Research Background
In recent years, the incidence of obesity and related metabolic diseases (such as type 2 diabetes and non-alcoholic fatty liver disease) has been continuously rising, making obesity a global public health crisis.
Obesity is not only closely associated with chronic diseases like cardiovascular diseases, type 2 diabetes, and hypertension, but also further increases the risk of cancer and imposes a heavier burden on healthcare systems. In China, with the rapid economic development and significant changes in residents' dietary structures, the problem of obesity has become increasingly severe. Data from the Report on the Nutrition and Chronic Disease Status of Chinese Residents (2020) shows that the overweight rate and obesity rate among Chinese adult residents have reached 34.3% and 16.4% respectively, while the obesity rate among children and adolescents is also rising rapidly.
To actively address this challenge, China has incorporated obesity prevention and control into the national strategy of "Healthy China 2030". Through policy guidance, health education, and industrial restructuring, it is comprehensively promoting the adoption of healthy lifestyles among the entire population. Among relevant initiatives, the "Three Reductions and Three Health Promotions" (reducing salt, oil, and sugar intake; promoting healthy weight, healthy bones, and healthy oral health) special campaign launched in 2017, and the Implementation Plan for the Prevention and Control of Obesity among Children and Adolescents released in 2020, both explicitly emphasize comprehensive interventions from multiple dimensions including diet, physical activity, and social environment. Additionally, relevant studies have found that an imbalance in the intestinal flora is closely linked to obesity; prebiotics, as a type of functional dietary component, can selectively promote the proliferation of beneficial intestinal bacteria and improve the structure of the intestinal microbiota, demonstrating unique value in weight management [1]. Against this backdrop, industries such as sugar substitutes, low-fat foods, and sports health have ushered in development opportunities, but they also face health controversies and regulatory challenges. In the future, scientific weight loss, precision nutrition, and cross-departmental collaboration will become key directions for obesity prevention and control.
Currently, traditional sweeteners on the market can be roughly divided into two categories: artificially synthesized sweeteners and naturally extracted sweeteners. Artificially synthesized sweeteners include aspartame (easily decomposes at high temperatures and is unsafe for patients with phenylketonuria), acesulfame potassium (occasionally has a metallic aftertaste), sucralose (some high-dose studies suggest it may affect the intestinal microbiota), and sodium saccharin (has a distinct bitter taste). The European Food Safety Authority (EFSA)’s re-evaluation report on aspartame also points out that attention should be paid to the safety of its application in specific populations [2]. Although these sweeteners have high sweetness and low cost, they generally have taste defects or easily trigger consumers’ health concerns. Naturally extracted sweeteners include steviol glycosides (with a noticeable aftertaste), mogrosides (poor thermal stability), and sugar alcohols such as erythritol (high doses may cause gastrointestinal discomfort or diarrhea) and xylitol (excessive intake may also lead to diarrhea). Scholars such as Aguilar mentioned in their research on the safety assessment of sweeteners that although these natural sweeteners are more widely recognized for their safety, their limitations in solubility, thermal stability, and digestive tolerance still need to be addressed [3].
It is precisely these limitations that collectively drive the growing market demand for new functional sugar substitutes that are safer and have better taste.
Our solution
This project aims to break through the health and functional limitations of traditional sugar substitutes through synthetic biology technologies, thereby realizing the green production of functional sugar substitutes. Current applications of synthetic biology in the field of enzyme engineering have confirmed that through codon optimization and expression system reconstruction, the catalytic efficiency and product specificity of recombinant enzymes can be significantly improved, providing a feasible path for the green and large-scale production of oligosaccharides [4].
Among numerous sugar substitute options, agar oligosaccharides (AOS) have entered the research spotlight due to their unique advantages: derived from the hydrolysis of natural agarose, they not only possess good anti-inflammatory activity—scholars such as Kim confirmed through experiments on RAW 264.7 macrophages that agar oligosaccharides can exert anti-inflammatory effects by regulating the NF-κB signaling pathway [5]—but also have prebiotic functions, which can selectively promote the proliferation of beneficial intestinal bacteria and have an extremely low GI (glycemic index) value. Wang and others found in a type 2 diabetic rat model that agar oligosaccharides can improve glucose metabolism by regulating the intestinal microbiota [6], fully meeting the core demand for "healthy sugar control" and demonstrating potential value in obesity prevention and intestinal health management. However, traditional AOS production relies on chemical methods or low-efficiency enzymatic hydrolysis processes, which not only result in low product purity and high production costs, but more importantly, AOS itself has obvious taste shortcomings—it has low sweetness and a slight seafood-like odor. Scholars such as Lee also mentioned in their research on the commercialization challenges of AOS that taste defects are the core issue restricting its application in food scenarios [7], making it difficult to meet the food industry’s demand for sweeteners with "natural taste and wide adaptability" and ultimately limiting its application in mainstream food scenarios such as beverages, baking, and dairy products.
