Glycerol Medium Research Articles

Effect of natural deep eutectic solvents on thermal stability, syneresis, and viscoelastic properties of high amylose starch

This work aimed to use natural deep eutectic solvents to modify the thermal, textural, freeze-thaw, and rheological properties of high amylose rice starch. Three different natural deep eutectic solvents (NADES) composed of sugar and organic acids were applied to modify the properties of starch dispersion. In presence of NADES, the onset temperature of starch was decreased, in comparison with starch in aqueous and glycerol medium. During thermal decomposition, starch with the aqueous and glycerol systems showed two-step weight losses whereas with NADES starch showed single-stage weight losses or decomposition. Moreover, negligible syneresis was observed for starch-NADES dispersion after 3rd cycle of the freeze-thaw process. The flow behavior of starch-NADES dispersion follows Herschel–Bulkley models as R2 (0.996 ≤ R2 ≤ 0.999) are higher than the Mizrahi-Berk model. The flow behavior index (n) of starch-NADES dispersion was closer to 1, indicated a nearly Newtonian fluid. The loss modulus (G″) value of starch-NADES dispersions was markedly higher than the corresponding storage modulus (G′) value and thus materials behaved like viscoelastic liquid. The present study manifested a green way to modify the properties of the high amylose starch to improve the processing stability.

Estimation of ground and excited-state dipole moments of three symmetric carbocyanine dyes via the analysis of luminescence properties

The solvatochromic effect of solvents on the absorption and fluorescence spectra of three carbocyanine dyes, namely 1,1′,3,3,3′,3′-hexamethylindocarbocyanine chloride (HIC); 1,1′,3,3,3′,3′-hexamethylindodicarbocyanine iodide (HIDC); and 3,3′-diethyloxadicarbocyanine iodide (DODC), have been investigated. The experimental ground and excited-state dipole moments of the dyes have been estimated via the well-known models by Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet, and the Dimroth-Reichardt’s empirical model. The influence of the solvation effect on the luminescence quantum yields was also examined and a strong correlation between the luminescence quantum yield values and the solvent viscosity was established. The fluorescence signal enhancement sensitivities between dyes were compared based on the Förster-Hoffmann equation. DFT and TDDFT calculations at the CAM-B3LYP/6-31G(d,p) level of theory were performed for the analysis of the nature of the electron transitions in absorption and excitation processes. Six phases different in polarity were considered during these computations, namely the gas, toluene, chloroform, acetone, methanol, and water. Transition electron density plots, Mulliken atomic partial charges, and Mayer bond orders were used for the analysis of the redistribution of electron density upon excitation. The specific behavior of the dyes in the glycerol medium was interpreted via the analysis of non-covalent interactions between the dye and glycerol molecules in terms of the reduced density gradient method.

Transcriptomic and metabolomic profiling of a Rhodotorula color mutant to improve its lipid productivity in fed-batch fermentation.

Lipids produced by oleaginous microorganisms enrich the supply of feedstock for bio-fuel. In this study, a mutant (Mut) obtained by UV-nitrosoguanidine mutagenesis turned its colony color from orange-red to light-yellow and showed higher lipid productivity at 37°C than the original strain Rhodotorula sp. U13N3 (Rht) in the glycerol medium. The metabolic changes between Mut and Rht in batch fermentation were investigated by transcriptomic and metabolomic profiling at the biomass accumulation (30h) and lipid production (96h) stages. The average base number in each strain was 5.80 × 109 ± 0.38 × 109bp (mean ± SD) with 62.43% ± 0.13% GC ratio, and 7499 unigenes were assembled after Illumina sequencing. Moreover, 33 metabolites were quantified by 1H NMR-based profiling. The multi-omics results demonstrated that Mut showed increased glycerol transport and utilization capabilities especially at the first stage (30h). Then the carbon flux shifted from the TCA cycle to lipid production (96h). The increased lipid productivity of Mut was partially attributed to the down-regulation of mannitol biosynthesis. However, the mechanism for color change was elusive. At 96h, the low level of cytosol glycerol probably restricted the lipid production. As a result, supplementation of glycerol in fed-batch fermentation remarkably improved the biomass, lipid production, and lipid content to 34.60g/L, 25.72g/L, and 74.3% (w/w dcw), respectively. The cell morphology implied that excessively prolonging the fermentation time was detrimental to the final lipid yield due to cell breakage. In conclusion, the Rhodotorula mutant provided a candidate strain for lipid production with glycerol as the carbon source.

