Biochemical characterization of raw-starch-digesting alpha amylase purified from Bacillus amyloliquefaciens

Efficacy of the Fruit and Vegetable Peels as Substrates for the Growth and Production of α-Amylases in Marine Actinobacteria

Enzymes from haloalkaliphilic microorganisms have recently focused attention on their potential and suitability in various applications. In this study, the growth and production of extracellular amylases in the marine actinomycetes, using kitchen waste as the raw starch source, have been investigated. Actinobacteria were isolated from the seawater of the Kachhighadi Coast near Dwarika, Gujarat. Seven Actinobacterial isolates of pre-monsoon, monsoon, and post-monsoon seasons belonging to different strains of Nocardiopsis genera were screened and selected for amylase production. The amylase production was initially assessed on the solid media supplemented with the extracts of different fruits and vegetable peels as a substrate by agar plate assay. The strains Kh-2(13), Kh-2(1), and Kh-3(12) produced maximum amylase with potato peel as a substrate, while no significant differences were found with the media containing other peels. Nevertheless, all strains produced amylases at a significant level with other raw substrates as well. For the optimization of the growth and enzyme production, the selected two isolates Kh-2(13) and Kh-3(12) of the monsoon and winter seasons were cultivated in a liquid medium under the submerged fermentation conditions, with potato peel as a substrate. In both organisms, the optimum amylase production was observed in the stationary phase of growth. For amylase production, the effect of different physical and chemical parameters was evaluated. The optimum growth and amylase production was achieved in 2% inoculum size, at pH 8.0, 28℃, and 5% salt concentration. On the basis of the amylase production index (API) (a ratio of the amylase units and cell growth), both isolates produced significant amylase with the only extract of potato peels, without any other supplements. The trends further indicated that while additional complex sources, such as yeast extract and peptone can enhance the cell growth of the actinobacteria, the amylase production remained unaltered. The study projects the significance of waste raw materials for the production of enzymes in extremophilic microorganisms.

Effective seed cake extract of O. sanctum inducing the p53 dependent apoptotic pathway in oral cancer cells

OBJECTIVE

Present study was to observe the therapeutic aspects of seed cake extracts of Ocimum sanctum against the oral cancer cell line with the activation of p53 apoptotic pathway.

METHOD

Seed cake extracts were characterized using GC-MS analysis. Cytotoxic activity was observed on KB cells and L929 cell through MTT assay and scratch assay. Antioxidant activity on KB cells were determined using enzymatic and non enzyme content in the treated cells. Chick chorioallantoic membrane (CAM) was established to check the presence of blood vessel formation and neuvasculature pattern in the treated fertilized eggs. DNA fragmentation and gene expression studies were also determined in the treated cells to check the upregulation of apoptotic pathways.

RESULTS

GC-MS analysis confirmed alkaloids, phenols, and many. The cytotoxic activity showed maximum antiproliferative potential with aqueous extract, whereas no cytotoxic effect was observed on L929 cells. The ethanolic and aqueous extract has shown a greater SI value. Scratch assay has signified that aqueous extract has a lower migration rate of KB cells. Aqueous extract showed maximum enzymatic activity and lower malondialdehyde content in cells treated with ethanolic extract. CAM model confirmed that eggs treated with aqueous extract has shown inhibition of vasculature pattern and dissolutions of blood vessels. DNA Fragmentation and Gene expression studies confirmed maximum fold in the KB cell treated with an aqueous extract of seed cake leading to activation of p53 dependent apoptotic pathway.

CONCLUSION

The potent therapeutic properties of seed cake extracts have been proven, and they can be used as herbal treatments to prevent oral cancer.