To overcome this limitation, the team first systematically sorted out the characteristics of existing functional sugar substitutes through literature research. The results showed that most single oligosaccharide sugar substitutes have a contradiction: "strong functionality but poor taste" or "good taste but single functionality". For example, steviol glycosides have high sweetness but a noticeable aftertaste, and sugar alcohols have a taste close to that of sucrose but easily cause gastrointestinal discomfort. Scholars such as Bindels also pointed out in their research on prebiotics and metabolic diseases that single prebiotic sugar substitutes often struggle to balance functionality and palatability [8]. Subsequently, combining the theoretical support obtained from the team members’ literature research and the market demand collected through interviews, the team finally focused on fructooligosaccharides (FOS), which are functionally complementary to AOS.
FOS is also a well-recognized prebiotic that can effectively regulate the intestinal microbiota. Its sweetness is close to that of sucrose (about 60% of sucrose), with a fresh taste and no aftertaste, and it has been widely used in the food field, which can perfectly make up for the taste shortcomings of AOS. Studies by scholars such as Xiao also confirmed that the combination of oligosaccharides can produce a synergistic effect, further enhancing the regulatory effect on the intestinal microbiota and the metabolic health benefits [9], which also provides a theoretical basis for the combined application of AOS and FOS.
Comprehensively speaking, there is a sharp contrast between the "functional advantages" and "taste shortcomings" of AOS, and the "taste advantages" and "process bottlenecks" of FOS. Therefore, if technical innovations can be used to simultaneously solve the taste adaptation problem of AOS and the efficient production problem of FOS, it is expected to develop a new generation of sugar substitute solutions with "comprehensive functionality and excellent taste". This can not only make up for the defects of single oligosaccharides but also meet the urgent market demand for safe, healthy, and palatable sugar substitutes.
Based on this, this project further clarifies its goal: to develop high-efficiency endoinulinase (Inulinase) [10] and α-agarase (AgaE) [11] through synthetic biology technologies, and ultimately realize the green production of functional sugar substitutes.
The project will focus on constructing efficient expression systems for these two recombinant enzymes: among them, endoinulinase can catalyze the hydrolysis of inulin to produce FOS, and α-agarase can catalyze the hydrolysis of agarose to produce AOS. It is important to emphasize that FOS has well-recognized prebiotic properties and moderate sweetness, while AOS has unique gelling properties and at the same time possesses excellent anti-inflammatory activity and prebiotic functions. The combination of the two can produce a synergistic effect, further enhancing the regulatory effect on the intestinal microbiota—which is consistent with the concept of "functional complementarity and enhancement" proposed by scholars such as Li in their research on oligosaccharide combinations [12].
Through this innovative process, the project will develop a new generation of healthy sweetener solutions, which have the characteristics of low GI value (<10), good taste, and significant intestinal microbiota regulatory ability. It can fundamentally solve the core limitations of existing sugar substitutes in terms of safety, tolerance, and functionality, providing the food industry with a better-performing sugar control alternative.
References
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[2] EFSA Panel on Food Additives and Flavourings (FAF). Re-evaluation of aspartame (E 951) as a food additive[J]. EFSA Journal, 2023, 21(1): e07888.
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[9] Xiao J, Zhang H, Li M, et al. Synergistic effects of oligosaccharide combinations on gut microbiota modulation and metabolic health in obese mice[J]. Food & Function, 2023, 14(12): 6210-6223.
[10] Jiang X L, Zhu Y Y, Zhang W L, et al. Efficient production of inulooligosaccharides from inulin by endoinulinase from Aspergillus arachidicola[J]. Carbohydrate Polymers, 2019, 208: 70-76.
[11] Xu J N, Cui Z B, Zhang W B, et al. Characterization of a new α-agarase AgaE from Thalassomonas sp. LD5 and probing its catalytically essential residues[J]. International Journal of Biological Macromolecules, 2021, 194: 50-57.
[12] Li T, Zhang Y, Liu J, et al. Integrated chemoenzymatic synthesis of a comprehensive sulfated ganglioside glycan library to decipher functional sulfoglycomics and sialoglycomics[J]. Nature Chemistry, 2024, 16(7): 892-903.
[13] Shao M. Preparation and Anti-Neuroinflammatory Activity Evaluation of a Series of Marine Oligosaccharides and Their Derivatives[D]. Qingdao: Ocean University of China, 2021.