Dry Cell Weight Research Articles

Airlift bioreactor–based strategies for prolonged semi-continuous cultivation of edible Agaricomycetes

Submerged cultivation of edible filamentous fungi (Agaricomycetes) in bioreactors enables maximum mass transfer of nutrients and has the potential to increase the volumetric productivity of fungal biomass compared to solid state cultivation. These aspects are paramount if one wants to increase the range of bioactives (e.g. glucans) in convenient time frames. In this study, Trametes versicolor (M9911) outperformed four other Agaricomycetes tested strains (during batch cultivations in an airlift bioreactor). This strain was therefore further tested in semi-continuous cultivation. Continuous and semi-continuous cultivations (driven by the dilution rate, D) are the preferred bioprocess strategies for biomass production. We examined the semi-continuous cultivation of T. versicolor at dilution rates between 0.02 and 0.1 h−1. A maximum volumetric productivity of 0.87 g/L/h was obtained with a D of 0.1 h−1 but with a lower total biomass production (cell dry weight, CDW 8.7 g/L) than the one obtained at lower dilution rates (12.3 g/L at D of 0.04 and vs 13.4 g/L, at a D of 0.02 h−1). However, growth at a D of 0.1 h−1 resulted in a very short fermentation (18 h) which terminated due to washout (the specific D exceeded the maximum growth rate of the fungal biomass). At a D of 0.04 h−1, a CDW of 12.3 g/L was achieved without compromising the total residence time (184 h) of the fermentation. While the D of 0.04 h−1 and 0.07 h−1 achieved comparable volumetric productivities (0.5 g/L/h), the total duration of the fermentation at D of 0.07 h−1 was only 85 h. The highest glucan content of cells (27.8 as percentage of CDW) was obtained at a D of 0.07 h−1, while the lowest glucan content was observed in T. versicolor cells grown at a D of 0.02 h−1.Key points• The highest reported volumetric productivity for fungal biomass was 0.87 g/L/h.• Semi-continuous fermentation at D of 0.02 h−1 resulted in 13.4 g/L of fungal biomass.• Semi-continuous fermentation at D of 0.07 h−1 resulted in fungal biomass with 28% of total glucans.

Development of an efficient process to extract C‐phycocyanin from marine cyanobacterial strains and evaluation of its bioactive potential

AbstractBACKGROUNDPhycocyanin (PC), a natural blue photosynthetic pigment found in cyanobacteria, rhodophyta and cryptophyta has numerous applications in biotechnology and the food industry. The phycocyanin extraction method has a significant impact on its bioactivities, purity index, cost and potential applications; thus, the development of an efficient extraction strategy continues to be a primary research goal.RESULTSThis study evaluated the efficacy of different methods for the extraction of cyanobacterial phycocyanin (C‐PC) from three marine cyanobacterial isolates, namely Arthrospira platensis, Phormidium sp. and Pseudoscillatoria sp. wet biomass. The pretreatment step of soaking biomass in extraction buffer for 60 min, followed by a combination of freeze–thaw (one cycle; 2 h) and sonication (2 min) treatment was found to be the most effective extraction strategy, producing the highest C‐PC yield (16.19 ± 0.34%, 15.89 ± 0.61% and 15.56 ± 0.69% dry cell weight for strains A. platensis, Phormidium sp. and Pseudoscillatoria sp., respectively). Furthermore, a biomass‐to‐solvent ratio of 0.02 g mL−1 was optimal to attain food‐grade purity ((A620/A280) ≥ 0.7). Bioactivity evaluation of crude and purified C‐PC exhibited its potential as antioxidant compounds and as an antimicrobial agent with significant inhibitory effects against various pathogenic microorganisms.CONCLUSIONThe study proposed an efficient and cost‐effective C‐PC extraction process for cyanobacteria and highlighted the potential of C‐PC as a valuable bioactive compound with various applications. © 2024 Society of Chemical Industry (SCI).

