a protein of 573 amino acids residues. Multiple alignments indicated Amy175 had seven highly conserved sequences and the putative catalytic triad (Asp²⁴⁴, Glu²⁸⁶, and Asp³⁷²). It was the first identified member of GH13_36 subfamily which contained QPDLN in the CSR V. The recombinant enzyme (Amy175) was purified to homogeneity with a molecular mass of about 62 kDa on SDS-PAGE. It had a mixed enzyme specificity of α-amylase and α-glucosidase. Amy175 displayed highest activity at pH 8.0 and 25°C and exhibited extreme salt-resistance with the maximum activity at 1 M NaCl. Amy175 was strongly stimulated by Mg²⁺, Ni²⁺, K⁺, 1 mM Ca²⁺, 1 mM Ba²⁺, 1 mM Pb²⁺, 1 mM sodium dodecyl sulphate (SDS), and 10% dimethyl sulfoxide (DMSO) but was significantly inhibited by Cu²⁺, Mn²⁺, Hg²⁺, 10 mM β-mercaptoethanol (β-ME), and 10% Tween 80. Amy175 demonstrated excellent resistance towards all the tested commercial detergents, and wash performance analysis displayed that the addition of Amy175 improved the stain removal efficiency. This study demonstrated that Amy175 would be proposed as a novel α-amylase source for industrial application in the future.

Purification and characterization of novel thermostable and Ca-independent α-amylase produced by Bacillus amyloliquefaciens BH072

In the present study, a novel α-amylase produced by Bacillus amyloliquefaciens BH072 was purified and characterized. The molecular weight of purified α-amylase was approximately 68 kDa, determined by Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) and ten amino acid of N-terminal was NSGLNGYLTH. The kinetic parameters K_m and V_max were 4.27 ± 0.21 mg/mL and 987.34 ± 23.34 U/mg, respectively. Purified α-amylase showed maximal activity at pH 7 and 60 °C. Enzyme remained stable in pH range 6.0-7.0 and 50-80 °C. The activity of the α-amylase was Ca²⁺ independent and stability in the presence of surfactant, oxidizing and bleaching agents. The β-mercaptoethanol and EDTA greatly enhanced and reduced α-amylase activity, respectively. This enzyme has high hydrolysis rate toward corn, wheat and potato starch and hydrolyzes soluble starch to glucose, maltose, maltotriose and maltotetraose, indicating that the α-amylase represents a promising candidate for applications in the food industry.

The response to selection in Glycoside Hydrolase Family 13 structures: A comparative quantitative genetics approach

The Glycoside Hydrolase Family 13 (GH13) is both evolutionarily diverse and relevant to many industrial applications. Its members hydrolyze starch into smaller carbohydrates and members of the family have been bioengineered to improve catalytic function under industrial environments. We introduce a framework to analyze the response to selection of GH13 protein structures given some phylogenetic and simulated dynamic information. We find that the TIM-barrel (a conserved protein fold consisting of eight α-helices and eight parallel β-strands that alternate along the peptide backbone, common to all amylases) is not selectable since it is under purifying selection. We also show a method to rank important residues with higher inferred response to selection. These residues can be altered to effect change in properties. In this work, we define fitness as inferred thermodynamic stability. We show that under the developed framework, residues 112Y, 122K, 124D, 125W, and 126P are good candidates to increase the stability of the truncated α-amylase protein from Geobacillus thermoleovorans (PDB code: 4E2O; α-1,4-glucan-4-glucanohydrolase; EC 3.2.1.1). Overall, this paper demonstrates the feasibility of a framework for the analysis of protein structures for any other fitness landscape.

Update on Marine Carbohydrate Hydrolyzing Enzymes: Biotechnological Applications

After generating much interest in the past as an aid in solving structural problems for complex molecules such as polysaccharides, carbohydrate-hydrolyzing enzymes of marine origin still appear as interesting biocatalysts for a range of useful applications in strong interdisciplinary fields such as green chemistry and similar domains. The multifaceted fields in which these enzymes are of interest and the scarce number of original articles in literature prompted us to provide the specialized analysis here reported. General considerations from modern (2016-2017 interval time) review articles are at start of this manuscript; then it is subsequently organized in sections according to particular biopolymers and original research articles are discussed. Literature sources like the Science Direct database with an optimized W/in search, and the Espacenet patent database were used.

Purification of an alpha amylase from Aspergillus flavus NSH9 and molecular characterization of its nucleotide gene sequence

In this study, an alpha-amylase enzyme from a locally isolated Aspergillus flavus NSH9 was purified and characterized. The extracellular α-amylase was purified by ammonium sulfate precipitation and anion-exchange chromatography at a final yield of 2.55-fold and recovery of 11.73%. The molecular mass of the purified α-amylase was estimated to be 54 kDa using SDS-PAGE and the enzyme exhibited optimal catalytic activity at pH 5.0 and temperature of 50 °C. The enzyme was also thermally stable at 50 °C, with 87% residual activity after 60 min. As a metalloenzymes containing calcium, the purified α-amylase showed significantly increased enzyme activity in the presence of Ca²⁺ ions. Further gene isolation and characterization shows that the α-amylase gene of A. flavus NSH9 contained eight introns and an open reading frame that encodes for 499 amino acids with the first 21 amino acids presumed to be a signal peptide. Analysis of the deduced peptide sequence showed the presence of three conserved catalytic residues of α-amylase, two Ca²⁺-binding sites, seven conserved peptide sequences, and several other properties that indicates the protein belongs to glycosyl hydrolase family 13 capable of acting on α-1,4-bonds only. Based on sequence similarity, the deduced peptide sequence of A. flavus NSH9 α-amylase was also found to carry two potential surface/secondary-binding site (SBS) residues (Trp 237 and Tyr 409) that might be playing crucial roles in both the enzyme activity and also the binding of starch granules.

Cohnella amylopullulanases: Biochemical characterization of two recombinant thermophilic enzymes

Some industries require newer, more efficient recombinant enzymes to accelerate their ongoing biochemical reactions in harsh environments with less replenishment. Thus, the search for native enzymes from extremophiles that are suitable for use under industrial conditions is a permanent challenge for R & D departments. Here and toward such discoveries, two sequences homologous to amylopullulanases (EC 3.2.1.41, GH57) from an endogenous Cohnella sp., [Coh00831 (KP335161; 1998 bp) and Coh01133 (KP335160: 3678 bp)] were identified. The genes were heterologously expressed in E. coli to both determine their type and further characterize their properties. The isolated DNA was PCR amplified with gene specific primers and cloned in pET28a, and the recombinant proteins were expressed in E. coli BL21 (DE3). The temperatures and pH optima of purified recombinants Coh 01133 and Coh 00831 enzymes were 70°C and 8, and 60°C and 6, respectively. These enzymes are stable more than 90% in 60°C and 50°C for 90 min respectively. The major reactions released sugars which could be fractionated by HPLC analysis, from soluble starch were mainly maltose (G2), maltotriose (G3) and maltotetraose (G4). The enzymes hydrolyzed pullulan to maltotriose (G3) only. Enzyme activities for both proteins were improved in the availability of Mn²⁺, Ba²⁺, Ca²⁺, and Mg²⁺ and reduced in the presence of Fe²⁺, Li²⁺, Na²⁺, Triton X100 and urea. Moreover, Co²⁺, K⁺, and Cu²⁺ had a negative effect only on Coh 01133 enzyme.