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Published in Joseph C. Salamone, Polymeric Materials Encyclopedia, 2020
If the 100% α stereoselectivity of D-glucosylation on the polymer is necessary, the enzymatic reaction can be attempted. However, glucosyltransferases have disadvantages for preparative scale synthesis, due to low availability and the expensive substrates (sugar nucleotides such as UDP-glucose). For glucosylation with glucosidases, organic solvent is necessary in order to dissolve 2,4-di-O-benzyl-(l → 6)-α-d-glucopyranan, which is the starting material for regioselective branching reaction with glucosidases and which seems to have a bad influence upon the stability and the activity of glucosidases. Moreover, it is difficult to make a concentrated solution of donor compound such as p-nitrophenyl α-d-glucopyranoside in organic solvent. In the case of chemical glucosylation, 100% α-stereoselectivity of D-glucosylation is hard to achieve, because the formation of 100% cis-glycoside linkage is quite difficult. When the acceptor is low molecular weight compound, 100% α stereoselectivity is not necessary. The two kinds of anomers that are obtained can be separated by crystallization or chromatography. However, when the acceptor is polymer such as polysaccharide, it is impossible to separate the amonomers because both anomers bind to the same polymer molecule. Therefore, 100% α stereoselectivity of d-glucosylation is essential for the formation of branched polysaccharide.
Multi-Cyclodextrin Supramolecular Encapsulation Entities for Multifaceted Topical Drug Delivery Applications
Published in Munmaya K. Mishra, Applications of Encapsulation and Controlled Release, 2019
P. D. Kondiah, Yahya E. Choonara, Zikhona Hayiyana, Pariksha J. Kondiah, Thashree Marimuthu, Lisa C. du Toit, Pradeep Kumar, Viness Pillay
Generally, cyclodextrins are produced by the enzymatic degradation of starch, specifically the amylase component. This reaction is catalyzed by the glucosyltransferase enzyme (Zhang et al. 2017). The production of α- and β-cyclodextrins occurs naturally in the presence of the bacterium Bacillus macerans (Pal, Gaba, and Soni 2018).
Effects of carbon sources on production and properties of curdlan using Agrobaterium sp. DH-2
Published in Preparative Biochemistry & Biotechnology, 2020
Jie Wan, Yifeng Wang, Deming Jiang, Hongliang Gao, Guang Yang, Xuexia Yang
Biosynthesis of curdlan in Agrobacterium spp. was believed to proceed by the repetitive addition of glucosyl residues from UDP-glucose by a (1,3)-β-D-glucan synthase. This synthase was designated UDP-glucose-(1,3)-β-D-glucan glucosyltransferase (EC 2.4.1.34) and was also known as curdlan synthase in bacteria.[30] The glucosyltransferase activity under various sugars is shown in Figure 1. The trend of enzyme activity was consistent with that of curdlan production. The use of sucrose as a carbon source resulted in the maximum glucosyltransferase activity (19.9 U/g biomass), while the use of xylose as a carbon source resulted in the lowest glucosyltransferase activity (8.6 U/g biomass). In curdlan production using cassava starch waste hydrolysates as carbon source, it was also found that glucosyltransferase activity was highly correlated with curdlan production.[22]
Flavonoids – flowers, fruit, forage and the future
Published in Journal of the Royal Society of New Zealand, 2023
Nick W. Albert, Declan J. Lafferty, Sarah M. A. Moss, Kevin M. Davies
Many ornamental species lack production of delphinidin-based anthocyanins, and associated purple-blue flower colours, including the three most valuable cut flowers: rose, carnation and chrysanthemum. These species lack the F3′5′H for generating the substrates necessary for delphinidin formation. Japanese and Australian researchers started a project in 1990 that identified the F3′H and F3′5′H genes and subsequently introduced them into rose, carnation and chrysanthemum (Katsumoto et al. 2007; Tanaka and Brugliera 2013; Noda 2018). The amount of delphinidin-based anthocyanins produced as a percentage of total anthocyanins varied among the transgenics, as did the resultant flower colours. Additionally, even with delphinidin production, other cellular factors need to be suitable to generate flowers with strong blue colours. These include appropriate vacuolar pH, appropriate co-pigments, and/or extensive secondary modifications to the core anthocyanidin, specifically, glycosylation and then acylation on the sugar residues (Andersen and Markham 2006; Houghton et al. 2021; Lu et al. 2021). For carnation, there were target genotypes available that contained mutations in endogenous anthocyanin biosynthetic genes that enabled the engineering of strong delphinidin production and excellent flower colour outcomes (Tanaka and Brugliera 2013). These transgenic carnations were commercialised in many regions of the world in the late-1990s, and have been joined by more cultivars with additional GM: more than 25 million GM carnations are now sold world-wide every year (Tanaka and Brugliera 2013). Similar approaches generated transgenic chrysanthemums with violet-blue flower colours (Brugliera et al. 2013). For rose, achieving blue flower colours from the introduction of the F3′5′H transgene proved challenging, even though cultivars that had relatively higher pH and no F3′H activity were identified as the recipients for the transgenes (Tanaka and Brugliera 2013). Trials of alternative F3′5′H transgenes and modification of other pathway factors did result in transgenics with almost 100% delphinidin production and mauve-blue petal colours, and the Suntory’s blue rose ‘Applause’ was commercialised in 2009 (Tanaka and Brugliera 2013). Addition of transgenes for the anthocyanin secondary modification activities (e.g. Kallam et al. 2017; Lu et al. 2021) could encourage a shift towards the blue spectrum. This was illustrated by the production of chrysanthemum with blue flower colours by the introduction of an uridine diphosphate (UDP)–glucose: anthocyanin 3′,5′-O-glucosyltransferase transgene along with the F3′5′H (Noda et al. 2017). Effective gene technologies for engineering floral vacuolar pH have proved elusive. Improving the blue flower colour of GM ornamentals thus remains an area of interest, as does conferring aurone production for yellow colours (Hoshino et al. 2019), and the possibilities offered for potential non-GM plant lines from gene editing using CRISPR technologies.