Cohesive phycoremediation of pyrene by freshwater microalgae Selenastrum sp. and biodiesel production and its assessment.

In this study, the freshwater microalgae Selenastrum sp. was assessed for the effective degradation of pyrene and simultaneous production of biodiesel from pyrene-tolerant biomass. The growth of algae was determined based on the cell dry weight, cell density, chlorophyll content, and biomass productivity under different pyrene concentrations. Further, lipids from pyrene tolerant culture were converted into biodiesel by acid-catalyzed transesterification, which was characterized for the total fatty acid profile by gas chromatography. Increased pyrene concentration revealed less biomass yield and productivity after 20days of treatment, indicating potent pyrene biodegradation by Selenastrum sp. Biomass yield was unaffected till the 20mg/L pyrene. A 95% of pyrene bioremediation was observed at 20days of culturing. Lipid accumulation of 22.14%, as evident from the estimation of the total lipid content, indicated a marginal increase in corroborating pyrene stress in the culture. Fatty acid methyl esters yield of 63.06% (% per 100g lipids) was noticed from the pyrene tolerant culture. Moreover, fatty acid profile analysis of biodiesel produced under 10mg/L and 20mg/L pyrene conditionshowed escalated levels of desirable fatty acids in Selenastrum sp., compared to the control. Further, Selenastrum sp. and other freshwater microalgae are catalogued for sustainable development goals attainment by 2030, as per the UNSDG (United Nations Sustainable Development Goals) agenda. Critical applications for the Selenastrum sp. in bioremediation of pyrene, along with biodiesel production, are enumerated for sustainableand renewable energy production and resource management.

Biosynthesis of polyhydroxybutyrate from methane and carbon dioxide using type II methanotrophs

Methane (CH4) and carbon dioxide (CO2) are the dominant greenhouse gases (GHGs) that are increasing at an alarming rate. Methanotrophs have emerged as potential CH4 and CO2 biorefineries. This study demonstrated the synchronous incorporation of CH4 and CO2 into polyhydroxybutyrate (PHB) for the first time using 13C-labeling experiments in methanotrophs. By supplying substantial amounts of CO2, PHB content was enhanced in all investigated type II methanotrophic strains by 140 %, 146 %, and 162 %. The highest content of PHB from CH4 and CO2 in flask-scale cultivation reached 38 % dry cell weight in Methylocystis sp. MJC1, in which carbon percentage in PHB from CO2 was 45 %. Flux balance analysis predicted the critical roles of crotonyl-CoA carboxylase/reductase and phosphoenolpyruvate carboxylase in CO2 recycling. This study provided proof of the conversion of GHGs into a valuable and practical product using methanotrophic bacteria, contributing to addressing GHG emissions.

Real-time detection of lysine decarboxylase activity and cellular energy pool under inducible CadA expression system in engineered Escherichia coli

BackgroundBiocatalysts hold significant promise in the production of 1,5-diaminopentane (cadAverine) due to its wide-ranging applications. However, the process of screening recombinant cells expressing lysine decarboxylase (LdcC or CadA) activity via high-performance liquid chromatography is labor-intensive and time-consuming. MethodsThis study has devised a straightforward colorimetric assay to quantify lysine decarboxylase activity. It utilizes the pH indicator bromocresol purple (BCP). As cadAverine is produced from l-lysine, it elevates the reaction pH, leading to a corresponding change in BCP color. Significant findingsReal-time monitoring of CadA activity was conducted using an inducible T7 promoter system, built upon the CadA/-CadB co-expression framework within Escherichia coli BL21(DE3). Analysis of Michaelis-Menten kinetics revealed that pyridoxal-5′-phosphate (PLP) was efficient in substrate conversion compared to pyridoxal (PL) and pyridoxine (PN) as cofactors. Supplementation of PN with ATP successfully restored Vmax to levels comparable with PLP. However, following freezer storage of biocatalysts, insufficient PLP generation from PN was observed due to variations in the cellular metabolic pool and ATP levels. The optimal conditions for CadA/B activity were achieved with 7 μM IPTG induction at 32 °C for 8 h, resulting in a maximum specific activity of 18.2 ± 1.1 mmol/min/g dried cell weight. The BCP-based colorimetric assay showcased its efficacy in rapidly detecting and quantifying CadA/B activity, thereby facilitating high-throughput screening of recombinant libraries.

