Filters
The Impact of Process Parameters on 1,3-Propanediol Production and 3-Hydroxypropionaldehyde Accumulation in Fed-Batch Fermentation of Glycerol with Citrobacter freundii AD119
Microbial production of 1,3-propanediol (1,3-PD) has attracted the interest of scientists for decades. Its product offers an environmentally friendly and sustainable alternative to fossil-based raw materials for chemical synthesis. Citrobacter freundii is one of the natural producers of 1,3-PD known for its ability to yield it in significant titers. An efficient bioprocess requires an in-depth understanding of the factors that influence the performance of its biocatalyst. The effects of pH, temperature, stirring rate, and substrate concentration on glycerol fermentation in fed-batch cultures of C. freundii AD119 were investigated in this study. In addition to monitoring the kinetics of substrate utilization and the formation of the final products, the concentration of 3-hydroxypropionaldehyde (3-HPA), an inhibitory intermediate of glycerol bioconversion, was analyzed. When the optimal working conditions were used (pH 7.0, temperature 30 °C, stirring rate of 80 rpm, and glycerol concentration below 15 g/L during the fed-batch phase), 53.44 g/L of 1,3-PD were obtained. When the process was performed at temperatures of 33 °C or higher or in acidic pH (6.5), an elevated concentration of 3-HPA was observed and the process halted prematurely.
The HECT ubiquitin-protein ligases UPL1 and UPL2 are involved in degradation of Arabidopsis thaliana ACC synthase 7
AbstractEthylene is an important plant hormone whose production relies on the action of key enzymes, one of which is 1‐aminocyclopropane‐1‐carboxylate synthase (ACS). There are three classes of ACS, which are all partially regulated by degradation through the ubiquitin‐proteasome system (UPS), which regulates ethylene production. Arabidopsis has a single class III ACS, ACS7, but although it is known to be degraded by the 26S proteasome, the UPS proteins involved are poorly characterised. In this work, we used mass spectrometry to identify novel components of the ubiquitin system that may contribute to the regulation of ethylene biosynthesis via ACS7. We found two HECT‐type ligases, UPL1 and UPL2, which regulate ACS7 stability. In vitro experiments showed that UPL1 and UPL2 E3 ligases directly control ACS7 turnover. In addition, increased ethylene levels were observed in UPL1‐ and UPL2‐knockout plants in response to NaCl and NaCl+MG132 treatment, respectively. Under the same conditions, we observed increased ACS7 transcript levels in upl1 compared to WT plants under control and stress conditions, further confirming that UPL1 and UPL2 regulate ACS7‐dependent ethylene production in response to stress. We used molecular modelling to predict ACS7 ubiquitylation sites and cell‐free degradation assays to verify that lysine residues at positions 174, 238 and 384 regulate ACS7 protein stability. Overall, this study provides new insights into the regulation of ACS7 protein stability, and hence ethylene production, in plant growth and development and the response to stress.
The Rheology, Texture, and Molecular Dynamics of Plant-Based Hot Dogs
The rising demand for plant-based alternatives to traditional meat products has led to the development of plant-based sausages (PBSs) that closely mimic the texture and taste of their meat counterparts. This study investigates the rheological and textural properties, as well as proton molecular dynamics, of hot dog-type PBSs and batters used in their production. Various formulations were analyzed to understand how different ingredients and processing methods affect the characteristics of the final products. Our findings reveal that the incorporation of specific plant proteins and hydrocolloids significantly influences the rheological behavior and texture profile of sausages. The hardness of the samples ranged from 4.33 to 5.09 N/mm and was generally higher for the products with inorganic iron sources. Regarding the viscoelastic properties, all the samples showed larger values of the storage modulus than the loss modulus, which indicates their solid-like behavior. Additionally, the study utilized advanced proton nuclear magnetic resonance (NMR) techniques to elucidate the molecular dynamics within plant-based matrices, providing insights into water distribution and mobility. Key findings highlight the impact of different plant proteins and additives on the texture and stability of sausage analogs.
Optimization and Modeling of Citrobacter freundii AD119 Growth and 1,3-Propanediol Production Using Two-Step Statistical Experimental Design and Artificial Neural Networks
1,3-propanediol (1,3-PD) has a wide range of industrial applications. The most studied natural producers capable of fermenting glycerol to 1,3-PD belong to the genera Klebsiella, Citrobacter, and Clostridium. In this study, the optimization of medium composition for the biosynthesis of 1,3-PD by Citrobacter freundii AD119 was performed using the one-factor-at-a-time method (OFAT) and a two-step statistical experimental design. Eleven mineral components were tested for their impact on the process using the Plackett–Burman design. MgSO4 and CoCl2 were found to have the most pronounced effect. Consequently, a central composite design was used to optimize the concentration of these mineral components. Besides minerals, carbon and nitrogen sources were also optimized. Partial glycerol substitution with other carbon sources was found not to improve the bioconversion process. Moreover, although yeast extract was found to be the best nitrogen source, it was possible to replace it in part with (NH4)2SO4 without a negative impact on 1,3-PD production. As a part of the optimization procedure, an artificial neural network model of the growth of C. freundii and 1,3-PD production was developed as a predictive tool supporting the design and control of the bioprocess under study.
The influence of red beet varieties and cultivation on their biochemical and sensory profile
Modern pharmacology shows that beetroot extracts exhibit antihypertensive and hypoglycaemic activity as well as excellent antioxidant activity. The promising results of the phytochemicals contained in the extracts suggest the opportunity for their use in functional foods.This study aimed to evaluate the biochemical profile (total ash and crude protein content, total polyphenols and betalains content) and sensory properties (5 points hedonic scale) of beetroot varieties from bio-B (B Taunus, B Boro, B Gesche) and traditional production-TP (TP Taunus, TP Boro, TP Rocket). The beetroots were obtained from a private producer from Austria. The crude protein content in evaluated red beetroots ranged from 1.54 % (B Taunus) to 5.32 % of fresh weight (TP Boro). The ash content range was 0.53 % (TP Rocket and TP Boro) to 0.63 % of fresh weight (TP Taunus). The total polyphenol content was the highest in sample of B Taunus – 3.29 mg GAE kg-1 of fresh weight (GAE – gallic acid equivalent). Betalains were determined separately as the red – violet betacyanins and the yellow betaxanthins. The concentration of betacyanins ranged from 5.7 mg.kg-1 (TP Boro) to 8.07 mg.kg-1 of fresh weight (B Gesche), while that of betaxanthins – from 2.77 mg.kg-1 (TP Boro) to 5.39 mg.kg-1 of fresh weight (B Gesche). Sensory properties (appearance, color, consistency, aroma, taste) of all the beetroot varieties were evaluated overall as good with the best score in a taste and overall appearance noted for TP Boro. The results improve our knowledge on beetroot as a valuable vegetable and indicate that further studies on the properties of different varieties of red beet are justified.