Heat transfer and thermoregulation within single cells revealed by transient plasmonic imaging

Summary Cells, as the basic unit of life, undergo continuous heat transfer and dissipation during their metabolism, which is related not only to fundamental cellular functions but also massive applications. Unfortunately, thus far, we still know little about the heat transfer properties at the cellular or subcellular levels. Here, we demonstrated a transient microscopic method to measure the heat transfer in single cells. The thermal conductivity of different regions within a single cell shows a wide heterogeneity, and heat transfer in the region near the cell membrane is more active than the central region. However, the median values of thermal conductivity between different individual cells are quite close. A cellular-level heat regulation that responds to environmental temperature is observed in warm-blooded humans and chickens rather than in cold-blooded bullfrogs. According to the temperature-dependent cell metabolism, we proposed a hypothesis for cellular control of heat dissipation, which might be the cellular-level foundation of body thermoregulation.

Fed-Batch Cultivation and Adding Supplements to Increase Yield of β-1,3-1,4-Glucanase by Genetically Engineered Escherichia coli

The aim of this study was to analyze the major influence factors of culture medium on the expression level of β-1,3-1,4-glucanase, and to further develop an optimized process for the extracellular production of β-glucanase at a bioreactor scale (7 L) with a genetically engineered Escherichia coli (E. coli) JM109-pLF3. In this study, batch cultivation and fed-batch cultivation including the constant rate feeding strategy and the DO-stat (DO: Dissolved Oxygen) feeding strategy were conducted. At a 7 L bioreactor scale for batch cultivation, biomass reached 3.14 g/L and the maximum β-glucanase activity was 506.94 U/mL. Compared with batch cultivation, the addition of glycerol, complex nitrogen and complete medium during fed-batch cultivation increased the production of biomass and β-1,3-1,4-glucanase. The maximum biomass and β-glucanase activity, which were 7.67 g/L and 1680 U/mL, respectively, that is, 2.45 and 3.31 times higher than those obtained with batch cultivation, were obtained by feeding a complex nitrogen source at a constant rate of 1.11 mL/min. Therefore, these nutritional supplements and strategies can be used as a reference to enhance the production of other bioproducts from E. coli.

Application of In-Situ and Soft-Sensors for Estimation of Recombinant P. pastoris GS115 Biomass Concentration: A Case Analysis of HBcAg (Mut+) and HBsAg (MutS) Production Processes under Varying Conditions.

Microbial biomass concentration is a key bioprocess parameter, estimated using various labor, operator and process cross-sensitive techniques, analyzed in a broad context and therefore the subject of correct interpretation. In this paper, the authors present the results of P. pastoris cell density estimation based on off-line (optical density, wet/dry cell weight concentration), in-situ (turbidity, permittivity), and soft-sensor (off-gas O2/CO2, alkali consumption) techniques. Cultivations were performed in a 5 L oxygen-enriched stirred tank bioreactor. The experimental plan determined varying aeration rates/levels, glycerol or methanol substrates, residual methanol levels, and temperature. In total, results from 13 up to 150 g (dry cell weight)/L cultivation runs were analyzed. Linear and exponential correlation models were identified for the turbidity sensor signal and dry cell weight concentration (DCW). Evaluated linear correlation between permittivity and DCW in the glycerol consumption phase (<60 g/L) and medium (for Mut+ strain) to significant (for MutS strain) linearity decline for methanol consumption phase. DCW and permittivity-based biomass estimates used for soft-sensor parameters identification. Dataset consisting from 4 Mut+ strain cultivation experiments used for estimation quality (expressed in NRMSE) comparison for turbidity-based (8%), permittivity-based (11%), O2 uptake-based (10%), CO2 production-based (13%), and alkali consumption-based (8%) biomass estimates. Additionally, the authors present a novel solution (algorithm) for uncommon in-situ turbidity and permittivity sensor signal shift (caused by the intensive stirrer rate change and antifoam agent addition) on-line identification and minimization. The sensor signal filtering method leads to about 5-fold and 2-fold minimized biomass estimate drifts for turbidity- and permittivity-based biomass estimates, respectively.

