Cereal α-amylases—an overview

Impact of Rye Malt with Various Diastatic Activity on Wholegrain Rye Flour Rheology and Sugar Formation in Scalding and Fermentation Processes

Amylase activity in rye flour plays a crucial role in the production of rye bread. When preparing a scald in rye bread production, diastatic rye malt is utilized to augment the amylase activity of the rye flour. This study investigated the effects of the diastatic power (DP) and concentration of rye malt on the Falling Number (FN) and the rheological properties of rye flour. Additionally, it examined reducing sugars in the scalding process and fermentation. Mixolab results provided comprehensive data on dough properties at different temperature stages, highlighting significant changes in starch gelatinization and enzyme activity due to varying malt diastatic power and concentrations. The decline in the gelatinization index (C3-C2) indicated faster starch gelatinization with increased diastatic power. Adding rye malt significantly increased maltose content in the saccharified and fermented scald, promoting a favorable environment for lactic acid bacteria and yeasts. FN and Amylograph results showed that less active malt (DP 170, 179 °WK), at a 1.5% concentration, could achieve similar effects as the more active malt (DP 362, 408 °WK) at 0.5%. Adding rye malt to rye flour allows for the regulation of the flour's rheological properties and FN, adjustable based on malt DP and concentration.

Effect of Microwave Treatment on Protease Activity, Dough Properties and Protein Quality in Sprouted Wheat

In this study, the effects of microwave treatment on protease activity, dough properties and protein quality in sprouted wheat were investigated. Microwave treatment led to a significant (p < 0.05) reduction in protease activity in sprouted wheat. Proteases with a pH optimum of 4.4 (cysteine proteinases) were more susceptible to microwave heating, which contributed mostly to protease inactivation. Significant improvements (p < 0.05) in the dough properties and gluten quality of sprouted wheat were observed, which are probably attributable to the synergistic effectiveness of protease inactivation and heat-induced gluten cross-linking. After microwave treatment, the decrease in the solubility and extractability of protein in sprouted wheat indicated protein polymerization, which was induced by intermolecular disulfide bond cross-linking. The changes in gliadin were less pronounced due to the relatively low temperature of the microwave treatment. The cross-linking in sprouted wheat that occurred after microwave treatment seemed to mainly involve glutenin, especially B/C low-molecular-weight glutenin subunits (B/C-LMW-GSs) in the range of 30-50 kD.

Structure and functional characteristics of starch from different hulled oats cultivated in China

This work aimed to evaluate the structure and functional characteristics of starch from ten hulled oat cultivars grown in different locations in China. The protein, phosphorus, amylose, and starch contents were 0.2-0.4 %, 475.7-691.8 ppm, 16.2-23.0 %, and 93.6-96.7 %, respectively. All the starches showed irregular polygonal shapes and A-type crystallization with molecular weights ranging from 7.2 × 107 to 4.5 × 108 g/mol. The amounts of amylopectin A (DP 6-12), B1 (DP 13-24), B2 (DP 25-36), and B3 (DP > 36) chains were in the ranges of 10.3-16.0 %, 54.5-64.8 %, 16.5-21.1 %, and 4.9-13.1 %, respectively. The starches differed significantly in gelatinization temperatures, pasting viscosity, solubility, swelling power, rheological properties, and digestion parameters. The results revealed that the larger particle size could increase the peak viscosity of the starch paste. The presence of phosphorus increased the gelatinization temperature and enhanced the resistant starch content. The starch granules with higher crystallinity contained a higher proportion of phosphate, which increased final viscosity and setback viscosity but decreased rapidly digestible starch. Overall, oat starch with a high phosphorus content could be used to prepare low-glycemic-index food for diabetes patients.

Effect of wheat roasting conditions and wheat type on short-wave infrared (SWIR) spectral data of whole and milled wheat by ANOVA-simultaneous component analysis