Integrative analysis of transcriptome and metabolome reveals the mechanism of foliar application of Bacillus amyloliquefaciens to improve summer tea quality (Camellia sinensis)

Bacillus amyloliquefaciens is a promising microbial agent for quality improvement in crops; however, the effects of B. amyloliquefaciens biofertilizers on tea leaf metabolites are relatively unknown. Herein, a combination of metabolome profiling and transcriptome analysis was employed to investigate the effects of foliar spraying with B. amyloliquefaciens biofertilizers on tea leaf quality. The tea polyphenol to amino acid ratio (TP/AA), catechin, and caffeine levels decreased, but theanine level increased in tea leaves after foliar spraying with B. amyloliquefaciens. The differentially accumulated metabolites included flavonoids, phenolic acids, organic acids, amino acids, and carbohydrates. The decrease in catechin was correlated with the catechin/flavonoid biosynthesis pathway. The AMPD gene was highly associated with caffeine content, while the GOGAT gene was associated with theanine accumulation. Foliar spraying with B. amyloliquefaciens biofertilizers may improve summer tea quality. Our findings provide a basis for the application of B. amyloliquefaciens biofertilizers in tea plants and new insights on summer tea leaf resource utilization.

In vitro and in vivo evaluation of probiotic potential and safety assessment of Bacillus coagulans SKB LAB-19 (MCC 0554) in humans and animal healthcare

Bacillus coagulans is Gram positive, spore forming and high lactic acid producing bacteria; however, probiotic and safety assessment of the isolated strain need to be investigated for commercial applications. Current study aimed to screen SKB LAB-19 for potential probiotic characteristics viz. enzyme production, antimicrobial properties, pH/bile salt tolerance, temperature stability, antidiarrheal activity in Swiss albino mice and Wistar rats; and acute oral toxicity in mice. The results showed that, SKB LAB-19 produces eight potential enzymes, effective against E. coli and C. perfringensis, tolerant to bile salt (0.3%)/gastric pH (2.5), stable at 40-90 °C and nontoxic to cells. SKB LAB-19 was found to be safe and displayed promising results to reverse E. coli and castor oil induced diarrhoea. Histopathological studies showed repair to damaged mucosal epithelium cells and improves integrity of the goblet cells of colon. SKB LAB-19 showed immunomodulatory effects with increased immunoglobulins in blood and augmented weight of spleen and thymus. In addition, SKB LAB-19 showed significant in-vitro antioxidant activity (82.93%), reducing capacity and ascorbate auto-oxidation inhibition effect (94.62%). These preliminary results suggested that, SKB LAB-19 was found to be safe and has the potential to be used as effective probiotic and anti-diarrhoeal agent in humans and animal healthcare.

Functional Characterization of Recombinant Raw Starch Degrading α-Amylase from Roseateles terrae HL11 and Its Application on Cassava Pulp Saccharification

Exploring new raw starch-hydrolyzing α-amylases and understanding their biochemical characteristics are important for the utilization of starch-rich materials in bio-industry. In this work, the biochemical characteristics of a novel raw starch-degrading α-amylase (HL11 Amy) from Roseateles terrae HL11 was firstly reported. Evolutionary analysis revealed that HL11Amy was classified into glycoside hydrolase family 13 subfamily 32 (GH13_32). It contains four protein domains consisting of domain A, domain B, domain C and carbohydrate-binding module 20 (CMB20). The enzyme optimally worked at 50 °C, pH 4.0 with a specific activity of 6270 U/mg protein and 1030 raw starch-degrading (RSD) U/mg protein against soluble starch. Remarkably, HL11Amy exhibited activity toward both raw and gelatinized forms of various substrates, with the highest catalytic efficiency (kcat/Km) on starch from rice, followed by potato and cassava, respectively. HL11Amy effectively hydrolyzed cassava pulp (CP) hydrolysis, with a reducing sugar yield of 736 and 183 mg/g starch from gelatinized and raw CP, equivalent to 72% and 18% conversion based on starch content in the substrate, respectively. These demonstrated that HL11Amy represents a promising raw starch-degrading enzyme with potential applications in starch modification and cassava pulp saccharification.

Stain removing, juice-clarifying, and starch-liquefying potentials of amylase from Pleurotus tuberregium in submerged fermentation system

Background

Amylase is used commercially in food, textiles, sugar syrup, paper, and detergent industries. Bacteria and fungi remain a significant source of industrial enzymes. Pleurotus tuberregium is a macro-fungi that can exist as a fruiting body, sclerotium, mycelium, and spores. Some studies have been conducted on this fungus, with minimal studies on its enzyme activity (s) using the submerged fermentation technique.