Paracoccus kondratievae produces poly(3-hydroxybutyrate) under elevated temperature conditions.

As part of ongoing efforts to discover novel polyhydroxyalkanoate-producing bacterial species, we embarked on characterizing the thermotolerant species, Paracoccus kondratievae, for biopolymer synthesis. Using traditional chemical and thermal characterization techniques, we found that P. kondratievae accumulates poly(3-hydroxybutyrate) (PHB), reaching up to 46.8% of the cell's dry weight after a 24-h incubation at 42°C. Although P. kondratievae is phylogenetically related to the prototypical polyhydroxyalkanoate producer, Paracoccus denitrificans, we observed significant differences in the PHB production dynamics between these two Paracoccus species. Notably, P. kondratievae can grow and produce PHB at elevated temperatures ranging from 42 to 47°C. Furthermore, P. kondratievae reaches its peak PHB content during the early stationary growth phase, specifically after 24 h of growth in a flask culture. This is then followed by a decline in the later stages of the stationary growth phase. The depolymerization observed in this growth phase is facilitated by the abundant presence of the PhaZ depolymerase enzyme associated with PHB granules. We observed the highest PHB levels when the cells were cultivated in a medium with glycerol as the sole carbon source and a carbon-to-nitrogen ratio of 10. Finally, we found that PHB production is induced as an osmotic stress response, similar to other polyhydroxyalkanoate-producing species.

Optimizing Sowing Density for Parsley, Cilantro, and Sage in Controlled Environment Production: Balancing Productivity and Plant Quality

Sowing density is a key management practice influencing productivity and quality of leafy greens and culinary herbs grown in controlled environments. However, research-based information on optimal density is limited for many culinary herbs. This greenhouse study aimed to quantify sowing density impacts on biomass output, individual plant growth, and morphological traits in hydroponically produced ‘Giant of Italy’ parsley (Petroselinum crispum), ‘Santo’ cilantro (Coriandrum sativum), and sage (Salvia officinalis). Seedlings were grown in phenolic foam cubes with 1, 5, 10, 15, or 20 seeds per cell, transplanted into an ebb-and-flow hydroponic system in a glass-glazed greenhouse with 23 °C target average daily temperature, 16-hour photoperiod, a target daily light integral of 13 mol·m−2·d−1, and harvested at 16 to 28 d after transplanting depending on species. ‘Giant of Italy’ parsley and ‘Santo’ cilantro fresh weight per cell increased quadratically by 274% (57.3 g) and 305% (19 g), respectively, as sowing density increased from 1 to 15 seeds per cell, then plateaued as density further increased. Sage fresh weight plateaued at 10 seeds per cell with an increase of 225% (29.2 g) compared with 1 seed per cell. Cilantro and sage dry weight per cell plateaued at 14 and 8 seeds per cell, respectively, and parsley dry weight quadratically increased as sowing density rose up to 20 seeds per cell. Although fresh and dry weight increased, individual plant height, stem diameter, and individual plant dry weight exhibited linear or quadratic declines as sowing density increased, indicating higher sowing densities restricted individual plant growth. In summary, as sowing density increased, fresh and dry weight per cell generally increased but individual plant quality decreased. For the greatest fresh and dry weight, 20, 18, and 10 seeds per cell should be sown for parsley, cilantro, and sage, respectively. However, to balance fresh weight and crop quality, our results suggest sowing density (seeds per cell) targets of 16 seeds for parsley, 18 seeds for cilantro, and 10 seeds for sage.

