Effect of Graphene Oxide Prepared Under Different Conditions on Immobilized α-Amylase

Challenges and prospects of microbial α-amylases for industrial application: a review

α-Amylases are essential biocatalysts representing a billion-dollar market with significant long-term global demand. They have varied applications ranging from detergent, textile, and food sectors such as bakery to, more recently, biofuel industries. Microbial α-amylases have distinct advantages over their plant and animal counterparts owing to generally good activities and better stability at temperature and pH extremes. With the scope of applications expanding, the need for new and improved α-amylases is ever-growing. However, scaling up microbial α-amylase technology from the laboratory to industry for practical applications is impeded by several issues, ranging from mass transfer limitations, low enzyme yields, and energy-intensive product recovery that adds to high production costs. This review highlights the major challenges and prospects for the production of microbial α-amylases, considering the various avenues of industrial bioprocessing such as culture-independent approaches, nutrient optimization, bioreactor operations with design improvements, and product down-streaming approaches towards developing efficient α-amylases with high activity and recyclability. Since the sequence and structure of the enzyme play a crucial role in modulating its functional properties, we have also tried to analyze the structural composition of microbial α-amylase as a guide to its thermodynamic properties to identify the areas that can be targeted for enhancing the catalytic activity and thermostability of the enzyme through varied immobilization or selective enzyme engineering approaches. Also, the utilization of inexpensive and renewable substrates for enzyme production to isolate α-amylases with non-conventional applications has been briefly discussed.

Immobilization of α-amylase on GO-magnetite nanoparticles for the production of high maltose containing syrup

Robust amylases with stability and catalysis at multitude of extremities are the need of an hour. Enzyme immobilization may prove beneficial at commercial scale to achieve such attributes. In the present study, a commercially available amylase was immobilized on graphene oxide (GO) - magnetite (Fe₃O₄) nanoparticles through covalent bonding. The structural and morphological characterizations were conducted by XRD, SEM and TEM. Further, FTIR and TGA confirmed the interaction between amylase, GO and nanoparticles. The variables, such as concentrations of GO (1.3 mg), Fe₃O₄ (58 μg), and amylase (4.5 mg) were optimized by the response surface methodology using central composite design. High loading capacity of 77.58 μg amylase over 1 μg GO-magnetite nanoparticles was achieved under optimum conditions. Biochemically, the pH optimum remained unaltered, i.e., pH 7, whereas, the alkalitolerance was increased by ~20% in relative activities upon immobilization. The half-life of soluble amylase was 13 h, which enhanced to 20 h upon immobilization in 20 mM phosphate buffer, pH 7 at 50 °C. Besides, the thermodynamic parameters supported the stability trends. The immobilized amylase could be used for 11 subsequent cycles. The mentioned attributes and the dextrose equivalent values during the production of high maltose containing syrup highlighted its commercialization.

Usability of graphene oxide as a mycotoxin binder: In vitro study

Mycotoxin management in agriculture is an essential challenge for maintaining the health of both animals and humans. Choosing the right adsorbent is still a question for many breeders and an important criterion for feed manufacturers. New adsorbents are still being sought. Graphene oxide is a promising material in the field of nanotechnology, which excels in its adsorption properties. Presented in vitro study investigates graphene oxide for the binding of mycotoxins from crushed wheat. The results show that graphene oxide has an adsorption capacity for aflatoxin 0.045 mg/g, zearalenone 0.53 mg/g and deoxynivalenol 1.69 mg/g at 37° C. In vitro simulation of crushed wheat digestion showed rapid adsorption during the gastric phase. Of the minerals, Mg, Cu and Zn were the most adsorbed. The applied dose of graphene oxide of 10 mg/g caused only a slight inhibition of the digestive enzymes α-amylase and trypsin compared to pepsin and gastric lipase. In vitro results indicated the suitability of graphene oxide in the adsorption of the aflatoxin, zearalenone and deoxynivalenol.