Cultivation properties and cell morphology of the Euglena gracilis SM-ZK strain under fed-batch cultivation conditions.

Cattle wastewater as a low-cost supplement augmenting microalgal biomass under batch and fed-batch conditions

Effects of organic carbon sources on cell growth and alpha-tocopherol productivity in wild and chloroplast-deficient W14ZUL strains of Euglena gracilis under photoheterotrophic culture were investigated. In both strains, the increase in cell growth was particularly high when glucose was added as the sole organic carbon source. On the other hand, alpha-tocopherol production per dry cell weight was enhanced by adding ethanol. Ethanol addition also increased the chlorophyll concentration in wild strain and mitochondria activity in W14ZUL strain. For effective alpha-tocopherol production, the effects of mixture of glucose and ethanol were investigated. The results showed that, when a mixture of glucose (6 g/l) and ethanol (4 g/l) was used, alpha-tocopherol productivity per culture broth was 3.89 x 10(-2) mg l(-1) h(-1), which was higher than the value obtained without addition of organic carbon source (0.92 x 10(-2) mg l(-1) h(-1)). In addition, under fed-batch cultivation using an internally illuminated photobioreactor, the alpha-tocopherol production per culture broth was 23.43 mg/l, giving a productivity of 16.27 x 10(-2) mg l(-1) h(-1).

Effects of hydrodynamic stress, dissolved oxygen (DO) concentration and carbon sources on heterotrophic α-tocopherol production by Euglena gracilis were investigated. In a jar fermentor without baffle plates, increasing the agitation speed up to 500 rpm had no significant effect on cell growth and α-tocopherol production. However, in a jar fermentor equipped with baffle plates, both the cell growth and α-tocopherol production were highly suppressed at 500 rpm. At high hydrodynamic stress, the cells secreted nucleic acid-related substances to the culture broth and the shape of the cells shifted from elongated toward spherical. High DO concentration had adverse effects on both cell growth and α-tocopherol production, the optimum DO concentration being below 0.8 ppm. In comparison with glucose, the growth rate was lower but the α-tocopherol content of the cells was almost four times higher when ethanol was used as the organic carbon source. In a fed-batch culture with ethanol, a very high cell concentration of 39.5 g L-1 was obtained with α-tocopherol content of 1200 µg g-cell-1. This α-tocopherol content is very close to the values reported for photoautotrophic and photoheterotrophic cultures. A very high α-tocopherol productivity of 102 µg L-1 h-1 was obtained, indicating that heterotrophic cultivation of E. gracilis has a very high potential as a substitute for the current method of extraction from vegetable oils.

Euglena gracilis (E. gracilis) accumulates paramylon, an immune-functional beta-glucan that can be used as a functional food. Paramylon production is strongly affected by the organic carbon source and the initial pH conditions. Food processing byproducts have attracted attention for microalgal cultivation because of their low cost and abundance of nutrients, including carbon and nitrogen. We investigated the optimal carbon source and its concentration for efficient paramylon production. A spent tomato byproduct (STB) generated from a tomato processing plant was applied for biomass and paramylon production from E. gracilis with respect to the initial pH condition. The highest paramylon concentration (1.2 g L−1) and content (58.2%) were observed with 15 g L−1 glucose. The biomass production increased when STB was used as compared with that when a synthetic medium was used (1.6-fold higher at pH 3 and 2-fold higher at pH 8). The optimal initial pH was determined according to the maximum production of biomass and paramylon. Upcycling the food processing byproduct, STB, can contribute not only to cost reduction of the biorefinery process using E. gracilis but also to environmental remediation by removing organic carbon and nitrogen from the byproducts.

Lutein production with wild-type and mutant strains of Chlorella sorokiniana MB-1 under mixotrophic growth

We investigated the effects of supplementing eight individual carbon sources and four combinations of organic and inorganic carbon sources on the biomass, chlorophyll (chl), and astaxanthin content of Haematococcus lacustris. The findings demonstrated that supplementing nitrogen-free Jaworski’s medium (JM [−N]) with both inorganic and organic carbon sources significantly enhanced the productivities of astaxanthin, chl a and b, and the biomass in H. lacustris. Among the individual supplements tested, NaHCO₃, mannitol, sodium pyruvate, glucose, ethanol, and asparagine notably enhanced astaxanthin production. Sodium bicarbonate, an inorganic carbon source, yielded the highest astaxanthin content among all tested supplements, whereas sodium pyruvate was the most effective among the organic carbon sources. These findings provide a foundation for optimizing carbon supplementation strategies to enhance pigment and biomass production during H. lacustris cultivation, thereby contributing to the potential commercial viability of astaxanthin production.

Alleviation of cadmium (Cd) toxicity and minimizing its uptake in wheat (Triticum aestivum) by using organic carbon sources in Cd-spiked soil

To reduce the cost of media components and consecutively enhance the amount of lipid formation, the effect of crude glycerol on Euglena gracilis is reported for the first time. Presently, E. gracilis has been chosen because of excellent capability of its growth and lipid synthesis in mixotrophic culture condition on organic carbon sources (Glucose and Glycerol). Biochemical composition of the cell in presence of both organic carbon sources were compared in mixotrophic condition. Glycerol was selected as most suitable carbon source and the highest biomass concentration of 2.63 g L -1 and lipid accumulation of 27.64 % were observed. The effect of biodiesel derived crude glycerol on the growth of E. gracilis was found very positive. A significant increase in lipid accumulation (49.46%) was noticed in presence of crude glycerol by optimizing concentration and other culture parameters. Fatty acid methyl esters (FAMEs) produced from lipid biomolecules by following transesterification reaction, were analysed through GC-MS. FAMEs governed by 93.458% C16-C18 fatty acids with appropriate quantities of Saturated fatty acids (SFA) and Unsaturated fatty acids (UFA). Several requisite fuel properties were estimated and found to be in accordance with American and European biodiesel standards. Hence, this study focuses the improved lipid synthesis in E. gracilis utilizing crude glycerol for the preparation of raw biodiesel and it supports biorefinery approach.

