Isolation, screening, and identification of lemon endophytic bacteria with cholesterol lowering activity in vitro
With the development of technology and the improvement of people’s living standards, people’s attention to hyperlipidemia and high cholesterol is becoming increasingly widespread. According to statistics, the number of deaths from cardiovascular diseases caused by hyperlipidemia in the world every day is nearly 4000. In China, the number of deaths from cardiovascular and cerebrovascular diseases caused by hyperlipidemia, such as atherosclerosis, coronary heart disease, hypertension, and stroke, increases at an annual rate of 12%. In order to reduce the occurrence of many complications caused by obesity, in recent years, more research has focused on reducing blood lipids through dietary therapy to reduce the incidence of diseases. Foreign literature studies have attempted to use lactic acid bacteria combined with diet to regulate abnormal fat metabolism. At the same time, other studies have concluded that beneficial lactic acid can directly improve the combined health problems of fat mass and glucose intolerance, thereby improving obesity.

According to multiple research results, different types of probiotics in microorganisms have the effect of lowering cholesterol and improving gut microbiota. For example, TMC3115 can improve the gut microbiota and glucose and lipid profile of elderly people. And it has been confirmed that the lipid-lowering effect and the improvement of intestinal microbiota are directly or indirectly related to microbial activity, with lipid-lowering activity being related to the type of microorganisms. For example, through research on the gut microbiota of patients with non-alcoholic fatty liver disease, it has been found that drug therapy is still the most important method at present. However, the combination of probiotics and other drugs can also have a good effect on improving gut microbiota and reducing cholesterol. Currently, there are few reports on the treatment of non-alcoholic fatty liver disease (NAFLD).

Lemon (L.) Burm f.)， It is a citrus plant belonging to the Rutaceae family of the dicotyledonous plant order, also known as Yimu fruit. It originates from Southeast Asia and is currently one of the main production areas in China, located in Yibin, Sichuan. Lemon, whether consumed as a traditional Chinese medicine or a fruit, has a sour and astringent taste. It is easier to accept when fermented into a fermented juice. In recent years, research on enzymes has just emerged in China, and new policies and laws and regulations have been continuously introduced. However, there is almost no research on the direct processing of Chinese medicinal materials into beverages. This experiment intends to use microbial technology to process lemon using fermentation techniques, cultivate and isolate probiotics, identify the isolated strains, and screen for lipid-lowering activity to achieve the goal of selecting probiotics with lipid-lowering function. This can provide theoretical basis for the application of cholesterol lowering probiotics in the later stage.

 

This experiment used cholesterol as the substrate and employed high-performance liquid chromatography to screen for the cholesterol degradation rate of endophytic bacteria in lemon, followed by identification using 16S or 26S rDNA gene sequences. 17 strains of bacteria were screened and found to have a cholesterol degradation rate of over 25%. The identification results showed 16 strains of yeast and 1 strain of Acetobacter, namely Candida albicans, Pichia pastoris, Wickham’s yeast, Pichia pastoris, and Acetobacter cloacae, respectively.
In 1963, Shaper Laboratory discovered that certain tribes in Africa generally had lower serum cholesterol levels after consuming large amounts of dairy products fermented with lactobacilli. Research has found that ordinary animals excrete more cholesterol in their feces than sterile animals, and when both animals are fed high cholesterol foods at the same time, the cholesterol content in the blood of sterile animals is twice that of ordinary animals. This suggests that gut microbiota may have an impact on the absorption of cholesterol in the intestine. So far, a large number of experiments have confirmed that different types of lactic acid bacteria have the effect of reducing cholesterol, among which Lactobacillus acidophilus is the most abundant material.
This experiment screened multiple strains of yeast and Acetobacter that have the effect of reducing cholesterol, providing more bacterial strains for the development of lipid-lowering fermented foods or drugs in the later stage.