ANOVA-simultaneous component analysis (ASCA) was used to investigate the effect of roasting and wheat type on shortwave-infrared (SWIR) spectra of whole wheat and flour through assessment of statistical significance and characterisation of the contributing spectral features. The full factorial experimental design included two wheat types, three roasting temperatures and three roasting frequencies. SWIR spectral images were collected from the two roasted wheat types and their two milled samples. Three ASCA models, one for each wheat conformation (kernel, whole wheat flour, white flour) were investigated. It was evidenced that all factors and interaction in the whole wheat flour model had a significant (p ≤ 0.05) effect on spectral data. Only the factor roasting frequency was not significant in white flour model and only the interaction between roasting frequency and wheat type was not significant for the kernel model. The main variations in the loading line plots were identified and characterised by chemical structural differences that occur within the sample. The effect of roasting frequency had a more adverse effect on protein stability, moisture evaporation, water soluble carbohydrates and aromatic amino acids, compared to roasting temperature. A Rapid Visco-Analyser (RVA) was used to further investigate difference in wheat type as almost all spectral data sets differed significantly. The most prominent difference between the two wheat types was observed as differences in amylase activity and presence of lipids. ASCA applied to SWIR whole wheat and flour spectral data effectively characterised the significant effect of roasting on wheat starch and protein structures.

α-Amylase purified and characterized from fenugreek (Trigonella foenum-graecum) showed substantial anti-biofilm activity against Staphylococcus aureus MTCC740

Starch hydrolyzing α-amylase from germinated fenugreek (Trigonella foenum-graecum) has been purified 104-fold to apparent electrophoretic homogeneity with a final specific activity of 297.5 units/mg. SDS-PAGE of the final preparation revealed a single protein band of 47.5 kDa, supported by LC/MS analysis and size-exclusion chromatography on the Superdex 200 (ÄKTA-FPLC). α-Amylase exhibited maximum activity at pH 5.5. An activation energy (Ea) of 9.12 kcal/mol was found to exist in the temperature range of 20 to 90 °C. When substrate concentrations were evaluated between 0.5 and 10 mg/mL, the Km and Vmax values for starch were observed to be 1.12 mg/mL and 384.14 μmol/min/mg, respectively. The major substrate starch exhibited high specificity for fenugreek α-amylase. In the presence of EDTA (5 mM), the activity was lost, however, it could be largely reversed with the addition of calcium. Furthermore, an effort was made to assess the ability of fenugreek seed-derived partially purified (DEAE-cellulose enzyme) and purified α-amylase to disperse inside 48 h-old biofilms of Staphylococcus aureus MTCC740. The outcomes clearly demonstrated that the purified and partially purified α-amylase both exhibited strong biofilm dispersion activity.

Structure, in vitro starch digestibility and physicochemical properties of starch isolated from germinated Bambara groundnut

This study investigated the effect of germination time (0, 24, 48 and 72 h) on the physicochemical characteristics, in vitro starch digestibility and microstructural changes in Bambara groundnut starch. The starch yield, lightness (L*) value, amylose content and resistant starch contents of isolated starches decreased significantly (p ≤ 0.05) with increasing germination time. Scanning electron microscopy revealed that starch from raw and germinated Bambara grains were smooth with no evidence of starch degradation and were mainly oval shaped, with some granule's irregular and kidney shaped. Water absorption capacity (1.33-1.90 g/g), swelling power (2.12-16.53 g/g), solubility index (1.14-13.04 g/g), and dispersibility (75.92-86.47%) greatly increased as germination timed increased. Germination did not alter the X-ray diffraction pattern (Type-A) but increased the relative crystallinity of the starches. The peak gelatinization temperatures (73.23-73.91 °C) of starch from germinated Bambara were significantly higher than native starch (72.81 °C). Native starch and starch from germinated Bambara grains had substantially high proportion of resistant starch (approx. 73%) and high pasting temperatures (approx. 88 °C). Conclusively, germination significantly changed starch structure at molecular level and impacted functionality.

Plant responses to hypergravity: a comprehensive review

Hypergravity is an effective novel stimulus to elucidate plant gravitational and mechanobiological behaviour. Here, we review the current understanding of phenotypic, physio-biochemical, and molecular plant responses to simulated hypergravity. Plants readily respond to altered gravity conditions, such as microgravity or hypergravity. Hypergravity-a gravitational force higher than that on the Earth's surface (> 1g)-can be simulated using centrifuges. Exposing seeds, seedlings, or plant cell cultures to hypergravity elicits characteristic morphological, physio-biochemical, and molecular changes. While several studies have provided insights into plant responses and underlying mechanisms, much is still elusive, including the interplay of hypergravity with gravitropism. Moreover, hypergravity is of great significance for mechano- and space/gravitational biologists to elucidate fundamental plant behaviour. In this review, we provide an overview of the phenotypic, physiological, biochemical, and molecular responses of plants to hypergravity. We then discuss the involvement of hypergravity in plant gravitropism-the directional growth along the gravity vector. Finally, we highlight future research directions to expand our understanding of hypergravity in plant biology.