Surface-Displayed Mannanolytic and Chitinolytic Enzymes Using Peptidoglycan Binding LysM Domains.

Using Lactiplantibacillus plantarum as a food-grade carrier to create non-GMO whole-cell biocatalysts is gaining popularity. This work evaluates the immobilization yield of a chitosanase (CsnA, 30 kDa) from Bacillus subtilis and a mannanase (ManB, 40 kDa) from B. licheniformis on the surface of L. plantarum WCFS1 using either a single LysM domain derived from the extracellular transglycosylase Lp_3014 or a double LysM domain derived from the muropeptidase Lp_2162. ManB and CsnA were fused with the LysM domains of Lp_3014 or Lp_2162, produced in Escherichia coli and anchored to the cell surface of L. plantarum. The localization of the recombinant proteins on the bacterial cell surface was successfully confirmed by Western blot and flow cytometry analysis. The highest immobilization yields (44-48%) and activities of mannanase and chitosanase on the displaying cell surface (812 and 508 U/g of dry cell weight, respectively) were obtained when using the double LysM domain of Lp_2162 as an anchor. The presence of manno-oligosaccharides or chito-oligosaccharides in the reaction mixtures containing appropriate substrates and ManB or CsnA-displaying cells was determined by high-performance anion exchange chromatography. This study indicated that non-GMO Lactiplantibacillus chitosanase- and mannanase-displaying cells could be used to produce potentially prebiotic oligosaccharides.

New Solutions in Single-Cell Protein Production from Methane: Construction of Glycogen-Deficient Mutants of Methylococcus capsulatus MIR

The biotechnology of converting methane to single-cell protein (SCP) implies using fast-growing thermotolerant aerobic methanotrophic bacteria. Among the latter, members of the genus Methylococcus received significant research attention and are used in operating commercial plants. Methylococcus capsulatus MIR is a recently discovered member of this genus with the potential to be used for the purpose of SCP production. Like other Methylococcus species, this bacterium stores carbon and energy in the form of glycogen, particularly when grown under nitrogen-limiting conditions. The genome of strain MIR encodes two glycogen synthases, GlgA1 and GlgA2, which are only moderately related to each other. To obtain glycogen-free cell biomass of this methanotroph, glycogen synthase mutants, ΔglgA1, ΔglgA2, and ΔglgA1ΔglgA2, were constructed. The mutant lacking both glycogen synthases exhibited a glycogen-deficient phenotype, whereas the intracellular glycogen content was not reduced in strains defective in either GlgA1 or GlgA2, thus suggesting functional redundancy of these enzymes. Inactivation of the glk gene encoding glucokinase also resulted in a sharp decrease in glycogen content and accumulation of free glucose in cells. Wild-type strain MIR and the mutant strain ΔglgA1ΔglgA2 were also grown in a bioreactor operated in batch and continuous modes. Cell biomass of ΔglgA1ΔglgA2 mutant obtained during batch cultivation displayed high protein content (71% of dry cell weight (DCW) compared to 54% DCW in wild-type strain) as well as a strong reduction in glycogen content (10.8 mg/g DCW compared to 187.5 mg/g DCW in wild-type strain). The difference in protein and glycogen contents in biomass of these strains produced during continuous cultivation was less pronounced, yet biomass characteristics relevant to SCP production were slightly better for ΔglgA1ΔglgA2 mutant. Genome analysis revealed the presence of glgA1-like genes in all methanotrophs of the Gammaproteobacteria and Verrucomicrobia, while only a very few methanotrophic representatives of the Alphaproteobacteria possessed these determinants of glycogen biosynthesis. The glgA2-like genes were present only in genomes of gammaproteobacterial methanotrophs with predominantly halo- and thermotolerant phenotypes. The role of glycogen in terms of energy reserve is discussed.

