Biochemical characterization of a highly thermostable amylosucrase from Truepera radiovictrix DSM 17093

Architecture, Function, Regulation, and Evolution of α-Glucans Metabolic Enzymes in Prokaryotes

Bacteria have acquired sophisticated mechanisms for assembling and disassembling polysaccharides of different chemistry. α-d-Glucose homopolysaccharides, so-called α-glucans, are the most widespread polymers in nature being key components of microorganisms. Glycogen functions as an intracellular energy storage while some bacteria also produce extracellular assorted α-glucans. The classical bacterial glycogen metabolic pathway comprises the action of ADP-glucose pyrophosphorylase and glycogen synthase, whereas extracellular α-glucans are mostly related to peripheral enzymes dependent on sucrose. An alternative pathway of glycogen biosynthesis, operating via a maltose 1-phosphate polymerizing enzyme, displays an essential wiring with the trehalose metabolism to interconvert disaccharides into polysaccharides. Furthermore, some bacteria show a connection of intracellular glycogen metabolism with the genesis of extracellular capsular α-glucans, revealing a relationship between the storage and structural function of these compounds. Altogether, the current picture shows that bacteria have evolved an intricate α-glucan metabolism that ultimately relies on the evolution of a specific enzymatic machinery. The structural landscape of these enzymes exposes a limited number of core catalytic folds handling many different chemical reactions. In this Review, we present a rationale to explain how the chemical diversity of α-glucans emerged from these systems, highlighting the underlying structural evolution of the enzymes driving α-glucan bacterial metabolism.

Mining thermophiles for biotechnologically relevant enzymes: evaluating the potential of European and Caucasian hot springs

The development of sustainable and environmentally friendly industrial processes is becoming very crucial and demanding for the rapid implementation of innovative bio-based technologies. Natural extreme environments harbor the potential for discovering and utilizing highly specific and efficient biocatalysts that are adapted to harsh conditions. This review focuses on extremophilic microorganisms and their enzymes (extremozymes) from various hot springs, shallow marine vents, and other geothermal habitats in Europe and the Caucasus region. These hot environments have been partially investigated and analyzed for microbial diversity and enzymology. Hotspots like Iceland, Italy, and the Azores harbor unique microorganisms, including bacteria and archaea. The latest results demonstrate a great potential for the discovery of new microbial species and unique enzymes that can be explored for the development of Circular Bioeconomy.Different screening approaches have been used to discover enzymes that are active at extremes of temperature (up 120 °C), pH (0.1 to 11), high salt concentration (up to 30%) as well as activity in the presence of solvents (up to 99%). The majority of published enzymes were revealed from bacterial or archaeal isolates by traditional activity-based screening techniques. However, the latest developments in molecular biology, bioinformatics, and genomics have revolutionized life science technologies. Post-genomic era has contributed to the discovery of millions of sequences coding for a huge number of biocatalysts. Both strategies, activity- and sequence-based screening approaches, are complementary and contribute to the discovery of unique enzymes that have not been extensively utilized so far.

Identification and characterization of a novel high-activity amylosucrase from Salinispirillum sp. LH10-3-1

In this study, a novel high-activity amylosucrase from Salinispirillum sp. LH10-3-1 (SaAS) was identified and characterized. The recombinant enzyme was determined as a monomer with a molecular mass of 75 kDa. SaAS protein exhibited the maximum total and polymerization activities at pH 9.0 and maximum hydrolysis activity at pH 8.0. The optimum temperature for total, polymerization, and hydrolysis activities were 40, 40, and 45 °C, respectively. Under the optimal pH and temperature, SaAS had a specific activity of 108.2 U/mg. SaAS also showed excellent salt tolerance and could retain 77.4% of its original total activity at 4.0 M NaCl. The addition of Mg²⁺, Ba²⁺, and Ca²⁺ enhanced the total activity of SaAS. When the conversion of 0.1 M and 1.0 M sucrose was catalyzed at pH 9.0 and 40 °C for 24 h, the ratios of hydrolysis, polymerization, and isomerization reactions were 11.9:77.4:10.7 and 15.3:53.5:31.2, respectively. The α-arbutin yield of 60.3% was achieved from 20 mM sucrose and 5 mM hydroquinone catalyzed by SaAS. KEY POINTS: • A novel amylosucrase from Salinispirillum sp. LH10-3-1 (SaAS) was characterized. • SaAS has the highest specific enzyme activity among all known amylosucrase. • SaAS has hydrolysis, polymerization, isomerization, and glucosyltransferase activities.

