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The antioxidant potential of various wheat crusts correlates with AGE content independently of acrylamide
(2023) Wächter, Kristin; Longin, Carl Friedrich H.; Winterhalter, Patrick R.; Bertsche, Ute; Szabó, Gábor; Simm, Andreas
Epidemiological studies have indicated that the consumption of whole-grain products is associated with a reduced risk of cardiovascular diseases, type II diabetes, and cancer. In the case of bread, high amounts of antioxidants and advanced glycation end products (AGEs) are formed during baking by the Maillard reaction in the bread crust; however, the formation of potentially harmful compounds such as acrylamide also occurs. This study investigated the antioxidant responses of different soluble extracts from whole-grain wheat bread crust extracts (WBCEs) in the context of the asparagine, AGE, and acrylamide content. For that, we analyzed nine bread wheat cultivars grown at three different locations in Germany (Hohenheim, Eckartsweier, and Oberer Lindenhof). We determined the asparagine content in the flour of the 27 wheat cultivars and the acrylamide content in the crust, and measured the antioxidant potential using the induced expression of the antioxidant genes GCLM and HMOX1 in HeLa cells. Our study uncovered, for the first time, that the wheat crust’s antioxidant potential correlates with the AGE content, but not with the acrylamide content. Mass spectrometric analyses of WBCEs for identifying AGE-modified proteins relevant to the antioxidant potential were unsuccessful. However, we did identify the wheat cultivars with a high antioxidant potential while forming less acrylamide, such as Glaucus and Lear. Our findings indicate that the security of BCEs with antioxidative and cardioprotective potential can be improved by choosing the right wheat variety.
Genetic dissection of phosphorus use efficiency in a maize association population under two P levels in the field
(2021) Li, Dongdong; Wang, Haoying; Wang, Meng; Li, Guoliang; Chen, Zhe; Leiser, Willmar L.; Weiß, Thea Mi; Lu, Xiaohuan; Wang, Ming; Chen, Shaojiang; Chen, Fanjun; Yuan, Lixing; Würschum, Tobias; Liu, Wenxin
Mono-digestion of 5-Hydroxymethylfurfural process-wastewater in continuously operated anaerobic filters: A cascade utilization approach
(2023) Khan, Muhammad Tahir; Krümpel, Johannes; Wüst, Dominik; Lemmer, Andreas
A proper remedy for the overexploitation of biomass and biobased materials in the bioeconomy is the valorization of biorefineries’ side streams into meaningful products. Hence, in pursuit of a cascade utilization of renewables, a unique biorefinery byproduct was investigated for its biogas potential, specifically methane, in continuously operated anaerobic filters. For this purpose, 5-Hydroxymethylfurfural process-wastewater, after supplementation of necessary nutrients, was diluted down to 10, 20, 30, 40, and 50 gCOD/L concentrations and thereafter tested individually at 43 °C and 55 °C. Maximum methane conversion efficiency at either temperature was observed for test substrates with 10 gCOD/L and 20 gCOD/L concentrations. At 43 °C, the anaerobic filters exhibited their highest biogas yields when supplied with the 30 gCOD/L feedstock. Further exposure of the mesophilic and thermophilic consortia to the ensuing 5-Hydroxymethylfurfural process-wastewater dilutions compromised the stability of the anaerobic process due to the soaring concentrations of short-chained volatile fatty acids. The supplementation of necessary nutrients to unlock the methane potential of the given recalcitrant substrate appears insufficient. Techniques like micro aeration, photolysis, or the use of activated carbon in the fixed bed might have the ability to enhance the biochemical methane conversion of such feedstock; otherwise, the introduction of trace elements alone may be adequate if aiming for platforms (volatile fatty acids) via anaerobic technologies.