Biofloc wastewater for microalgae (Chlorella ellipsoidea) production: an approach to algal biomass production and nutrient remediation

ABSTRACT Bold Basal Medium (BBM) is a standard but expensive medium for Chlorella ellipsoidea culture. This study evaluated the effect of biofloc wastewater (BWW) on the growth and pigment content of C. ellipsoidea and also investigated its bioremediation potential. The experiment was conducted for 24 d in five treatments, each with three replications. BBM was replaced with BWW at 0, 25, 50, 75, and 100% levels and considered as control (0% BWW), 25% BWW, 50% BWW, 75% BWW, and 100% BWW treatment, respectively. During the exponential period, the cell dry weight, optical density, cell density, specific growth rate, chlorophyll a, b, and β-carotene content were significantly (P ˂ 0.05) higher in 75% BWW treatment, which was followed by 0% BWW, 50% BWW, 100% BWW, and 25% BWW, correspondingly. NH3, NO2, and PO4 recovery efficiency were also higher in 75% BWW treatment. Therefore, the study proves that 75% BWW has the potential to culture C. ellipsoidea as an alternative to expensive BBM along with nutrient recovery from BWW.

Development of an H2 fuel cell electrochemical system powered by Escherichia coli cells

Because of the growing high importance of the development of biocatalytic fuel cell (FC) technologies for renewable energy-producing and testing systems for medical or environmental purposes, in this study, we constructed and demonstrated an H2 FC voltammeter working with graphite sample testing micro-strips and based on Escherichia coli microbial cells. Presented H2 FC voltammeter that provides fast and precise testing of bio-electrochemical possible reactions in biosamples for H2 and other gases, is automated with software which works in NI LabVIEW programming environment, has amplifier cascade system with high internal resistance, temperature controlling and resistance cascade. Microbial Hydrogenase (Hyd) enzymes reversibly catalyze the formation and oxidation of H2. Isolation and characterization of O2-tolerant [NiFe]-hydrogenases (Hyds) have given rise to new concepts in H2 FC. Escherichia coli and [NiFe]-Hyds can be applied as a biocatalyst anode in biofuel cells (BFCs). We evaluated the efficiency of applying the 3 µl (1.5 mg cell dry weight) E. coli intact cells or crude extracts on 0.5 cm2 as anode catalyzers in the bio-electrochemical system. The highest electrical potential (up to 0.7 V) was achieved with bacterial whole cells, which were grown on glucose and glycerol.

Understanding exopolysaccharide byproduct formation in Komagataella phaffii fermentation processes for recombinant protein production

BackgroundKomagataella phaffii (Pichia pastoris) has emerged as a common and robust biotechnological platform organism, to produce recombinant proteins and other bioproducts of commercial interest. Key advantage of K. phaffii is the secretion of recombinant proteins, coupled with a low host protein secretion. This facilitates downstream processing, resulting in high purity of the target protein. However, a significant but often overlooked aspect is the presence of an unknown polysaccharide impurity in the supernatant. Surprisingly, this impurity has received limited attention in the literature, and its presence and quantification are rarely addressed.ResultsThis study aims to quantify this exopolysaccharide in high cell density recombinant protein production processes and identify its origin. In stirred tank fed-batch fermentations with a maximal cell dry weight of 155 g/L, the polysaccharide concentration in the supernatant can reach up to 8.7 g/L. This level is similar to the achievable target protein concentration. Importantly, the results demonstrate that exopolysaccharide production is independent of the substrate and the protein production process itself. Instead, it is directly correlated with biomass formation and proportional to cell dry weight. Cell lysis can confidently be ruled out as the source of this exopolysaccharide in the culture medium. Furthermore, the polysaccharide secretion can be linked to a mutation in the HOC1 gene, featured by all derivatives of strain NRRL Y-11430, leading to a characteristic thinner cell wall.ConclusionsThis research sheds light on a previously disregarded aspect of K. phaffii fermentations, emphasizing the importance of monitoring and addressing the exopolysaccharide impurity in biotechnological applications, independent of the recombinant protein produced.

