DOI: 10.14457/tu.the.2021.792
title: Enzymatic production and characterization of glucosyl-polyols

description: For the first part of this study, the glucosyl-erythritol (EGn) was produced by the transglycosylation reaction of recombinant amylomaltase (AMase) from Thermus sp. with tapioca starch and erythritol as glucosyl donor and acceptor, respectively. The optimal condition for the synthesis of EGn was found to be an incubation of 2.5% (w/v) tapioca starch and 2% (w/v) erythritol with 180 U/ml of AMase in 20 mM phosphate buffer at pH 6.0, 60oC for 72 hours. Upon analysis of the product at the optimal condition by TLC, the yield of synthesized EGn was 29.3% (w/w) of the total products. These transferred products were formed with molecular weights of 307.1, 469.2 and 631.2 daltons as determined by mass spectrometry analysis; these values were in accordance with glucosyl-erythritol (EG1), maltosyl-erythritol (EG2) and maltotriosyl-erythritol (EG3), respectively. Then, EG1 and EG2 products were prepared on a large scale and subsequently purified by HPLC. The possible structures of EG1 (1-O- or 4-O-α-glucosyl-erythritol) and EG2 (1-O- or 4-O-α-maltosyl-erythritol) were confirmed by the combination of 1H- and 13C-NMR data analysis. In addition, their relative sweetness value of EGn displayed higher sweetness level than that of erythitol. The results showed that the properties of water solubility, acidic-, heat-, digestive-enzyme resistance, and prebiotic of EGn were greater than that of erythritol. Furthermore, the obtained products in this study have the anticariogenic properties, exhibiting a growth inhibition of Streptococcus mutans, tooth-decayed bacteria. Thus, the current study suggests that EG1 and EG2 can be used as non-cariogenic sweeteners and tooth-friendly and functional food ingredients from their desirable characteristics.The second part of this study was focused on the synthesis of maltitol, having property in the prevention of tooth decay. The synthetic reaction was performed using recombinant CGTase from Bacillus circulans A11 with β-cyclodextrin (β-CD) and sorbitol as glucosyl donor and acceptor, respectively. The optimal condition for the synthesis of maltitol was to incubate 1 % (w/v) of β-CD and sorbitol with 400 U/ml of CGTase in 20 mM phosphate buffer at pH 6.0, 50oC for 72 hours. Under the optimal condition, the yield of synthesized maltitol was 14.3% (w/w) of the total products. Subsequently, maltitol was prepared on a large-scale production and purified by HPLC. The molecular weight of synthesized maltitol was 379.08 daltons corresponding to standard maltitol as analyzed by mass spectrometry. The relative sweetness of synthesized and std. maltitol was about 90% of sucrose. In addition, the growth inhibitory effect of maltitol on Streptococcus mutans DMST 18777 was also studied by spot assay. The result showed the decrease of S. mutans colonies in BHI agar. For antibacterial activities, the MIC and MBC values of synthesized and std. maltitol against S. mutans were equal at 20 and 40 mg/ml, respectively. These results showed that the synthesized maltitol has a potential to be an anticariogenic agent. Moreover, it could be applicable in various food and dental care products.