Sucrose isomers as alternative sweeteners: properties, production, and applications

Biosynthesis of Natural Acylsucroses from Sucrose and Short Branched-Chain Fatty Acids via Artificially Engineered Escherichia coli

Natural acylsucrose, often found in the glandular trichomes of Solanaceae plants, has potential applications in many industries, including food, cosmetics, and pharmaceuticals. In this study, we engineered an Escherichia coli strain to complete the biosynthesis of acylsucroses through whole-cell transformation. Using acylsucrose acyltransferases and CoA ligases, acylsucroses, including monoacylsucrose S1:5 ("S" represents an acylsucrose backbone, the number before the colon indicates the number of acyl chains, and the number after the colon indicates the sum of carbons in all acyl chains), diacylsucrose S2:10, triacylsucrose S3:14, and triacylsucrose S3:15 were synthesized from the substrate sucrose and short branched-chain fatty acids by the engineered E. coli EcoSE07, of which S3:15 was the primary product. Several strategies were applied to improve acylsucrose production, including codon optimization, constitutive promoter replacement, and serial resting cell assays. The use of fed-batch fermentation with an engineered E. coli strain of EcoSE22 containing a constitutive promoter further improved the production of acylsucroses. Serial resting cell assays with an optical density of 50 at 600 nm significantly increased the production of acylsucroses S3:15 and S2:10. These findings will facilitate the synthesis of natural acylsucroses through whole-cell transformations and provide the potential for future industrial applications.

Osmoregulation by sucrose isomerization in the phloem-feeding whitefly Bemisia tabaci involves members of the glycoside hydrolase family 13

A phloem-sap based diet requires unique enzymatic skills for regulating the osmotic pressure differences in the gut lumen between the sucrose-rich ingested sap and the body fluids, which can lead to desiccation and death. In the phloem-feeding whitefly Bemisia tabaci, members of the glycoside hydrolase family 13 (GH13) are likely to play a critical role in mitigating this risk by oligomerizing and isomerizing the products of sucrose hydrolysis. So far, however, the identities of the family members acting as sucrose isomerases (mainly isomerizing trehalulose) remain unknown. In this study, we focused on four putative sucrose isomerase coding genes of B. tabaci that belong to the GH13 family. The four coding genes were selected based on their phylogeny, expression patterns, and motif analyses. We used artificial diets of sucrose and dsRNA to knockdown the expression of each of the target genes and analyzed the sugar composition of the secreted honeydew. We found that in all cases, gene silencing resulted in a significant reduction of the fractions of trehalulose accompanied by an increase in the fractions of the trisaccharide melezitose, suggesting that the insects attempt to compensate for the inability to isomerize sucrose by synthesizing oligosaccharides. In addition, we found that the downregulation of the target genes also resulted in a significant increase in the mortality rates of the silenced insects and a significant delay in the development of their progeny. Taken together, these findings demonstrate the importance of the osmoregulation-by-isomerization strategy in B. tabaci.

Health effects of synthetic additives and the substitution potential of plant-based additives

The growth of the world population and the rapid industrialization of food have led to food producers' increased reliance on food additives. While food additives offer numerous conveniences and advantages in food applications, the potential risks associated with synthetic additives remain a significant concern. This report examines the current status of safety assessment and toxicity studies of common synthetic additives, including flavorings (sweeteners and flavor enhancers), colorants, preservatives (antimicrobials and antioxidants), and emulsifiers. The report also examines recent advances in promising plant-based alternative additives in terms of active ingredients, sensory properties, potential health benefits, food application challenges, and their related technologies (edible coatings/films and nanoencapsulation technologies), providing valuable references and insights for the sustainable development of food additives.

Exploring formation of turanose in honey via stable isotope labelling and high-resolution mass spectrometry analysis

Turanose, an isomer of sucrose, naturally exists in honey. Previous study indicated that turanose content increased gradually in acacia honey as honeybees brewed honey in the hive. However, it is unclear how turanose is generated in honey. We hypothesised that turanose was produced by enzymes from honeybees and performed a series of simulation experiments to prove this hypothesis. We found turanose in honey was produced by honeybees processing sucrose. Furthermore, we determined that sugar composition of simulated nectar influenced the turanose concentration in honey: when sucrose concentration was below 5%, turanose was difficult to form, whereas high concentration of fructose and limited glucose were beneficial in producing turanose. Using 13C-labelled sucrose tests combined with proteomics analysis, we identified that α-glucosidase converted sucrose to turanose through an intermolecular isomerisation process. This study reveals the formation mechanism of turanose in honey and assists in the scientific control and improvement of honey quality.

