Impact of β-amylase degradation on properties of sugary maize soluble starch particles

Insights into the catalytic properties of 4,3-α-glucanotransferase to guide the biofabrication of α-glucans with low digestibility

The effect of the starch chain structure on 4,3-α-glucanotransferase's (4,3-α-GTase) catalytic properties was investigated to modulate the digestibility of starch. Three starches with diverse amylose contents were used, and the enzymatic kinetic reaction of 4,3-α-GTase was fitted using the Michaelis-Menten equation. The results revealed that the linear substrate was more suitable for modification by 4,3-α-GTase. Linear starch chains were then selected with various degrees of polymerization (DP) as substrates of 4,3-α-GTase modification. Additionally, the structures and in vitro digestion of 4,3-α-GTase derived α-glucans were studied. The results showed that enzyme catalysis increased the amount of α-1,3 glycosidic linkages in products (highest 33.5%), the digestibility of 4,3-α-GTase derived α-glucans conformed to a first-order two-phase equation, and the equilibrium digestibility was controlled between 43.2-72.1%. It was observed that the structure of α-glucans could be managed to attain low digestibilities (43.2%) by selecting maltodextrin with DE 2 as the substrate. These findings offer valuable insights into the fabrication of α-glucans and their potential applications in various fields.

Differentiated digestion resistance and physicochemical properties of linear and α-1,2/α-1,3 branched isomaltodextrins prepared by 4,6-α-glucanotransferase and branching sucrases

Isomaltodextrins (IMDs) are starch-based dietary fibers (DF) prepared enzymatically, which show great potential as a functional food ingredient. In this study, a series of novel IMDs with diverse structures were generated by 4,6-α-glucanotransferase GtfBΔN from Limosilactobacillus fermentum NCC 3057, combined with two α-1,2 and α-1,3 branching sucrases. Results indicated that α-1,2 and α-1,3 branching significantly improved the DF contents of α-1,6 linear products up to 60.9-62.8%. When altering the ratios of [sucrose]/[maltodextrin], IMDs containing 25.8-89.0% α-1,6 bonds, 0-59.6% α-1,2 bonds and 0-35.1% α-1,3 bonds and Mw ranged from 1967 to 4876 Da were obtained. Physicochemical property analysis showed that grafting with α-1,2 or α-1,3 single glycosyl branches can improve the solubility of the α-1,6 linear product, in which α-1,3 branched products were better. Moreover, α-1,2 or α-1,3 branching did no effect on the viscosity of the products but Mw did, the larger Mw the greater viscosity. In addition, α-1,6 linear and α-1,2 or α-1,3 branched IMDs all exhibited strong acid-heating stabilities, freeze-thaw stabilities, and good resistance to browning caused by the Maillard reaction. Branched IMDs showed excellent storage stabilities at room temperature for one year at a concentration of 60%, whereas 45% α-1,6 linear IMD precipitated quickly within 12 h. Most importantly, α-1,2 or α-1,3 branching remarkably increased the contents of resistant starch in the α-1,6 linear IMDs to 74.5-76.8%. These clear qualitative assessments demonstrated the outstanding processing and application properties of the branched IMDs and were expected to provide valuable perspectives toward the technological innovation of functional carbohydrates.

Advanced dendritic glucan-derived biomaterials: From molecular structure to versatile applications

There is considerable interest in the development of advanced biomaterials with improved or novel functionality for diversified applications. Dendritic glucans, such as phytoglycogen and glycogen, are abundant biomaterials with highly branched three-dimensional globular architectures, which endow them with unique structural and functional attributes, including small size, large specific surface area, high water solubility, low viscosity, high water retention, and the availability of numerous modifiable surface groups. Dendritic glucans can be synthesized by in vivo biocatalysis reactions using glucosyl-1-phosphate as a substrate, which can be obtained from plant, animal, or microbial sources. They can also be synthesized by in vitro methods using sucrose or starch as a substrate, which may be more suitable for large-scale industrial production. The large numbers of hydroxyl groups on the surfaces of dendritic glucan provide a platform for diverse derivatizations, including nonreducing end, hydroxyl functionalization, molecular degradation, and conjugation modifications. Due to their unique physicochemical and functional attributes, dendritic glucans have been widely applied in the food, pharmaceutical, biomedical, cosmetic, and chemical industries. For instance, they have been used as delivery systems, adsorbents, tissue engineering scaffolds, biosensors, and bioelectronic components. This article reviews progress in the design, synthesis, and application of dendritic glucans over the past several decades.

