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Natural enzymes used to convert feedstock to substrate
Published in Ruben Michael Ceballos, Bioethanol and Natural Resources, 2017
Several other types of pectinases are not well studied. These include pectin acetyl esterases (PAEs); rhamnogalacturonase (RGase) also known as rhamnogalacturonan hydrolases (RGHs); rhamnogalacturonan rhamnohydrolases (RGRHs); rhamnogalacturonan galacturonohydrolases (RGGHs); rhamnogalacturonan endolyases (RGLs); rhamnogalacturonan acetylesterases (RGAs); xylogalacturonan hydrolases (XGHs); and other accessory enzymes (Figure 3.7). These enzymes are either backbone-degrading enzymes or debranching enzymes. PAE hydrolyzes the acetyl ester group of homogalacturonan (HG) and rhamnogalacturonan (RGI) forming pectic acid and acetate (Williamson et al., 1990; Williamson, 1991; Shevchik and Hugouvieux-Cotte-Pattat, 1997; Bolvig et al., 2003; Bonnin et al., 2008). It belongs to carbohydrate esterase families 12 and 13 (Lombard et al., 2014; CAZy, 2015). RGase/RGH (EC 3.2.1.171) is an endoacting enzyme capable of randomly hydrolyzing the α-d-1,4-GalpA-α-l-1,2-Rhap linkage in the RGI backbone, thereby producing oligogalacturonates. RGase/RGH is not efficient on the substrate that includes acetyl esterification of the RGI backbone (Schols et al., 1990; Kofod et al., 1994). RGase/RGH is grouped into glycosyl hydrolase family 28 (Lombard et al., 2014; CAZy, 2015). RGRH (EC 3.2.1.174) is an exoacting pectinase that catalyzes the hydrolytic cleavage of the rhamnogalacturonan chain of RGI at the nonreducing ends yielding rhamnose (Mutter et al., 1994).
Microbial Enhanced Oil Recovery: A Technological Perspective
Published in Subrata Borgohain Gogoi, Advances in Petroleum Technology, 2020
The first rhamnolipid was reported from Pseudomonas aeruginosa by Bergstrom in 1946 with the structural components of L-rhamnose and β-hydroxydecanoic acid [193]. But the exact chemical structure of rhamnolipid produced by P. aeruginosa was first revealed by Jarvis and Johnson in 1949 [194]. The carbohydrate part of rhamnolipids is made up of a rhamnose group ( C6H12O5 ), and on the basis of that number in the hydrophilic head, rhamnolipids are divided into mono-rhamnolipids (presence of one rhamnose group) and di-rhamnolipids (presence of two rhamnose groups). In di-rhamnolipids, rhamnose moieties are linked with each other through an α-1,2-glycosidic linkage, as mentioned by Edwards and Hayashi (1965) [195]. The proportion of mono- and di-rhamnolipids in the produced rhamnolipids is mainly dependent on bacterial strains [196], different environmental conditions such as pH, temperature, salinity and medium compositions, including C and N2 sources [197]. The hydrophobic tails of rhamnolipids are β-hydroxy fatty acid chains with a chain length of C8H to C16H , and the fatty acid chains are linked by an ester bond [191, 198, 199]. According to Abdel-Mawgoud et al. (2010) [200], there are 60 numbers of rhamnolipid congeners and homologues reported so far. Different rhamnolipid congeners produced by different bacterial strains are summarised in Table 9.2.
Facile Chemical Fabrication of Designer Biofunctionalized Nanomaterials
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials I, 2020
Carbohydrates are one among the other three major classes (lipids, proteins, and nucleic acids) of biomolecules. They have unique application in nanobiomedicine due to their biocompatibility, biodegradability, and water solubility, and are a natural ligand molecule for various cellular receptors mediating cellular events such as cell adhesion, normal tissue growth, signal transducer, and antigenic nature in viral/bacterial infection. The chemically defined structures of carbohydrates with unique physical, chemical, biological, optical, and stereochemical properties offer an advantage to biofunctionalize and design nanomaterials for biological applications. Surface-functionalized silica with mannose attached via thiol group shows specific binding to MCF-7 human breast-cancer cells, and this could be used to design a nanocarrier for drug delivery. Carboxylated forms of carbohydrates such as mannose, galactose, fucose, and sialic acid are coupled to amino-functionalized magnetic nanoparticles via an amide linkage and used to image malignant cells by magnetic resonance imaging. Oligomannosides are functionalized with thiols coupled to gold nanoparticles to produce glycosylated Au nanoparticles. These glycosylated Au nanoparticles bind strongly to a C-type lectin on the surface of dendritic cells compared to gp120, which is a protein essential for the entry of HIV virus into cells and could serve as a potential carbohydrate-based drug against HIV. Rhamnose is a mannose-related 6-deoxy hexose and occurs naturally in the cell walls of bacteria and plants. Phosphonate strongly binds to metal in magnetic nanoparticles through which rhamnose is anchored. These rhamnose biofunctionalized magnetic nanoparticles bind to specific cell types, and due to the paramagnetic property of iron oxide nanoparticles they can be used as MRI contrast agents with specific cell targeting (Kang et al., 2015).
A Review on Bioflotation of Coal and Minerals: Classification, Mechanisms, Challenges, and Future Perspectives
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Kaveh Asgari, Qingqing Huang, Hamid Khoshdast, Ahmad Hassanzadeh
As mentioned, rhamnose is one of the most common biosurfactants which is produced by Pseudomonas aeruginosa strains through a biosynthesis process (Wood et al. 2018). As shown in Figure 4, from the rhamnolipid production pathway, RhlA synthesizes 3-(3-hydroxyakanoyloxy) alkanoic acids (HAA), and RhlB uses HAA to make mono-rhamnolipids. Therefore, the compounds required for SRB biofilm dispersal are HAA or mono/di-rhamnolipids. This bacterium can be found in a variety of habitats such as soil, plants, and water. The biosurfactants of this bacterium are usually a combination of two or four species, and their hydrophobic chain lengths vary (from C8 to C12), with some being unsaturated with one double bond. While, under a normal growth condition, two main homologs of monorhamnolipid (RL-1) and dirhamnolipid (RL-2) (Das and Mukherjee 2005) are produced (Figure 4).