Enhancing the thermostability of recombinant cyclodextrin glucanotransferase via optimized stabilizer

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.

An integrated approach to the sustainable production of xylanolytic enzymes from Aspergillus niger using agro-industrial by-products

Xylanolytic enzymes were produced by Aspergillus niger NRRL3 grown on agro-industrial by-products obtained from the processing of wheat flour without pretreatment. Significant parameters for xylanase production were screened and optimized. The xylanolytic activity obtained in the optimized extract was 138.3 ± 2.6 U/mL, higher than the activity obtained in an unoptimized medium (14.5 ± 0.3 U/mL) in previous work. The optimized fermentation process was performed in a successful 40-fold scale-up. The optimized enzymatic extract obtained was characterized by LC-MS. Nine enzymes were identified as constituents of the xylanolytic complex. Moreover, the xylanolytic enzymes were stable until 60 °C and over a broad range of pH. Sodium, calcium, cobalt and manganese had no inhibitory effect, meanwhile 1% w/v polyvinylpyrrolidone and 1% w/v dextran increased the xylanolytic activity. The saccharification efficiency was evaluated and the surface morphology of the lignocellulosic substrate was monitored by using scanning electron microscopy (SEM). The synergistic combination of the extracted (o purified) xylanolytic enzymes permitted a higher xylan conversion beneficial for diverse applications, such as bioethanol production. Thus, these agroindustrial by-products can be used within the framework of a circular economy, rendering an added value bioproduct, which is reused in the industry.

Optimization of defined medium for recombinant Komagataella phaffii expressing cyclodextrin glycosyltransferase

The cyclodextrin glycosyltransferase (CGTase) is an important enzyme for cyclodextrin (CD) production, and is also widely used in the biotechnology, food, and pharmaceuticals industries. Secretory CGTase production by recombinant Komagataella phaffii using defined medium is a promising approach because of low cost, less impurity protein. It was found that no CGTase was expressed using traditional defined medium (basal salt medium [BSM]) because of pH value decreasing significantly. CGTase was expressed by recombinant K. phaffii through pH maintenance in range of 5.5-7.0. β-CGTase activity increased to 122.0 U/mL after optimization of glycerol, phosphate buffer, pH value, ammonium sulfate, temperature, methanol, and additives based on BSM, establishing a modified defined medium. These results showed that it was necessary to establish recombinant K. phaffii-based special defined medium although the same host cell used for different heterologous protein expression.

Catalytic, thermodynamic and structural properties of an immobilized and highly thermostable alkaline protease from a haloalkaliphilic actinobacteria, Nocardiopsis alba TATA-5

A highly thermostable protease from a haloalkaliphilic actinobacteria was immobilized employing 5 different approaches on 24 carriers. On immobilization, the activation energy and deactivation rate constant decreased, which makes the immobilized protease favourable for applications. Similarly, pH and temperature stability was enhanced, while the V_max and K_m changed upon immobilization. The immobilized enzyme had greater stability in various metal ions and detergents. The structural topography of the immobilized enzyme elucidated by the FTIR suggested the function of aliphatic amines, alkenes and esters since amide I and II bands were affected. Noticeable decrease in the Amide A band suggests interaction between the immobilization carriers and -NH groups of the protease molecule. The suitability of the immobilized protease was established by designing a continuous flow enzyme bioreactor, displaying the enzyme half-life of 916.15 min at 60 °C. The enzyme reactor was highly efficient in the treatment of the municipal and dairy wastewater.