Purification and characterization of a truncated Bacillus subtilis alpha-amylase produced by Escherichia coli

Biochemical characterization and structural insights into the high substrate affinity of a dimeric and Ca2+ independent Bacillus subtilis α-amylase

An extracellular amylase (AmyKS) produced by a newly isolated Bacillus subtilis strain US572 was purified and characterized. AmyKS showed maximal activity at pH 6 and 60°C with a half-life of 10 min at 70°C. It is a Ca²⁺ independent enzyme and able to hydrolyze soluble starch into oligosaccharides consisting mainly of maltose and maltotriose. When compared to the studied α-amylases, AmyKS presents a high affinity toward soluble starch with a K_m value of 0.252 mg ml^-1 . Coupled with the size-exclusion chromatography data, MALDI-TOF/MS analysis indicated that the purified amylase is a dimer with a molecular mass of 136,938.18 Da. It is an unusual feature of a non-maltogenic α-amylase. A 3D model and a dimeric model of AmyKS were generated showing the presence of an additional domain suspected to be involved in the dimerization process. This dimer arrangement could explain the high substrate affinity and catalytic efficiency of this enzyme.

Marine Microbiological Enzymes: Studies with Multiple Strategies and Prospects

Marine microorganisms produce a series of promising enzymes that have been widely used or are potentially valuable for our daily life. Both classic and newly developed biochemistry technologies have been broadly used to study marine and terrestrial microbiological enzymes. In this brief review, we provide a research update and prospects regarding regulatory mechanisms and related strategies of acyl-homoserine lactones (AHL) lactonase, which is an important but largely unexplored enzyme. We also detail the status and catalytic mechanism of the main types of polysaccharide-degrading enzymes that broadly exist among marine microorganisms but have been poorly explored. In order to facilitate understanding, the regulatory and synthetic biology strategies of terrestrial microorganisms are also mentioned in comparison. We anticipate that this review will provide an outline of multiple strategies for promising marine microbial enzymes and open new avenues for the exploration, engineering and application of various enzymes.

Development of a β-glucosidase hyperproducing mutant by combined chemical and UV mutagenesis

The extracellular β-glucosidase from microorganisms is generally produced in low levels. Therefore, in this study, a β-glucosidase hyperproducing mutant was developed by multiple exposures of ethyl methyl sulfonate (EMS) and ultraviolet (UV) radiation (both individually and jointly) to Bacillus subtilis strain (PS). The developed mutants were screened, selected and characterized. The mutant, PS-UM1 developed after UV exposure alone, indicated a small increase in β-glucosidase production (718 U/l) in comparison to the wild-type strain, PS (675 U/l). The mutant, PS-CM5 developed after EMS exposure alone, displayed a slightly better production (762 U/l) than both the above strains. However, after exposure of the wild-type strain to both UV and EMS mutagens jointly, a better mutant (PS-CM5-UM3) was developed with 1.2-fold increase in production (806 U/l). Further, optimization of culture conditions by classical "one-variable-at-a-time" approach was done to determine the optimum, pH, temperature and nitrogen sources. The selected mutant (PS-CM5-UM3) produced up to 1,797 U/l enzyme and was found to be stable for ten generations. The β-glucosidase from the selected mutant (PS-CM5-UM3) was concentrated and purified using ammonium sulfate, dialysis and size-exclusion chromatography. The enzyme displayed maximal activity at 60 °C and it was found to be fairly stable at temperatures up to 70 °C for 30 min. Its molecular weight was determined to be around 60 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

Biochemical and Structural Characterization of Amy1: An Alpha-Amylase from Cryptococcus flavus Expressed in Saccharomyces cerevisiae

An extracellular alpha-amylase (Amy1) whose gene from Cryptococcus flavus was previously expressed in Saccharomyces cerevisiae was purified to homogeneity (67 kDa) by ion-exchange and molecular exclusion chromatography. The enzyme was activated by NH₄⁺ and inhibited by Cu⁺² and Hg⁺². Significant biochemical and structural discrepancies between wild-type and recombinant α-amylase with respect to K_m values, enzyme specificity, and secondary structure content were found. Far-UV CD spectra analysis at pH 7.0 revealed the high thermal stability of both proteins and the difference in folding pattern of Amy1 compared with wild-type amylase from C. flavus, which reflected in decrease (10-fold) of enzymatic activity of recombinant protein. Despite the differences, the highest activity of Amy1 towards soluble starch, amylopectin, and amylase, in contrast with the lowest activity of Amy1_w, points to this protein as being of paramount biotechnological importance with many applications ranging from food industry to the production of biofuels.

Purification and characterization of novel α-amylase from Bacillus subtilis KIBGE HAS

Purification of extracellular α-amylase from Bacillus subtilis KIBGE HAS was carried out by ultrafiltration, ammonium sulfate precipitation and gel filtration chromatography. The enzyme was purified to homogeneity with 96.3-fold purification with specific activity of 13011 U/mg. The molecular weight of purified α-amylase was found to be 56,000 Da by SDS-PAGE. Characteristics of extracellular α-amylase showed that the enzyme had a Km and V (max) value of 2.68 mg/ml and 1773 U/ml, respectively. The optimum activity was observed at pH 7.5 in 0.1 M phosphate buffer at 50 °C. The amino acid composition of the enzyme showed that the enzyme is rich in neutral/non polar amino acids and less in acidic/polar and basic amino acids. The N-terminal protein sequence of 10 residues was found to be as Ser-Ser-Asn-Lys-Leu-Thr-Thr-Ser-Trp-Gly (S-S-N-K-L-T-T-S-W-G). Furthermore, the protein was not N-terminally blocked. The sequence of α-amylase from B. subtilis KIBGE HAS was a novel sequence and showed no homology to other reported α-amylases from Bacillus strain.

Effective solubilization and single-step purification of Bacillus licheniformis alpha-amylase from insoluble aggregates

A high level expression of thermostable alpha-amylase gene from Bacillus licheniformis in Escherichia coli was obtained. The recombinant enzyme was mainly produced in the form of insoluble aggregates. The enzyme was solubilized without using denaturing agents and purified to homogeneity in a single step by ion exchange chromatography. The enzyme was purified 138-fold with a final yield of 349 %; the specific activity of the purified enzyme was 1343 U/mg.