Effects and mechanisms of ultrasound- and alkali-assisted enzymolysis on production of water-soluble yeast β-glucan

Abstract This study investigated the effects and related mechanisms of ultrasound- and alkali-assisted enzymolysis on production of water-soluble yeast β-glucan (WSYG). Results indicated that ultrasound and alkali pretreatments reduced the particle size of yeast β-glucan (YG) from 8.80 μm to 1.77 and 7.19 μm, respectively. Ultrasound-induced cavitation disrupted YG aggregates to a coarse appearance and exposed internal structure. Alkali penetrated into YG particles and broke the YG aggregates into a flake-like morphology by cleaving the linkages within YG chains. Both pretreatments facilitated enzymolysis by enlarging the YG surface area and increased the WSYG yield to 32.3% and 36.2%, respectively. Meanwhile, the purity of WSYG reached 98.8% after zymoprotein removal by DEAE-Sepharose fast flow column. This work not only provides a green method for producing high-purity and high-yield WSYG, but also reveals the mechanisms of ultrasound and alkali pretreatments for improving enzymolysis efficiency by loosening the YG structure and increasing the surface area.