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Xanthan gum (XG), a bacterial polysaccharide has numerous valuable characteristics in the food, biomedical, pharmaceuticals, and agriculture sector. However, XG has also its particular limitations such as its vulnerability to microbial contamination, inadequate mechanical and thermal stability, unusable viscosity, and poor water solubility. Therefore, XG's structure and conformation need to be modified enzymatically, chemically, or physically to improve its optimistic features and decrease the formation of crystals, increase antioxidant ability, and radical scavenging activity. We have found out different means to modify XG and elaborate the importance and significance of the modified structure of XG. In this review, different enzymes are reviewed for XG degradation, which modifies their structure from different points (main chain or side chain). This article also reviews various physical methods (ultrasound, shear, pressure, sonication, annealing, and heat treatments) based on prevailing publications to alter XG conformation and produce low molecular weight (LMW) and less viscous end-product. Moreover, some chemical means are also discussed that result in modified XG through crosslinking, grafting, acetylation, pyruvation, as well as by applying different chemical agents. Overall, the current progress on XG degradation is very auspicious to develop a new molecule with considerable uses, in various industries with future assessments., (Copyright © 2021. Published by Elsevier B.V.)

Galacto-oligosaccharides (GOS) are the prebiotic constituents with various functional qualities that promote the optimal proliferation of gut microbiota and are consequently beneficial to human health. GOS are not absorbed by humans and animals, but they play numerous health-related positive roles in the human body. Currently, their production has occupied much attention due to the increasing demand for functional foods. It could be produced by enzymatic and chemical approaches. Many microbial enzymes have been utilized for GOS production but the main source of these enzymes is lactose. Moreover, characterization of GOS structures is also a necessary and critical effort for understanding their mechanism of action. Hence, this review is written to understand the extensive but related features for the synthesis of GOS which includes: the enzymatic production of GOS through various enzymes and the types of enzymes such as free, immobilized, recombinant, crude, and purified enzymes that are involved in their synthesis, the techniques used in the purification of GOS, the analysis and quantification of GOS through various practices, and the functional properties of GOS are also discussed in this review. It also aims to combine new findings with current information in order to improve understanding of GOS formation and other factors related to its functionality. [ABSTRACT FROM AUTHOR]

L-Fuculose and D-ribulose are kinds of rare sugars used in food, agriculture, and medicine industries. These are pentoses and categorized into the two main groups, aldo pentoses and ketopentoses. There are 8 aldo- and 4 ketopentoses and only fewer are natural, while others are rare sugars found in a very small amount in nature. These sugars have great commercial applications, especially in many kinds of drugs in the medicine industry. The synthesis of these sugars is very expensive, difficult by chemical methods due to its absence in nature, and could not meet industry demands. The pentose izumoring strategy offers a complete enzymatic tactic to link all kinds of pentoses using different enzymes. The enzymatic production of L-fuculose and D-ribulose through L-fucose isomerase (L-FI) and D-arabinose isomerase (D-AI) is the inexpensive and uncomplicated method up till now. Both enzymes have similar kinds of isomerizing mechanisms and each enzyme can catalyze both L-fucose and D-arabinose. In this review article, the enzymatic process of biochemically characterized L-FI & D-AI, their application to produce L-fuculose and D-ribulose and its uses in food, agriculture, and medicine industries are reviewed. • L-FI & D-AI are important L-fuculose, and D-ribulose producing enzymes are reviewed. • All the enzymatic properties of L-FI & D-AI are comprehensively discussed. • Mechanisms for aldose-ketose transformation are discussed. • Application of L-fuculose and D-ribulose is described. • Future prospects are required for further research to industrial uses of L-FI & D-AI. [ABSTRACT FROM AUTHOR]

• A novel d -arabinose isomerase was characterized from Thermanaeromonas toyohensis. • The enzyme showed activity at 75 °C and pH 9.0 for both d -arabinose and l -fucose. • The specific activities 98 and 85.52 U mg−1 for d -arabinose and l -fucose, respectively. • The enzyme produced 27% (21 g L−1) d -ribulose and 24.88% (19.92 g L−1) l -fuculose. • Its half life at 75 °C was 10 h. d -Ribulose and l -fuculose are potentially valuable rare sugars useful for anticancer and antiviral drugs in the agriculture and medicine industries. These rare sugars are usually produced by chemical methods, which are generally expensive, complicated and do not meet the increasing demands. Furthermore, the isomerization of d -arabinose and l -fucose by D d -arabinose and l -fucose by d -arabinose isomerase from bacterial sources for the production of d -ribulose and l -fuculose have not yet become industrial due to the shortage of biocatalysts, resulting in poor yield and high cost of production. In this study, a thermostable d -ribulose- and l -fuculose producing d -arabinose isomerase from the bacterium Thermanaeromonas toyohensis was characterized. The recombinant d -arabinose isomerase from T. toyohensis (Thto-DaIase) was purified with a single band at 66 kDa using His-trap affinity chromatography. The native enzyme existed as a homotetramer with a molecular weight of 310 kDa, and the specific activities for both d -arabinose and l -fucose were observed to be 98.08 and 85.52 U mg−1, respectively. The thermostable recombinant Thto-DaIase was activated when 1 mM Mn2+ was added to the reactions at an optimum pH of 9.0 at 75 °C and showed approximately 50% activity for both d -arabinose and l -fucose at 75 °C after 10 h. The Michaelis-Menten constant (K m), the turnover number (k cat) and catalytic efficiency (k cat / K m) for d -arabinose/ l -fucose were 111/81.24 mM, 18,466/10,688 min−1, and 166/132 mM−1 min−1, respectively. When the reaction reached to equilibrium, the conversion rates of d -ribulose from d -arabinose and l -fuculose from l -fucose were almost 27% (21 g L−1) and 24.88% (19.92 g L−1) from 80 g L−1 of d -arabinose and l -fucose, respectively. [ABSTRACT FROM AUTHOR]