Heterologous expression of cyclodextrin glycosyltransferase from Bacillus stearothermophilus in Bacillus subtilis and its application in glycosyl rutin production

Enhancing trehalose production via Bacillus species G1 cyclodextrin glucanotransferase mutants: modifying disproportionation characteristics and thermal stability

Inefficient conversion of small molecule maltooligosaccharides into trehalose greatly affects the cost of the production of trehalose by double enzyme method [maltooligosyl trehalose synthase (MTSase) and maltooligosyl trehalose trehalohyrolase (MTHase)]. This study used directed evolution to increase oligosaccharide utilization by the cyclomaltodextrin glucanotransferase (CGTase) from Bacillus species G1. This enzyme was chosen for its adaptability and stability in trehalose production. Model analysis revealed that the hydrogen bond distance between the N33K mutant and maltose reduced from 2.6 Å to 2.3 Å, increasing maltose affinity and boosting transglycosylation activity by 2.1-fold compared to the wild type. Further mutations improved thermal stability and optimum temperature, resulting in the N33K/S211G mutant. Consistent results from repeated experiments showed that the N33K/S211G mutant increased trehalose yield by 32.6% using maltodextrin. The results enhanced the double-enzyme method formed by MTSase and MTHase for trehalose production. Overall, we have identified optimal catalytic conditions, demonstrating significant potential for industrial-scale trehalose production with enhanced efficiency and cost-effectiveness.

Efficient glycosylation of polyphenols via dynamic complexation of cyclodextrin and synchronous coupling reaction with cyclodextrin glycosyltransferase in water

Glycosylation is an effective way to promote the total intake of polyphenols in humans by increasing the solubility of polyphenols. In this study, an efficient glycosylation system was built via the dynamic complexation of CD with polyphenols and synchronous coupling reaction with cyclodextrin glycosyltransferase (CGTase) in water. The glycosylation efficiencies of quercetin, naringenin, rutin, resveratrol and caffeic acid were 20.9, 3.6, 2.7, 3.4 and 1.5 times higher than the non-complexed system. To quantify conversion rate and determine the rate-limiting step, the mixed product was treated with amyloglucosidase to obtain α-glucosyl rutin, which was identified as rutin 4"-O-α-D-glucopyranoside with purity of 93.6 % and yield of 34.8 % from NMR, MS and HPLC analysis. The results of half-reaction kinetics showed that the catalytic efficiencies of ring-opening of γ-CD (k1) and glycosylation reaction of rutin (k2) were 621.92 and 9.43 mM-1·s-1. The rate-limiting step was clarified for the first time, showing that the ring-opening ability of CGTase to CD was much higher than its glycosylation ability to polyphenols. It is speculated that the rapid ring-opening reaction of CD affected its dynamic complexation, releasing many polyphenols which were not utilized by CGTase in time. Therefore, adjusting the ratio and concentration of CD resulted in an optimal glycosylation molar yield of 84.1 % for rutin, which was the highest yield reported so far in water. This study established a universal system and clarified the rate-limiting step in the enzymatic glycosylation, providing theoretical guidance for efficient production of polyphenol glycosylation.

A review on recent upgradation and strategies to enhance cyclodextrin glucanotransferase properties for its applications

Cyclodextrin glycosyltransferase (CGTase) is a significant extracellular enzyme with diverse functions. CGTase is widely used in production of cyclic α-(1,4)-linked oligosaccharides (cyclodextrins) from starch via transglycosylation reaction. Recent discoveries of novel CGTases from different microorganisms have expanded its applications but natural CGTase have lower yield, leading to heterologous expression for increased production to meet various needs. Moreover, significant advancements in directed evolution approach have been explored to alter the molecular structure of CGTase to enhance its performance. This review comprehensively summarizes the strategies employed in heterologous expression to boost CGTase production and secretion in various host. It also outlines molecular engineering approaches aimed to improving CGTase properties, including product and substrate specificity, catalytic efficiency, and thermal stability. Additionally, a considerable stability against changes in temperature and organic solvents can be obtained by immobilization.