Purification, characterization and partial biological activities of exopolysaccharide produced by Saccharomyces cerevisiae Y3.

In this study, the exopolysaccharide (EPS) from Saccharomyces cerevisiae Y3 was extracted and purified, the preliminary structure characteristics and biological activities was investigated. The S. cerevisiae Y3 EPS was obtained by ethanol precipitation and gel filtration chromatography. MW of purified Y3 EPS was 93,477 Da. High-performance liquid chromatography (HPLC), fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and methylation analyses showed that the EPS was a heteropolysaccharide, which composed of 1-α-D mannose (39.8%), 1,2-α-D mannose (19.6%), 1,6-α-D linked mannose (10.4%), 1,3,6-ß-D glucose (27.5%), and 1-ß-D linked glucose (1.9%). Scanning electron microscope (SEM) and atomic force microscope (AFM) further revealed smooth and dense sheet-like structure with reticular configuration. The Congo red test and X-ray diffraction (XRD) reflected an irregular coil conformation and non-crystalline amorphous nature. The EPS exhibited good hydrophilicity, thermal stability and antioxidation ability for DPPH radicals, hydroxyl radicals and NO2-, as well as good prebiotic properties. These results indicated that Y3 EPS could be explored as a promising functional adjunct for application in probiotics and antioxidation.

The response surface optimization of ß-mannanase produced by Weissella cibaria F1 and its potential in juice clarification.

A ß-mannanase-producing lactic acid bacteria (LAB) was identified as Weissella cibaria F1 according to physiological and biochemical properties, morphological observations, partial sequence of 16S rRNA gene and API 50 CHL test. In order to improve the yield of ß-mannanase, the response surface methodology (RSM) was originally used to optimize the fermentation conditions. The optimization results showed that when the konjac powder, glucose, and initial pH were 9.46 g/L, 14.47 g/L and 5.67, respectively, the ß-mannanase activity increased to 38.81 ± 0.33 U/mL, which was 1.33 times compared to initial yield (29.28 ± 0.26 U/mL). This result was also supported by larger clearance on the konjac powder-MRS agar plate through Congo Red dyeing. The W. cibaria F1 ß-mannanase could improve the clarity of five fruits juice, i.e., apple, orange, peach, persimmon and blue honeysuckle. Among these, peach juice was the most obvious, clarity increasing by 12.8%. These results collectively indicated that W. cibaria F1 ß-mannanase had an applicable potential in food-level fields.