The effect of fermentation broth of Guantu San Nang bacteria on obesity and intestinal microbiota in high-fat diet rats
Obesity refers to the excessive accumulation of fat in the body due to abnormal energy metabolism. High fat and high sugar diet has become the most common diet mode in the world today. Excessive intake of high fat and high sugar components will lead to fat accumulation and obesity. Excessive obesity not only affects people’s mental health, but also can lead to a variety of metabolic diseases such as diabetes, cardiovascular disease, hyperlipidemia, hypertension and so on. Obesity has become a global public health issue, posing a serious threat to human health. The gut microbiota is a large microbial community that resides in the host’s gut, primarily responsible for maintaining homeostasis within the body. Research has shown that gut microbiota can effectively regulate the body’s metabolism and energy balance, playing a crucial role in preventing the occurrence and development of obesity.
Eurotium cristatum, also known as “Golden Flower Fungus”, is a potential probiotic fungus belonging to the Ascomycota order, Aspergillus family, and Ascomycota genus. It is a key microorganism in the “flowering” process of traditional Fuzhuan tea. During the fermentation process, Guantu San Nang bacteria can produce various bioactive metabolites, such as flavonoids, alkaloids, piperazinedione derivatives, and fungal polysaccharides, which have the effects of lipid-lowering and weight loss, regulating gut microbiota, and inhibiting bacteria, effectively regulating human metabolism. Guantu sporangium is widely used in the fermentation fields of food and traditional Chinese medicine. As a safe and environmentally friendly probiotic fungus, Candida albicans not only improves the flavor of the substrate, but also has biological activities such as cholesterol lowering, antioxidant, and blood sugar lowering. Numerous studies have also shown that both intracellular and extracellular polysaccharides of Streptococcus pneumoniae can increase the body’s immune function by regulating gut microbiota and improving the intestinal barrier, and have good lipid-lowering and weight loss effects. At present, the fermentation process of Colletotrichum coronatum is mainly in solid form, with less liquid form. This study aims to obtain the fermentation broth of Colletotrichum coronatum through liquid culture method. At the same time, a foodborne obese rat model was established to investigate the effects of fermentation broth of Streptococcus pneumoniae on metabolism and gut microbiota disorders in obese rats.

Obesity is a disease associated with many health issues, widely believed to be caused by less physical exertion and more high calorie intake, closely related to chronic and low-grade inflammation in the body. The results of this study showed that a high-fat diet significantly increased the body weight and fat deposition of rats, exacerbating metabolic disorders. During the growth period of Candida albicans, various beneficial metabolites can be produced, such as fungal polysaccharides such as rhamnose and galactose, which have strong inhibitory effects on obesity, and have a certain regulatory effect on the blood lipid levels of obese mice. The study also found that the fermented extract of Colletotrichum coronatum can further regulate liver inflammation and fat accumulation caused by foodborne obesity by modulating the IL-6/STAT3 signaling pathway in the liver. This experiment also showed that the fermentation broth of Candida albicans has an inhibitory effect on diet induced obesity levels, alleviates fat accumulation to varying degrees, and reduces the levels of TG, TC, and LDH-C in rat serum, which helps regulate the metabolic balance of cholesterol. The level of LDH-C in serum is one of the risk factors for atherosclerosis. Lipid peroxidation is also related to the occurrence and development of atherosclerosis. Therefore, the fermentation liquid of Sarcocystis coronarius can not only effectively regulate the metabolic disorder induced by high-fat diet, but also prevent atherosclerosis.
The decrease in diversity of gut microbiota is a high-risk factor for obesity. Analysis using 16S rDNA amplification sequencing technology showed that under high-fat diet induction, the diversity of gut microbiota in rats significantly decreased, and the F/B ratio also significantly decreased. This result is consistent with the research of Lin, Zhang, and others, that the imbalance of F/B ratio in the intestine helps promote the occurrence of host obesity. The decrease in abundance of Firmicutes is related to a higher polysaccharide diet and the production of lipopolysaccharides. After intervention with the fermentation broth of Guantu San Nang bacteria, the F/B ratio was upregulated, and the diversity of the microbiota was restored, effectively improving the intestinal microbiota imbalance caused by fat intake. There are studies indicating that Helicobacter pylori is a known beneficial bacterium in the gut, and there are also reports that an increase in NK4A214_group abundance increases the release of antimicrobial peptides in the gut, enhancing its defense and protective functions. The Christensennellacee_R-7 group is a potential probiotic widely present in the intestine and mucosa, which can downregulate pro-inflammatory cytokines and improve intestinal mucosal barrier function. These microorganisms related to the intestinal mucosa may exert their anti obesity effects by reducing intestinal inflammation and intestinal mucosal barrier disruption. Lactobacillus is a hallmark microbiota of the high-dose group and the most important probiotic in the human and animal gut microbiota. It has been proven to alleviate obesity in humans and animals caused by high-fat diets. Bacteria of the Turicibacter genus have a pathogenic lifestyle, and an increase in their abundance is one of the signs of disrupted gut microbiota structure. There are also studies indicating that there are a large number of pathogenic bacteria in the genus Bacteroidetes that can produce acetic acid. An increase in their abundance can stimulate the production of peroxidation inflammatory factors and lipid inhibitory factors in the intestine, inhibit lipid oxidation metabolism, and promote lipid accumulation in the body. The enrichment of pathogens can cause host systemic inflammation, which is related to obesity and related metabolic disorders. The fermentation broth of Colletotrichum coronatum can improve obesity caused by high-fat diet, enhance intestinal defense function, and reduce inflammation by increasing the abundance of beneficial bacteria such as NK4A214_group, UCG-005, Christensennellacee_R-7_group, and Lactobacillus in the intestine, and reducing the abundance of Turicibacter and Bacteroides.
In summary, the occurrence and development of obesity are closely related to the imbalance of gut microbiota. The fermentation broth of Guantu San Nang bacteria can effectively improve the obesity status of high-fat diet rats, regulate the abundance of beneficial microbial communities in the host’s intestinal tract, exert their beneficial vitality, and reduce the abundance of harmful microbial communities, achieving the effect of weight loss and lipid-lowering. However, the structure and composition of the gut microbiota in the body are relatively complex, and the specific molecular mechanisms by which the fermentation broth of Colletotrichum coronatum regulates the gut microbiota, as well as which components have anti obesity activity, still require further research.