Development of phytoglycogen-derived core-shell-corona nanoparticles complexed with conjugated linoleic acid

Phytoglycogen-derived self-assembled nanoparticles (SMPG/CLA) and enzymatic-assembled nanoparticles (EMPG/CLA) were fabricated for delivery of conjugated linoleic acid (CLA). After measuring the loading rate and yield, the optimal ratio for both assembled host-guest complexes was 1 : 10, and the maximum loading rate and yield for EMPG/CLA were 1.6% and 88.1%, respectively, higher than those of SMPG/CLA. Structural characterization studies showed that the assembled inclusion complexes were successfully constructed, and had a specific spatial architecture with inner-core amorphous and external-shell crystalline parts. A higher protective effect against oxidation of EMPG/CLA was observed than that of SMPG/CLA, supporting efficient complexation for a higher order crystalline structure. After 1 h of gastrointestinal digestion under the simulated conditions, 58.7% of CLA was released from EMPG/CLA, which was lower than that released from SMPG/CLA (73.8%). These results indicated that in situ enzymatic-assembled phytoglycogen-derived nanoparticles might be a promising carrier platform for protection and targeted delivery of hydrophobic bioactive ingredients.

Molecular structure and characteristics of phytoglycogen, glycogen and amylopectin subjected to mild acid hydrolysis

The structure and properties of phytoglycogen and glycogen subjected to acid hydrolysis was investigated using amylopectin as a reference. The degradation took place in two stages and the degree of hydrolysis was in the following order: amylopectin > phytoglycogen > glycogen. Upon acid hydrolysis, the molar mass distribution of phytoglycogen or glycogen gradually shifted to the smaller and broadening distribution region, whereas the distribution of amyopectin changed from bimodal to monomodal shape. The kinetic rate constant for depolymerization of phytoglycogen, amylopectin, and glycogen were 3.45 × 10-5/s, 6.13 × 10-5/s, and 0.96 × 10-5/s, respectively. The acid-treated sample had the smaller particle radius, lower percentage of α-1,6 linkage as well as higher rapidly digestible starch fractions. The depolymerization models were built to interpret the structural differences of glucose polymer during acid treatment, which would provide guideline to improve the structure understanding and precise application of branched glucan with desired properties.

Multi-Scale Structural Insights into Enzymatically Hydrolyzed Lentil Starch Concentrates Prepared by In Vitro Method Using Different Types of Enzymes

This study was undertaken to investigate the enzymatic hydrolysis of lentil starch concentrates from conventional cooked seeds (CCLSC) by the action of different types of enzymes, including pancreatin (PC-EHSC), heat-stable α-amylase (HS-EHSC), β-amylase (βA-EHSC), amyloglucosidase (AMG-EHSC), and multi-enzymes (βA-HS-AMG-EHSC); their multi-scale structural characteristics of the enzymatic hydrolysis products of lentil starch concentrates were compared. The morphological features distinguished among different samples. The Fourier-transform infrared spectroscopy and solid-state ¹³C CP/MAS NMR spectral features indicated the possible formation of a binary and ternary complex among amylose, protein and lipids. The X-ray diffraction results revealed that the V-type characteristic diffraction peaks were more obvious for samples including PC-EHSC and βA-EHSC, which was in line with their lowest polydispersity index (DP_n). PC-EHSC and βA-EHSC also showed an increased peak intensity of the scattering maximum on the small-angle X-ray scattering spectra, whereas CCLSC exhibited an overall lower peak intensity within the studied q range of scattering. The highest XRD crystallinity and the lowest DP_n value obtained for PC-EHSC indicated that the starch polymers modified by pancreatin could produce glucan chains with a comparatively homogenous M_w distribution that are readily recrystallized by hydrogen bonding through chain aggregation. Comparatively, the lowest relative crystallinity for HS-EHSC obtained from XRD suggested that thermostable α-amylolysis was unfavorable for the formation of starch structure with a higher degree of molecular order. This study could provide useful information for the needed research to obtain a deeper understanding of the impact of different amylolysis actions on the structural organization of starch hydrolysates and to provide a theoretical foundation for the development of fermentable enzymatically hydrolyzed starch with well-tailored physiological properties.

