Partial purification and properties of cyclodextrin glycosiltransferase (CGTase) from alkalophilic Bacillus species

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.

MOFs as Potential Matrices in Cyclodextrin Glycosyltransferase Immobilization

Cyclodextrins (CDs) and their derivatives have attracted significant attention in the pharmaceutical, food, and textile industries, which has led to an increased demand for their production. CD is typically produced by the action of cyclodextrin glycosyltransferase (CGTase) on starch. Owing to the relatively high cost of enzymes, the economic feasibility of the entire process strongly depends on the effective retention and recycling of CGTase in the reaction system, while maintaining its stability. CGTase enzymes immobilized on various supports such as porous glass beads or glyoxyl-agarose have been previously used to achieve this objective. Nevertheless, the attachment of biocatalysts on conventional supports is associated with numerous drawbacks, including enzyme leaching prominent in physical adsorption, reduced activity as a result of chemisorption, and increased mass transfer limitations. Recent reports on the successful utilization of metal-organic frameworks (MOFs) as supports for various enzymes suggest that CGTase could be immobilized for enhanced production of CDs. The three-dimensional microenvironment of MOFs could maintain the stability of CGTase while posing minimal diffusional limitations. Moreover, the presence of different functional groups on the surfaces of MOFs could provide multiple points for attachment of CGTase, thereby reducing enzyme loss through leaching. The present review focuses on the advantages MOFs can offer as support for CGTase immobilization as well as their potential for application in CD production.

High-level production of γ-cyclodextrin glycosyltransferase in recombinant Escherichia coli BL21 (DE3): culture medium optimization, enzymatic properties characterization, and product specificity analysis

Purpose

γ-Cyclodextrin glycosyltransferase (γ-CGTase) catalyzes the biotransformation of low-cost starch into valuable γ-cyclodextrin (γ-CD), which is widely applied in biotechnology, food, and pharmaceutical industries. However, the low specificity and activity of soluble γ-CGTase increase the production cost of γ-CD, thereby limiting its applications. Therefore, the present study aimed at optimizing an economical medium for high production of γ-CGTase by the recombinant Escherichia coli (E. coli) BL21 (DE3) and evaluating its enzymatic properties and product specificity.

Methods

The γ-CGTase production was optimized using the combination of Plackett-Burman experimental design (PBD) and Box-Behnken design-response surface methodology (BBD-RSM). The hydrolysis and cyclization properties of γ-CGTase were detected under the standard assay conditions with buffers of various pHs and different reaction temperatures. The product specificity of γ-CGTase was investigated by high-performance liquid chromatography (HPLC) analysis of three CDs (α-, β-, γ-CD) in the biotransformation product of cassava starch.

Results

The γ-CGTase activity achieved 53992.10 U mL−1 under the optimum conditions with the significant factors (yeast extract 38.51 g L−1, MgSO4 4.19 mmol L−1, NiSO4 0.90 mmol L−1) optimized by the combination of PBD and BBD-RSM. The recombinant γ-CGTase exhibited favorable stability in a wide pH and temperature range and maintained both the hydrolysis and cyclization activity under the pH 9.0 and 50 °C. Further analysis of the products from cassava starch catalyzed by the γ-CGTase reported that the majority (90.44%) of product CDs was the γ form, which was nearly 11% higher than the wild enzyme. Cyclododecanone added to the transformation system could enhance the γ-CD purity to 98.72%, which is the highest purity value during the transformation process reported so far.

Conclusion

The yield of γ-CGTase activity obtained from the optimized medium was 2.83-fold greater than the unoptimized medium, and the recombinant γ-CGTase exhibited a favorable thermal and pH stability, and higher γ-cyclization specificity. These results will provide a fundamental basis for the high productivity and purity of γ-CD in the industrial scale.

Is there still room to explore cyclodextrin glycosyltransferase-producers in Brazilian biodiversity?

In the present work, different Brazilian biomes aiming to identify and select cyclodextrin glycosyltransferase-producer bacteria are explored. This enzyme is responsible for converting starch to cyclodextrin, which are interesting molecules to carry other substances of economic interest applied by textile, pharmaceutical, food, and other industries. Based on the enzymatic index, 12 bacteria were selected and evaluated, considering their capacity to produce the enzyme in culture media containing different starch sources. It was observed that the highest yields were presented by the bacteria when grown in cornstarch. These bacteria were also characterized by sequencing of the 16S rRNA region and were classified as Bacillus, Paenibacillus, Gracilibacillus and Solibacillus.

Purification and properties of beta-cyclomaltodextrin glucanotransferase from Bacillus flexus SV 1

Cyclomaltodextrin glucanotransferase is a unique enzyme that degrades starch into cyclic oligosaccharides called cyclodextrins, which have numerous applications in various industries such as pharmaceutical, textile, agricultural, cosmetics etc. Due to its wide applications, microorganism producing one type of cyclodextrin is of interest as it simplifies the down streaming process of separating mixture of cyclodextrins. In the present study, β-CGTase was isolated from Bacillus flexus SV 1 and biochemically characterized. Enzyme was purified by starch adsorption followed by DEAE cellulose column chromatography which resulted in a fold purification of 6.1, with a yield of 44.07%. Molecular weight of the purified enzyme was found to be 96.68 kDa, enzyme was monomeric in nature with a K_m and V_max of 0.08976 μmol mL^-1 and 585.1 μmol/ml/min, respectively. Optimum pH and temperature of the purified enzyme was found to be 8.0 and 60 °C. Ca²⁺ showed significant increase in enzyme activity. The inhibition of enzyme by EDTA indicates that CGTase is a metalloenzyme. CGTase produced majorly β-CD and was alkalotolarent and active at high temperatures which is a promising candidate for various industries such as textile, food, agriculture, and pharmaceuticals.

