Enhancement of large ring cyclodextrin production using pretreated starch by glycogen debranching enzyme from Corynebacterium glutamicum

Green Synthesis of Magnetic Supramolecules β-Cyclodextrin/Iron Oxide Nanoparticles for Photocatalytic and Antibacterial Applications

Iron oxide nanoparticles (Fe3O4NPs) are a fascinating field of study due to their wide range of practical applications in environmental and medical contexts. This study presents a straightforward, environmentally friendly method for producing Fe3O4NPs utilizing β-cyclodextrin (β-CD) as a reducing and capping agent. This approach results in the rapid and effective eco-friendly synthesis of β-CD/Fe3O4NPs. The properties and characteristics of β-CD/Fe3O4NPs were investigated using various methods, including ultraviolet-visible (UV/vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetry analysis (TGA), and vibrating-sample magnetometry (VSM). The absorption of β-CD/Fe3O4NPs caused a distinct peak at 349 nm, as evidenced by the results of UV/vis studies. This peak was attributed to the absorption of surface plasmon resonance. The crystalline nature of β-CD/Fe3O4NPs was confirmed through XRD analysis. The SEM and TEM analyses have verified the geometry and structural characteristics of β-CD/Fe3O4NPs. The β-CD/Fe3O4NPs exhibited remarkable effectiveness in the decomposing efficiency (%) of methylene blue (MB) dye with 52.2, 94.1, and 100% for 0.2, 0.4, and 0.6 g β-CD/Fe3O4NPs, respectively. In addition, the highest efficiency in hunting radicals was observed (347.2 ± 8.2 mg/g) at 100 mg/mL β-CD/Fe3O4NPs; the combination of β-CD/Fe3O4NPs exhibited remarkable effectiveness in inhibiting the growth of some bacteria that cause infections. The capabilities of β-CD/Fe3O4NPs for various applications showed that these materials could be used in photocatalytic, antioxidants, and antibacterial. Additionally, the eco-friendly synthesis of these materials makes them a promising option for the remediation of harmful pollutants and microbes.

Impact of Starch Binding Domain Fusion on Activities and Starch Product Structure of 4-α-Glucanotransferase

A broad range of enzymes are used to modify starch for various applications. Here, a thermophilic 4-α-glucanotransferase from Thermoproteus uzoniensis (TuαGT) is engineered by N-terminal fusion of the starch binding domains (SBDs) of carbohydrate binding module family 20 (CBM20) to enhance its affinity for granular starch. The SBDs are N-terminal tandem domains (SBD_St1 and SBD_St2) from Solanum tuberosum disproportionating enzyme 2 (StDPE2) and the C-terminal domain (SBD_GA) of glucoamylase from Aspergillus niger (AnGA). In silico analysis of CBM20s revealed that SBD_GA and copies one and two of GH77 DPE2s belong to well separated clusters in the evolutionary tree; the second copies being more closely related to non-CAZyme CBM20s. The activity of SBD-TuαGT fusions increased 1.2-2.4-fold on amylose and decreased 3-9 fold on maltotriose compared with TuαGT. The fusions showed similar disproportionation activity on gelatinised normal maize starch (NMS). Notably, hydrolytic activity was 1.3-1.7-fold elevated for the fusions leading to a reduced molecule weight and higher α-1,6/α-1,4-linkage ratio of the modified starch. Notably, SBD_GA-TuαGT and-SBD_St2-TuαGT showed K_d of 0.7 and 1.5 mg/mL for waxy maize starch (WMS) granules, whereas TuαGT and SBD_St1-TuαGT had 3-5-fold lower affinity. SBD_St2 contributed more than SBD_St1 to activity, substrate binding, and the stability of TuαGT fusions.

Identification of crucial amino acid residues involved in large ring cyclodextrin synthesis by amylomaltase from Corynebacterium glutamicum

Amylomaltase can be used to synthesize large ring cyclodextrins (LR-CDs), applied as drug solubilizer, gene delivery vehicle and protein aggregation suppressor. This study aims to determine the functional amino acid positions of Corynebacterium glutamicum amylomaltase (CgAM) involved in LR-CD synthesis by site-directed mutagenesis approach and molecular dynamic simulation. Mutants named Δ167, Y23A, P228Y, E231Y, A413F and G417F were constructed, purified, and characterized. The truncated CgAM, Δ167 exhibited no starch transglycosylation activity, indicating that the N-terminal domain of CgAM is necessary for enzyme activity. The P228Y, A413F and G417F produced larger LR-CDs from CD36-CD40 as compared to CD29 by WT. A413F and G417F mutants produced significantly low LR-CD yield compared to the WT. The A413F mutation affected all tested enzyme activities (starch tranglycosylation, disproportionation and cyclization), while the G417F mutation hindered the cyclization activity. P228Y mutation significantly lowered the k _cat of disproportionation activity, while E231Y mutant exhibited much higher k _cat and K _m values for starch transglycosylation, compared to that of the WT. In addition, Y23A mutation affected the kinetic parameters of starch transglycosylation and cyclization. Molecular dynamic simulation further confirmed these mutations' impacts on the CgAM and LR-CD interactions. Identified functional amino acids for LR-CD synthesis may serve as a model for future modification to improve the properties and yield of LR-CDs.

Production of Large-Ring Cyclodextrins by Amylomaltases

Amylomaltase is a well-known glucan transferase that can produce large ring cyclodextrins (LR-CDs) or so-called cycloamyloses via cyclization reaction. Amylomaltases have been found in several microorganisms and their optimum temperatures are generally around 60–70 °C for thermostable amylomaltases and 30–45 °C for the enzymes from mesophilic bacteria and plants. The optimum pHs for mesophilic amylomaltases are around pH 6.0–7.0, while the thermostable amylomaltases are generally active at more acidic conditions. Size of LR-CDs depends on the source of amylomaltases and the reaction conditions including pH, temperature, incubation time, and substrate. For example, in the case of amylomaltase from Corynebacterium glutamicum, LR-CD productions at alkaline pH or at a long incubation time favored products with a low degree of polymerization. In this review, we explore the synthesis of LR-CDs by amylomaltases, structural information of amylomaltases, as well as current applications of LR-CDs and amylomaltases.