Results

The purified amylase has a specific activity of 5.26 U/mg, total activity of 189.20 U, maximally active at 70 °C, pH of 5, and retaining 100% of its activity at 30 ^oC for 4 min. P. tuberregium amylase showed optimal activity with plantain peel, followed by starch and pineapple peel (42, 30, and 29 μg/mL/min respectively). The presence of Ca²⁺, Mg²⁺, and Na⁺ ions in the reaction mixture activated the enzyme activity, but was slightly and moderately inhibited by KCl and Na₂H₂PO₄ respectively. The crude enzyme effectively clarified juice, liquefied soluble cassava starch (with a release of appreciable glucose quantity), and partially de-stained white fabric.

Conclusions

The amylase obtained from the submerged fermentation of Pleurotus tuberregium has potential applications in food and detergent industries.

Enhancing thermostabilization of a newly discovered α-amylase from Bacillus cereus GL96 by combining computer-aided directed evolution and site-directed mutagenesis

This study has described the characterization of a new a-amylase from the recently isolated Bacillus cereus GL96. Subsequently, an in-silico approach was taken into account to redesign the enzyme to meet higher thermal stability. Finally, the engineered enzyme was constructed experimentally using side-directed mutagenesis (SDM) and characterized accordingly. The enzyme was stable over pH 4-11, with the highest activity at 9.5. The temperature profile of the wild-type enzyme showed optimum activity at 50 °C plus 40% of stability at temperatures up to 70 °C. The in-silico result was indicated D162W, D162R, and D162K as the three stabilizing mutations. Among them, D162K showed better results, especially in the molecular dynamics simulation, and therefore, it was constructed by SDM. This variant was shown 5 °C higher optimum temperature (55 °C) with increasing activity than the native enzyme. In addition, it was significantly more stable than the native form. For example, while the latter almost wholly lost its function at a temperature above 70 °C, the D162K can retain more than 40% of its initial activity up to 80 °C. Considering the promising properties that the mutant enzyme showed, it can be considered for further investigation to meet the industrial requirement completely.

A highly stable raw starch digesting α-amylase from Nile tilapia (Oreochromis niloticus) viscera

A raw starch digesting α-amylase from Nile tilapia (Oreochromis niloticus) intestine was identified. The α-amylase, AMY-T, had an estimated molecular weight of 60 kDa and purified to near homogeneity. AMY-T showed an apparent K_M 4.78 mg/mL and V_max 0.44 mg/mL/min) towards soluble starch. It was highly stable for 24 h in the pH range 3.0-10.0, and to solvents like methanol, isopropanol, butanol, dimethylformamide, DMSO and ethyl-ether. AMY-T was able to digest different carbohydrates, mainly showing endo-activity. Importantly, AMY-T was catalytically efficient and adsorbing towards raw potato starch at temperature documented for other raw starch digesting α-amylases. Thin layer and anion exchange chromatography characterization showed that the end products of raw starch hydrolysis were glucose, maltose and maltodextrins, with degree of polymerisation ranging 1-8. Scanning electron microscopy analysis of the AMY-T treated starch granules documented both granular exo- and endo-attack by AMY-T. These catalytic capabilities suggest high potential for AMY-T for industrial use.

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.