Trehalulose: Exploring its benefits, biosynthesis, and enhanced production techniques

The increasing concern over sugar-related health issues has sparked research interest in seeking alternatives to sucrose. Trehalulose, a beneficial structural isomer of sucrose, is a non-cariogenic sugar with a low glycemic and insulinemic index. Besides its potential as a sugar substitute, trehalulose exhibits high antioxidant properties, making it attractive for various industrial applications. Despite its numerous advantages and potential application in various sectors, the industrial adoption of trehalulose has yet to be established due to lack of studies on its characteristics and practical uses. This review aims to provide a comprehensive overview of the properties of trehalulose, emphasizing its health benefits. The industrial prospects of trehalulose as sweetener and reducing agent, particularly in food and beverages pharmaceutical, and cosmeceutical sectors, are explored. Additionally, the review delves into the sources of trehalulose and the diverse organisms capable of producing trehalulose. The biosynthesis of this sugar primarily involves an enzyme-mediated process. Thus, these enzymes' properties, mechanisms, and the heterologous expression of genes associated with trehalulose production are explored. The strategies discussed in this review can be improved and applied to establish trehalulose bio-factories for efficient synthesis of trehalulose in the future. With further research and development, trehalulose holds promise as a valuable component across various industries.

Enhanced production of turanose using a mutant amylosucrase from Bifidobacterium thermophilum immobilized on silica carriers

Turanose (α-d-glucopyranosyl-(1→3)-α-d-fructose) is a rare disaccharide that is a potential low-calorigenic sweetener. This novel sucrose isomer has been efficiently synthesized by the amylosucrase from Bifidobacterium thermophilum (BtAS). In this study, we aimed to enhance turanose biosynthesis by designing a BtAS variant (BtAS-G374S) with improved thermal stability. The BtAS variant was immobilized on porosity-controlled silica carrier, and its enzymatic properties were thoroughly investigated. Using response surface methodology with central composite design, optimal immobilization conditions were determined to significantly boost the biosynthetic efficiency. The BtAS-G374S showed 1.6-fold higher specific activity (2.2 U/mg) than the wild-type enzyme (1.4 U/mg). Additionally, the turanose production yield of BtAS-G374S was significantly enhanced, reaching 65 %, compared to 25 % for the wild-type enzyme when reacting with 2 M sucrose. Immobilization of BtAS-G374S was optimized on controlled porosity carrier (CPC) silica carrier using Response Surface Methodology, achieving an enzyme activity of 7.89 U and an immobilization efficiency of 68.98 % under optimal conditions. Immobilization of BtAS-G374S on CPC silica carriers enhanced its pH and thermal stability. The immobilized enzyme showed a half-life of 50.23 h at 55 °C and retained 68 % of its initial biosynthetic yield after 10 reuses. These properties suggest its potential for efficient industrial turanose production.

Enzymatic Production of Trehalose and Trehalulose by Immobilized Thermostable Trehalose Synthase

Trehalose, a versatile disaccharide renowned for its unique physical and chemical properties, finds extensive application in the food, pharmaceutical, and cosmetic industries. While conventional extraction methods face challenges, enzymatic conversion offers a promising avenue for the industrial production of trehalose. This study delves into a novel synthetic approach utilizing a recombinant enzyme, merging the thermostable trehalose synthase domain from Thermus thermophiles with a cellulose binding domain. Immobilization of this enzyme on cellulose matrices enhances stability and facilitates product purification, opening avenues for efficient enzymatic synthesis. Notably, the engineered enzyme demonstrates additional activity, converting sucrose into trehalulose. This dual functionality, combined with immobilization strategies, holds immense potential for scalable and cost-effective production of trehalose and trehalulose, offering promising prospects in various industrial and biomedical applications.