A unique biochemical reaction pathway towards trehalulose synthesis by an amylosucrase isolated from Deinococcus deserti

The aim of this study was to establish an efficient bioprocess for the synthesis of trehalulose as a novel sweetener. This disaccharide has 70% of the sweetness of sucrose and bioactive properties such as anti-cariogenicity and anti-oxidizing activity. In this study, amylosucrase from the Deinococcus deserti (DdAS) gene was expressed and purified. When DdAS was reacted with 2M sucrose at 35 °C for 120h, the yield ratio of trehalulose to turanose was approximately 2:1. The trehalulose yield increased when extrinsic fructose was added. Under optimum conditions for trehalulose synthesis, the yield reached 36% (246g/L, sucrose basis) starting with 2M sucrose + 0.75M fructose and showed the highest trehalulose productivity (1.94g/L/h). As a result, a novel amylosucrase that synthesized trehalulose as the major product was developed, in contrast to other studied amylosucrase-type enzymes. DdAS could be utilized industrially in a bioprocess for producing trehalulose as a functional sucrose alternative.

Site-Directed Mutagenic Engineering of a Bifidobacterium Amylosucrase toward Greater Efficiency of Turanose Synthesis

The aim of this study was to establish one of the most efficient biocatalytic processes for turanose production by applying a robust Bifidobacterium thermophilum (BtAS) mutant developed through site-directed mutagenesis. A gene encoding the amylosucrase of B. thermophilum (BtAS) was cloned and used as a mutagenesis template. Among the BtAS variants generated by the site-directed point mutation, four different single-point mutants (P200R, V202I, Y265F, and Y414F) were selected to create double-point mutants, among which BtAS_Y414F/P200R displayed the greatest turanose productivity without losing the thermostability of native BtAS. The turanose yield of BtAS_Y414F/P200R reached 89.3% at 50 °C after 6 h with 1.0 M sucrose + 1.0 M fructose. BtAS_Y414F/P200R produced significantly more turanose than BtAS-wild type (WT) by 2 times and completed the reaction faster by another 2 times. Thus, turanose productivity (82.0 g/(L h)) by BtAS_Y414F/P200R was highly improved from 28.1 g/(L h) of BtAS-WT with 2.0 M sucrose + 0.75 M fructose.

Simultaneous profiling and cultivation of the skin microbiome of healthy young adult skin for the development of therapeutic agents

Background

Studies on the impact of the skin microbiota on human health have been gaining more attention. Bacteria are associated with various diseases, although certain strains of bacteria, which are known as probiotics, are considered beneficial. Mixtures of several bacteria (bacterial cocktail) isolated from targeted organs have shown promising modulatory activities for use in skin therapeutics. The objectives of this study were to determine and identify the microbial communities on the skin that can potentially be used as probiotics, as determined by bacterial isolation and cultivation, followed by next-generation sequencing (NGS).

Results

Samples were collected by swabbing on forehead and cheek skin. Genomic DNA from bacterial swab samples were directly extracted to be further processed into NGS. Cultivation of skin bacteria was carried out in subsequent medium. Thus, around twenty bacterial isolates with different characteristics were selected and identified by both culture-based method and 16sRNA sequencing. We found that Actinobacteria and Firmicutes are the most abundant phylum present on the skin as presented by NGS data, which constitute to 67% and 28.59% of the whole bacterial population, consecutively. However, Staphylococcus hominis, Staphylococcus warneri, and Micrococcus luteus (AN MK968325.1; AN MK968315.1; and MK968318.1 respectively) were able to be obtained in the samples of cultivable, and could be potentially developed as probiotics in skin microbiome therapeutic as well as for postbiotic formulation.

Conclusion

Skin microbiome is considered to provide several probiotics for skin therapeutic. However, some opportunistic pathogens were discovered in this study population. Thus, the promising formula of bacterial cocktail for skin microbiome therapeutic must be thoroughly elucidated to avoid unwanted species. Our study is the first human skin microbiome profile of Indonesia resulted from a Next Generation Sequencing as an effort to show a representative of tropical country profile.