Impact of Sunflower Meal Protein Isolate Supplementation on Pasta Quality

Globally, there is an increased demand for plant- and animal-derived proteins. However, animal-derived proteins are still expensive and expected to negatively impact the environment. Sunflower seeds, an excellent source of proteins, are one of the most critical oilseeds produced in the world markets. This study used sunflower meal protein isolate (SMPI), wheat flour (WF), and their blends to make pasta with good sensory features and higher nutritional value. The chemical and amino acid compositions, rheological properties, color attributes, cooking quality, sensory properties, and texture analysis of pasta were evaluated. SMPI showed a high protein content (87.12%) compared to WF (10.90%). The pasta was made from WF with supplementing SMPI at three concentrations (3.0, 6.0, and 9.0% w/w) to improve the nutritional quality. Farinograph parameters showed that water absorption, arrival time, dough development time, mixing tolerance index, dough weakening, and dough stability increased as the percentage of SMPI in the blends increased. The results also showed that the color (L*, a*, and b*) of pasta samples was darker as the mixing level of SMPI increased. The obtained sensorial results confirmed this result. The cooking quality of pasta revealed that the weight, volume, and cooking loss of prepared pasta with SMPI (3.0–9.0%) increased compared to the control sample (pasta with 100% WF). Moreover, sensory evaluation of pasta revealed that all samples were acceptable. Nonetheless, mouth feel and overall acceptability of pasta reinforced with 3.0 and 6.0% SMPI did not notably impact the pasta compared to the control sample, while flavor did not significantly influence the pasta with 3.0% SMPI. These findings demonstrated that pasta supplemented with SMPI could benefit the pasta industry, which requires a suitable technological process to obtain novel products.

Holistic View of Starch Chemistry, Structure and Functionality in Dry Heat-Treated Whole Wheat Kernels and Flour

Heat treatment is used as a pre-processing step to beneficially change the starch properties of wheat flour to enhance its utilisation in the food industry. Heat-treated wheat flour may provide improved eating qualities in final wheat-based products since flour properties predominantly determine the texture and mouthfeel. Dry heat treatment of wheat kernels or milled wheat products involves heat transfer through means of air, a fluidising medium, or radiation—often resulting in moisture loss. Heat treatment leads to changes in the chemical, structural and functional properties of starch in wheat flour by inducing starch damage, altering its molecular order (which influences its crystallinity), pasting properties as well as its retrogradation and staling behaviour. Heat treatment also induces changes in gluten proteins, which may alter the rheological properties of wheat flour. Understanding the relationship between heat transfer, the thermal properties of wheat and the functionality of the resultant flour is of critical importance to obtain the desired extent of alteration of wheat starch properties and enhanced utilisation of the flour. This review paper introduces dry heat treatment methods followed by a critical review of the latest published research on heat-induced changes observed in wheat flour starch chemistry, structure and functionality.

Sprouting of Sorghum (Sorghum bicolor [L.] Moench): Effect of Drying Treatment on Protein and Starch Features

The nutritional and physicochemical properties of sorghum proteins and starch make the use of this cereal for food production challenging. Sprouting is a cost-effective technology to improve the nutritional and functional profile of grains. Two drying treatments were used after sorghum sprouting to investigate whether the drying phase could improve the protein and starch functionalities. Results showed that the drying treatment at lower temperature/longer time (40 °C for 12 h) extended the enzymatic activity that started during sprouting compared to the one performed at higher temperature/shorter time (50 °C for 6 h). An increased protein hydrolysis and water- and oil-holding capacity were found in the flour obtained by the former treatment. Higher protein matrix hydrolysis caused high exposure of starch to enzymes, thus increasing its digestibility, while worsening the technological functionality. Overall, modulating drying conditions could represent a further way, in addition to sprouting, to improve sorghum flour’s nutritional profile.