Antibiotic-free production of sucrose isomerase in Bacillus subtilis by genome integration

Sucrose isomerase (SIase) catalyzes the hydrolysis and isomerization of sucrose to form isomaltulose, a valuable functional sugar widely used in the food industry. However, the lack of safe and efficient heterologous expression systems hinders SIase production and application. In this study, we achieved antibiotic-free SIase expression in Bacillus subtilis through genome integration. Using CRISPR/Cas9 system, SIase expression cassettes were integrated into various genomic loci, including amyE and ctc, both individually and in combination, resulting in single-copy and muti-copy integration strains. Engineered strains with a maltose-inducible promoter effectively expressed and secreted SIase. Notably, multi-copy strain exhibited enhanced SIase production, achieving 4.4 U/mL extracellular activity in shake flask cultivations. Furthermore, crude enzyme solution from engineered strain transformed high concentrations sucrose into high yields of isomaltulose, reaching a maximum yield of 94.6%. These findings demonstrate antibiotic-free SIase production in B. subtilis via genome integration, laying the foundation for its industrial production and application.

Efficient production of isomaltulose using engineered Yarrowia lipolytica strain facilitated by non-yeast signal peptide-mediated cell surface display

BACKGROUND

Isomaltulose is a 'generally recognized as safe' ingredient and is widely used in the food, pharmaceutical and chemical industries. The exploration and development of efficient technologies is essential for enhancing isomaltulose yield.

RESULTS

In the present study, a simple and efficient surface display platform mediated by a non-yeast signal peptide was developed in Yarrowia lipolytica and utilized to efficiently produce isomaltulose from sucrose. We discovered that the signal peptide SP1 of sucrose isomerase from Pantoea dispersa UQ68J (PdSI) could guide SIs anchoring to the cell surface of Y. lipolytica, demonstrating a novel and simple cell surface display strategy. Furthermore, the PdSI expression level was significantly increased through optimizing the promoters and multi-site integrating genes into chromosome. The final strain gained 451.7 g L-1 isomaltulose with a conversion rate of 90.3% and a space-time yield of 50.2 g L-1 h-1.

CONCLUSION

The present study provides an efficient way for manufacturing isomaltulose with a high space-time yield. This heterogenous signal peptide-mediated cell surface display strategy featured with small fusion tag (approximately 2.2 kDa of SP1), absence of enzyme leakage in fermentation broth and ample room for optimization, providing a convenient way to construct whole-cell biocatalysts to synthesize other products and broadening the array of molecular toolboxes accessible for engineering Y. lipolytica. © 2024 Society of Chemical Industry.

Discrimination of Disaccharide Isomers of Different Glycosidic Linkages Using a Modified MspA Nanopore

Disaccharides are composed of two monosaccharide subunits joined by a glycosidic linkage in an α or β configuration. Different combinations of isomeric monosaccharide subunits and different glycosidic linkages result in different isomeric disaccharide products. Thus, direct discrimination of these disaccharide isomers from a mixture is extremely difficult. In this paper, a hetero-octameric Mycobacterium smegmatis porin A (MspA) nanopore conjugated with a phenylboronic acid (PBA) adapter was applied for disaccharide sensing, with which three most widely known disaccharides in nature, including sucrose, lactose and maltose, were clearly discriminated. Besides, all six isomeric α-D-glucopyranosyl-D-fructoses, differing only in their glycosidic linkages, were also well resolved. Assisted by a custom machine learning algorithm, a 0.99 discrimination accuracy is achieved. Nanopore discrimination of disaccharide isomers with different glycosidic linkages, which has never been previously demonstrated, is inspiring for nanopore saccharide sequencing. This sensing capacity was also applied in direct identification of isomaltulose additives in a commercial sucrose-free yogurt, from which isomaltulose, lactose and L-lactic acid were simultaneously detected.