Cellular iron homeostasis is critical for survival and growth. Bacteria employ a variety of strategies to sequester iron from the environment and to store intracellular iron surplus that can be utilized in iron-restricted conditions while also limiting the potential for the production of iron-induced reactive oxygen species (ROS). Here, we report that membrane-derived oligosaccharide (mdo) glucan, an intrinsic component of Gram-negative bacteria, sequesters the ferrous form of iron. Iron-binding, uptake, and localization experiments indicated that both secreted and periplasmic β-(1,2)-glucans bind iron specifically and promote growth under iron-restricted conditions. Xanthomonas campestris and Escherichia coli mutants blocked in the production of β-(1,2)-glucan accumulate low amounts of intracellular iron under iron-restricted conditions, whereas they exhibit elevated ROS production and sensitivity under iron-replete conditions. Our results reveal a critical role of glucan in intracellular iron homeostasis conserved in Gram-negative bacteria.

Quantification of sedimentary organic carbon sources in a land–river–lake continuum combined with multi-fingerprint and un-mixing models

The colonization of pozzolana by an As(III)-oxidizing bacterial consortium was monitored from the first hours of bacterial adhesion to 6 weeks of development under fed-batch conditions, using adapted ultrasonic dislodging and crystal-violet staining procedures to determine the biofilm adhering to the complex surfaces. The effect of temperature, arsenic concentration, and presence or absence of yeast extract (YE) on the amount of biofilm biomass and on the As(III)-oxidation were assessed to test the biofilm's resilience and optimize the colonization. Fed-batch cultures allow twice as much pozzolana colonization as that obtained under batch conditions. In addition, As(III) oxidation and the quantities of biomass under fed-batch culture conditions were the same at 14 degrees C and 25 degrees C. Whereas YE improves (+150%) bacterial adhesion during the first 2 h, its impact in the longer term appears to be less significant-biofilm formation in presence of YE after 5 weeks was no greater than biofilm formation in the absence of YE. Finally, YE involves a drastic (-70%) decrease of As(III) oxidation. Preliminary tests for drinking-water bioremediation revealed the ability of Chéni Arsenic Oxidizing 1 biofilms to remain and retain As(III) oxidation activity at low As(III) concentrations (50 microg l(-1)).

Production of probiotic biomass (Lactobacillus casei) in goat milk whey: Comparison of batch, continuous and fed-batch cultures

Organic carbon determines nitrous oxide consumption activity of clade I and II nosZ bacteria: Genomic and biokinetic insights

Effect of organic carbon sources on growth, lipid production and fatty acid profile in mixotrophic culture of Scenedesmus dimorphus (Turpin) Kützing

BackgroundSubstrate-limited fed-batch conditions have the favorable effect of preventing overflow metabolism, catabolite repression, oxygen limitation or inhibition caused by elevated substrate or osmotic concentrations. Due to these favorable effects, fed-batch mode is predominantly used in industrial production processes. In contrast, screening processes are usually performed in microtiter plates operated in batch mode. This leads to a different physiological state of the production organism in early screening and can misguide the selection of potential production strains. To close the gap between screening and production conditions, new techniques to enable fed-batch mode in microtiter plates have been described. One of these systems is the ready-to-use and disposable polymer-based controlled-release fed-batch microtiter plate (fed-batch MTP). In this work, the fed-batch MTP was applied to establish a glucose-limited fed-batch screening procedure for industrially relevant protease producing Bacillus licheniformis strains.ResultsTo achieve equal initial growth conditions for different clones with the fed-batch MTP, a two-step batch preculture procedure was developed. Based on this preculture procedure, the standard deviation of the protease activity of glucose-limited fed-batch main culture cultivations in the fed-batch MTP was ± 10%. The determination of the number of replicates revealed that a minimum of 6 parallel cultivations were necessary to identify clones with a statistically significant increased or decreased protease activity. The developed glucose-limited fed-batch screening procedure was applied to 13 industrially-relevant clones from two B. licheniformis strain lineages. It was found that 12 out of 13 clones (92%) were classified similarly as in a lab-scale fed-batch fermenter process operated under glucose-limited conditions. When the microtiter plate screening process was performed in batch mode, only 5 out of 13 clones (38%) were classified similarly as in the lab-scale fed-batch fermenter process.ConclusionThe glucose-limited fed-batch screening process outperformed the usual batch screening process in terms of the predictability of the clone performance under glucose-limited fed-batch fermenter conditions. These results highlight that the implementation of glucose-limited fed-batch conditions already in microtiter plate scale is crucial to increase the precision of identifying improved protease producing B. licheniformis strains. Hence, the fed-batch MTP represents an efficient high-throughput screening tool that aims at closing the gap between screening and production conditions.