Purification and characterization of thermostable α-amylase from germinating Sword bean (Canavalia gladiata (Jacq.) DC.) seeds

The thermostable α-amylase from germinating sword bean (Canavalia gladiata (Jacq.) DC.) seeds (CgAmy) was successfully purified by a combination of ammonium sulphate fractionation and Epoxy-activated Sepharose 6B affinity chromatography. The purified α-amylase showed 507.8 fold with a specific activity of 750.0 U/mg. SDS-PAGE of the purified enzyme revealed a single protein band of 50.0 kDa. Purified enzyme was confirmed as α-amylase type by LC-MS/MS analysis and activity on specific substrate of ethylidene-pNP-G7. The CgAmy revealed extreme activity at a high temperature of 50.0-70.0°C with optimum activity at 70.0°C. The optimal pH of enzyme activity was observed at 6.0. The CgAmy exhibited stability in pH range of 5.0-8.0 and highly thermostable with a temperature of 40.0-60.0°C. The kinetic parameters K _m for hydrolysis of starch were found to be 3.12 mg/ml. The α-amylase activity was enhanced in the presence of Co²⁺ and β-mercaptoethanol. While, Na²⁺, K²⁺, Ca²⁺, Mg²⁺, Zn²⁺, Ba²⁺, Fe²⁺ and Cd²⁺ slightly inhibited α-amylase activity. Interestingly, the CgAmy displayed stability towards some organic solvents and detergents. Stability at high temperature and some metal ions, organic solvents and detergents indicated that this enzyme has potential for various applications.

Analysis of the structure-function relationship of alpha amylase complexed with polyacrylic acid

Alpha-amylase is frequently used in technologies that require its immobilization, stabilization or encapsulation. Polyacrylic acid is a very suitable polymer for these purposes because it can bind to enzymes and then be released under certain conditions without altering the functional capacity of enzymes. The consequences produced by polyacrylic acid on alpha-amylase structure and function have been investigated through various techniques. Calorimetric measurements allowed examining the nature of the binding reaction, stoichiometry and affinity, while spectroscopic techniques provided additional information about functional and structural perturbations of the enzyme. Isothermal titration calorimetry (ITC) revealed a mixed interaction and a binding model with a large number of molecules of protein per molecule of polyacrylic acid. One the one hand circular dichroism (CD) spectroscopy showed that alpha-amylase loses its secondary structure in the presence of increasing concentrations of polyacrylic acid, while it is stabilized by the polyelectrolyte at low pH. On the other hand, fluorescence spectra revealed that the three-dimensional enzyme structure was not affected in the microenvironment of tryptophan residues. Differential scanning calorimetry (DSC) thermograms showed that only one domain of alpha-amylase is affected in its conformational stability by the polymer. The unfolding process proved to be partially reversible. Finally, the enzyme retained more than 90 % of its catalytic activity even in excess of the polymer.

Site-saturation mutagenesis at amino acid 329 of Klebsiella pneumoniae halophilic α-amylase affects enzymatic properties

Halophilic α-amylases possess optimal activity in high salt concentrations. Therefore, they can be used in many extreme conditions in industrialised production. In the present work, a halophilic α-amylase (KP) from Klebsiella pneumoniae was characterised, and it exhibited a high specific activity of 3512 U/mg under optimal conditions of 2 M NaCl at 50°C and pH 6.5, but only 97 U/mg in the absence of salt. Furthermore, threonine at position 329 (Thr-329) was found to be related to the non-halophilic properties of KP according to PCR-based site-saturation mutagenesis. The activity of a mutant KP in which this threonine was replaced by aspartic acid was improved 14.6-fold compared with the native enzyme under salt-free conditions, and was increased by 14.8% in the absence of salt. Additionally, the optimal enzymatic properties of KP, including pH and temperature, were altered very little by the amino acid replacement. A further three halophilic α-amylases displayed similar mutational results. The findings provide a reference for bidirectional transformation of KP and similar halophilic enzymes.

Effect of electrolyzed water on enzyme activities of triticale malt during germination

Triticale malt can be used as a source of enzymes or as a raw material for the production of functional foods. In this study, triticale malt was produced by soaking triticale seeds either in tap water (TW) or slightly acidic electrolyzed water (SAEW) and then rinsing with TW, SAEW, or alkaline electrolyzed water (AEW). We determined the length of the hypocotyl of triticale malt and the activities of α-amylase, phytase, proteases, and lipase during 4 days of germination. The electrolyzed water (EW) treatments promoted the growth of triticale malt. On the 4th day of germination, the hypocotyl length of triticale malt soaked in TW and watered with SAEW was 24.57% longer than that of triticale malt soaked and watered with TW. The α-amylase, phytase, acidic protease, and lipase activities of triticale malt soaked in SAEW and watered with AEW were high on the 4th germination day (0.11, 1.24 × 10^-4, 0.62, and 0.51 units/mg protein, respectively). The main finding of this study is that the use of EW, especially during the soaking procedure, may be a promising way to obtain triticale malt with high enzyme activity for use in the production of functional foods.