Studies on the Changes of Fermentation Metabolites and the Protective Effect of Fermented Edible Grass on Stress Injury Induced by Acetaminophen in HepG2 Cells

In this study, gas chromatography-mass spectrometry (GC-MS) based untargeted metabolomics was used to describe the changes of metabolites in edible grass with Lactobacillus plantarum (Lp) fermentation durations of 0 and 7 days, and subsequently to investigate the protective effect of fermented edible grass on acetaminophen-induced stress injury in HepG2 cells. Results showed that 53 differential metabolites were identified, including 31 significantly increased and 22 significantly decreased metabolites in fermented edible grass. Fermented edible grass protected HepG2 cells against acetaminophen-induced stress injury, which profited from the reduction in lactate dehydrogenase (LDH) and malondialdehyde (MDA) levels and the enhancement in superoxide dismutase (SOD) activity. Cell metabolomics analysis revealed that a total of 13 intracellular and 20 extracellular differential metabolites were detected. Fermented edible grass could regulate multiple cell metabolic pathways to exhibit protective effects on HepG2 cells. These findings provided theoretical guidance for the formation and regulation of bioactive metabolites in fermented edible grass and preliminarily confirmed the protective effects of fermented edible grass on drug-induced liver damage.

Tune in to the terrific applications of turanose

Turanose, a rare sugar with low calorific value and glycemic index, used as an alternative to sucrose and other artificial sweeteners. The occurrence of turanose is in limited quantities, especially found in honey. Thus, it should be produced by either chemical or biological means. Turanose is released as a by-product during synthesis of the linear α-(1,4)-glucan from sucrose by the action of amylosucrase. In recent times, turanose attracted interest in several industries such as agricultural, food, and pharmaceuticals due to its feasible production. Hence, this review outlines about the history of turanose, its physiochemical properties, production along with inhibition and inducing effects. It is high time to tune in the terrific applications of turanose, as it retains the potential for more than a century of discovery, since 1889. These applications include detection of pathogens, facilitation of cellular respiration, regulation of inflammation, authentication of honey, phagodeterrency effects, osmoprotection, stabilization of therapeutical proteins, and edibility enhancement of foods.

Whitefly-Plant Interactions: An Integrated Molecular Perspective

The rapid advances in available transcriptomic and genomic data and our understanding of the physiology and biochemistry of whitefly-plant interactions have allowed us to gain new and significant insights into the biology of whiteflies and their successful adaptation to host plants. In this review, we provide a comprehensive overview of the mechanisms that whiteflies have evolved to overcome the challenges of feeding on phloem sap. We also highlight the evolution and functions of gene families involved in host perception, evaluation, and manipulation; primary metabolism; and metabolite detoxification. We discuss the emerging themes in plant immunity to whiteflies, focusing on whitefly effectors and their sites of action in plant defense-signaling pathways. We conclude with a discussion of advances in the genetic manipulation of whiteflies and the potential that they hold for exploring the interactions between whiteflies and their host plants, as well as the development of novel strategies for the genetic control of whiteflies.

Two-dimensional isomer differentiation using liquid chromatography-tandem mass spectrometry with in-source, droplet-based derivatization

Saccharides are increasingly used as biomarkers and for therapeutic purposes. Their characterization is challenging due to their low ionization efficiencies and inherent structural heterogeneity. Here, we illustrate how the coupling of online droplet-based reaction, in a form of contained electrospray (ES) ion source, with liquid chromatography (LC) tandem mass spectrometry (MS/MS) allows the comprehensive characterization of sucrose isomers. We used the reaction between phenylboronic acid and cis-diols for on-the-fly derivatization of saccharides eluting from the LC column followed by in situ MS/MS analysis, which afforded diagnostic fragment ions that enabled differentiation of species indistinguishable by chromatography or mass spectrometry alone. For example, chromatograms differing only by 2% in retention times were flagged to be different based on incompatible MS/MS fragmentation patterns. This orthogonal LC-contained-ES-MS/MS method was applied to confirm the presence of turanose, palatinose, maltulose, and maltose, which are structural isomers of sucrose, in three different honey samples. The reported workflow does not require modification to existing mass spectrometers, and the contained-ES platform itself acts both as the ion source and the reactor, all promising widespread application.

Potential of Natural Honey in Controlling Obesity and its Related Complications

Honey has a long history of therapeutic properties for multiple diseases, including inflammation and oxidative stress. This review aimed to provide a better understanding and renewed interest in the potential role of honey in obesity control, obesity-related diseases treatment and weight management, with specific reference to its components and the effect of honey overall. There is compelling evidence that honey possesses the desired properties for this purpose, as seen in the in vitro, in silico, in vivo and clinical analyses discussed in this review. This review also highlights the components potentially responsible for the health benefits of honey. Honey and its components reduce blood sugar levels, improve insulin sensitivity and lipid metabolism by reducing triglycerides, and reduce total cholesterol and LDL levels while increasing HDL levels that prevent excessive weight gain and reduce the risk of obesity and its complications. Further controlled studies are necessary to validate the role of honey in the management of obesity, both as a preventive and as a therapeutic agent.