Identification and characterization of thermophilic amylase producing bacterial isolates from the brick kiln soil

The present experiment was designed to isolate bacterial strains from the brick kiln soil and to check the activity and enzyme kinetics of amylase from these isolates. The bacterial colonies were isolated from soil samples through the serial dilution method. The bacterial isolates were identified through morphological, electron microscopic and molecular analysis. The 16S ribosomal RNA sequences of the isolates IR-1, IR-2, IR-3, IR-8, and IR-9 showed high similarities with Bacillus tequilensis, Bacillus paramycoides, Proteus alimentorum, Bacillus wiedmannii, and Pseudomonas aeruginosa, respectively. All of the bacterial isolates showed a positive catalase activity except IR-9. Furthermore, the isolates showed variable antagonistic effects against different bacterial pathogens. All of the strains produced indole acetic acid (IAA), and the concentrations increased in the presence of tryptophan application. The isolates showed the amylase enzyme activity and maximum activity of isolates was achieved in 4% starch concentration. The IR-9 isolate showed the highest amylase activity of 5.9 U/ml. The V max values of the extracellular amylase from different bacterial isolates ranged between 12.90 and 50.00 IU ml-1. The lowest K m value of 6.33 mg starch was recorded for IR-8 and the maximum K cat value of 2.50 min-1 was observed for IR-3. The amylase activity of the isolates was significantly affected by a range of different incubation time, temperature, and pH values. Further tests are required before the potential utilization of these isolates for amylase production, and in the biopesticide and biofertilizer applications.

Production, purification and applications of raw starch degrading and calcium-independent α-amylase from soil rich in extremophile

Calcium independent, raw starch hydrolyzing, acidic α-amylase (66 kDa) was synthesized by Bacillus subtilis S113 that is an aerobic, rod-shaped and Gram +ve bacteria. Purification of the enzyme was performed by HiTrap Capto Q (Ion-exchange chromatography; 19.28 fold; 22.41% yield). The purified enzyme was found stable at broad acidic pH (4-6.5) and high-temperature range (40-80 °C), that fulfilled the necessary criteria and laid the foundation to be utilized in starch saccharification industry. Kinetic studies of the enzyme revealed that K_m and V_max of the enzyme was 0.22% and 357.14 U/mg respectively. Scanning electron microscopy studies showed that the enzyme was capable of completely hydrolyzing raw wheat and potato starch, further confirming its role in the starch industry. It was found that only 7.93% of the activity was loss at 4 °C when kept for one year.

Response surface methodology based optimization and scale-up production of amylase from a novel bacterial strain, Bacillus aryabhattai KIIT BE-1

A novel strain KIIT BE-1 isolated from a specialized environment, screened through starch iodine test from a set of eighty-five biodigestate isolates, produced amylase maximally when cultured for 48 h at 37 °C. The molecular and biochemical characterization confirmed it as a strain of Bacillus aryabhattai. It exhibited optimal amylase activity (3.20 U/ml) at 36 h post incubation with a media combination of starch and yeast extract for C-N source respectively. Statistical optimisation by response surface modeling showed R² values of 0.9645 for biomass and 0.9831 for amylase activity, suggesting the significance of the model. The optimised medium (10.25 % starch, 5.0 % peptone, 5.18 % yeast extract, pH 7.3) enhanced the enzyme activity to 4.16 U/ml (1.39-fold) from 3.20 U/ml of un-optimised medium. Further, the biomass yield and the enzymatic activity in optimized medium and process conditions increased by 1.14 and 1.21 folds subjected to a 5 l scaled-up operation in a lab-scale bioreactor.

Catalytic and thermodynamic properties of an acidic α-amylase produced by the fungus Paecilomyces variotii ATHUM 8891

An extracellular acid stable α-amylase from Paecilomyces variotii ATHUM 8891 (PV8891 α-amylase) was purified to homogeneity applying ammonium sulfate fractionation, ion exchange and gel filtration chromatography and exhibited a reduced molecular weight of 75 kDa. The purified enzyme was optimally active at pH 5.0 and 60 °C and stable in acidic pH (3.0-6.0). K _m, v _max and k _cat for starch hydrolysis were found 1.1 g L^-1, 58.5 μmole min^-1 (mg protein)^-1, and 73.1 s^-1, respectively. Amylase activity was marginally enhanced by Ca²⁺ and Fe²⁺ ions while Cu²⁺ ions strongly inhibited it. Thermodynamic parameters determined for starch hydrolysis (Ε _α, ΔH*, ΔG*, ΔS*, Δ G E - S ∗ and Δ G E - T ∗ ) suggests an effective capacity of PV8891 α-amylase towards starch hydrolysis. Thermal stability of PV8891 α-amylase was assessed at different temperatures (30-80 ^οC). Thermodynamic parameters ( E a d , ΔH*, ΔG*, ΔS*) as well as the integral activity of a continuous system for starch hydrolysis by the PV8891 α-amylase revealed satisfactory thermostability up to 60 °C. The acidic nature and its satisfactory performance at temperatures lower than the industrially used amylases may represent potential applications of PV8891 α-amylase in starch processing industry.