Structural characterization of potato starch modified by a 4,6-α-glucanotransferase B from Lactobacillus reuteri E81

The recent reports have revealed that increase in amount of α-1,6 linkages by modification of potato starch with enzyme (glycosyltransferases) treatment gains slowly digestible properties to the starch; however, the formation of new α-1,6-glycosidic linkages diminish the thermal resistance of the starch granules. In this study, a putative GtfB-E81, (a 4,6-α-glucanotransferase-4,6-αGT) from L. reuteri E81 was firstly used to produce a short length of α-1,6 linkages. NMR results revealed that external short chains mostly comprised of 1-6 glucosyl units were newly produced in potato starch, and the α-1,6 linkage ratio was significantly increased from 2.9 % to 36.8 %, suggesting that this novel GtfB-E81 might have potentially an efficient transferase activity. In our study, native and GtfB-E81 modified starches showed fundamental similarities with respect to their molecular properties and treatment of native potato starch with GtfB-E81 did not remarkably change thermal stability of the potato starch, which seems to be very prominent for the food industry given the significantly decreased thermal stability results obtained for the enzyme modified starches reported in the literature. Therefore, the results of this study should open up emerging perspectives for regulating slowly digestible characteristics of potato starch in future studies without a significant change in the molecular, thermal, and crystallographic properties.

Biosynthesis of maltodextrin-derived glucan dendrimer using microbial branching enzyme

Glucan dendrimers were developed with microbial branching enzyme (BE) treated maltodextrin. The molecular weight (M_w) of recombinant BE was 79.0 kDa, and its optimum activity was observed at pH 7.0 and 70 °C. BE converted different maltodextrins with dextrose equivalent value of 6 (MD6), 12 (MD12), or 19 (MD19) into the given glucan dendrimers, along with the marked increment of the molecular density (approximately 30-60 folds) and α-1,6 linkage percentage (up to 7.3-9.7%). Among three glucan dendrimers, the enzyme-treated MD12 showed a more homogeneous M_w distribution with the maximum M_w of 5.5 × 10⁶ g/mol, indicating that higher substrate catalytic specificity of BE for MD12 substrate. During transglycosylation with MD12 for 24 h, the shorter chains (degree of polymerization, DP < 13) increased from 73.9% to 83.0%, accompanying by a reduction of medium chains (DP13-24) and long chains (DP > 24). Moreover, the slowly digestible and resistant nutritional fractions were increased by 6.2% and 12.5%, respectively. The results suggested that the potentiality of BE structuring glucan dendrimer with tailor-made structure and functionality for industrial application.

Fabrication of phytoglycogen-derived core-shell nanoparticles: Structure and characterizations

The objective of this work was to investigate the fabrication of core-shell nanoparticles using phosphorylase-catalyzed chain extension of phytoglycogen, and to analyze the changes of structure and characterizations in detail. During the glucosylation reaction, the inorganic phosphate increased substantially up to 2.3 mg/mL in the initial 12 h, and then increased incrementally to 2.5 mg/mL at 24 h. The similar to trends was observed for increasing Mw and Rz over time, due to glucosyl transfers on the surface chain to form a corona around the phytoglycogen core with a larger size. Phosphorylase modification increases the percentages of longer chain fractions and the average chain length increased from degree of polymerization (DP) 11.6 to DP 48.2. The modified phytoglycogen exhibited the characteristic of B-type crystalline structure, indicating that the specific core-shell nanoparticle with inner amorphous nature and outer crystalline layer. The above results revealed that the potentiality of enzymatic chain elongation of phytoglycogen to design novel core-shell nanoparticle with tailor-made structure and functionality.

