Sucrose phosphorylase from Lactobacillus reuteri: Characterization and application of enzyme for production of 2-O-α-d-glucopyranosyl glycerol

Identification of a sucrose phosphorylase variant from Streptococcus mutans for production of epigallocatechin gallate glucosides

Epigallocatechin gallate (EGCG) primarily extracted from green tea, exhibits significant antioxidant, hypolipidemic, and anticancer properties. Nevertheless, the limited aqueous solubility and bioavailability of EGCG impede its practical applications. Glycosylation modification of EGCG is an effective method for enhancing its properties. In the present study, a thermally stable variant of sucrose phosphorylase from Streptococcus mutans (SmSP) was identified as having catalytic activity for glycosylation of EGCG. The optimal temperature and pH for SmSP were determined to be 45°C and 6, respectively. The mono-glycosylation product of EGCG was structurally characterized as (-)-epigallocatechin gallate 4'-O-α-D-glucopyranoside. Under optimal reaction conditions (8 % methanol, 10 g/L EGCG, 300 g/L sucrose, 40 U/mL crude enzyme, 35°C, and 24 h), the conversion rate of EGCG reached 80.79 %. Hydrogen bonding interactions between the enzyme and ligands may enhance the stability and catalytic activity of SmSP. Two active site loops significantly influence the selective formation of EGCG glycosides. These insights expand our understanding of the structural basis of sucrose phosphorylases in the synthesis of EGCG glycosides.

2-O-α-D-glucosyl glycerol production by whole-cell biocatalyst of lactobacilli encapsulating sucrose phosphorylase with improved glycerol affinity and conversion rate

BACKGROUND

2-O-α-D-glucosyl glycerol (2-αGG) is a valuable ingredient in cosmetics, health-care and food fields. Sucrose phosphorylase (SPase) is a favorable choice for biosynthesis of 2-αGG, while its glucosyl-acceptor affinity and thermodynamic feature remain largely unknown, limiting 2-αGG manufacturing.

RESULTS

Here, three SPases were obtained from lactobacilli and bifidobacteria, and the one encoded by Lb. reuteri SDMCC050455 (LrSP) had the best transglucosylation ability, with 2-αGG accounting for 86.01% in the total product. However, the LrSP exhibited an initial forward reaction rate of 11.83/s and reached equilibrium of 56.90% at 110 h, indicating low glycerol affinity and conversion rate. To improve catalytic efficiency, the LrSP was overexpressed in Lb. paracasei BL-SP, of which the intracellular SPase activity increased by 6.67-fold compared with Lb. reuteri SDMCC050455. After chemically permeabilized with Triton X-100, the whole-cell biocatalysis of Lb. paracasei BL-SP was prepared and showed the highest activity, with the initial forward reaction rate improved to 50.17/s and conversion rate risen to 80.79% within 17 h. Using the whole-cell biocatalyst, the final yield of 2-αGG was 203.21 g/L from 1 M sucrose and 1 M glycerol.

CONCLUSION

The food grade strain Lb. paracasei was used for the first time as cell factory to recombinantly express the LrSP and construct a whole-cell biocatalyst for the production of 2-αGG. After condition optimization and cell permeabilization, the whole-cell biocatalyst exhibited 23.89% higher equilibrium conversion and 9.10-fold of productivity compared with the pure enzyme catalytic system. This work would provide a reference for large-scale bioprocess of 2-αGG.

Advancements in the Heterologous Expression of Sucrose Phosphorylase and Its Molecular Modification for the Synthesis of Glycosylated Products

Sucrose phosphorylase (SPase), a member of the glycoside hydrolase GH13 family, possesses the ability to catalyze the hydrolysis of sucrose to generate α-glucose-1-phosphate and can also glycosylate diverse substrates, showcasing a wide substrate specificity. This enzyme has found extensive utility in the fields of food, medicine, and cosmetics, and has garnered significant attention as a focal point of research in transglycosylation enzymes. Nevertheless, SPase encounters numerous obstacles in industrial settings, including low enzyme yield, inadequate thermal stability, mixed regioselectivity, and limited transglycosylation activity. In-depth exploration of efficient expression strategies and molecular modifications based on the crystal structure and functional information of SPase is now a critical research priority. This paper systematically reviews the source microorganisms, crystal structure, and catalytic mechanism of SPase, summarizes diverse heterologous expression systems based on expression hosts and vectors, and examines the application and molecular modification progress of SPase in synthesizing typical glycosylated products. Additionally, it anticipates the broad application prospects of SPase in industrial production and related research fields, laying the groundwork for its engineering modification and industrial application.