High capacities of carbon capture and photosynthesis of a novel organic carbon-fixing microalgae in municipal wastewater: From mutagenesis, screening, ability evaluation to mechanism analysis

The development of wastewater treatment processes capable of reducing and fixing carbon is currently a hot topic in the wastewater treatment field. Microalgae possess a natural carbon-fixing advantage, and microalgae that can symbiotically coexist with indigenous bacteria in actual wastewater attract more significant attention. Ultraviolet (UV) mutagenesis and dissolved organic carbon (DOC) acclimation were applied to strengthen the carbon-fixing performance of microalgae in this study. The mechanisms associated with microalgal water purification ability, gene regulation at the molecular level and photosynthetic potential under different trophic modes resulting from carbon fixation and transformation were disclosed. The superior performance of Chlorella sp. MHQ2 was eventually screened out among a large number of mutants generated from 3 wild-type Chlorella strains. Results indicated that the dry cell weight of the optimal species Chlorella sp. HQ mutant MHQ2 was 1.91 times that of the wild strain in the pure algal system, more carbon from municipal wastewater (MW) were transferred to the microalgae and re-entered into the biological cycle through resource utilization. In addition, COD, NH3-N and TP removal efficiencies of MW by Chlorella sp. MHQ2 were found to increase to 95.8% (1.1-times), 96.4% (1.4-times), and 92.9% (1.2-times), respectively, under the extra DOC supply and the assistance of indigenous bacteria in the MW. In the transcriptome analysis of the logarithmic phase, the glycolytic pathway was inhibited, and the pentose phosphate pathway was mainly carried out for microalgal life activities, further promoting efficient energy utilization. Upon analysis of carbon capture capacity and photosynthetic potential in trophic mode, the addition of NaHCO3 increased the photosynthetic rate of Chlorella sp. MHQ2 in mixotrophy whereas it was attenuated in autotrophy. This study could provide a new perspective for the study of resource utilization and microalgae carbon- fixing mechanisms in the actual wastewater treatment process.

Enhancing astaxanthin accumulation through the expression of the plant-derived astaxanthin biosynthetic pathway in Dunaliella salina

Dunaliella salina, a microalga that thrives under high-saline conditions, is notable for its high β-carotene content and the absence of a polysaccharide cell wall. These unique characteristics render it a prime candidate as a cellular platform for astaxanthin production. In this study, our initial tests in an E. coli revealed that β-ring-4-dehydrogenase (CBFD) and 4-hydroxy-β-ring-4-dehydrogenase (HBFD) genes from Adonis aestivalis outperformed β-carotene hydroxylase (BCH) and β-carotene ketolase (BKT) from Haematococcus pluvialis counterparts by two-fold in terms of astaxanthin biosynthesis efficiency. Subsequently, we utilized electroporation to integrate either the BKT gene or the CBFD and HBFD genes into the genome of D. salina. In comparison to wild-type D. salina, strains transformed with BKT or CBFD and HBFD exhibited inhibited growth, underwent color changes to shades of red and yellow, and saw a nearly 50% decline in cell density. HPLC analysis confirmed astaxanthin synthesis in engineered D. salina strains, with CBFD + HBFD-D. salina yielding 134.88 ± 9.12 μg/g of dry cell weight (DCW), significantly higher than BKT-D. salina (83.58 ± 2.40 μg/g). This represents the largest amount of astaxanthin extracted from transgenic D. salina, as reported to date. These findings have significant implications, opening up new avenues for the development of specialized D. salina-based microcell factories for efficient astaxanthin production.

Formulation of biogenic fluorescent pigmented PHB nanoparticles from Rhodanobacter sp. for drug delivery.