Dnm1 deletion blocks mitochondrial fragmentation in Δfzo1 cells.

Mitochondrial division and fusion play critical roles in maintaining functional mitochondria. Fzo1 is an outer mitochondrial membrane GTPase that played an essential role in mitochondrial fusion in budding yeast Saccharomyces cerevisiae. Here, we report the characterization of the Schizosaccharomyces pombe homologue of S. cerevisiae Fzo1p, Fzo1. Disruption of the fzo1 gene in S. pombe results in a fragmented mitochondrial morphology and a dramatically reduced growth on glycerol medium phenotype, indicating that deletion of fzo1 compromises respiratory function. Fluorescence microscopy shows that Fzo1p is located in the mitochondria. Overexpressing Fzo1 from a heterologous promoter induces mitochondrial aggregation. We also find that dnm1 mutations could both block mitochondrial fragmentation and rescue respiration growth defect in Δfzo1 single mutant cells. Our results proposed that a genetic interaction between fzo1 and a balance between division- and fusion-controlled mitochondrial shape and function in S. pombe. This study represents the first report of Fzo1 mediator of mitochondrial fusion in S. pombe.

Quantitative proteomic analysis to reveal expression differences for butanol production from glycerol and glucose by Clostridium sp. strain CT7

Clostridium sp. strain CT7 is a new emerging microbial cell factory with high butanol production ratio owing to its non-traditional butanol fermentation mode with uncoupled acetone and 1,3-propanediol formation. Significant changes of metabolic products profile were shown in glycerol- and glucose-fed strain CT7, especially higher butanol and lower volatile fatty acids (VFAs) production occurred from glycerol-fed one. However, the mechanism of this interesting phenomenon was still unclear. To better elaborate the bacterial response towards glycerol and glucose, the quantitative proteomic analysis through iTRAQ strategy was performed to reveal the regulated proteomic expression levels under different substrates. Proteomics data showed that proteomic expression levels related with carbon metabolism and solvent generation under glycerol media were highly increased. In addition, the up-regulation of hydrogenases, ferredoxins and electron-transferring proteins may attribute to the internal redox balance, while the earlier triggered sporulation response in glycerol-fed media may be associated with the higher butanol production. This study will pave the way for metabolic engineering of other industrial microorganisms to obtain efficient butanol production from glycerol.

Microbial lipid and biodiesel production from municipal sludge fortified with crude glycerol medium using pH-based fed-batch strategy

To achieve a good performance in fed-batch fermentation, the feeding strategy is essential and important. In this study, pH-based (pH 6.0) fed-batch fermentation has been conducted on municipal sludge fortified with crude glycerol medium using Y. lipolytica SKY7 (YL). No additional nitrogen source and trace elements had to be added as secondary municipal sludge had sufficient nitrogen and trace elements to support growth of YL. At 72 h of fed-batch fermentation, high biomass (59.67 g/L) and lipid concentration (31.44 g/L) was obtained. The biodiesel produced using sludge cultivated YL had similar fatty acid ester profile as that of vegetable oil. It was revealed from energy balance that biodiesel production using pH-based fed-batch strategy was energetically favorable and has unit production cost of 0.67 $/L B10.

Study on the Function of the Inositol Polyphosphate Kinases Kcs1 and Vip1 of Candida albicans in Energy Metabolism.

