Plant‐derived carbohydrates are an abundant renewable resource. Transformation of carbohydrates into new products, including amine‐functionalized building blocks for biomaterials applications, can lower reliance on fossil resources. Herein, biocatalytic production routes to amino carbohydrates, including oligosaccharides, are demonstrated. In each case, two‐step biocatalysis was performed to functionalize d‐galactose‐containing carbohydrates by employing the galactose oxidase from Fusarium graminearum or a pyranose dehydrogenase from Agaricus bisporus followed by the ω‐transaminase from Chromobacterium violaceum (Cvi‐ω‐TA). Formation of 6‐amino‐6‐deoxy‐d‐galactose, 2‐amino‐2‐deoxy‐d‐galactose, and 2‐amino‐2‐deoxy‐6‐aldo‐d‐galactose was confirmed by mass spectrometry. The activity of Cvi‐ω‐TA was highest towards 6‐aldo‐d‐galactose, for which the highest yield of 6‐amino‐6‐deoxy‐d‐galactose (67 %) was achieved in reactions permitting simultaneous oxidation of d‐galactose and transamination of the resulting 6‐aldo‐d‐galactose.
Pyranose dehydrogenases (PDHs; EC 1.1.99.29; AA3_2) demonstrate ability to oxidize diverse carbohydrates. Previous studies of these enzymes have also uncovered substrate-dependent regioselectivity, along with potential to introduce more than one carbonyl into carbohydrate substrates. Enzymatic oxidation of carbohydrates facilitates their further derivatization or polymerization into bio-based chemicals and materials with higher value; accordingly, PDHs that show activity on xylooligosaccharides could offer a viable approach to extract higher value from hemicelluloses that are typically fragmented during biomass processing. In this study, AbPDH1 from Agaricus bisporus and AmPDH1 from Leucoagaricus meleagris were tested using linear xylooligosaccharides, along with xylooligosaccharides substituted with either arabinofuranosyl or 4-O-(methyl)glucopyranosyluronic acid residues with degree of polymerization of two to five. Reaction products were characterized by HPAEC-PAD to follow substrate depletion, UPLC-MS-ELSD to quantify the multiple oxidation products, and ESI-MS n to reveal oxidized positions. A versatile method based on product reduction using sodium borodeuteride, and applicable to carbohydrate oxidoreductases in general, was established to facilitate the identification and quantification of oxidized products. AbPDH1 activity toward the tested xylooligosaccharides was generally higher than that measured for AmPDH1. In both cases, activity values decreased with increasing length of the xylooligosaccharide and when using acidic rather than neutral substrates; however, AbPDH1 fully oxidized all linear xylooligosaccharides, and 60-100% of all substituted xylooligosaccharides, after 24 h under the tested reaction conditions. Oxidation of linear xylooligosaccharides mostly led to double oxidized products, whereas single oxidized products dominated in reactions containing substituted xylooligosaccharides. Notably, oxidation of specific secondary hydroxyls vs. the reducing end C-1 depended on both the enzyme and the substrate. For all substrates, however, oxidation by both AbPDH1 and AmPDH1 was clearly restricted to the reducing and non-reducing xylopyranosyl residues, Karppi et al. Pyranose Dehydrogenases Oxidize Substituted Xylooligosaccharides where increasing the length of the xylooligosaccharide did not lead to detectable oxidation of internal xylopyranosyl substituents. This detailed analysis of AbPDH1 and AmPDH1 action on diverse xylooligosaccharides reveals an opportunity to synthesize bifunctional molecules directly from hemicellulose fragments, and to enrich for specific products through appropriate PDH selection.
a High-temperature thermomechanical pulps (HT-TMP, defibrated at 150 to 170 °C) were compared to a reference TMP (defibrated at 130 °C) as a reinforcement for polylactic acid (PLA). Composites were prepared by melt compounding, followed by injection molding, gradually increasing the used fiber content from 0 to 20 wt.%. The injection-molded specimens were characterized by tensile and impact strength tests, scanning electron microscopy, water absorption tests, and differential scanning calorimetry. The TMP fiber damage was also characterized before and after melt compounding by optical analysis. At 20% fiber content, the Young's modulus increased significantly, while the tensile strength remained unchanged and the impact strength decreased slightly. All fibers suffered damage during melt compounding, but the tensile strength remained about the same as in pure PLA. All types of TMP were able to increase the PLA rate of crystallization. The HT-TMP fibers were dispersed more evenly in PLA than the 130 °C TMP. The 170 °C TMP produced composites of lower water absorption than the other two TMP types, probably because of its lower hemicellulose content and its higher surface coverage by lignin.
When producing regenerated cellulose materials, e.g., fibers and films, pulp fibers are first dissolved in a solvent and then regenerated in an antisolvent. The pulp properties have a significant impact on the dissolution. This study examines the effect of pulp prehydrolysis conditions on pulp structure, subsequent dissolution in cold aqueous NaOH/ZnO solvent, and regenerated cellulose film properties. The fiber and regenerated cellulose swelling and pore structure is addressed. Once-dried kraft pulp was activated in acid hydrolysis at two temperatures, 60 and 80 °C. The hydrolysis primarily affected the cellulose degree of polymerization (DP), and its reduction dramatically improved the pulp dissolution. Surprisingly, higher hydrolysis temperature did not increase the fiber hornification. DP reduction marginally effected the pulp swelling properties but had a significant effect on the regenerated film swelling. The regenerated films contained cellulose II, and their wet porosity correlated inversely with the DP. Low hydrolysis temperature films remained more porous after critical point drying.
Reliable risk management is based on informative decision making. The key to improve decision making is to combine information and create new predictive measurements. Predictive indirect measurements can include open data, process measurements, and modelling. Varying information sources enables viewing the situation from several differing angles and can give the decision maker more time to react. Different datasources strengthen each other narrowing the uncertainty of predictions. Robust self-monitoring is also needed for the predictive system to be reliable. Mining industry has three major risk sources: water handling in the environmental focus area, condition of machines and process devices, and health and safety of personnel. This article focuses on environmental monitoring in vast mining environment and its surroundings but connects process monitoring and control to subject.
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