Biogenic nanoparticles (NPs) have emerged as promising therapeutic formulations in effective drug delivery. Despite of various positive attributes, these NPs are often conjugated with various cytotoxic organic fluorophores for bioimaging, thereby reducing its effectiveness as a potential carrier. Herein, we aim to formulate biogenic fluorescent pigmented polyhydroxybutyrate (PHB) NPs from Rhodanobacter sp. strain KT31 (OK001852) for drug delivery. The bacterial strain produced 0.5g L-1 of polyhydroxyalkanoates (PHAs) from 2.04g L-1 of dry cell weight (DCW) under optimised conditions via submerged fermentation. Further, structural, thermal, and morphological charactersiation of the extracted PHAs was conducted using advance analytical technologies. IR spectra at 1719.25cm-1 confirmed presence of C = O functional group PHB. NMR and XRD analysis validated the chemical structure and crystallinity of PHB. TG-DTA revealed Tm (168 °C), Td (292 °C), and Xc (35%) of the PHB. FE-SEM imaging indicated rough surface of the PHB film and the biodegradability was confirmed from open windro composting. WST1 assay showed no significant cell death (> 50%) from 100 to 500µg/mL, endorsing non-cytotoxic nature of PHB. PHB NPs were uniform, smooth and spherical with size distribution and mean zeta potential 44.73nm and 0.5mV. IR and XRD peaks obtained at 1721.75cm-1 and 48.42Å denoted C = O and crystalline nature of PHB. Cell proliferation rate of PHB NPs was quite significant at 50µg/mL, establishing the non-cytotoxic nature of NPs. Further, in vitro efficacy of the PHB NPs needs to be evaluated prior to the biomedical applications.

WITHDRAWN: Efficient β-carotene production in engineered Saccharomyces cerevisiae using simple sugars and agricultural waste-based carbon and nitrogen sources

β-carotene, a precursor to vitamin A, holds significant promise for health and nutrition applications. This study introduces an optimized approach for β-carotene production in Saccharomyces cerevisiae, leveraging metabolic engineering and a novel use of agricultural waste. The GAL80 gene deletion facilitated efficient β-carotene synthesis from sucrose, avoiding the costly galactose induction, and achieved titers up to 727.8 ± 68.0 mg/L with content levels of 71.8 ± 0.4 mg/g dry cell weight (DCW). Furthermore, the application of agricultural by-products, specifically molasses and fish meal as carbon and nitrogen sources, was investigated. This approach yielded a substantial β-carotene titer of 354.9 ± 8.2 mg/L and a content of 60.5 ± 4.3 mg/g DCW, showcasing the potential of these sustainable substrates for industrial-scale production. This study sets a new benchmark for cost-effective, green manufacturing of vital nutrients, demonstrating a scalable, eco-friendly alternative for β-carotene production.

Production of polyhydroxybutyrate from industrial flue gas by microbial electrosynthesis

The aim of this work was to produce the biopolymer polyhydroxybutyrate (PHB) from industrial flue gas as CO2 source and electrolysis originating hydrogen via microbial electrosynthesis. Besides the laboratory experiments, the experiments were carried out under industrial conditions directly on-site in a cogeneration plant. We were able to demonstrate that the use of flue gas as a CO2 source has no detectable negative effect on bacterial growth and PHB production in comparison to a pure gas mixture. In an electrochemical H-cell 333 ± 44 mg L−1 PHB were obtained, which corresponds to a PHB content of 43 ± 3 % of the cell dry weight. By using flue gas for the production of the biopolymer PHB, not only CO2 emissions are reduced, but also possible environmental pollution from non-biodegradable plastics. To the best of our knowledge, this is the first time that the production of PHB from flue gas has been demonstrated using Cupriavidus necator.