In Saccharomyces cerevisiae, inositol polyphosphate kinase KCS1 but not VIP1 knockout is of great significance for maintaining cell viability, promoting glycolysis metabolism, and inducing mitochondrial damage. The functions of Candida albicans inositol polyphosphate kinases Kcs1 and Vip1 have not yet been studied. In this study, we found that the growth rate of C. albicans vip1Δ/Δ strain in glucose medium was reduced and the upregulation of glycolysis was accompanied by a decrease in mitochondrial activity, resulting in a large accumulation of lipid droplets, along with an increase in cell wall chitin and cell membrane permeability, eventually leading to cell death. Relieving intracellular glycolysis rate or increasing mitochondrial metabolism can reduce lipid droplet accumulation, causing a reduction in chitin content and cell membrane permeability. The growth activity and energy metabolism of the vip1Δ/Δ strains in a non-fermentable carbon source glycerol medium were not different from those of the wild-type strains, indicating that knocking out VIP1 did not cause mitochondria damage. Moreover, C. albicans KCS1 knockout did not affect cell activity and energy metabolism. Thus, in C. albicans, Vip1 is more important than Kcs1 in regulating cell viability and energy metabolism.

A Time-Resolved Cryo-EM Study of Saccharomyces cerevisiae 80S Ribosome Protein Composition in Response to a Change in Carbon Source.

The role of the ribosome in the regulation of gene expression has come into increased focus. It is proposed that ribosomes are catalytic engines capable of changing their protein composition in response to environmental stimuli. Time-resolved cryo-electron microscopy (cryo-EM) techniques are employed to identify quantitative changes in the protein composition and structure of the Saccharomyces cerevisiae 80S ribosomes after shifting the carbon source from glucose to glycerol. Using cryo-EM combined with the computational classification approach, it is found that a fraction of the yeast cells' 80S ribosomes lack ribosomal proteins at the entrance and exit sites for tRNAs, including uL16(RPL10), eS1(RPS1), uS11(RPS14A/B), and eS26(RPS26A/B). This fraction increased after a change from glucose to glycerol medium. The quantitative structural analysis supports the hypothesis that ribosomes are dynamic complexes that alter their composition in response to changes in growth or environmental conditions.

Optimization of Cultivation Conditions for the Lactobacillus reuteri LR1 Strain to Improve the Biosynthesis of Bacteriocin-Like Substances

The article presents the results of optimization of the culturing conditions to increase the production of bacteriocin-like compounds (presumably including reuterin) by the Lactobacillus reuteri strain LR1. The strain Escherichia coli ATCC 25922, an opportunistic microorganism, the content of which is standardized in foods by the Food Safety Legislation, was selected as an indicator strain of antimicrobial activity. The nutrient medium for L. reuteri LR1 cultivation was optimized to increase the production of bacteriocin-like compounds, and the parameters of two-stage growth of the producer were established: (1) cultivation on the initial medium for biomass accumulation and (2) growth on a water–glycerol medium to convert glycerol to antimicrobial compounds, presumably reuterin. The first stage was carried out as follows: the L. reuteri LR1 culture (5%) was inoculated into a medium with the following composition: hydrolyzed milk—250 mL/L; yeast extract—10 g/L; peptone—5 g/L; glucose—20 g/L; sodium acetate—5.0 g/L; monosubstituted potassium phosphate—2.0 g/L; magnesium sulfate—0.2 g/L, and manganese sulfate—0.5 g/L, pH 6.4–6.6. The cultivation was carried out for 18 h at (37 ± 1)°С. The second stage included the incubation of the obtained biomass in 200 mM of glycerol-containing aqueous solution, pH 6.6, for 2 h at 37°С. The zone of E. coli inhibition caused by the produced bacteriocin-like compounds was 25 mm.

Biofilm Producing Rhizobacteria With Multiple Plant Growth-Promoting Traits Promote Growth of Tomato Under Water-Deficit Stress.