The Rice Alpha-Amylase, Conserved Regulator of Seed Maturation and Germination

Alpha-amylase, the major form of amylase with secondary carbohydrate binding sites, is a crucial enzyme throughout the growth period and life cycle of angiosperm. In rice, alpha-amylase isozymes are critical for the formation of the storage starch granule during seed maturation and motivate the stored starch to nourish the developing seedling during seed germination which will directly affect the plant growth and field yield. Alpha-amylase has not yet been studied intensely to understand its classification, structure, expression trait, and expression regulation in rice and other crops. Among the 10-rice alpha-amylases, most were exclusively expressed in the developing seed embryo and induced in the seed germination process. During rice seed germination, the expression of alpha-amylase genes is known to be regulated negatively by sugar in embryos, however positively by gibberellin (GA) in endosperm through competitively binding to the specific promoter domain; besides, it is also controlled by a series of other abiotic or biotic factors, such as salinity. In this review, we overviewed the research progress of alpha-amylase with focus on seed germination and reflected on how in-depth work might elucidate its regulation and facilitate crop breeding as an efficient biomarker.

Prediction and analysis of GH14 family β-amylases in oat seedling extract: Structure and function insights using in silico approaches

Oat (Avena sativa L.) seedling extract exhibited a high degree of catalytic activities. Bioinformatics were used to identify β-amylases as abundant enzymes in the oat seedling extract. These identified oat enzymes are a member of the GH14 family. Proteins in the Avena sativa seedling extract were separated by SDS-PAGE and 2 major protein bands with an apparent molecular weights of 53 and 42 kDa were the subject of this study. These materials were digested with trypsin and the amino acid sequences of the tryptic peptides were determined by LC/ESI/MS/MS and database searches. These sequences were used to identify cDNAs from expressed sequence tags (EST) and Transcriptome Shotgun Assembly (TSA) of Avena sativa. Based upon EST and TSA sequences, at least 6 predicted different sequences were identified and assigned as β-amylases. Insights into structural characterization of the oat predicted β-amylases were analyzed using in silico approaches. The identified β-amylases conserved the two Glu residues assigned as the "putative" catalytic residues, which would act as an acid and base pair in the catalytic process. A similar core (β/α)₈-barrel architecture was found in the predicted oat β-amylases with a specific location of the active site in a pocket-like cavity structure made at one end of this core (β/α)₈-barrel domain. This suggests an accessibility of the non-reducing end of the substrate towards the oat β-amylases and thus confirming that are exo-acting hydrolases. The results provide a detailed view of the main residues involved in catalysis in this kind of enzyme.

Predicting enzymatic starch hydrolysis mechanism during paddy malting by vibrational spectroscopy and multivariate calibration analysis

Vibrational spectroscopic techniques were employed to predict the mechanism of starch hydrolysis based on structural changes during germination of paddy. The proposed mechanism for starch hydrolysis dealt with the synthesis of amylase at the onset of germination, depicting an increased intensity of spectral bands at amide I, II and III regions. The process commenced with the enzyme actions on skeletal mode of pyranose ring structure of glucose units followed by cleavage of the glycosidic linkage by the process of multiple and multi-chain attack resulting in decrease of the bands (400-900 cm^-1). The increased intensity of the bands (1200-1500 cm^-1) indicated the process of starch hydrolysis and formation of d-glucose. Multivariate calibration analysis (PCA and PLS) was employed to correlate Raman spectral data with biochemical changes during germination and to develop a calibration model. The model showed a high prediction ability with low root mean square error of prediction (RMSEP) (0.043-0.568).

Tolerance and accumulation of lithium in Apocynum pictum Schrenk

Primarily, lithium (Li) resource development and wider application of Li-ion batteries result in Li pollution and concomitantly poses increasing and inevitable problems to environmental health and safety. However, information is rare about the scope of the remediation of Li contaminated soil. Apocynum venetum is already proved to be a Li-accumulator with high Li tolerance and accumulation (Jiang et al., 2014). However, it is not clear whether Apocynum pictum, another species of the same genus with the same uses as A. venetum, is also a Li-accumulator. We investigated germination, growth and physiological responses of A. pictum to different levels of LiCl. Germination was not significantly affected by low Li concentration (0-100 mmol L-1). As LiCl increased from 100 to 400 mmol L-1, both germination percentage and index decreased gradually. For germination of A. pictum seeds, the critical value (when germination percentage is 50%) in LiCl solution was 235 mmol L-1, and the limit value (when germination percentage is 0%) was 406 mmol L-1. A. pictum could accumulate >1,800 mg kg-1 Li in leaves, and still survived under 400 mg kg-1 Li supply. The high Li tolerance of A. pictum during germination and growth stage was also reflected by activity of α-amylase and contents of soluble sugar, proline and photosynthetic pigments under different Li treatments. The bioconcentration factors (BCF) (except control) and translocation factors (TF) were higher than 1.0. High tolerance and accumulation of Li indicated that A. pictum is Li-accumulator. Therefore, this species could be useful for revegetation and phytoremediation of Li contaminated soil.

