High-Yield Synthesis of Transglycosylated Mogrosides Improves the Flavor Profile of Monk Fruit Extract Sweeteners

Recent advancements in mogrosides: A review on biological activities, synthetic biology, and applications in the food industry

Mogrosides are low-calorie, biologically active sweeteners that face high production costs due to strict cultivation requirements and the low yield of monk fruit. The rapid advancement in synthetic biology holds the potential to overcome this challenge. This review presents mogrosides exhibiting antioxidant, anti-inflammatory, anti-cancer, anti-diabetic, and liver protective activities, with their efficacy in diabetes treatment surpassing that of Xiaoke pills (a Chinese diabetes medication). It also discusses the latest elucidated biosynthesis pathways of mogrosides, highlighting the challenges and research gaps in this field. The critical and most challenging step in this pathway is the transformation of mogrol into a variety of mogrosides by different UDP-glucosyltransferases (UGTs), primarily hindered by the poor substrate selectivity, product specificity, and low catalytic efficiency of current UGTs. Finally, the applications of mogrosides in the current food industry and the challenges they face are discussed.

Solubilization mechanism of α-glycosylated naringin based on self-assembled nanostructures and its application to skin formulation

We previously reported that α-glycosylated naringin (naringin-G), synthesized by enzyme-catalyzed transglycosylation, can enhance the solubility of poorly water-soluble compounds without surface-active property. However, the solubilization mechanism has not been fully elucidated. In this study, the solubilization mechanism of naringin-G was investigated using nuclear magnetic resonance (NMR) spectroscopy, and its application in skin formulations was further investigated. 1H NMR and dynamic light scattering measurements at various concentrations confirmed the self-assembled nanostructures of naringin-G above a critical aggregation concentration of approximately 2.2 mg/mL. Two-dimensional 1H-1H nuclear Overhauser effect spectroscopy and solubility tests revealed that flavone with poor water solubility, could be solubilized in its self-assembled structure with a stoichiometric relationship with naringin-G. When naringin-G was included in the skin formulation, the permeated amount and permeability coefficient (Papp) of flavones improved up to four times with increasing amounts of naringin-G. However, flavone solubilization by adding an excessive amount of naringin-G resulted in a decreased permeated amount and Papp of flavones, indicating the interplay between the apparent solubility and skin permeability of flavones. Naringin-G, which forms a nanoaggregate structure without exhibiting surface-active properties, has the potential to enhance the solubility and skin permeation of poorly water-soluble compounds.

Plant endophytic fungi exhibit diverse biotransformation pathways of mogrosides and show great potential application in siamenoside I production

Fungal endophytes, as an untapped resource of glycoside hydrolase biocatalysts, need to be further developed. Mogroside V, the primary active compound in Siraitia grosvenorii fruit, can be converted into other various bioactive mogrosides by selective hydrolysis of glucose residues at C3 and C24 positions. In present study, 20 fungal strains were randomly selected from our endophytic fungal strain library to assess their capability for mogroside V transformation. The results revealed that relatively high rate (30%) endophytic fungal strains exhibited transformative potential. Further analysis indicated that endophytic fungi could produce abundant mogrosides, and the pathways for biotransforming mogroside V showed diverse. Among the given fungal endophytes, Aspergillus sp. S125 almost completely converted mogroside V into the end-products mogroside II A and aglycone within just 2 days of fermentation; Muyocopron sp. A5 produced rich intermediate products, including siamenoside I, and the end-product mogroside II E. Subsequently, we optimized the fermentation conditions for Aspergillus sp. S125 and Muyocopron sp. A5 to evaluate the feasibility of large-scale mogroside V conversion. After optimization, Aspergillus sp. S125 converted 10 g/L of mogroside V into 4.5 g/L of mogroside II A and 3.6 g/L of aglycone after 3 days of fermentation, whereas Muyocopron sp. A5 selectively produced 4.88 g/L of siamenoside I from 7.5 g/L of mogroside V after 36 h of fermentation. This study not only identifies highly effective biocatalytic candidates for mogrosides transformation, but also strongly suggests the potential of plant endophytic fungi as valuable resources for the biocatalysis of natural compounds.

Siraitia grosvenorii As a Homologue of Food and Medicine: A Review of Biological Activity, Mechanisms of Action, Synthetic Biology, and Applications in Future Food

Siraitia grosvenorii (SG), also known as Luo Han Guo or Monk fruit, boasts a significant history in food and medicine. This review delves into SG's historical role and varied applications in traditional Chinese culture, examining its phytochemical composition and the health benefits of its bioactive compounds. It further explores SG's biological activities, including antioxidant, anti-inflammatory, and antidiabetic properties and elucidates the mechanisms behind these effects. The review also highlights recent synthetic biology advances in enhancing the production of SG's bioactive compounds, presenting new opportunities for broadening their availability. Ultimately, this review emphasizes SG's value in food and medicine, showcasing its historical and cultural importance, phytochemistry, biological functions, action mechanisms, and the role of synthetic biology in its sustainable use.