Plant growth-promoting rhizobacteria (PGPR) not only enhance plant growth but also control phytopathogens and mitigate abiotic stresses, including water-deficit stress. In this study, 21 (26.9%) rhizobacterial strains isolated from drought-prone ecosystems of Bangladesh were able to form air–liquid (AL) biofilms in the glass test tubes containing salt-optimized broth plus glycerol (SOBG) medium. Based on 16S rRNA gene sequencing, Pseudomonas chlororaphis (ESR3 and ESR15), P. azotoformans ESR4, P. poae ESR6, P. fluorescens (ESR7 and ESR25), P. gessardii ESR9, P. cedrina (ESR12, ESR16, and ESR23), P. veronii (ESR13 and ESR21), P. parafulva ESB18, Stenotrophomonas maltophilia ESR20, Bacillus cereus (ESD3, ESD21, and ESB22), B. horikoshii ESD16, B. aryabhattai ESB6, B. megaterium ESB9, and Staphylococcus saprophyticus ESD8 were identified. Fourier transform infrared spectroscopy studies showed that the biofilm matrices contain proteins, polysaccharides, nucleic acids, and lipids. Congo red binding results indicated that these bacteria produced curli fimbriae and nanocellulose-rich polysaccharides. Expression of nanocellulose was also confirmed by Calcofluor binding assays and scanning electron microscopy. In vitro studies revealed that all these rhizobacterial strains expressed multiple plant growth-promoting traits including N2 fixation, production of indole-3-acetic acid, solubilization of nutrients (P, K, and Zn), and production of ammonia, siderophores, ACC deaminase, catalases, lipases, cellulases, and proteases. Several bacteria were also tolerant to multifarious stresses such as drought, high temperature, extreme pH, and salinity. Among these rhizobacteria, P. cedrina ESR12, P. chlororaphis ESR15, and B. cereus ESD3 impeded the growth of Xanthomonas campestris pv. campestris ATCC 33913, while P. chlororaphis ESR15 and B. cereus ESD21 prevented the progression of Ralstonia solanacearum ATCC® 11696TM. In a pot experiment, tomato plants inoculated with P. azotoformans ESR4, P. poae ESR6, P. gessardii ESR9, P. cedrina ESR12, P. chlororaphis ESR15, S. maltophilia ESR20, P. veronii ESR21, and B. aryabhattai ESB6 exhibited an increased plant growth compared to the non-inoculated plants under water deficit-stressed conditions. Accordingly, the bacterial-treated plants showed a higher antioxidant defense system and a fewer tissue damages than non-inoculated plants under water-limiting conditions. Therefore, biofilm-producing PGPR can be utilized as plant growth promoters, suppressors of plant pathogens, and alleviators of water-deficit stress.

Impact of nitrogen on the industrial feasibility of biodiesel production from lipid accumulated in oleaginous yeast with wastewater sludge and crude glycerol

In this study, oleaginous yeast Trichosporon oleaginosus was cultivated in wastewater sludge and crude glycerol medium for lipid production. The sufficiency of nitrogen in sludge was verified by conducting the experiments with and without the addition of NH4Cl in the medium. Biomass production, lipid production and lipid content of the fermentation with NH4Cl addition were 55.33 g/L, 26.98 g/L and 48.77% (w/w), respectively; however, they were 42.66 g/L, 17.88 g/L and 41.91% (w/w) in the one without addition of NH4Cl, respectively. The process of biodiesel produced from the lipid cultivated with sludge and crude glycerol could provide net energy gain and greenhouse gas emission reduction. The estimated biodiesel production cost in this study was 630 US $/tonne with NH4Cl addition and 860 $/tonne without NH4Cl addition, respectively. Compared to the current commercial biodiesel price (900 US $/tonne), biodiesel production from wastewater sludge and crude glycerol is very competitive. The study provides an insight of sustainable bioenergy production system from wastewater sudge.

Evaluation and prediction of the biogenic amines in Chinese traditional broad bean paste.