Recombinant expression, purification, and characterization of a cyclodextrinase from Massilia timonae

Some microorganisms can produce cyclodextrin glycosyltransferases, which degrades starch by catalyzing cyclization and giving rise to cyclodextrin. Thus, to fully degrade starch, microorganisms can also synthesize cyclodextrinases, which hydrolyze cyclodextrins. In this work, a truncated gene, without the signal peptide coding sequence, encoding a cyclodextrinase from Massilia timonae was PCR amplified, cloned, and expressed in E. coli. The histidine-tagged recombinant enzyme was purified by immobilized metal ion affinity chromatography. The purified protein was found to be a tetramer of about 260 kDa, with monomers of about 65 kDa, as estimated by gel filtration and SDS-PAGE, respectively. The enzyme presented an optimum temperature of 40 °C, optimum pH of 7.0, and remained stable after 30 min of incubation at 45 °C, with a T₅₀ of 48.45 °C. The enzyme showed a higher activity toward β-cyclodextrin compared to that for maltodextrin and starch. K_M for β-cyclodextrin was 2.1 mM, V_max was 0.084 μmol/min, k_cat was 8326 min^-1, and k_cat/K_M was 4.1 × 10⁶ M^-1min^-1. Calcium acted as an activator and SDS, CTAB, several cations, and EDTA acted as strong inhibitors. The purified cyclodextrinase produced glucose and maltose as final products by hydrolysis of β-cyclodextrin, maltotetraose, and maltoheptaose. This novel cyclodextrinase could be a promising alternative for the enzymatic hydrolysis of starch.

Impact of Preharvest Sprouting on Endogenous Hydrolases and Technological Quality of Wheat and Bread: A Review

The cereal-based food industry faces the challenge to produce food of high and uniform quality to meet consumer demands. However, adverse weather conditions, including prolonged and repeated rainfall, before harvest time evoke germination of the kernels in the ear of the parent plant, which is known as preharvest sprouting (PHS). PHS results in the production of several hydrolytic enzymes in the kernel, which decreases the technological quality of wheat and causes problems during processing of the flour into cereal-based products. Therefore, wheat that is severely sprouted in the field is less suitable for products for human consumption, and is often discounted to animal feed. Up till now, most knowledge on PHS is obtained by research on laboratory-sprouted wheat as a proxy for field-sprouted wheat. Knowledge on PHS in the field itself is more scarce. This review gives a comprehensive overview of the recent findings on PHS of wheat in the field, compared to knowledge on controlled sprouting. The physiological and functional changes occurring in wheat during PHS and their impact on wheat and bread quality are discussed. This review provides a useful background for further research concerning the potential of field-sprouted wheat to be used as raw material in the food industry.

High lithium tolerance of Apocynum venetum seeds during germination

Identification and use of lithium (Li) accumulator plants is a promising strategy to remediate Li-contaminated soil. Apocynum venetum is reported as a Li accumulator. However, its tolerance to Li salt during germination is still unknown. The primary aim of this study was to investigate the effects of two Li salts on seed germination of A. venetum. At the same concentrations, germination percentages in LiCl solution were higher than that in Li₂CO₃ solution. At 25 °C, seeds germinated to 4-90% at 0-400 mmol L^-1 LiCl and 3-91% at 0-150 mmol L^-1 Li₂CO₃. Low concentration (0-50 mmol L^-1) of LiCl did not significantly affect germination percentage. The simulated critical value (when germination percentage is 50%) in LiCl solution is 196 mmol L^-1, and 36 mmol L^-1 for Li₂CO₃. Activity of α-amylase, contents of MDA, soluble sugar, and proline were dramatically affected by Li salts, especially at medium and late germination stages. When compared with control, α-amylase activity of seeds under 25 mmol L^-1 LiCl and 10 mmol L^-1 Li₂CO₃ did not show significant difference. Germination percentage and index, radicle length, and physiological parameters indicate A. venetum seeds are highly tolerant to Li salts during germination, especially LiCl.