Biomimetic synthesis of maltodextrin-derived dendritic nanoparticle and its structural characterizations

The maltodextrin-derived dendritic nanoparticle was fabricated using microbial branching enzyme and its structural characterizations were investigated. During biomimetic synthesis, molecular weight distribution of maltodextrin substrate with 6.8 × 10⁴ g/mol shifted to the narrower and uniform distribution region with the larger molecular weight up to 6.3 × 10⁶ g/mol (MD12). The enzyme-catalyzed product had the larger size, higher molecular density as well as higher percentage of α-1,6 linkage, accompanying by more chain accumulations of DP 6-12 and disappearance of DP > 24, suggesting the biosynthesized glucan dendrimer had a compact tighter branched structure. The interaction of molecular rotor CCVJ and local structure of dendrimer was monitored, displaying there was a higher intensity related with the numerous nano-pockets at the branch points of MD12. The maltodextrin-derived dendrimers had the single spherical particulate shape with the size range of 10-90 nm. The mathematical models were also established to reveal the chain structuring during enzymatic reaction. The above results showed that the biomimetic strategy for novel dendritic nanoparticle with controllable structure arising from branching enzyme treated maltodextrin, which would help to enlarge the panel of available dendrimer.

Identifying Signal-Crosstalk Mechanism in Maize Plants during Combined Salinity and Boron Stress Using Integrative Systems Biology Approaches

Combined stress has been seen as a major threat to world agriculture production. Maize is one of the leading cereal crops of the world due to its wide spectrum of growth conditions and is moderately sensitive to salt stress. A saline soil environment is a major factor that hinders its growth and overall yield and causes an increase in the concentration of micronutrients like boron, leading to excess over the requirement of the plant. Boron toxicity combined with salinity has been reported to be a serious threat to the yield and quality of maize. The response signatures of the maize plants to the combined effect of salinity and boron stress have not been studied well. We carried out an integrative systems-level analysis of the publicly available transcriptomic data generated on tolerant maize (Lluteño maize from the Atacama Desert, Chile) landrace under combined salt and boron stress. We identified significant biological processes that are differentially regulated in combined salt and boron stress in the leaves and roots of maize, respectively. Protein-protein interaction network analysis identified important roles of aldehyde dehydrogenase (ALDH), galactinol synthase 2 (GOLS2) proteins of leaf and proteolipid membrane potential regulator (pmpm4), metallothionein lea protein group 3 (mlg3), and cold regulated 410 (COR410) proteins of root in salt tolerance and regulating boron toxicity in maize. Identification of transcription factors coupled with regulatory network analysis using machine learning approach identified a few heat shock factors (HSFs) and NAC (NAM (no apical meristem, Petunia), ATAF1-2 (Arabidopsis thaliana activating factor), and CUC2 (cup-shaped cotyledon, Arabidopsis)) family transcription factors (TFs) to play crucial roles in salt tolerance, maintaining reactive oxygen species (ROS) levels and minimizing oxidative damage to the cells. These findings will provide new ways to design targeted functional validation experiments for developing multistress-resistant maize crops.

Curdlan production from cassava starch hydrolysates by Agrobacterium sp. DH-2

Curdlan is an edible microbial polysaccharide and can be used in food, biomedical and biomaterial fields. To reduce the cost of curdlan production, this study investigated the suitability of cassava starch hydrolysates as carbon source for curdlan production. Cassava starch was hydrolyzed into maltose syrup using β-amylase and pullulanase at various enzyme dosages, temperature, time and addition order of two enzymes. The maltose yield of 53.17% was achieved at starch loading 30% by simultaneous addition β-amylase 210 U/g starch and pullulanase 3 U/g starch at 60 °C for 9 h. Cassava starch hydrolysates were used as carbon source for curdlan production by Agrobacterium sp. DH-2. The curdlan production reached 28.4 g/L with the yield of 0.79 g/g consumed sugar and molecular weight of 1.26 × 10⁶ Da at 96 h with cassava starch hydrolysate at 90 g/L initial sugar concentration. Curdlan produced from cassava starch hydrolysates was characterized using FT-IR spectra and thermo gravimetric analysis. This work indicated that cassava starch was a potential renewable feedstock for curdlan production.

