Glucansucrase is an enzyme classified as a glycoside hydrolase (GH) 70 family, which catalyzes the synthesis of glucooligosaccharides with a low molecular weight using sucrose as a donor of D-glucopyranose and maltose as a carbohydrate acceptor. In this study, glucansucrase-producing lactic acid bacteria strain was isolated from the fermented foods collected in traditional markets, and the optimum conditions for the oligosaccharide production were investigated. The strain CCK940 isolated from Chinese cabbage kimchi was selected as an oligosaccharide-producing strain due to its high glucansucrase activity, with 918.2 mU/mL, and identified as Leuconostoc lactis. The optimum conditions for the production of oligosaccharides using Leu. lactis CCK940 were to adjust the initial pH to 6.0, add 5% (w/v) sucrose and 10% (w/v) maltose as a donor and acceptor molecules, respectively, and feed 5% (w/v) sucrose at 4 and 8 h of cultivation. When Leu. lactis CCK940 was cultured for 12 h at optimum conditions, at least four oligosaccharides with a polymerization degree of 2-4 were produced.

Glucansucrase is an enzyme classified as a glycoside hydrolase (GH) 70 family, which catalyzes the synthesis of various glucans and glucooligosaccharides with a low molecular weight using sucrose as a donor of D-glucopyranose and maltose as a carbohydrate acceptor. Oligosaccharides are indigestiable carbohydrate with low calories, which have various positive effects on the health of intestinal track. In this study, oligosaccharide produced from Leuconostoc lactis CCK940 was purified and its prebiotics effect was investigated. Leuconostoc lactis CCK940 which isolated from Chinese cabbage kimchi produced oligosaccharide using 5%(w/v) sucrose as a donor and 3%(w/v) maltose as an acceptor. Oligosaccharide produced was purified using Bio-gel P2 column chromatography and DPs of the resulting oligosaccharide were ranged from 3 to 7. When the prebiotics effects of freeze dried oligosaccharide were examined, 1%(w/v) of purified oligosaccharide added to carbohydrate-free MRS showed good prebiotics effects on Lactobacillus plantarum KCCM 12116, L. reuteri KCTC40417, and Bifidobacterium animalis KCCM1209.

Light characteristics are very specific in the aquatic environment. Fish vision and different light spectra perception are related to each species’ natural habit. Light is one of the main environmental conditions and can be easily manipulated in artificial rearing settings. Cholecystokinin (CCK) and mucus-secreting goblet cells are the main regulators of digestion. In this study, we established whether the light spectrum (natural condition, full spectrum: green, 520 nm; red, 590 nm, and blue, 480 nm) influences growth performance and digestive activity related to CCK mRNA expression and mucus-secreting goblet cell activity in order to develop a good management protocol and optimal rearing system for the longtooth grouper. For each light spectrum, fish were reared 12 weeks under a flow-through system and fed commercial pellet diets once daily. At the end of the experiment, the final body weights differed among the fish reared under different light spectra. The highest growth performance value was observed in fish reared under the green light condition. On the other hand, the growth performances of fish in the natural and blue light conditions were drastically decreased in last 3 weeks of the experiment. CCK mRNA expression and mucus-secreting goblet cell activity were significantly higher in the fish under green light condition than in the fish under the natural, red, and blue light conditions. Rearing of the longtooth grouper under the green light condition had positive effects on fish growth performance and digestion. We recommend that the appropriate light spectrum for the artificial culture of the longtooth grouper is the green light condition from the perspective of growth performance and the synergistic effects of CCK and mucus-secreting goblet cells. However, longer light treatment periods are needed in future investigations to clarify the effects of light spectrum on the longtooth grouper. Together with the findings of the present study, such studies would result in better understanding of the digestive physiology and contribute to the development of optimal rearing management for commercial production of the longtooth grouper.