The Potential of Cyclodextrins as Novel Active Pharmaceutical Ingredients: A Short Overview

Cyclodextrins (CDs) are cyclic oligosaccharides of natural origin that were discovered more than 100 years ago. The peculiar cone-like conformation of the sugar ring, expressing a lipophilic cavity and a hydrophilic external surface, allows these substances to spontaneously complex poorly soluble compounds in an aqueous environment. For more than 50 years, these substances have found applicability in the pharmaceutical and food industries as solubilizing agents for poorly soluble chemical entities. Nowadays, several research groups all over the world are investigating their potential as active pharmaceutical ingredients (APIs) for the treatment of several illnesses (e.g., hypercholesterolemia, cancer, Niemann-Pick Type C disease). The aim of this review is to briefly retrace cyclodextrins’ legacy as complexing agents and describe the current and future prospects of this class of chemical entities in pharmaceutics as new APIs.

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

Cyclodextrin glycosyltransferase (CGTase) is an enzyme that produces cyclodextrins (CDs) from starch and related carbohydrates, producing a mixture of α-, β-, and γ-CDs in different amounts. CGTase production, mainly by Bacillus sp., depends on fermentation conditions such as pH, temperature, concentration of nutrients, carbon and nitrogen sources, among others. Bacillus megaterium CGTase produces those three types of CDs, however, β-CD should prevail. Although, waxy corn starch (CS) is used industrially to obtain CGTase and CDs because of its high amylopectin content, alternative sources such as amaranth starch (AS) could be used to accomplish those purposes. AS has high susceptibility to the amylolytic activity of CGTase because of its 80% amylopectin content. Therefore, the aim of this work was evaluate the AS as carbon source for CGTase production by B. megaterium in a submerged fermentation. Afterwards, the CGTase was purified partially and its activity to synthesize α-, β-, and γ-CDs was evaluated using 1% AS as substrate. B. megaterium produced a 66 kDa CGTase (Topt = 50°C; pHopt = 8.0), from the early exponential growth phase which lasted 36 h. The maximum CGTase specific activity (106.62 ± 8.33 U/mg protein) was obtained after 36 h of culture. CGTase obtained with a Km = 0.152 mM and a Vmax = 13.4 μM/min yielded 40.47% total CDs using AS which was roughly twice as much as that of corn starch (CS; 24.48%). High costs to produce CDs in the pharmaceutical and food industries might be reduced by using AS because of its higher α-, β- and γ-CDs production (12.81, 17.94, and 9.92%, respectively) in a shorter time than that needed for CS.

A new alkalophilic isolate of Bacillus as a producer of cyclodextrin glycosyltransferase using cassava flour

Cyclodextrin glycosyltransferase (CGTase) catalyzes the conversion of starch into non-reducing cyclic sugars, cyclodextrins, which have several industrial applications. This study aimed to establish optimal culture conditions for β-CGTase production by Bacillus sp. SM-02, isolated from soil of cassava industries waste water lake. The optimization was performed by Central Composite Design (CCD) 2, using cassava flour and corn steep liquor as substrates. The maximum production of 1087.9UmL(-1) was obtained with 25.0gL(-1) of cassava flour and 3.5gL(-1) of corn steep after 72h by submerged fermentation. The enzyme showed optimum activity at pH 5.0 and temperature 55°C, and maintained thermal stability at 55°C for 3h. The enzymatic activity was stimulated in the presence of Mg(+2), Ca(+2), EDTA, K(+), Ba(+2) and Na(+) and inhibited in the presence of Hg(+2), Cu(+2), Fe(+2) and Zn(+2). The results showed that Bacillus sp. SM-02 have good potential for β-CGTase production.

Stepwise error-prone PCR and DNA shuffling changed the pH activity range and product specificity of the cyclodextrin glucanotransferase from an alkaliphilic Bacillus sp

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We performed random mutagenesis experiments with a cyclodextrin glucanotransferase.

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Error-prone PCR and DNA shuffling steps were combined.

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Variants with a broad pH activity range could be obtained.

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Several variants showed increased product specificity for γ-cyclodextrin.

Cyclodextrin glucanotransferase (EC 2.4.1.19) from the alkaliphilic Bacillus sp. G-825-6 converts starch mainly to γ-cyclodextrin (CD₈). A combination of error-prone PCR and DNA shuffling was used to obtain variants of this enzyme with higher product specificity for CD₈ and a broad pH activity range. The variant S54 with seven amino acid substitutions showed a 1.2-fold increase in CD₈-synthesizing activity and the product ratio of CD₇:CD₈ was shifted to 1:7 compared to 1:3 of the wild-type enzyme. Nine amino acid substitutions of the cyclodextrin glucanotransferase were performed to generate the variant S35 active in a pH range 4.0–10.0. Compared to the wild-type enzyme which is inactive below pH 6.0, S35 retained 70% of its CD₈-synthesizing activity at pH 4.0.