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This study aimed to establish the optimal production conditions for mealworm chitosan oligosaccharides (MCOS) using the response surface methodology and measure the prebiotic effect of MCOS prepared on cecal microbiota through in vitro anaerobic fermentation. The optimal conditions for MCOS production using chitosanase were 2.5% substrate, 30 mg/g enzyme, and 6 h reaction time. Matrix-assisted laser desorption ionization-time of flight mass spectrometry, Fourier transform infrared spectroscopy, and in vitro assays to confirm that the chemical structure and physicochemical properties of MCOS are similar to those of commercially available chitosan oligosaccharides. The growth of Lactobacillus acidophilus, Lacticaseibacillus casei, and Bifidobacterium bifidumwas increased by MOCS and confirmed that the prebiotic effect of MCOS was significant in a concentration-dependent manner. The addition of 1% and 2% MCOS to in vitro anaerobic fermentation resulted in changes in the content of short-chain fatty acids (SCFAs) and an increase in Verrucomicrobiotaabundance compared with the control. In the case of Romboutsia,Turicibacter, and Akkermansia, a significant increase was confirmed in the MCOS-containing groups compared to that in the control group. Compared to 2% MCOS, 1% MCOS more significantly affected Lactobacilluslevels. MCOS produced by chitosanase under optimal conditions contains oligosaccharides with 2–6 degree of polymerization and exerts a prebiotic effect that affects changes in the SCFA content and microbiota composition in the cecum.

Kombucha is a healthy carbonated beverage made by fermenting tea extracts such as green tea and black tea through symbiotic culture of bacteria and yeast. In this study, fermentation characteristics and radical scavenging activity of ginseng berry kombucha (GBK) by Saccharomyces cerevisiaeM-5 and Gluconobacter oxydanswere measured. As fermentation time increased, pH decreased and titratable acidity increased. Reducing sugars decreased rapidly on day 3. Alcohol content increased dramatically during this period and then decreased. GBK showed increased radical scavenging activity and increased total flavonoid content on day 18 of fermentation compared to before fermentation. In particular, during GBK fermentation, the content of phenolic compounds such as gallic acid (2.09-fold) and chlorogenic acid (2.11-fold) increased, contributing to antioxidant activity. In addition, the major ginsenosides of GBK were identified as Rg2 (10.1 μg/mg) and Re (6.59 μg/mg), and the content of minor ginsenosides, which are easily absorbed forms, increased 2.19-fold by fermentation. GBK also extended survival in a Drosophilamodel treated with 15% hydrogen peroxide. GBK also reduced reactive oxygen species (p < 0.001) through upregulation of gene expression of antioxidant enzymes such as catalase (p < 0.001), superoxide dismutase (p < 0.05), and glutathione peroxidase (p < 0.001). Therefore, GBK can be presented as a functional food that inhibits oxidative stress by increasing radical scavenging activity during fermentation.