Enhancing the Enantioselectivity and Catalytic Efficiency of Esterase from Bacillus subtilis for Kinetic Resolution of l-Menthol through Semirational Design

Enzymatic kinetic resolution is a promising way to produce l-menthol. However, the properties of the reported biocatalysts are still unsatisfactory and far from being ready for industrial application. Herein, a para-nitrobenzylesterase (pnbA) gene from Bacillus subtilis was cloned and expressed to produce l-menthol from d,l-menthyl acetate. The highest enantiomeric excess (ee) value of the product generated by pnbA was only approximately 80%, with a high conversion rate (47.8%) of d,l-menthyl acetate with the help of a cosolvent, indicating high catalytic activity but low enantioselectivity (E = 19.95). To enhance the enantioselectivity and catalytic efficiency of pnbA to d,l-menthyl acetate in an organic solvent-free system, site-directed mutagenesis was performed based on the results of molecular docking. The F314E/F315T mutant showed the best catalytic properties (E = 36.25) for d,l-menthyl acetate, with 92.11% ee and 30.58% conversion of d,l-menthyl acetate. To further improve the properties of pnbA, additional mutants were constructed based on the structure-guided triple-code saturation mutagenesis strategy. Finally, four mutants were screened for the best enantioselectivity (ee > 99%, E > 300) and catalytic efficiency at a high substrate concentration (200 g/L) without a cosolvent. This work provides several generally applicable biocatalysts for the industrial production of l-menthol.

Efficient 2-O-α-D-glucopyranosyl-sn-glycerol production by single whole-cell biotransformation through combined engineering and expression regulation with novel sucrose phosphorylase from Leuconostoc mesenteroides ATCC 8293

2-O-α-D-glucopyranosyl-sn-glycerol (2-αGG) is a high value product with wide applications. Here, an efficient, safe and sustainable bioprocesses for 2-αGG production was designed. A novel sucrose phosphorylase (SPase) was firstly identified from Leuconostoc mesenteroides ATCC 8293. Subsequently, SPase mutations were processed with computer-aided engineering, of which the activity of SPaseK138C was 160% higher than that of the wild-type. Structural analysis revealed that K138C was a key functional residue moderating substrate binding pocket and thus influences catalytic activity. Furthermore, Corynebacterium glutamicum was employed to construct microbial cell factories along with ribosome binding site (RBS) fine-tuning and a two-stage substrate feeding control strategy. The maximum production of 2-αGG by these combined strategies reached 351.8 g·L^-1 with 98% conversion rate from 1.4 M sucrose and 3.5 M glycerol in a 5-L bioreactor. This was one of the best performance reported in single-cell biosynthesis of 2-αGG, which paved effective ways for industrial-scale preparation of 2-αGG.

Efficient production of α-monoglucosyl hesperidin by cyclodextrin glucanotransferase from Bacillus subtilis

α-Monoglucosyl hesperidin is a promising food additive with various activities. However, there are a few reports about the production of α-monoglucosyl hesperidin. Here, to develop a practical and safe process for α-monoglucosyl hesperidin synthesis, we used nonpathogenic Bacillus subtilis as a host to express cyclodextrin glucanotransferase (CGTase) from Bacillus sp. A2-5a. The promoters and signal peptides were screened to optimize the transcription and secretion of CGTase in B. subtilis. The results of optimization showed that the best signal peptide and promoter were YdjM and P_aprE, respectively. Finally, the enzyme activity increased to 46.5 U mL^-1, 8.7 times that of the enzyme expressed from the strain containing pP_HpaII-LipA, and the highest yield of α-monoglucosyl hesperidin was 2.70 g L^-1 by enzymatic synthesis using the supernatant of the recombinant B. subtilis WB800 harboring the plasmid pP_aprE-YdjM. This is the highest α-monoglucosyl hesperidin production level using recombinant CGTase to date. This work provides a generally applicable method for the scaled-up production of α-monoglucosyl hesperidin. KEY POINTS: • A three-step procedure was created for high throughput signal peptide screening. • YdjM and P_aprE were screened from 173 signal peptides and 13 promoters. • α-Monoglucosyl hesperidin was synthesized by CGTase with a yield of 2.70 g L^-1.