Temperature profile optimization: potential for multi-enzymatic biopolymer depolymerization processes

Optimal control of temperature was applied to a population balance model of enzymatically catalyzed depolymerization of a soluble polymer coupled with denaturation of enzyme. The reaction time required to reach a desired yield was predicted to be reduced by more than 10[Formula: see text] compared with isothermal operation. Also the yield within a given time could be increased by more than 5[Formula: see text] points. It was also possible to increase the yield and reduce the reaction time if a time-varying temperature profile was used. Furthermore, a simple-to-implement linear increasing temperature profile was shown to realize most of the saving potential. Rigorous optimization of the enzyme mixture and composition was predicted to have an even greater potential for improving the economic feasibility of the process. Optimization coupled with optimal control can be performed quickly in silico using the algorithm developed in this study if a validated and parameterized population balance model is available.

Cell wall degradation is required for normal starch mobilisation in barley endosperm

Starch degradation in barley endosperm provides carbon for early seedling growth, but the control of this process is poorly understood. We investigated whether endosperm cell wall degradation is an important determinant of the rate of starch degradation. We identified iminosugar inhibitors of enzymes that degrade the cell wall component arabinoxylan. The iminosugar 1,4-dideoxy-1, 4-imino-l-arabinitol (LAB) inhibits arabinoxylan arabinofuranohydrolase (AXAH) but does not inhibit the main starch-degrading enzymes α- and β-amylase and limit dextrinase. AXAH activity in the endosperm appears soon after the onset of germination and resides in dimers putatively containing two isoforms, AXAH1 and AXAH2. Upon grain imbibition, mobilisation of arabinoxylan and starch spreads across the endosperm from the aleurone towards the crease. The front of arabinoxylan degradation precedes that of starch degradation. Incubation of grains with LAB decreases the rate of loss of both arabinoxylan and starch, and retards the spread of both degradation processes across the endosperm. We propose that starch degradation in the endosperm is dependent on cell wall degradation, which permeabilises the walls and thus permits rapid diffusion of amylolytic enzymes. AXAH may be of particular importance in this respect. These results provide new insights into the mobilization of endosperm reserves to support early seedling growth.

Use of enzymes to minimize the rheological dough problems caused by high levels of damaged starch in starch-gluten systems

BACKGROUND

During wheat milling, starch granules can experience mechanical damage, producing damaged starch. High levels of damaged starch modify the physicochemical properties of wheat flour, negatively affecting the dough behavior as well as the flour quality and cookie and bread making quality. The aim of this work was to evaluate the effect of α-amylase, maltogenic amylase and amyloglucosidase on dough rheology in order to propose alternatives to reduce the issues related to high levels of damaged starch.

RESULTS

The dough with a high level of damaged starch became more viscous and resistant to deformations as well as less elastic and extensible. The soluble fraction of the doughs influenced the rheological behavior of the systems. The α-amylase and amyloglucosidase reduced the negative effects of high damaged starch contents, improving the dough rheological properties modified by damaged starch. The rheological behavior of dough with the higher damaged-starch content was related to a more open gluten network arrangement as a result of the large size of the swollen damaged starch granules.

CONCLUSION

We can conclude that the dough rheological properties of systems with high damaged starch content changed positively as a result of enzyme action, particularly α-amylase and amyloglucosidase additions, allowing the use of these amylases and mixtures of them as corrective additives. Little information was reported about amyloglucosidase activity alone or combined with α-amylase. The combinations of these two enzymes are promising to minimize the negative effects caused by high levels of damaged starch on product quality. More research needs to be done on bread quality combining these two enzymes. © 2015 Society of Chemical Industry.

Production of alpha-amylase from Aspergillus oryzae for several industrial applications in a single step

A one-step method as a strategy of alpha-amylase concentration and purification was developed in this work. This methodology requires the use of a very low concentration of biodegradable polyelectrolyte (Eudragit(®) E-PO) and represents a low cost, fast, easy to scale up and non-polluting technology. Besides, this methodology allows recycling the polymer after precipitation. The formation of reversible soluble/insoluble complexes between alpha-amylase and the polymer Eudragit(®) E-PO was studied, and their precipitation in selected conditions was applied with bioseparation purposes. Turbidimetric assays allowed to determine the pH range where the complexes are insoluble (4.50-7.00); pH 5.50 yielded the highest turbidity of the system. The presence of NaCl (0.05M) in the medium totally dissociates the protein-polymer complexes. When the adequate concentration of polymer was added under these conditions to a liquid culture of Aspergillus oryzae, purification factors of alpha-amylase up to 7.43 and recoveries of 88% were obtained in a simple step without previous clarification. These results demonstrate that this methodology is suitable for the concentration and production of alpha-amylase from this source and could be applied at the beginning of downstream processing.