Development of dendrimer-like glucan-stabilized Pickering emulsions incorporated with β-carotene

The impact of sugary maize dendrimer-like glucan octenyl succinate (OSA-SMDG) on the storage stability and antioxidant activity of β-carotene (BC)-loaded emulsions as well as bioaccessibility were investigated. The encapsulation efficiency of β-carotene in emulsions containing 3% OSA-SMDG (3OSA-SMDG-BC) or 5% OSA-SMDG (5OSA-SMDG-BC) was 89.6% and 94.9%, respectively. The antioxidant activity of both emulsions was higher than that of pure β-carotene. During simulated digestion, the particle size of emulsions was immediately reduced, whereas zeta-potential was continuously increased in intestinal digestion. After 2 h digestion, the free fatty acids (FFA) release rate of 3OSA-SMDG-BC and 5OSA-SMDG-BC was significantly higher than that of blank emulsion. Bioaccessibility of β-carotene encapsulated in 3OSA-SMDG-BC and 5OSA-SMDG-BC was also significantly higher than that of blank emulsion. FFA release rate and β-carotene bioaccessibility of 5OSA-SMDG-BC were higher than that of 3OSA-SMDG-BC. These results demonstrated that OSA-SMDG could be used to fabricate food-grade O/W Pickering emulsion as a delivery system for bioactive compounds.

Stimulus-Responsive Nanoconjugates Derived from Phytoglycogen Nanoparticles

Plant-derived phytoglycogen nanoparticles (PhG NPs) have the advantages of size uniformity, dispersibility in water, excellent lubrication properties, and lack of cytotoxicity; however, their chemical functionalization may lead to loss of NP structural integrity. Here, we report a straightforward approach to the generation of PhG NP conjugates with biologically active molecules. Hydrogen bonding of bovine serum albumin with electroneutral PhG NPs endows them with additional ligand binding affinity and enables the electrostatically governed attachment of methotrexate (MTX), a therapeutic agent commonly used in the treatment of cancer and arthritis diseases, to the protein-capped NPs. We showed stimuli-responsive release of MTX from the PhG-based nanoconjugates under physiological cues such as temperature and ionic strength. The results of this study stimulate future exploration of biomedical applications of nanoconjugates of PhG NPs.

Expression, biochemical and structural characterization of high-specific-activity β-amylase from Bacillus aryabhattai GEL-09 for application in starch hydrolysis

BACKGROUND

β-amylase (EC 3.2.1.2) is an exo-enzyme that shows high specificity for cleaving the α-1,4-glucosidic linkage of starch from the non-reducing end, thereby liberating maltose. In this study, we heterologously expressed and characterized a novel β-amylase from Bacillus aryabhattai.

RESULTS

The amino acid-sequence alignment showed that the enzyme shared the highest sequence identity with β-amylase from Bacillus flexus (80.73%) followed by Bacillus cereus (71.38%). Structural comparison revealed the existence of an additional starch-binding domain (SBD) at the C-terminus of B. aryabhattai β-amylase, which is notably different from plant β-amylases. The recombinant enzyme purified 4.7-fold to homogeneity, with a molecular weight of ~ 57.6 kDa and maximal activity at pH 6.5 and 50 °C. Notably, the enzyme exhibited the highest specific activity (3798.9 U/mg) among reported mesothermal microbial β-amylases and the highest specificity for soluble starch, followed by corn starch. Kinetic analysis showed that the K_m and k_cat values were 9.9 mg/mL and 116961.1 s^- 1, respectively. The optimal reaction conditions to produce maltose from starch resulted in a maximal yield of 87.0%. Moreover, molecular docking suggested that B. aryabhattai β-amylase could efficiently recognize and hydrolyze maltotetraose substrate.

