Efficient preparation of cycloamylose from potato starch using recombinant 4-α-glucanotransferase

This study utilized natural potato starch and optimized process conditions to establish an efficient cyclodextrin (CA) production system through the combination of a mutant 4-α-glucosyltransferase (TaAM-Y54G) from Thermus aquaticus and pullulanase from Bacillus deramificans. Under optimal conditions (1% potato starch concentration, 65 °C for 12 h), CA conversion rate reached 43.2%, a new record for natural industrializable substrates. To address solubility issues, TaAM-Y54G was used for liquefaction at 70 °C for 10 min, stabilizing conversion rates at 29.6% and 22.3% under 5% and 10% substrate concentrations, respectively. Furthermore, this study optimized the fermentation process of the mutant recombinant strain, achieving the highest enzyme activity of TaAM-Y54G at 2525.9 U/mL, significantly improving the fermentation level to the highest reported level. These innovations significantly increased CA yield, laying a solid foundation for industrial production and showing broad application potential.