Characterization and Application of BiLA, a Psychrophilic α-Amylase from Bifidobacterium longum

In this study, a novel α-amylase was cloned from Bifidobacterium longum and named BiLA. The enzyme exhibited optimal activity at 20 °C and a pH value of 5.0. Kinetic analysis using various carbohydrate substrates revealed that BiLA had the highest k(cat/)K(m) value for amylose. Interestingly, analysis of the enzymatic reaction products demonstrated that BiLA specifically catalyzed the hydrolysis of oligosaccharides and starches up to G5 from the nonreducing ends. To determine whether BiLA can be used to generate slowly digestible starch (SDS), starch was treated with BiLA, and the kinetic parameters were analyzed using porcine pancreatic α-amylase (PPA) and amyloglucosidase (AMG). Compared to normal starch, BiLA-treated starch showed lower k(cat)/K(m) values with PPA and AMG, suggesting that BiLA is a potential candidate for the production of SDS.

Acute effects of traditional Japanese alcohol beverages on blood glucose and polysomnography levels in healthy subjects

Background. Alcohol consumption is a lifestyle factor associated with type 2 diabetes. This relationship is reportedly different depending on the type of alcohol beverage. The purpose of this study was to examine the acute effects of traditional Japanese alcohol beverages on biochemical parameters, physical and emotional state, and sleep patterns.

Methods. Six healthy subjects (three men and three women; age, 28.8 ± 9.5 years; body mass index, 21.4 ± 1.6 kg/m²) consumed three different types of alcohol beverages (beer, shochu, and sake, each with 40 g ethanol) or mineral water with dinner on different days in the hospital. Blood samples were collected before and 1, 2, and 12 h after drinking each beverage, and assessments of physical and emotional state were administered at the same time. In addition, sleep patterns and brain waves were examined using polysomnography.

Results. Blood glucose levels at 1 h and the 12-h area under the curve (AUC) value after drinking shochu were significantly lower than that with water and beer. The 12-h blood insulin AUC value after drinking shochu was significantly lower than that with beer. Blood glucose × insulin level at 1 h and the 2-h blood glucose × insulin AUC value with shochu were significantly lower than that with beer. The insulinogenic indexes at 2 h with beer and sake, but not shochu, were significantly higher than that with water. The visual analogue scale scores of physical and emotional state showed that the tipsiness levels with beer, shochu, and sake at 1 h were significantly higher than that with water. These tipsiness levels were maintained at 2 h. The polysomnography showed that the rapid eye movement (REM) sleep latency with shochu and sake were shorter than that with water and beer.

Conclusions. Acute consumption of alcohol beverages with a meal resulted in different responses in postprandial glucose and insulin levels as well as REM sleep latency. Alcohol beverage type should be taken into consideration for people with impaired glucose tolerance.

The Maltase Involved in Starch Metabolism in Barley Endosperm Is Encoded by a Single Gene

During germination and early seedling growth of barley (Hordeum vulgare), maltase is responsible for the conversion of maltose produced by starch degradation in the endosperm to glucose for seedling growth. Despite the potential relevance of this enzyme for malting and the production of alcoholic beverages, neither the nature nor the role of maltase is fully understood. Although only one gene encoding maltase has been identified with certainty, there is evidence for the existence of other genes and for multiple forms of the enzyme. It has been proposed that maltase may be involved directly in starch granule degradation as well as in maltose hydrolysis. The aim of our work was to discover the nature of maltase in barley endosperm. We used ion exchange chromatography to fractionate maltase activity from endosperm of young seedlings, and we partially purified activity for protein identification. We compared maltase activity in wild-type barley and transgenic lines with reduced expression of the previously-characterised maltase gene Agl97, and we used genomic and transcriptomic information to search for further maltase genes. We show that all of the maltase activity in the barley endosperm can be accounted for by a single gene, Agl97. Multiple forms of the enzyme most likely arise from proteolysis and other post-translational modifications.