Enhanced Extracellular Production and Characterization of Sucrose Isomerase in Bacillus subtilis with Optimized Signal Peptides

Sucrose isomerase (SIase) catalyzes the hydrolysis and isomerization of sucrose into isomaltulose, which is an important functional sugar widely used in the food industry. However, the lack of safe and efficient expression systems for recombinant SIase has impeded its production and application. In this study, enhanced expression of a SIase from Klebsiella sp. LX3 (referred to as KsLX3-SIase) was achieved in Bacillus subtilis WB800N, by optimizing the signal peptides. First, 13 candidate signal peptides were selected using a semi-rational approach, and their effects on KsLX3-SIase secretion were compared. The signal peptide WapA was most efficient in directing the secretion of KsLX3-SIase into the culture medium, producing a specific activity of 23.0 U/mL, as demonstrated by shake flask culture. Using a fed-batch strategy, the activity of KsLX3-SIase in the culture medium was increased to 125.0 U/mL in a 5-L fermentor. Finally, the expressed KsLX3-SIase was purified and was found to have maximum activity at 45 °C and pH 5.5. Its K_m for sucrose was 267.6 ± 18.6 mmol/L, and its k_cat/K_m was 10.1 ± 0.2 s⁻¹mM⁻¹. These findings demonstrated an efficient expression of SIase in B. subtilis, and this is thought to be the highest level of SIase produced in a food-grade bacteria to date.

Comprehensive utilization of sucrose resources via chemical and biotechnological processes: A review

Sucrose, one of the most widespread disaccharides in nature, has been available in daily human life for many centuries. As an abundant and cheap sweetener, sucrose plays an essential role in our diet and the food industry. However, it has been determined that many diseases, such as obesity, diabetes, hyperlipidemia, etc., directly relate to the overconsumption of sucrose. It arouses many explorations for the conversion of sucrose to high-value chemicals. Production of valuable substances from sucrose by chemical methods has been studied since a half-century ago. Compared to chemical processes, biotechnological conversion approaches of sucrose are more environmentally friendly. Many enzymes can use sucrose as the substrate to generate functional sugars, especially those from GH68, GH70, GH13, and GH32 families. In this review, enzymatic catalysis and whole-cell fermentation of sucrose for the production of valuable chemicals were reviewed. The multienzyme cascade catalysis and metabolic engineering strategies were addressed.

Effect of Isomaltulose on Glycemic and Insulinemic Responses: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Evidence regarding the effect of isomaltulose on glycemic and insulinemic responses is still conflicting, which limits isomaltulose's application in glycemic management. The purpose of this study was to comprehensively evaluate its effectiveness and evidence quality. We systematically searched PubMed, Embase, and the Cochrane Library for randomized controlled trials (RCTs) prior to October 2021. RCTs were eligible for inclusion if they enrolled adults to oral intake of isomaltulose or other carbohydrates dissolved in water after an overnight fast and compared their 2-h postprandial glucose and insulin concentrations. The DerSimonian-Laird method was used to pool the means of the circulating glucose and insulin concentrations. Both random-effects and fixed-effects models were used to calculate the weighted mean difference in postprandial glucose and insulin concentrations in different groups. Subgroup, sensitivity, and meta-regression analyses were also conducted. Grading of Recommendations Assessment, Development, and Evaluation (GRADE) was used to assess the certainty of evidence. Finally, 11 RCTs (n = 175 participants) were included. The trials were conducted in 4 countries (Japan, Brazil, Germany, and the Netherlands), and all of the enrolled participants were >18 y of age with various health statuses (healthy, type 2 diabetes, impaired glucose tolerance, and hypertension). Moderate evidence suggested that oral isomaltulose caused an attenuated glycemic response compared with sucrose at 30 min. Low evidence suggested that oral isomaltulose caused an attenuated but more prolonged glycemic response than sucrose and an attenuated insulinemic response. Low-to-moderate levels of evidence suggest there may be more benefit of isomaltulose for people with type 2 diabetes, impaired glucose tolerance, or hypertension; older people; overweight or obese people; and Asian people. The study was registered on PROSPERO (International Prospective Register of Systematic Reviews) as CRD42021290396 (available at https://www.crd.york.ac.uk/prospero/).