Evaluation of Ca(NO3)2 and various container cell size effects on some growth attributes and nutrient content of tomato transplants

Optimizing container cell size and nutrition is crucial for enhancing the quality of vegetable transplants. The current study evaluated the effect of different cell sizes and Ca(NO3)2 on some properties of tomato (Solanum lycopersicum L.) transplants. Experimental treatment included four levels (0, 50, 100, and 150 mg L–1) of Ca(NO3)2 and 5 different cell sizes of containers (1, 2, 3, 4, and 5) in a factorial experiment based on a completely randomized design (CRD) with three replications under greenhouse conditions. Ca(NO3)2 and larger cell size, increased height, stem diameter, fresh and dry weights of roots and shoots, and concentration of chlorophyll, protein, SPAD, carbohydrates, and macro/micronutrients. The results revealed that maximum shoot and root fresh and dry weight, photosynthesis pigments, N, P, K, Ca, and Fe concentrations were recorded at 150 mg L–1 × cell size 5. In comparison, the highest Zn and Mn concentrations were recorded at 100 mg L–1 × cell size 4 and 5. Our results demonstrated that applying Ca(NO3)2 and increasing the cell size of the containers improved the traits evaluated, so Ca(NO3)2 at 10 and 15 mg L–1 with cell size 5 can be recommended to transplant producers.

Resource recovery through bioremediation of fuel-synthesis wastewater in a biofilm photobioreactor using purple non-sulfur bacteria: A circular bioeconomy approach

In the current era of wastewater treatment, integrating reusable water production with resource recovery is a key goal. This study aims to treat fuel-synthesis wastewater (FSW), intending to recover various resources, including polyhydroxybutyrate (PHBs), single cell protein, bacteriochlorophylls, carotenoids, and coenzyme Q10 from suspended and biofilm growth to decrease the harvesting costs. The study considered the treatment process, biofilm growth, and resource recovery potential in a mixed-culture system enriched with purple non-sulfur bacteria for treating FSW. Specifically, the effects of four different FSW strengths (25–100 %) and nitrogen sufficiency (N+) or deficiency (N−) were evaluated in eight biofilm photobioreactors. This study observed a direct correlation between the concentration of FSW and PHB content; specifically, as the FSW content decreased from 100 % (undiluted) to 25 % the PHB content decreased. The undiluted condition achieved 17 % dry cell weight as PHB in the suspended growth and 22.6 % in the biofilm growth under N− condition. The protein content ranged between 33 and 44 %, and the presence of nitrogen had a slight positive effect on higher protein content. No trend was observed for carotenoids or bacteriochlorophylls in the N− condition. In contrast, for the N+ condition, the concentration of bacteriochlorophylls increased with decreasing wastewater concentration under suspended growth, while it decreased with decreasing wastewater concentration under biofilm growth. Coenzyme Q10 concentration was enhanced under the most growth-limited condition (25 %, N−). PHB and protein content of these resources seem most promising when using N− and N+ conditions, respectively.

Enhancing the biosynthesis of polyunsaturated fatty acids by Rhodotorula mucilaginosa and Lodderomyces elongisporus

Single-cell oils (SCO) produced by oleaginous yeast hold promise as a sustainable alternative for producing nutritionally and pharmaceutically valuable lipids. However, the accumulation of oils varies substantially between yeast spp. Consequently, identifying well-suited producers with a high innate capacity for lipids biosynthesis is paramount. Equally important is optimizing culturing and processing conditions to realize the total lipids production potential of selected strains. The marine Rhodotorula mucilaginosa and Lodderomyces elongisporus yeast were investigated to explore their potential for polyunsaturated fatty acids (PUFAs) production on high glucose media (HGM) using two-stage culture mode. Both strains accumulated > 20% (w/w) of their dry cell weight as lipids when grown on HGM using a two-stage culture system. Both yeast isolates exhibited a maximal lipid/biomass coefficient (YL/X) of 0.58–0.66 mg/mg at 7 °C and 0.49–0.53 mg/mg at 26 °C when grown on 8% glucose and produced monounsaturated and PUFAs similar to that of Menhaden and Salmon marine oils. For the first time, significant amounts of Eicosapentaenoic acid (19%) and Eicosadienoic acid (19.6%) were produced by L. elongisporus and R. mucilaginosa, respectively. Thus, the SCO derived from these wild strains possesses significant potential as a substitute source for the industrial-scale production of long-chain PUFAs, making them a promising contender in the market.Graphical