Integral Use of Amaranth Starch to Obtain Cyclodextrin Glycosyltransferase, by Bacillus megaterium, to Produce β-Cyclodextrin

Medium Optimization for Submerged Fermentative Production of β-Cyclodextrin Glucosyltransferase by Isolated Novel Alkalihalophilic Bacillus sp. NCIM 5799 Using Statistical Approach

β-cyclodextrin glucosyltransferase (β-CGTase) is an essential enzyme to catalyze the biotransformation of starch into β-cyclodextrins (β-CD). β-CD has widespread applications in the biomedical, pharmaceutical, and food industries. The present study focused on β-CGTase production using an efficient natural microbial strain and statistical production optimization for enhanced production. The isolated organism Bacillus sp. NCIM 5799 was found to be 5μm short bacilli under FE-SEM and alkalihalophilic in nature. The β-CGTase production was optimized using a combination of Plackett-Burman design (PBD) and Central Composite Design - Response Surface Methodology (CCD-RSM). On PBD screening Na₂ CO₃ , peptone, and MgSO₄ .7H₂ O were found to be significant for optimal β-CGTase production, whereas the soluble starch and K₂ HPO₄ concentrations were found to be non-significant for β-CGTase production. The significant factors obtained after PBD were further optimized using CCD-RSM design. Peptone was found to have a significant interaction effect with Na₂ CO₃ , and MgSO₄ .7H₂ O and Na₂ CO₃ exhibited significant effect on production of CGTase. The production of β-CGTase was enhanced in the presence of peptone (3%) and Na₂ CO₃ (0.8%). CGTase production obtained was 156.76 U/ml when optimized using CCD-RSM. The final optimized medium (RSM) shows 7.7 and 5.4 fold high production as compared to un-optimized and one factor at a time production media.

Fisetin glycosides synthesized by cyclodextrin glycosyltransferase from Paenibacillus sp. RB01: characterization, molecular docking, and antioxidant activity

Fisetin is a flavonoid that exhibits high antioxidant activity and is widely employed in the pharmacological industries. However, the application of fisetin is limited due to its low water solubility. In this study, glycoside derivatives of fisetin were synthesized by an enzymatic reaction using cyclodextrin glycosyltransferase (CGTase) from Paenibacillus sp. RB01 in order to improve the water solubility of fisetin. Under optimal conditions, CGTase was able to convert more than 400 mg/L of fisetin to its glycoside derivatives, which is significantly higher than the previous biosynthesis using engineered E. coli. Product characterization by HPLC and LC-MS/MS revealed that the transglycosylated products consisted of at least five fisetin glycoside derivatives, including fisetin mono-, di- and triglucosides, as well as their isomers. Enzymatic analysis by glucoamylase and α-glucosidase showed that these fisetin glycosides were formed by α-1,4-glycosidic linkages. Molecular docking demonstrated that there are two possible binding modes of fisetin in the enzyme active site containing CGTase-glysosyl intermediate, in which O7 and O4' atoms of fisetin positioned close to the C1 of glycoside donor, corresponding to the isomers of the obtained fisetin monoglucosides. In addition, the water solubility and the antioxidant activity of the fisetin monoglucosides were tested. It was found that their water solubility was increased at least 800 times when compared to that of their parent molecule while still maintaining the antioxidant activity. This study revealed the potential application of CGTase to improve the solubility of flavonoids.

Gamma cyclodextrin glycosyltransferase from evansella caseinilytica: production, characterization and product specificity

Alkalohalophilic Evansella caseinilytica produced an extracellular cyclodextrin glycosyltransferase (CGTase) with cyclization activity of 43.5 ± 4.4 U/L in M1 medium containing 1% starch and 6% NaCl in nutrient broth at 37 ºC, pH 9.0, after 48 h. This is the first report of CGTase from this bacterium. 0.1% starch was found to induce CGTase, and further optimization using one variable at a time approach followed by statistical optimization led to 5.5-fold enhancement resulting in 240.5 ± 5.46 U/L. Six parameters were identified as positive signals using Plackett-Burman (PB). Of these, yeast extract, MgSO4 and tryptone were taken further for Response Surface Methodology (RSM) by disposing beef extract and fixing starch and soya peptone. The optimized M4 medium consisted of tryptone (0.1%, w/v), yeast extract (0.25%, w/v), MgSO4 (8 mM, w/v), potato starch (0.1%, w/v) and soya peptone (0.2%, w/v). CGTase was further purified with 6.44-fold purification and 19.32% yield employing starch affinity. It was found to be monomeric, corresponding to a size of 68 kDa as estimated by SDS-PAGE and was further confirmed to be 65 kDa by size exclusion chromatography. γ-Cyclodextrins were produced as the major product with a conversion of 5% soluble starch into 20.38% γ-cyclodextrins after 24 h reaction, as determined by HPLC. Peptide fingerprint after LC-MS analysis matched with IPT/TIG domain-containing protein within the genome of E. caseinilytica. Further blastp analysis revealed the closest homology with γ-CGTase from an alkalophilic E. clarkii, thereby confirming CGTase from E. caseinilytica as γ-CGTase.

Heterologous Expression of Cyclodextrin Glycosyltransferase my20 in Escherichia coli and Its Application in 2-O-α-D-Glucopyranosyl-L-Ascorbic Acid Production

In this study, the cgt gene my20, which encodes cyclodextrin glycosyltransferase (CGTase) and was obtained by the metagenome sequencing of marine microorganisms from the Mariana Trench, was codon optimized and connected to pET-24a for heterologous expression in Escherichia coli BL21(DE3). Through shaking flask fermentation, the optimized condition for recombinant CGTase expression was identified as 20°C for 18 h with 0.4 mM of isopropyl β-D-L-thiogalactopyranoside. The recombinant CGTase was purified by Ni²⁺-NTA resin, and the optimum pH and temperature were identified as pH 7 and 80°C, respectively. Activity was stable over wide temperature and pH ranges. After purification by Ni²⁺-NTA resin, the specific activity of the CGTase was 63.3 U/mg after 67.3-fold purification, with a final yield of 43.7%. In addition, the enzyme was used to transform L-ascorbic acid into 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G). The maximal AA-2G production reached 28 g/L, at 40°C, pH 4, 24 h reaction time, 50 g/L donor concentration, and 50 U/g enzyme dosage. The superior properties of recombinant CGTase strongly facilitate the industrial production of AA-2G.

A two-stage temperature control strategy enhances extracellular secretion of recombinant α-cyclodextrin glucosyltransferase in Escherichia coli

The effects of temperature on extracellular secretion of the α-cyclodextrin glucosyltransferase (α-CGTase) from Paenibacillus macerans JFB05-01 by Escherichia coli were investigated. When protein expression was induced at constant temperature, the greatest amount of extracellular recombinant α-CGTase was produced at 25 °C. Higher or lower induction temperatures were not conducive to extracellular secretion of recombinant α-CGTase. To enhance extracellular secretion of α-CGTase by E. coli, a two-stage temperature control strategy was adopted. When expression was induced at 25 °C for 32 h, and then the temperature was shifted to 30 °C, the extracellular α-CGTase activity at 90 h was 45% higher than that observed when induction was performed at a constant temperature of 25 °C. Further experiments suggested that raising the induction temperature can benefit the transport of recombinant enzyme and compensate for the decreased rate of recombinant enzyme synthesis during the later stage of expression. This report provides a new method of optimizing the secretory expression of recombinant enzymes by E. coli.