CONCLUSIONS

These results suggested that B. aryabhattai β-amylase could be a potential candidate for use in the industrial production of maltose from starch.

Cold Atmospheric Pressure Plasma Treatment of Maize Grains-Induction of Growth, Enzyme Activities and Heat Shock Proteins

Zea mays L. is one of the most produced crops, and there are still parts of the world where maize is the basic staple food. To improve agriculture, mankind always looks for new, better methods of growing crops, especially in the current changing climatic conditions. Cold atmospheric pressure plasma (CAPP) has already showed its potential to enhance the culturing of crops, but it still needs more research for safe implementation into agriculture. In this work, it was shown that short CAPP treatment of maize grains had a positive effect on the vitality of grains and young seedlings, which may be connected to stimulation of antioxidant and lytic enzyme activities by short CAPP treatment. However, the prolonged treatment had a negative impact on the germination, growth, and production indexes. CAPP treatment caused the increased expression of genes for heat shock proteins HSP101 and HSP70 in the first two days after sowing. Using comet assay it was observed that shorter treatment times (30-120 s) did not cause DNA damage. Surface diagnostics of plasma-treated grains showed that plasma increases the hydrophilicity of the surface but does not damage the chemical bonds on the surface.

Development of a novel starch-based dietary fiber using glucanotransferase

In this study, a glucanotransferase from prokaryotic Azotobacter chroococcum NCIMB 8003 was recombinantly expressed and its biochemical characteristics and bioconversion ability for starch were investigated. The purified enzyme has the optimum activity at 55 °C and pH 6.5-7.0, as well as a melting temperature of 62 °C. The double-charged ion Ca2+ stimulated the activity of the enzyme by approximately 2.4 times. The kinetic parameters and specificity analysis revealed that this glucanotransferase had a higher affinity for high-amylose starch. During the transglycosylation reaction, the starch molecule was converted into a relatively small polymer with a narrow size distribution. For the enzyme modification of high-amylose starch for 72 h, the amount of α-1,6 linkages increased from 1.9% to 22.7% and the content of resistant starch (RS) increased from 3.18% to 17.83%. In addition, the fine structure displayed the reuteran-like highly branched glucan linked by single linear α-1,6 linkages and α-1,4/6 branching points. These results revealed that a promising prebiotic dietary fiber was synthesized from starch with glucanotransferase modification.

Chemical Modification of Sweet Potato β-amylase by Mal-mPEG to Improve Its Enzymatic Characteristics

The sweet potato β-amylase (SPA) was modified by 6 types of methoxy polyethylene glycol to enhance its specific activity and thermal stability. The aims of the study were to select the optimum modifier, optimize the modification parameters, and further investigate the characterization of the modified SPA. The results showed that methoxy polyethylene glycol maleimide (molecular weight 5000, Mal-mPEG5000) was the optimum modifier of SPA; Under the optimal modification conditions, the specific activity of Mal-mPEG5000-SPA was 24.06% higher than that of the untreated SPA. Mal-mPEG5000-SPA was monomeric with a molecular weight of about 67 kDa by SDS-PAGE. The characteristics of Mal-mPEG5000-SPA were significantly improved. The K_m value, V_max and Ea in Mal-mPEG5000-SPA for sweet potato starch showed that Mal-mPEG5000-SPA had greater affinity for sweet potato starch and higher speed of hydrolysis than SPA. There was no significant difference of the metal ions’ effect on Mal-mPEG5000-SPA and SPA.