Comparative study on four amylosucrases from Bifidobacterium species

Amylosucrase (ASase) is α-glucan-producing enzyme. Four putative ASase genes (bdas, blas, bpas, and btas) were cloned from Bifidobacterium sp. and expressed in Escherichia coli. All ASases from Bifidobacterium sp. (BAS) displayed typical ASase properties with slightly different characteristics. Among the BASs studied, BdAS and BpAS showed maximal enzyme activities at 35 and 30 °C, respectively, whereas BlAS and BtAS were maximally active at higher temperatures, i.e., 45 and 50 °C, respectively. BpAS exhibited optimum pH under slightly basic conditions (pH 8.0), while BdAS, BlAS, and BtAS preferred weakly acidic conditions (pH 5.0-6.0). All BASs showed higher isomerization activities. Particularly, BlAS produced more trehalulose than turanose. Although polymerization was the highest for BtAS, BtAS synthesized α-1, 4-glucans with a lower degree of polymerization than that of the other BASs. The versatile properties of the BASs described could contribute to the efficient production of highly valuable biomaterials for the agriculture, food, and pharmaceutical industries.

Thermostable Amylosucrase from Calidithermus timidus DSM 17022: Insight into Its Characteristics and Tetrameric Conformation

Amylosucrase (EC 2.4.1.4, ASase), a typical carbohydrate-active enzyme, can catalyze 5 types of reactions and recognize more than 50 types of glycosyl acceptors. However, most ASases are unstable even at 50 °C, which limits their practical industrial applications. In this study, an extremely thermostable ASase was discovered from Calidithermus timidus DSM 17022 (CT-ASase) with an optimal activity temperature of 55 °C, half-life of 1.09 h at 70 °C, and melting temperature of 74.47 °C. The recombinant CT-ASase was characterized as the first tetrameric ASase, and a structure-based truncation mutation was conducted to confirm the effect of tetrameric conformation on its thermostability. In addition, α-1,4-glucan was found to be the predominant product of CT-ASase at pH 6.0-8.0 and 30-60 °C.

Characterization of a novel amylosucrase gene from the metagenome of a thermal aquatic habitat, and its use in turanose production from sucrose biomass

Turanose is a natural isomer of sucrose. It is an emerging functional sweetener of the next generation. Turanose is catalytically synthesized from the sucrose biomass by employing amylosucrase enzyme. In this study, a novel gene encoding amylosucrase (As_met) has been identified from the metagenome of a thermal aquatic habitat. As_met exhibits 37-55% identity at the protein level with the known amylosucrases characterized till date. As_met was cloned and expressed in Escherichia coli, followed by protein purification, and characterization. As_met protein exhibited the maximum total activity at 9.0 pH and 60 °C temperature, whereas, 8.0 pH and 50 °C temperature were found optimum for transglycosylation activity. As_met showed fairly high thermal tolerance at 50 °C. The conjugation of As_met protein with functionalized iron nanoparticles significantly improved its thermal tolerance, showing hardly any loss in the enzyme's activity even after 72 h of heat (50 °C) exposure. The turanose yield of about 47% was achieved from 1.5 M sucrose, containing 0.5 M fructose in the reaction. Turanose was purified (˜95%) via a bio-physical process, and characterized by TLC, HPLC, and NMR. The novel amylosucrase gene was demonstrated to be a potential candidate for turanose production, utilizing various sucrose containing feedstocks.

Study on Transglucosylation Properties of Amylosucrase from Xanthomonas campestris pv. Campestris and Its Application in the Production of α-Arbutin

α-Arbutin (4-hydroquinone-α-D-glucopyranoside), an effective skin-lightening agent due to its considerable inhibitory effect on human tyrosinase activity, is widely used in the pharmaceutical and cosmetic industries. Recently, α-arbutin was prepared through transglucosylation of hydroquinone using microbial glycosyltransferases as catalysts. However, the low yield and prolonged reaction time of the biotransformation process of α-arbutin production limited its industrial application. In this work, an amylosucrase (ASase) from Xanthomonas campestris pv. campestris str. ATCC 33913 (XcAS) was expressed efficiently in Escherichia coli JM109. The catalytic property of the purified XcAS for the synthesis of α-arbutin was tested. The recombinant strain was applied for highly efficient synthesis of α-arbutin using sucrose and hydroquinone as glucosyl donor and acceptor, respectively. By optimizing the biotransformation conditions and applying a fed-batch strategy, the final production yield and conversion rate of α-arbutin reached 60.9 g/L and 95.5%, respectively, which is the highest reported yield by engineered strains. Compared to the highest reported value (<1.4 g/L/h), our productivity (7.6 g/L/h) was improved more than five-fold. This work represents an efficient and rapid method for α-arbutin production with potential industrial applications.