Prebiotic potential of new sweeteners based on the simultaneous biosynthesis of galactooligosaccharides and enzymatically modified steviol glycosides

Prebiotics are known for their health-promoting functions associated with the modulation of the colonic microbiota and the products of fermentation. Recently, single-pot syntheses of galactooligosaccharides in combination with steviol glycosides (mSG-GOS) have been developed. This work was conducted to evaluate their prebiotic effect by using faecal inoculum from healthy human donors during in vitro batch fermentations. Additionally, their relative sweetness was evaluated to determine their suitability as food ingredients. The results showed a significant growth (p < 0.05) of bacteria, including the genera Bifidobacterium, Bacteroides and Clostridium, and a corresponding increase in short-chain fatty acids (SCFA) in comparison to either positive and negative controls. The sweetness equivalence to 1 % w:v of SG-GOS was 0.8 % w:v when compared to sucrose. Considering the bacteria and organic acids analyses and their sweetness values of these new biosynthesized compounds, SG-GOS could act as a prebiotic sweetener with potential health benefits warranting further evaluation through human studies.

Characterization and sweetness-enhancing effect of peptides from yeast extract based on sensory evaluation and molecular docking approaches

Yeast extract (YE) is derived from the soluble component in yeast cells, which is rich in peptides and has been used as a sweet-enhancing agent. It has the potential to be utilized to produce natural sweet-flavored peptides or sweet-enhancing peptides. To study the synergistic effect and mechanism of sweetness-enhancing peptides derived from YE, ultrafiltration fraction with molecular weight less than 1 kDa was screened according to sensory analysis, which showed a synergistic sweetening effect in stevioside and mogroside solution. Twenty potential taste peptides were identified from the screened fractions, among which EV, AM, AVDNIPVGPN and VDNIPVGPN showed sweetness-enhancing effects on both stevioside and mogroside. The sweetener-receptor-peptide complex was constructed to investigate the interaction of stevioside and mogroside to taste receptor type 1 member 2 accompanied by these peptides. The results of the molecular docking indicated that new hydrophobic interactions (Leu 279, Pro 308, Val 309, etc.) and hydrogen bonds (Ser 40, Ala 43, Asp 278, etc.) were formed between sweeteners and active sites in the venus flytrap domain. In conclusion, the presence of sweetness-enhancing peptides from YE improved the binding stability of sweeteners and receptors by increasing the binding interaction, especially the hydrophobic interactions, which contribute to the synergistic effect of sweetness-enhancing peptides.

Bibliometric analysis on the literature of monk fruit extract and mogrosides as sweeteners

The evolution of research literature on monk fruit extract and mogroside as sweeteners has yet to be investigated. No study has evaluated this literature from a bibliometric perspective. This bibliometric study analyzed the relevant research literature indexed in Web of Science, to unveil its growth and the most productive authors, institutions, countries, journals, and journal categories. In addition, this study aimed to identify the recurring themes of the literature. On July 2023, the Web of Science Core Collection database was accessed with the following search query: TS = (*mogroside* OR "luo han guo" OR "lo han kuo" OR "monk fruit*" OR "monkfruit*" OR "Siraitia grosvenorii") AND TS = (sweet*). The search identified publications mentioning these terms in their title, abstract, or keywords. Only articles and reviews were included. No additional filters were placed on publication year, language, etc. Basic publication and citation frequency counts were recorded directly from the database. The complete record of the publications were exported into VOSviewer and CRExplorer, for visualization of recurring terms and identification of commonly cited references, respectively. The search yielded 155 publications. Publication and citation counts have increased steadily since the 2010s. The most productive authors and institutions were mostly based in Asian countries, such as China, Japan, and Singapore. Nearly half of the publications had contributions from China and were published in journals concerning food science technology. The health effects and biosynthesis of mogrosides were the recurring themes among the top 10 most cited publications. Most of the health effects, such as anti-hyperglycemic, anti-hyperlipidemic, and anti-diabetic properties, were demonstrated in animal models with limited evidence from clinical trials. Future studies should focus on testing in humans. Since monk fruit extracts were generally recognized as safe (GRAS) according to the Food and Drug Administration (FDA), the affirmation of these health benefits in humans by future studies should advocate its use in the food industry and the society to generally improve the public health.

