Influence of additives on Saccharomyces cerevisiae β-glucan production.
In Saccharomyces cerevisiae, many changes in carbohydrate composition of cell wall occur when cells grow under various conditions. In this study, effects of sole additives (SDS, EDTA, and NaCl) including SDS in combination with NaCl and EDTA were studied in order to enhance β-glucan production in S. cerevisiae Angel®. The results showed that all media supplemented with the studied additives could be able to enhance b-glucan production in different levels (7-40%). Yeast cultured in YPD medium supplemented with 100 ppm SDS produced the highest β-glucan content, followed by one supplemented with a combination of 20 ppm SDS and 3000 ppm NaCl. This indicated that sole SDS was the best additive to enhance β-glucan production, compared with control. Consequently, the β-glucan from yeast cultured with this condition was extracted and characterized. Its chemical structure was revealed by 13C-NMR. Not only the highest β-glucan content but also the lowest proteins determined using FTIR were found in yeast cells cultured with this condition. In addition, it was found that β-glucan from all additives addition cultures seemed to possess higher branching chains than control, with exception in EDTA 50 ppm. Apart from the composition, changes in morphology of yeast cells when cultured in various studied conditions were investigated by confocal microscope and SEM. Furthermore, based on aspect ratio, cells cultured with sole SDS were slightly more spherical than other treatments. Overall, the obtained results implied that the additives could activate cell wall synthesis of yeast cell, relevant to β-glucan content and β-glucan branching formation.