Properties and applications of starch modifying enzymes for use in the baking industry

Enzyme technology has many potential applications in the baking industry because carbohydrate-active enzymes specifically react with carbohydrate components, such as starch, in complex food systems. Amylolytic enzymes are added to starch-based foods, such as baking products, to retain moisture more efficiently and to increase softness, freshness, and shelf life. The major reactions used to modify the structure of food starch include: (1) hydrolysis of α-1, 4 or α-1, 6 glycosidic linkages, (2) disproportionation by the transfer of glucan moieties, and (3) branching by formation of α-1, 6 glycosidic linkage. The catalytic reaction of a single enzyme or a mixture of more than two enzymes has been applied, generating novel starches, with chemical changes in the starch structure, in which the changes of molecular mass, branch chain length distribution, and the ratio of amylose to amylopectin may occur. These developments of enzyme technology highlight the potential to create various structured-starches for the food and baking industry.

Physical structure and absorption properties of tailor-made porous starch granules produced by selected amylolytic enzymes

Porous starch granules (PSGs) with various pores and cavity sizes were prepared by amylolysis enzymes. The greatest hydrolysis rate on corn starch granule was observed with α-amylase, followed by gluco- and β-amylases. Temperature increase enhanced glucoamylase reaction rate more drastically than other enzyme treatments. Final hydrolysis level with glucoamylase reached to 66.9%, close to 67.5% of α-amylolysis. The α-amylase-treated PSGs displayed the greatest pore size and ratio of cavity-to-granule diameters. Gelatinization onset temperatures of PSGs increased to 72.1 (α-), 68.7 (β-), and 68.1°C (gluco-amylolysis) after 8 h; enthalpy changes of β- and gluco-amylase-treated PSGs increased to 13.4, and 13.1 J/g but α-amylase-treated one showed slightly reduced value of 8.5 J/g. Water holding capacities of PSGs were 209.7 (α-), 94.6 (β-), and 133.8% (gluco-amylolysis), and the untreated control had 89.1%; oil holding capacities of them showed 304.5, 182.7, and 211.5%, respectively, while the untreated control had 161.8%. Thus, enzyme types and their reaction conditions can be applied to generate desirable cavity and pore sizes in starch granules. This biocatalytic approach could contribute to develop tailor-made PSGs with distinct internal structure for specific uses in wide range of food, pharmaceutical and other industrial applications.

Catalytic hydrolysis of starch for biohydrogen production by using a newly identified amylase from a marine bacterium Catenovulum sp. X3

An identified cold-adaptive, organic solvents-tolerant alkaline α-amylase (HP664) from Catenovulum sp. strain X3 was heterologously expressed and characterized in E. coli, and it was further applied to starch saccharification for biohydrogen production. The recombinant HP664 belongs to a member of glycoside hydrolase family 13 (GH13), with a molecular weight of 69.6kDa without signal peptides, and also shares a relatively low similarity (49%) to other reported amylases. Biochemical characterization demonstrated that the maximal enzymatic activity of HP664 was observed at 35°C and pH 9.0. Most metal ions inhibited its activity; however, low polar organic solvents (e.g., benzene and n-hexane) could enhance the activity by 35-50%. Additionally, HP664 also exhibited the catalytic capability on various polysaccharides, including potato starch, amylopectin, dextrin and agar. In order to increase the bioavailability of starch for H₂ production, HP664 was utilized to elevate fermentable oligosaccharide level, and the results revealed that the maximal hydrolytic percentage of starch was up to 44% with 12h of hydrolysis using 5.63U of HP664. Biohydrogen fermentation of the starch hydrolysate by Clostridium sp. strain G1 yielded 297.7mL of H₂ after 84h of fermentation, which is 3.73-fold higher than the control without enzymatic treatment of HP664.

