A novel maltooligosaccharide-forming amylase from Bacillus stearothermophilus

Engineering hyperthermophilic pullulanase to efficiently utilize corn starch for production of maltooligosaccharides and glucose

Pullulanase is a starch-debranching enzyme that hydrolyzes side chain of starch, oligosaccharides and pullulan. Nevertheless, the limited activities of pullulanases constrain their practical application. Herein, the hyperthermophilic type II pullulanase from Pyrococcus yayanosii CH1 (PulPY2) was evolved by synergistically engineering the substrate-binding pocket and active-site lids. The resulting mutant PulPY2-M2 exhibited 5-fold improvement in catalytic efficiency (kcat/Km) compared to that of PulPY2. PulPY2-M2 was utilized to develop a one-pot reaction system for efficient production of maltooligosaccharides. The maltooligosaccharides conversion rate of PulPY2-M2 reached 96.1%, which was increased by 5.4% compared to that of PulPY2. Furthermore, when employed for glucose production, the glucose productivity of PulPY2-M2 was 25.4% and 43.5% higher than that of PulPY2 and the traditional method, respectively. These significant improvements in maltooligosaccharides and glucose production and the efficient utilization of corn starch demonstrated the potential of the engineered PulPY2-M2 in starch sugar industry.

Enhanced Thermostability of Geobacillus stearothermophilus α-Amylase by Rational Design of Disulfide Bond and Application in Corn Starch Liquefaction and Bread Quality Improvement

α-Amylase (EC 3.2.1.1) from Geobacillus stearothermophilus (generally recognized as safe) exhibited thermal inactivation, hampering its further application in starch-based industries. To address this, we performed structural analyses based on molecular dynamics targeting the flexible regions of α-amylase. Subsequently, we rationally designed a thermostable mutant, AmyS1, by introducing disulfide bonds to stabilize the flexible regions. AmyS1 showed excellent thermostability without any stability-activity trade-off, giving a 40-fold longer T1/2 (1359 min) at 90 °C. Thermostability mechanism analysis revealed that the introduction of disulfide bonds in AmyS1 refined weak spots and reconfigured the protein's force network. Moreover, AmyS1 exhibited improved pH compatibility and enhanced corn starch liquefaction at 100 °C with a 5.1-fold increased product concentration. Baking tests confirmed that AmyS1 enhanced bread quality and extended the shelf life. Therefore, mutant AmyS1 is a robust candidate for the starch-based industry.

Maltooligosaccharides: Properties, Production and Applications

Maltooligosaccharides (MOS) are homooligosaccharides that consist of 3-10 glucose molecules linked by α-1,4 glycosidic bonds. As they have physiological functions, they are commonly used as ingredients in nutritional products and functional foods. Many researchers have investigated the potential applications of MOS and their derivatives in the pharmaceutical industry. In this review, we summarized the properties and methods of fabricating MOS and their derivatives, including sulfated and non-sulfated alkylMOS. For preparing MOS, different enzymatic strategies have been proposed by various researchers, using α-amylases, maltooligosaccharide-forming amylases, or glycosyltransferases as effective biocatalysts. Many researchers have focused on using immobilized biocatalysts and downstream processes for MOS production. This review also provides an overview of the current challenges and future trends of MOS production.

Malto-oligosaccharides as critical functional ingredient: a review of their properties, preparation, and versatile applications

Malto-oligosaccharides (MOS) are α-1,4 glycosidic linked linear oligosaccharides of glucose, which have a diverse range of functional applications in the food, pharmaceutical, and other industries. They can be used to modify the physicochemical properties of foods thereby improving their quality attributes, or they can be included as prebiotics to improve their nutritional attributes. The degree of polymerization of MOS can be controlled by using specific enzymes, which means their functionality can be tuned for specific applications. In this article, we review the chemical structure, physicochemical properties, preparation, and functional applications of MOS in the food, health care, and other industries. Besides, we offer an overview for this saccharide from the perspective of prospect functional ingredient, which we feel lacks in the current literature. MOS could be expected to provide a novel promising substitute for functional oligosaccharides.

A novel low temperature active maltooligosaccharides-forming amylase from Bacillus koreensis HL12 as biocatalyst for maltooligosaccharide production

Maltooligosaccharide-forming amylases (MFAses) are promising enzymes for a variety of industrial applications. In this study, a maltooligosaccharide-forming amylase (BkAmy) isolated from Bacillus koreensis HL12 was first heterologous expressed and characterized. According to structural-sequence alignment, BkAmy contained seven conserved regions which are the signature of a novel GH13 subfamily. The gene was expressed in Pichia pastoris KM71 as an extracellular protein with a volumetric activity of 3.38 U/mL culture medium after 72 h induction by 3% (w/v) of methanol. The recombinant BkAmy migrated as a single protein band with an expected size approximately of 55 kDa. BkAmy exhibited the highest catalytic activity on soluble starch with a specific activity of 42.2 U/mg at 40 °C, pH 7.0. The enzyme exhibited 65% relative activity at 30 °C, indicating its advantage on application at moderate reaction temperature desirable for energy saving and reduction of side unwanted reactions. The enzyme exhibited a specific cleavage pattern by releasing maltose (G2), maltotriose (G3) and maltotetraose (G4) from cassava starch with the highest yield of 363 mg/g substrate equivalent to 36% conversion using 40 U/g substrate at 60 min. The work demonstrates the potential of this enzyme on maltooligosaccharide production from starch to create high value-added products in starch processing industries.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03188-1.