Optimization of thermodynamic parameters of the biological hydrogen methanation in a trickle-bed reactor for the conditioning of biogas to biomethane
(2023) Holl, Elena; Oskina, Anastasia; Baier, Urs; Lemmer, Andreas
The increased demand for resources and energy that is developing with rising global consumption represents a key challenge for our generation. Biogas production can contribute to sustainable energy production and closing nutrient cycles using organic residues or as part of a utilization cascade in the case of energy crops. Compared to hydrogen (H2), biogas with a high methane (CH4) content can be fed into the gas grid without restrictions. For this purpose, the CH4 content of the biogas must be increased from 52 to 60% after anaerobic digestion to more than 96%. In this study, biological hydrogen methanation (BHM) in trickling-bed reactors (TBR) is used to upgrade biogas. Design of experiments (DoE) is used to determine the optimal process parameters. The performance of the reactors is stable under all given conditions, reaching a “low” gas grid quality of over 90%. The highest CH4 content of 95.626 ± 0.563% is achieved at 55 °C and 4 bar, with a methane formation rate (MFR) of 5.111 ± 0.167 m3/(m3·d). The process performance is highly dependent on the H2:CO2 ratio in the educts, which should be as close as possible to the stochiometric ratio of 4. In conclusion, BHM is a viable approach to upgrade biogas to biomethane quality and can contribute to a sustainable energy grid.
Orotic acid production by Yarrowia lipolytica under conditions of limited pyrimidine
(2021) Swietalski, Paul; Hetzel, Frank; Klaiber, Iris; Pross, Eva; Seitl, Ines; Fischer, Lutz
Orotic acid (OA) is an intermediate of the pyrimidine biosynthesis with high industrial relevance due to its use as precursor for production of biochemical pyrimidines or its use as carrier molecule in drug formulations. It can be produced by fermentation of microorganisms with engineered pyrimidine metabolism. In this study, we surprisingly discovered the yeast Yarrowia lipolytica as a powerful producer of OA. The overproduction of OA in the Y. lipolytica strain PO1f was found to be caused by the deletion of the URA3 gene which prevents the irreversible decarboxylation of OA to uridine monophosphate. It was shown that the lack of orotidine‐5′‐phosphate decarboxylase was the reason for the accumulation of OA inside the cell since a rescue mutant of the URA3 deletion in Y. lipolytica PO1f completely prevented the OA secretion into the medium. In addition, pyrimidine limitation in the cell massively enhanced the OA accumulation followed by secretion due to intense overflow metabolism during bioreactor cultivations. Accordingly, supplementation of the medium with 200 mg/L uracil drastically decreased the OA overproduction by 91%. OA productivity was further enhanced in fed‐batch cultivation with glucose and ammonium sulfate feed to a maximal yield of 9.62 ± 0.21 g/L. Y. lipolytica is one of three OA overproducing yeasts described in the literature so far, and in this study, the highest productivity was shown. This work demonstrates the potential of Y. lipolytica as a possible production organism for OA and provides a basis for further metabolic pathway engineering to optimize OA productivity.
Surfactin shows relatively low antimicrobial activity against Bacillus subtilis and other bacterial model organisms in the absence of synergistic metabolites
(2022) Lilge, Lars; Ersig, Nadine; Hubel, Philipp; Aschern, Moritz; Pillai, Evelina; Klausmann, Peter; Pfannstiel, Jens; Henkel, Marius; Morabbi Heravi, Kambiz; Hausmann, Rudolf
Surfactin is described as a powerful biosurfactant and is natively produced by Bacillus subtilis in notable quantities. Among other industrially relevant characteristics, antimicrobial properties have been attributed to surfactin-producing Bacillus isolates. To investigate this property, stress approaches were carried out with biotechnologically established strains of Corynebacterium glutamicum, Bacillus subtilis, Escherichia coli and Pseudomonas putida with the highest possible amounts of surfactin. Contrary to the popular opinion, the highest growth-reducing effects were detectable in B. subtilis and E. coli after surfactin treatment of 100 g/L with 35 and 33%, respectively, while P. putida showed no growth-specific response. In contrast, other antimicrobial biosurfactants, like rhamnolipids and sophorolipids, showed significantly stronger effects on bacterial growth. Since the addition of high amounts of surfactin in defined mineral salt medium reduced the cell growth of B. subtilis by about 40%, the initial stress response at the protein level was analyzed by mass spectrometry, showing induction of stress proteins under control of alternative sigma factors σB and σW as well as the activation of LiaRS two-component system. Overall, although surfactin is associated with antimicrobial properties, relatively low growth-reducing effects could be demonstrated after the surfactin addition, challenging the general claim of the antimicrobial properties of surfactin.

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