Feeding Sugars to Stingless Bees: Identifying the Origin of Trehalulose-Rich Honey Composition

The beneficial disaccharide, trehalulose, is a feature of stingless bee honey, while not dominant in any other foods. By experimentally feeding sugar solutions to confined colonies of the Australian stingless bee Tetragonula carbonaria, the origin of trehalulose has now been established. Complete conversion of fed sucrose was observed, by analysis of the honey, forming trehalulose (64-72%) with lesser erlose (18-23%), fructose (9-12%), and minor glucose detected. Remarkably, feeding solutions of glucose/fructose (1:1) mixtures did not result in trehalulose/erlose formation. Hence, stingless bees with natural access to floral nectar high in sucrose will produce honey high in trehalulose, with its associated beneficial properties. Any temptation to artificially increase trehalulose content by feeding sucrose to stingless bees would produce "fake" honey lacking key natural phytochemicals available to the foraging bee. The sucrose-fed fake and natural honey were however readily distinguished via isotope ratio mass spectrometry δ¹³C values, to combat such potential indirect adulteration.

Direct Isomaltulose Synthesis From Beet Molasses by Immobilized Sucrose Isomerase

Isomaltulose is becoming a focus as a functional sweetener for sucrose substitutes; however, isomaltulose production using sucrose as the substrate is not economical. Low-cost feedstocks are needed for their production. In this study, beet molasses (BM) was introduced as the substrate to produce isomaltulose for the first time. Immobilized sucrose isomerase (SIase) was proved as the most efficient biocatalyst for isomaltulose synthesis from sulfuric acid (H₂SO₄) pretreated BM followed by centrifugation for the removal of insoluble matters and reducing viscosity. The effect of different factors on isomaltulose production is investigated. The isomaltulose still achieved a high concentration of 446.4 ± 5.5 g/L (purity of 85.8%) with a yield of 0.94 ± 0.02 g/g under the best conditions (800 g/L pretreated BM, 15 U immobilized SIase/g dosage, 40°C, pH of 5.5, and 10 h) in the eighth batch. Immobilized SIase used in repeated batch reaction showed good reusability to convert pretreated BM into isomaltulose since the sucrose conversion rate remained 97.5% in the same batch and even above 94% after 11 batches. Significant cost reduction of feedstock costs was also confirmed by economic analysis. The findings indicated that this two-step process to produce isomaltulose using low-cost BM and immobilized SIase is feasible. This process has the potential to be effective and promising for industrial production and application of isomaltulose as a functional sweetener for sucrose substitute.

Stingless bee honey, a novel source of trehalulose: a biologically active disaccharide with health benefits

Stingless bee (Meliponini) honey has long been considered a high-value functional food, but the perceived therapeutic value has lacked attribution to specific bioactive components. Examination of honey from five different stingless bee species across Neotropical and Indo-Australian regions has enabled for the first time the identification of the unusual disaccharide trehalulose as a major component representing between 13 and 44 g per 100 g of each of these honeys. Trehalulose is an isomer of sucrose with an unusual α-(1 → 1) glucose-fructose glycosidic linkage and known acariogenic and low glycemic index properties. NMR and UPLC-MS/MS analysis unambiguously confirmed the identity of trehalulose isolated from stingless bee honeys sourced across three continents, from Tetragonula carbonaria and Tetragonula hockingsi species in Australia, from Geniotrigona thoracica and Heterotrigona itama in Malaysia and from Tetragonisca angustula in Brazil. The previously unrecognised abundance of trehalulose in stingless bee honeys is concrete evidence that supports some of the reported health attributes of this product. This is the first identification of trehalulose as a major component within a food commodity. This study allows the exploration of the expanded use of stingless bee honey in foods and identifies a bioactive marker for authentication of this honey in associated food standards.