Overexpression of an endogenous raw starch digesting mesophilic α-amylase gene in Bacillus amyloliquefaciens Z3 by in vitro methylation protocol

BACKGROUND

Mesophilic α-amylases function effectively at low temperatures with high rates of catalysis and require less energy for starch hydrolysis. Bacillus amyloliquefaciens is an essential producer of mesophilic α-amylases. However, because of the existence of the restriction-modification system, introducing exogenous DNAs into wild-type B. amyloliquefaciens is especially tricky.

RESULTS

α-Amylase producer B. amyloliquefaciens strain Z3 was screened and used as host for endogenous α-amylase gene expression. In vitro methylation was performed in recombinant plasmid pWB980-amyZ3. With the in vitro methylation, the transformation efficiency was increased to 0.96 × 10² colony-forming units μg^-1 plasmid DNA. A positive transformant BAZ3-16 with the highest α-amylase secreting capacity was chosen for further experiments. The α-amylase activity of strain BAZ3-16 reached 288.70 ± 16.15 U mL^-1 in the flask and 386.03 ± 16.25 U mL^-1 in the 5-L stirred-tank fermenter, respectively. The Bacillus amyloliquefaciens Z3 expression system shows excellent genetic stability and high-level extracellular production of the target protein. Moreover, the synergistic interaction of AmyZ3 with amyloglucosidase was determined during the hydrolysis of raw starch. The hydrolysis degree reached 92.34 ± 3.41% for 100 g L^-1 raw corn starch and 81.30 ± 2.92% for 100 g L^-1 raw cassava starch after 24 h, respectively.

CONCLUSION

Methylation of the plasmid DNA removes a substantial barrier for transformation of B. amyloliquefaciens strain Z3. Furthermore, the exceptional ability to hydrolyze starch makes α-amylase AmyZ3 and strain BAZ3-16 valuable in the starch industry. © 2020 Society of Chemical Industry.

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.

Purification and biochemical characterization of extracellular glucoamylase from Paenibacillus amylolyticus strain

In the present study, glucoamylase produced from a soil bacterium Paenibacillus amylolyticus NEO03 was cultured under submerged fermentation conditions. The extracellular enzyme was purified by starch adsorption chromatography and further by gel filtration, with 2.73-fold and recovery of 40.02%. The protein exhibited molecular mass of ∼66,000 Da as estimated by SDS-PAGE and depicted to be a monomer. The enzyme demonstrated optimum activity at pH range 6.0-7.0 and temperature range 30-40 °C. Glucoamylase was mostly activated by Mn²⁺ metal ions and depicted no dependency on Ca²⁺ ions. The enzyme preferentially hydrolyzed all the starch substrates. High substrate specificity was demonstrated towards soluble starch and kinetic values K_m and V_max were 2.84 mg/ml and 239.2 U/ml, respectively. The products of hydrolysis of soluble starch were detected by thin layer chromatography which showed only _D -glucose, indicating a true glucoamylase. The secreted glucoamylase from P. amylolyticus strain possesses properties suitable for saccharification processes such as biofuel production.

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.