Bioaugmentation of Bacillus amyloliquefaciens-Bacillus kochii co-cultivation to improve sensory quality of flue-cured tobacco

Flue-cured tobacco (FCT) with irritating and undesirable flavor must be aged. However, the spontaneous aging usually takes a very long time for the low efficiency. Bioaugmentation with functional strains is a promising method to reduce aging time and improve sensory quality. To eliminate the adverse effect of excessive starch or protein content on the FCT quality, we used the flow cytometry to sort Bacillus amyloliquefaciens LB with high alpha-amylase and Bacillus kochii SC with high neutral protease from the FCT microflora. The mono, co-culture of strains was performed the solid-state fermentation with FCT. Bacillus amyloliquefaciens monoculture for 2 days and Bacillus kochii monoculture for 2.5 days achieved the optimum quality. B. amyloliquefaciens-B. kochii co-culture at a ratio of 3:1 for 2 days of fermentation showed a more comprehensive quality enhancement and higher functional enzyme activity than mono-cultivation. Through OPLS-DA model (orthogonal partial least-squares-discriminant analyzes), there were 38 differential compounds between bioaugmentation samples. In co-cultivation, most of Maillard reaction products and terpenoid metabolites were at a higher level than other samples, which promoted an increase in aroma, softness and a decrease in irritation. This result validated the hypothesis of quality improvement via the co-culture. In our study, we presented a promising bioaugmentation technique for changing the sensory attributes of FCT in a short aging time.

Purification and characterization of thermostable α-amylase produced from Bacillus licheniformis So-B3 and its potential in hydrolyzing raw starch

AIMS

This work was achieved to obtain the optimum culture conditions of the thermostable alpha-amylase produced by thermophilic Bacillus licheniformis SO-B3. Furthermore, the α-amylase was purified and then characterized, and also its kinetic parameters were determined.

MATERIALS AND METHODS

A new thermotolerant bacteria called Bacillus licheniformis SO-B3 employed in this work was isolated from a sample of thermal spring mud in Şırnak (Meyremderesi). Several parameters such as the impact of temperature, time, and pH on enzyme production were examined. Thin-Layer Chromatography (TLC) was employed to analyze the end-products of soluble starch hydrolysis, and the utilization of purified α-amylase in the clarification of unripe apple juices was studied.

KEY FINDINGS

The highest enzyme production conditions were determined as 35 °C, 36th hour, and pH 7.0. Thermostable α-amylase was purified by 70% ammonium sulfate precipitation, DEAE-cellulose ion-exchange chromatography, and dialysis, with a 51-purification fold and 30% yield recovery. The K_m and V_max values for this enzyme were 0.004 mM and 3.07 μmol min^-1 at 70 °C, respectively. The α-amylase's molecular weight was found as 74 kDa. In addition, α-amylase showed a good degradation rate for raw starch.

SIGNIFICANCE

It was hypothesized that Bacillus licheniformis SO-B3 could be used as an α-amylase source. These findings displayed that purified enzyme could be utilized in fruit juice industries for clarification of apple juice and raw starch hydrolyzing.

A microplate assay for extracellular hydrolase detection

This article presents a new qualitative method to detect enzyme activity replacing the conventional Agar-Petri dishes. This new method is a simple rapid and low-cost technique that uses 24-well microplates. The detection of hydrolases producing microorganisms in bioprospecting studies by qualitative methods is time consuming, costly and requires a large quantity of strains or enzymatic extracts. Tests with different substrate concentrations (0 to 20 g/L) in agar solution for the enzymatic hydrolysis analysis were performed to determine the best substrate concentrations in 24-well microplates. Other quantitative and analytical methods, such as enzymatic assays and thin layer chromatography, were performed to validate this new method and to compare the relationship between enzymatic activity and substrate degradation. Statistically relevant results were observed for amylase, endoglucanase and polygalacturonase enzymes, even when there was a low substrate concentration in agar, where the halo diameter was high. The results also indicated that the concentrations for efficient enzyme index measurements were 4 g/L carboxymethylcellulose for endoglucanase detection and 8 g/L for amylase and polygalacturonase assays. The results were presented according to the traditional methods for detection of enzymatic activity. This new method can be used as a general test for the detection of important industrial hydrolases. It is a faster and less costly alternative for screening microbial enzyme producing microorganisms and is useful for studying the production of microbial enzymes under different growing conditions.