Identification of an α-(1,4)-Glucan-Synthesizing Amylosucrase from Cellulomonas carboniz T26

Amylosucrase, catalyzing the synthesis of α-(1,4)-glucan from sucrose, has been widely studied and used in carbohydrate biotransformation because of its versatile activities. In this study, a novel amylosucrase was characterized from Cellulomonas carboniz T26. The recombinant enzyme was overexpressed in Escherchia coli and purified by nickel affinity chromatography. It was determined to be a monomeric protein with a molecular mass of 72 kDa. The optimum pH and temperature for transglucosylation were measured to be pH 7.0 and 40 °C. The transglucosylation activity was significantly higher than the hydrolytic activity. The main product generated from sucrose was structurally determined to be α-(1,4)-glucan. A small amount of glucose was produced by hydrolysis, and sucrose isomers including turanose and trehalulose were generated as minor products. The ratio of hydrolytic, polymerization, and isomerization reactions was calculated to be 5.8:84.0:10.2. The enzyme favored production of long-chain insoluble α-glucan at lower temperature.

Characterization of thermostable β-amylase isozymes from Lactobacillus fermentum

A strain of Lactobacillus fermentum producing two isozymes of a 20kDa β-amylase was isolated from the faecal sample of a newborn. The starin was identified by sequencing its 16S rRNA gene. The two β-amylase isozymes were resolved and visualized by two dimensional protein gel electrophoresis (2-D gel electrophoresis). Some of the physical and biochemical properties of the enzymes were characterized. The β-amylase displayed two optimum pH s, 5.0 and 10.0 and two optimum temperatures, 45°C and 37°C, respectively. The isozymes hydrolyzed different substrates: glycogen at pH 5.0, and corn starch at pH 10.0. The activity did not require Ca²⁺, though the activity at pH 10.0 was enhanced in the presence of 5.0mM and 10.0mM CaCl_2, 110% and 130%, respectively.

Identification of Key Proteins and Networks Related to Grain Development in Wheat (Triticum aestivum L.) by Comparative Transcription and Proteomic Analysis of Allelic Variants in TaGW2-6A

In wheat, coding region allelic variants of TaGW2-6A are closely associated with grain width and weight, but the genetic mechanisms involved remain unclear. Thus, to obtain insights into the key functions regulated by TaGW2-6A during wheat grain development, we performed transcriptional and proteomic analyses of TaGW2-6A allelic variants. The transcription results showed that the TaGW2-6A allelic variants differed significantly by several orders of magnitude. Each allelic variant of TaGW2-6A reached its first transcription peak at 6 days after anthesis (DAA), but the insertion type TaGW2-6A allelic variant reached its second peak earlier than the normal type, i.e., at 12 DAA rather than 20 DAA. In total, we identified 228 differentially accumulated protein spots representing 138 unique proteins by two-dimensional gel electrophoresis and tandem MALDI-TOF/TOF-MS in these three stages. Based on the results, we found some key proteins that are closely related to wheat grain development. The results of this analysis improve our understanding of the genetic mechanisms related to TaGW2-6A during wheat grain development as well as providing insights into the biological processes involved in seed formation.

Synthesis, characterization, and antibacterial property of novel starch derivatives with 1,2,3-triazole

Four novel starch-linked-1,2,3-triazole derivatives were synthesized including 6-hydroxymethyltriazole-6-deoxy starch (HMTST), 6-bromomethyltriazole-6-deoxy starch (BMTST), 6-chloromethyltriazole-6-deoxy starch (CMTST), and 6-carboxyltriazole-6-deoxy starch (CBTST). Their antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were evaluated in vitro, respectively. The inhibitory property of the obtained amphiprotic starch derivatives exhibited a remarkable improvement over starch. And the antibacterial indices of most of the products were higher than 60% and 40% at 1.0 mg/mL when the culture time was 8 h and 16 h, respectively. Moreover, the inhibitory index of CBTST attained 97% above at 1.0 mg/mL. Generally, the inhibitory activity decreased in the order: CBTST>CMTST>BMTST>HMTST>starch. Furthermore, the order of their antibacterial activity was consistent with the electron-withdrawing property of different substituted groups of the 1,2,3-triazole groups. The substituted groups with stronger electron withdrawing ability relatively possessed greater antibacterial activity.

Controlled biodegradation of polymers using nanoparticles and its application

Controlled biodegradation mechanism has been revealed using different nanoparticles which eventually regulate pH of media.