Production, purification and characterization of raw starch hydrolyzing thermostable acidic α-amylase from hot springs, India

Alpha-amylase is an important hydrolytic enzyme used for various industrial processes. In the present study, Geobacillus bacterium (K1C), producing a thermostable α-amylase was isolated from Manikaran hot springs, India. We have purified and characterized the biochemical properties of α-amylase. The optimum temperature and pH for α-amylase activity was 80 °C and pH 6.0 respectively. The far-UV CD spectra of the enzyme indicated the presence of random coil conformation and showed an intermediate phase during temperature-induced unfolding. In the presence of substrate, thermostability of the α-amylase was increased as 50% initial activity was retained at 70 °C for 6 h and at 80 °C for 2 h. Moreover, the enzyme also showed remarkable pH stability as 90% of the initial activity was retained even after 48 h of incubation at pH 5.0, 6.0 and 7.0. Interestingly, amylase activity of the purified enzyme was Ca²⁺independent, whereas the complete inhibition of activity was observed in the presence of Cu²⁺, Pb²⁺, and Hg²⁺. The purified α-amylase was stable in the presence of detergents, organic solvents and Proteinase K. Furthermore, it exhibited the ability to hydrolyze raw starches (e.g. rice, wheat, corn, potato) efficiently; thus this enzyme has the potential to be used for industrial applications.

Effect of differential processing of the native and recombinant α-amylase from Bacillus amyloliquefaciens JJC33M on specificity and enzyme properties

AmyJ33, an α-amylase isolated from Bacillus amyloliquefaciens JJC33M, has been characterized as a non-metalloenzyme that hydrolyzes raw starch. In this work, the gene that codifies for AmyJ33 was isolated and cloned. The recombinant α-amylase (AmyJ33r) produced had a molecular weight of 72 kDa, 25 kDa higher than the native α-amylase (AmyJ33). Our results suggest that the C-terminal was processed in a different way in the native and the recombinant enzyme causing the difference observed in the molecular weight. Additionally, the enzyme activity, specificity and biochemical behavior were affected by this larger C-terminal extra region in AmyJ33r, since the enzyme lost the ability to hydrolyze raw starch compared to the native but increased its thermal stability and pH stability, and modified the profile of activity toward alkaline pH. It is suggested that the catalytic domain in recombinant enzyme, AmyJ33r, could be interfered or blocked by the amino acids involved in the C-terminal additional region producing changes in the enzyme properties.

Thioglycolic Acid-Capped CdS Quantum Dots Conjugated to α-Amylase as a Fluorescence Probe for Determination of Starch at Low Concentration

In the present research, water soluble thioglycolic acid-capped CdS quantum dots (QDs) were synthesized by chemical precipitation method. The characteristics of prepared quantum dots were determined using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). The obtained results revealed that CdS QDs have 5.60 nm crystallite size, hexagonal wurtzite structure and spherical morphology with less than 10 nm diameter. The photoluminescence (PL) spectroscopy was performed in order to study the effect of the presence of starch solutions. Blue emission peaks were positioned at 488 nm and its intensity quenched by increasing the concentration of starch solutions. The result of PL quenches in range of studied concentrations (0-100 ppm) was best described by Michaelis-Menten model. The amount of Michaelis constant (Km) for immobilized α-amylase in this system was about 68.08 ppm which showed a great tendency of enzyme to hydrolyze the starch as substrate. Finally, the limit of detection (LOD) was found to be about 2.24 ppm.

Efficient hydrolysis of raw starch and ethanol fermentation: a novel raw starch-digesting glucoamylase from Penicillium oxalicum

BACKGROUND

Starch is a very abundant and renewable carbohydrate and is an important feedstock for industrial applications. The conventional starch liquefaction and saccharification processes are energy-intensive, complicated, and not environmentally friendly. Raw starch-digesting glucoamylases are capable of directly hydrolyzing raw starch to glucose at low temperatures, which significantly simplifies processing and reduces the cost of producing starch-based products.

