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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 relation between phytochemical composition and sensory traits of selected Brassica vegetables
Elicitation as a Process of Enhancing Bioactive Compounds Concentration in Sprouts
During growth, plants produce bioactive compounds—secondary metabolites. Their concentration can be stimulated by the presence of a stressful factor—an elicitor. Since chlorine dioxide is commonly used in water plants to disinfect drinking water, its application as a plant elicitor seems to be very attractive. The aim of this work was to investigate the influence of a new elicitor, ClO2, on the quality of seeds and bioactive compounds of sprouts. Elicitation of radish and broccoli seeds using ClO2 solutions did not significantly reduce their germination percentage (GP remained over 90%). Radish sprouts sprouted from seeds elicited in chlorine dioxide solutions with concentrations up to 800 ppm did not differ statistically significantly in terms of polyphenol content. Sprouts which were grown in the presence of ClO2 contained significantly fewer polyphenolic compounds. Elicitation of broccoli seeds in 800–1000 ppm ClO2 solutions causes an increase in total phenolic content and concentration of ascorbic acid in sprouts. Elicitation in chlorine dioxide solutions not only increased concentrations of selected bioactive compounds but also improved the microbiological quality of sprouts.
Biocontrol of Cercospora leaf spot in sugar beet by a novel Bacillus velezensis KT27 strain: Enhanced antifungal activity and growth promotion in laboratory and field conditions
Diseases in crops are a major contributor to yield reduction and economic losses. Cercospora leaf spot (CLS), caused by Cercospora beticola, is among the most severe diseases affecting sugar beet and other crops. The increasing resistance of C. beticola to conventional chemical fungicides, along with their excessive application, exacerbates environmental pollution. This study investigates the antagonistic activity of a newly isolated strain, Bacillus velezensis KT27, against Cercospora beticola, Rhizoctonia cerealis, and Fusarium oxysporum under laboratory conditions. The bacterium’s ability to produce lipopeptides (surfactin, iturin, and fengycin) and solubilize phosphorus, potassium, and zinc was also assessed. In vitro assays revealed that B. velezensis KT27 effectively inhibited C. beticola growth (60.2%), though it exhibited lower antagonistic activity against R. cerealis (22.5%) and F. oxysporum (15.5%). The elimination of bacterial biomass by centrifugation and the use of sterile supernatant reduced antifungal activity by more than 3.5-fold for all tested fungi, highlighting the importance of direct bacterial interactions. Notably, the antagonistic effect of B. velezensis KT27 against C. beticola significantly increased when bacterial cultures were supplemented with thermally inactivated fungal biomass of C. beticola especially R. cerealis. Field experiments demonstrated the high efficacy of B. velezensis KT27 biological control agent, particularly when induced by R. cerealis. The level of CLS protection achieved with the bacterial treatment was only 9.1% lower than that obtained using a combination of three chemical fungicides. Additionally, the biocontrol agent positively influenced sugar beet growth, leading to a root yield increase of up to 15.2% compared to the untreated control. These findings highlight the potential of B. velezensis KT27 as an effective and environmentally sustainable biocontrol agent against CLS in sugar beet cultivation.
Sposób przygotowania inokulum bakterii celulolitycznych do wytwarzania biopreparatów poprawiających właściwości gleby
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.