Identification of Yeast Strain YA176 for Bio-Purification of Soy Molasses to Produce Raffinose Family Oligosaccharides and Optimization of Fermentation Conditions

Soybean molasses, which contains high levels of raffinose family oligosaccharides (RFOs) such as stachyose and raffinose, is subjected to a process of bio-purification to remove sucrose while maintaining the RFOs, consequently increasing its value. This study employed morphological observation, physiological and biochemical studies, and molecular biology techniques to identify YA176, a yeast strain renowned for its effective bio-purification of soy molasses. Through single-factor and orthogonal experiments, optimal bio-purification conditions were established. YA176, belonging to Wickerhamomyces anomalus, demonstrated robust growth across a wide range of temperature and pH levels, coupled with remarkable tolerance to glucose, sucrose, and NaCl up to 41.2%, 47.3%, and 10%, respectively. Under these optimized conditions, YA176 efficiently utilized sucrose while preserving 93.3% of raffinose and 78.6% of stachyose, ensuring the retention of functional RFOs. In summary, yeast strain YA176 exhibits exceptional bio-purification abilities, making it an ideal candidate for producing functional RFOs from soy molasses.