RESULTS

A novel raw starch-digesting glucoamylase PoGA15A with high enzymatic activity was purified from Penicillium oxalicum GXU20 and biochemically characterized. The PoGA15A enzyme had a molecular weight of 75.4 kDa, and was most active at pH 4.5 and 65 °C. The enzyme showed remarkably broad pH stability (pH 2.0-10.5) and substrate specificity, and was able to degrade various types of raw starches at 40 °C. Its adsorption ability for different raw starches was consistent with its degrading capacities for the corresponding substrate. The cDNA encoding the enzyme was cloned and heterologously expressed in Pichia pastoris. The recombinant enzyme could quickly and efficiently hydrolyze different concentrations of raw corn and cassava flours (50, 100, and 150 g/L) with the addition of α-amylase at 40 °C. Furthermore, when used in the simultaneous saccharification and fermentation of 150 g/L raw flours to ethanol with the addition of α-amylase, the ethanol yield reached 61.0 g/L with a high fermentation efficiency of 95.1 % after 48 h when raw corn flour was used as the substrate. An ethanol yield of 57.0 g/L and 93.5 % of fermentation efficiency were achieved with raw cassava flour after 36 h. In addition, the starch-binding domain deletion analysis revealed that SBD plays a very important role in raw starch hydrolysis by the enzyme PoGA15A.

CONCLUSIONS

A novel raw starch-digesting glucoamylase from P. oxalicum, with high enzymatic activity, was biochemically, molecularly, and genetically identified. Its efficient hydrolysis of raw starches and its high efficiency during the direct conversion of raw corn and cassava flours via simultaneous saccharification and fermentation to ethanol suggests that the enzyme has a number of potential applications in industrial starch processing and starch-based ethanol production.

Cloning, expression, and purification of insect (Sitophilus oryzae) alpha-amylase, able to digest granular starch, in Yarrowia lipolytica host

Raw-starch-digesting enzymes (RSDE) are of major importance for industrial applications, as their usage greatly simplifies the starch processing pipeline. To date, only microbial RSDE have gained considerable attention, since only microbial production of enzymes meets industrial demands. In this study, α-amylase from rice weevil (Sitophilus oryzae), the major rice pest, was cloned and expressed in Yarrowia lipolytica Po1g strain. The enzyme was secreted into the culture medium, and the peak activity (81 AU/L) was reached after only 29 h of culturing in 5-L bioreactors. Through simple purification procedure of ammonium sulfate precipitation and affinity chromatography, it was possible to purify the enzyme to apparent homogeneity (25-fold purification factor, at 5 % yield). The optimal conditions for the α-amylase activity were pH 5.0 and a temperature of 40 °C. The α-amylase studied here did not show any obligate requirement for Ca²⁺ ions. The recombinant α-amylase appeared to efficiently digest granular starch from pea, amaranth, waxy corn, and waxy rice.

Solid State Fermentation of a Raw Starch Digesting Alkaline Alpha-Amylase from Bacillus licheniformis RT7PE1 and Its Characteristics

The thermodynamic and kinetic properties of solids state raw starch digesting alpha amylase from newly isolated Bacillus licheniformis RT7PE1 strain were studied. The kinetic values Q_p, Y_p/s, Y_p/X, and q_p were proved to be best with 15% wheat bran. The molecular weight of purified enzyme was 112 kDa. The apparent K_m and V_max values for starch were 3.4 mg mL⁻¹ and 19.5 IU mg⁻¹ protein, respectively. The optimum temperature and pH for α-amylase were 55°C, 9.8. The half-life of enzyme at 95°C was 17h. The activation and denaturation activation energies were 45.2 and 41.2 kJ mol⁻¹, respectively. Both enthalpies (ΔH^∗) and entropies of activation (ΔS^∗) for denaturation of α-amylase were lower than those reported for other thermostable α-amylases.

Production of raw-starch-digesting α-amylase isoform from Bacillus sp. under solid-state fermentation and biochemical characterization