Molecular mechanism of acceptor selection in cyclodextrin glycosyltransferases catalyzed ginsenoside transglycosylation

Understanding the mechanisms of enzyme specificity is increasingly important from a fundamental viewpoint and for practical applications. Transglycosylation has attracted many attentions due to its importance in improving the functional properties of acceptor substrates both in vivo and in vitro. Cyclodextrin glucanotransferase (CGTase) is one of the key enzymes in transglycosylation, it has a broad substrate spectrum and utilizes sugar as the donor. However, little is known about the acceptor selectivity of CGTase, which greatly hampers efforts toward the rational design of desirable transglycosylated derivatives. In this study, we found that the CGTase from Bacillus circulans, BcCGTase, was able to form glycosylated products with diverse ginsenosides. In particular, it not only carries out diverse mono-, di-, and even higher-order glycosylations via the transfer of glucose moieties to the COGlc positions, but also can glycosylate the C3-OH position of ginsenosides. In contrast, another CGTase from Bacillus licheniformis (BlCGTase) showed relatively specific acceptor preference with only several ginsenosides. Structural comparison between BcCGTase and BlCGTase revealed that the Arg74/K81 position within the acceptor-binding sites of BcCGTase/BlCGTase was responsible for the differences in catalytic specificity for ginsenoside F1. Further mutagenesis confirmed their roles in the acceptor selection. In conclusion, our study not only demonstrates the acceptor selectivity of CGTases, but also provides insight into the catalytic mechanism of CGTases, which will potentially increase the utility of CGTase for biosynthesis of new, rationally designed transglycosylated derivatives.

Prebiotic Potential of a New Sweetener Based on Galactooligosaccharides and Modified Mogrosides

This study was conducted to investigate the sweetness intensity and the potential fecal microbiome modulation of galactooligosaccharides in combination with enzymatically modified mogrosides (mMV-GOS), both generated through a patented single-pot synthesis. Sweetness intensity was performed in vivo by trained sensory panelists. The impact on the human fecal microbiome was evaluated by in vitro pH-controlled batch fermentation, and bacterial populations and organic acid concentrations were measured by qPCR and GC-FID, respectively. Significant growth (p ≤ 0.05) during the fermentation at 10 h of bacterial populations includes Bifidobacterium (8.49 ± 0.44 CFU/mL), Bacteroides (9.73 ± 0.32 CFU/mL), Enterococcus (8.17 ± 0.42 CFU/mL), and Clostridium coccoides (6.15 ± 0.11 CFU/mL) as compared to the negative control counts for each bacterial group (7.94 ± 0.27, 7.84 ± 1.11, 7.52 ± 0.37, and 5.81 ± 0.08 CFU/mL, respectively) at the same time of fermentation. Likewise, the corresponding significant increase in production of SCFA in mMV-GOS at 10 h of fermentation, mainly seen in acetate (20.32 ± 2.56 mM) and propionate (9.49 ± 1.44 mM) production compared to a negative control at the same time (8.15 ± 1.97 and 1.86 ± 0.24 mM), is in line with a positive control (short-chain fructooligosaccharides; 46.74 ± 12.13 and 6.51 ± 1.91 mM, respectively) revealing a selective fermentation. In conclusion, these substrates could be considered as novel candidate prebiotic sweeteners, foreseeing a feasible and innovative approach targeting the sucrose content reduction in food. This new ingredient could provide health benefits when evaluated in human studies by combining sweetness and prebiotic fiber functionality.

Heterologous expression of 4α-glucanotransferase: overproduction and properties for industrial applications

4α-Glucanotransferase (4α-GTase) is unique in its ability to form cyclic oligosaccharides, some of which are of industrial importance. Generally, low amount of enzymes is produced by or isolated from their natural sources: animals, plants, and microorganisms. Heterologous expressions of these enzymes, in an attempt to increase their production for applicable uses, have been widely studied since 1980s; however, the expressions are mostly performed in the prokaryotic bacteria, mostly Escherichia coli. Site-directed mutagenesis has added more value to these expressed enzymes to display the desired properties beneficial for their applications. The search for further suitable properties for food application leads to an extended research in expression by another group of host organism, the generally-recognized as safe host including the Bacillus and the eukaryotic yeast systems. Herein, our review focuses on two types of 4α-GTase: the cyclodextrin glycosyltransferase and amylomaltase. The updated studies on the general structure and properties of the two enzymes with emphasis on heterologous expression, mutagenesis for property improvement, and their industrial applications are provided.