Biochemical characterization and kinetic comparison of encapsulated haze removing acidophilic xylanase with partially purified free xylanase isolated from Aspergillus flavus MTCC 9390

Application of Immobilized Enzymes in Juice Clarification

Immobilized enzymes are currently being rapidly developed and are widely used in juice clarification. Immobilized enzymes have many advantages, and they show great advantages in juice clarification. The commonly used methods for immobilizing enzymes include adsorption, entrapment, covalent bonding, and cross-linking. Different immobilization methods are adopted for different enzymes to accommodate their different characteristics. This article systematically reviews the methods of enzyme immobilization and the use of immobilized supports in juice clarification. In addition, the mechanisms and effects of clarification with immobilized pectinase, immobilized laccase, and immobilized xylanase in fruit juice are elaborated upon. Furthermore, suggestions and prospects are provided for future studies in this area.

Alginate Encapsulation Stabilizes Xylanase Toward the Laccase Mediator System

Xylanase, a hydrolytic enzyme, is susceptible to inactivation by the oxidative conditions generated by the laccase mediator system (LMS). Given the impetus to develop a mixed enzyme system for application in biomass processing industries, xylanase was encapsulated with either Cu²⁺- or Ca²⁺-alginate and then exposed to the LMS with variations such as mediator type, mediator concentration, and treatment pH. Results demonstrate that alginate-encapsulated xylanase retains substantial activity (> 80%) when exposed to the LMS relative to non-encapsulated xylanase. Cu²⁺-alginate generally provided better protection than Ca²⁺-alginate for all mediators, and protection was observed even at a low pH, where the LMS is most potent. Despite encapsulation, xylanase was still capable of hydrolyzing its polymeric substrate xylan, given k_cat/K_m values within an order of magnitude of that for non-encapsulated xylanase. The alginate matrix does not impede the function of the oxidized mediator, since comparable V_max values were observed for the conversion of veratryl alcohol to veratraldehyde by free and Cu²⁺-alginate encapsulated laccase. Overall, these results support development of a mixed enzyme system for biomass delignification and, more broadly, show potential for protecting protein function in an oxidative environment.

A multifaceted enzyme conspicuous in fruit juice clarification: An elaborate review on xylanase

Xylanase enzyme has been classified as an enzyme belonging to the glycoside hydrolase family. The catalytic action of xylanase is focused on the degradation of xylan, a substrate for this enzyme comprising of a complex arrangement of monosaccharides interlinked with the help of ester and glycosidic bonds. Xylan represents the second most profuse renewable polysaccharide present on earth. Breakage of the β- 1, 4-glycoside linkage in the xylan polymer is what makes xylanase enzyme an important biocatalyst favoring various applications including treatment of pulp for improving paper quality, improvement of bread quality, treatment of lignocelluloses waste, production of xylose sugar and production of biological fuels. Most recently, xylanase has been exploited in the food industry for the purpose of fruit juice clarification. Turbidity caused by the colloidal polysaccharides present in the freshly squeezed fruit juice poses a setback to the fruit juice industry since the commercial product must be clear and free of excess polysaccharides to improve juice quality and storage life. This review gives an overview of the recent advancements made in regards to xylanase enzyme being used commercially with main focus on its role in fruit juice clarification.

Purification and characterization of a novel -glucosidase from Aspergillus flavus and its application in saccharification of soybean meal

Aspergillus flavus has been regarded as a potential candidate for its production of industrial enzymes, but the details of β-glucosidase from this strain is very limited. In herein, we first reported a novel β-glucosidase (AfBglA) with the molecular mass of 94.2 kDa from A. flavus. AfBglA was optimally active at pH 4.5 and 60 °C and is stable between pH 3.5 and 9.0 and at a temperature of up to 55 °C for 30 min remaining more than 90% of its initial activity. It showed an excellent tolerance to Trypsin, Pepsin, Compound Protease, and Flavourzyme and its activity was not inhibited by specific certain cations. AfBglA displayed broad substrate specificity, it acted on all tested pNP-glycosides and barley glucan, indicating this novel β-glucosidase exhibited a β-1, 3-1, 4-glucanase activity. Moreover, the AfBglA could effectively hydrolyze the soybean meal suspension into glucose and exhibit a strong tolerance to the inhibition of glucose at a concentration of 20.0 g/L during the saccharification. The maximum amount of the glucose obtained by AfBglA corresponded to 67.0 g/kg soybean meal. All of these properties mentioned above indicated that the AfBglA possibly attractive for food and feed industry and saccharification of cellulolytic materials.

Improved Enzyme Catalytic Characteristics upon Glutaraldehyde Cross-Linking of Alginate Entrapped Xylanase Isolated from Aspergillus flavus MTCC 9390

Purified fungal xylanase was entrapped in alginate beads. Its further cross-linking using glutaraldehyde resulted in large enzyme aggregates which may function as both a catalyst and a support material for numerous substrate molecules. Enzyme cross-linking presented a negative impact on enzyme leaching during repeated washings and recovery of enzyme activity was substantial after twelve cycles of usage. The entrapment followed by cross-linking doubled the total bound activity and also greatly improved the enzyme stability at extreme chemical environment. The wide pH stability, better thermo- and storage stability, lowered K_m value, and protection from some metal ions are salient achievements of present immobilization. The study shows the efficacy, durability, and sustainability of immobilized catalytic system which could be efficiently used for various juice processing operations.