1. Fermentative indole production via bacterial tryptophan synthase alpha subunit and plant indole-3-glycerol phosphate lyase enzymesLenny Ferrer, Melanie Mindt, Maria Suarez-Diez, Tatjana Jilg, Maja Zagorščak, Jin-Ho Lee, Kristina Gruden, Volker F. Wendisch, Katarina Cankar, 2022, original scientific article Abstract: Indole is produced in nature by diverse organisms and exhibits a characteristic odor described as animal, fecal, and floral. In addition, it contributes to the flavor in foods, and it is applied in the fragrance and flavor industry. In nature, indole is synthesized either from tryptophan by bacterial tryptophanases (TNAs) or from indole-3-glycerol phosphate (IGP) by plant indole-3-glycerol phosphate lyases (IGLs). While it is widely accepted that the tryptophan synthase α-subunit (TSA) has intrinsically low IGL activity in the absence of the tryptophan synthase β-subunit, in this study, we show that Corynebacterium glutamicum TSA functions as a bona fide IGL and can support fermentative indole production in strains providing IGP. By bioprospecting additional bacterial TSAs and plant IGLs that function as bona fide IGLs were identified. Capturing indole in an overlay enabled indole production to titers of about 0.7 g L–1 in fermentations using C. glutamicum strains expressing either the endogenous TSA gene or the IGL gene from wheat.
Keywords: Corynebacterium glutamicum, indole, indole-3-glycerol phosphate lyase, tryptophan synthase α-subunit, bioprospecting, fermentative production
Published in DiRROS: 16.07.2024; Views: 21; Downloads: 4
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2. RILEM TC 247-DTA round robin test : sulfate resistance, alkali-silica reaction and freeze-thaw resistance of alkali-activated concretesFrank Winnefeld, Gregor J. G. Gluth, Susan A. Bernal, Maria Chiara Bignozzi, Lorenza Carabba, Sundararaman Chithiraputhiran, Alireza Dehghan, Sabina Dolenec, Katja Dombrowski-Daube, Ashish Dubey, Vilma Ducman, Yu Jin, Karl Peterson, Stephen Dietmar, John L. Provis, 2020, original scientific article Abstract: The RILEM technical committee TC 247-DTA ‘Durability Testing of Alkali-Activated Materials’ conducted a round robin testing programme to determine the validity of various durability testing methods, originally developed for Portland cement based-concretes, for the assessment of the durability of alkali-activated concretes. The outcomes of the round robin tests evaluating sulfate resistance, alkali-silica reaction (ASR) and freeze–thaw resistance are presented in this contribution. Five different alkali-activated concretes, based on ground granulated blast furnace slag, fly ash, or metakaolin were investigated. The extent of sulfate damage to concretes based on slag or fly ash seems to be limited when exposed to an Na2SO4 solution. The mixture based on metakaolin showed an excessive, very early expansion, followed by a dimensionally stable period, which cannot be explained at present. In the slag-based concretes, MgSO4 caused more expansion and visual damage than Na2SO4; however, the expansion limits defined in the respective standards were not exceeded. Both the ASTM C1293 and RILEM AAR-3.1 test methods for the determination of ASR expansion appear to give essentially reliable identification of expansion caused by highly reactive aggregates. Alkali-activated materials in combination with an unreactive or potentially expansive aggregate were in no case seen to cause larger expansions; only the aggregates of known very high reactivity were seen to be problematic. The results of freeze–thaw testing (with/without deicing salts) of alkali-activated concretes suggest an important influence of the curing conditions and experimental conditions on the test outcomes, which need to be understood before the tests can be reliably applied and interpreted.
Keywords: alkali-activated materials/geopolymers, sulphate resistance, alkali silica reactivity, freeze-thaw resistance, Rilem TC
Published in DiRROS: 17.08.2023; Views: 382; Downloads: 242
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3. Effect of the N[sub]2/Ar flow ratio on the microstructure and mechanical properties of TiSiCN coatingsJin Wang, Mengting Wang, Yongqiang Wang, Dayan Ma, Hao Li, 2021, original scientific article Keywords: TiSiCN, multi-arc ion plating, magnetron sputtering, N[sub]2/Ar flow ratio, mechanical properties, tribological properties
Published in DiRROS: 06.05.2022; Views: 541; Downloads: 161
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4. In-situ regeneration of Au nanocatalysts by atmospheric-pressure air plasma : significant contribution of water vaporBin Zhu, Xiao-Song Li, Jing-Lin Liu, Jin-Bao Liu, Xiaobing Zhu, Ai-Min Zhu, 2015, original scientific article Keywords: Au catalyst, air plasma, in-situ regeneration, water vapor, CO oxidation
Published in DiRROS: 07.04.2016; Views: 4543; Downloads: 1036
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