α-Amylase production by solid-state fermentation of different Bacillus sp. was studied previously on different fermentation media. However, no study has been reported on the influence of selected media on expression of desired amylase isoforms such as raw-starch-digesting amylase (RSDA). In this paper, the influence of different inexpensive and available agro-resources as solid media (corn, wheat and triticale) on α-amylase isoform induction from three wild-type Bacillus sp., selected among one hundred strains tested, namely 9B, 12B and 24A was investigated. For all three strains, tested amylases were detected in the multiple forms; however, number and intensity of each form differed depending on the solid media used for growth. To determine which isoform from Bacillus sp. 12B was RSDA, the suspected isoform was purified. The optimum pH for the purified α-amylase isoform was 6.0-8.0, while the optimum temperature was 60-90 °C. Isoform was considerably thermostable and Ca(2+)-independent, and actually the only α-amylase active towards raw starch. Purification and characterization of RSDA showed that not all of the solid media tested induced RSDA. From an economic point of view, it might be significant to obtain pure isoenzyme for potential use in the raw-starch hydrolysis, since it was 5 times more efficient in raw corn starch hydrolysis than the crude amylase preparation.

Altered growth and enzyme expression profile of ZnO nanoparticles exposed non-target environmentally beneficial bacteria

The extensive production and usage of nanoparticles with ultimate disposal in the environment leads to unintentional exposure of non-target environmentally beneficial bacteria thereby posing a serious threat to the native soil inhabitants. Soil microflora is an important link in the biogeochemical cycling of nutrients, affecting ecosystem functioning and productivity. This study evaluates the effect of one of the widely used nanoparticles, zinc oxide on two predominant soil bacteria, Gram-positive Bacillus subtilis and Gram-negative Pseudomonas aeruginosa with respect to their biocatalytic activities. Growth profiles of these bacteria in the presence of zinc oxide nanoparticles (ZnONPs) at a concentration of 20 ppm exhibited a prolonged lag phase in B. subtilis, whereas no significant effect was observed in the case of P. aeruginosa even at 200 ppm. Interestingly, the enzymatic profile of both the organisms was affected at non-lethal ZnONPs concentrations. The most pronounced effect was on the enzymes associated with amylolytic activity, denitrification and urea degradation wherein total inhibition of activity was noted in B. subtilis. The enzyme activities were lowered in the case of P. aeruginosa. The results presented here reiterate a critical need for exposure assessment and risk characterization of nanomaterial disposal on soil microflora while formalizing waste management strategies.

Purification and biochemical characterization of an acidophilic amylase from a newly isolated Bacillus sp. DR90

An acidophilic and Ca(2+)-independent amylase was purified from a newly isolated Bacillus sp. DR90 by ion-exchange chromatography, and exhibited a molecular weight of 68.9 kDa by SDS-PAGE. The optimum pH and temperature of the enzyme were found to be 4.0 and 45 °C, respectively. The enzyme activity was increased by Ba(2+), Fe(2+) and Mg(2+), and decreased by Hg(2+) and Zn(2+), while it was not affected by Na(+), K(+), phenylmethylsulfonyl fluoride and β-mercaptoethanol. Ca(2+) and EDTA did not have significant effect on the enzyme activity and thermal stability. The values of K m and V max for starch as substrate were 4.5 ± 0.13 mg/ml and 307 ± 12 μM/min/mg, respectively. N,N-dialkylimidazolium-based ionic liquids such as 1-hexyl-3-methylimidazolium bromide [HMIM][Br] have inhibitory effect on the enzyme activity. Thin layer chromatography analyses displayed that maltose and glucose are the main products of the enzyme reaction on starch. Regarding the features of the enzyme, it may be utilized as a novel candidate for industrial applications.

Preliminary Gene Characterization of α-Amylase from Bacillus amyloliquefaciens UMAS 1002

Characterization of α-amylase gene sequence produced by Bacillus amyloliquefaciens UMAS 1002, acellulolytic and amylolytic bacilli isolated from sago pith waste is described here. The amyE gene encoding theα-amylase was isolated by polymerase chain reaction. The 1,980 bp of amyE gene corresponding to 660 aminoacids showed 99% homology to the α-amylase sequence from Bacillus subtilis X-23 (GenBank: BAA31528).The α-amylase sequence of B. amyloliquefaciens UMAS 1002 (GenBank: KC800929) differs from that of B.subtilis X-23 by 5 amino acids. In silico analysis of α-amylase from B. amyloliquefaciens UMAS 1002 showedsimilar characteristics compared to α-amylase from B. subtilis X-23.