Biogenic amines (BAs) are a threat to the safety of broad bean paste, and biosynthetic mechanism of BA and its regulation are unknown. This study aimed to assess microbial BA synthesis in Chinese traditional broad bean paste and determine favorable fermentation conditions for BA regulation. The BAs content in 27 pastes was within the safe range. 64 strains with potential decarboxylation were screened in Luria-Bertani Glycerol medium and identified as Bacillus spp. Although Bacillus amyloliquefaciens produced highest levels of BAs (70.14 ± 2.69mg/L) in LBAA, Bacillus subtilis produced 6% more BAs than B. amyloliquefaciens. Meanwhile, temperature was the most remarkable factor affecting BAs production by B. amyloliquefaciens 1-13. Furthermore, the fermented broad bean paste model revealed that BA content increased by 61.2mg/kg every 10days at 45°C, which was approximately threefold of that at 25°C. An ARIMA prediction model of BAs content was constructed, and the total BAs content of 40mg/100g was set as the critical value. This study not only contributed to understanding the BAs formation mechanism, but also provided potential measures to control the BAs in fermented soybean products.

Elucidating the effect of impurities present in different crude glycerol sources on lipid and citric acid production by Yarrowia lipolyticaSKY7

AbstractBACKGROUNDCrude glycerol is an industrial by‐product of biodiesel producing companies and requires a high cost for purification. In fact, it is a good carbon source and can be used for lipid production from oleaginous microbes. However, crude glycerol has several impurities that may impact the cellular metabolism for lipid production.RESULTSIn this study, crude glycerol from different sources was employed for lipid production and the effect of its impurities on the biomass and lipid production was investigated on Yarrowia lipolytica SKY7, which is a well‐known yeast for lipid and citric acid production. Growth inhibition was observed in BIOCARDEL, BIOLIQ, and ROTHSAY glycerol when compared with pure glycerol. This was due to high sodium concentrations in BIOCARDEL, high potassium concentrations in BIOLIQ, and high sulphur concentrations in ROTHSAY glycerol. Among three crude glycerol sources, the highest lipid concentration (14.78 g L−1) was obtained using BIOCARDEL glycerol at 96 h. However, the higher citric acid concentrations of 18.70 g L−1 in ROTHSAY glycerol and 12.00 g L−1 in BIOLIQ were obtained at 96 h when compared with 8.30 g L−1 in BIOCARDEL glycerol.CONCLUSIONA high potassium and sulphur concentration in glycerol medium inhibits cell growth and lipid production in Yarrowia lipolytica SKY7, while it favors citric acid production. © 2020 Society of Chemical Industry

The Spo7 sequence LLI is required for Nem1-Spo7/Pah1 phosphatase cascade function in yeast lipid metabolism

The Nem1-Spo7 complex in the yeast Saccharomyces cerevisiae is a protein phosphatase that catalyzes the dephosphory-lation of Pah1 phosphatidate phosphatase, required for its translocation to the nuclear/endoplasmic reticulum membrane. The Nem1-Spo7/Pah1 phosphatase cascade plays a major role in triacylglycerol synthesis and in the regulation of phospholipid synthesis. In this work, we examined Spo7, a regulatory subunit required for Nem1 catalytic function, to identify residues that govern formation of the Nem1-Spo7 complex. By deletion analysis of Spo7, we identified a hydrophobic Leu-Leu-Ile (LLI) sequence comprising residues 54-56 as being required for the protein to complement the temperature-sensitive phenotype of an spo7Δ mutant strain. Mutational analysis of the LLI sequence with alanine and arginine substitutions showed that its overall hydrophobicity is crucial for the formation of the Nem1-Spo7 complex as well as for the Nem1 catalytic function on its substrate, Pah1, in vivo Consistent with the role of the Nem1-Spo7 complex in activating the function of Pah1, we found that the mutational effects of the Spo7 LLI sequence were on the Nem1-Spo7/Pah1 axis that controls lipid synthesis and related cellular processes (e.g. triacylglycerol/phospholipid synthesis, lipid droplet formation, nuclear/endoplasmic reticulum membrane morphology, vacuole fusion, and growth on glycerol medium). These findings advance the understanding of Nem1-Spo7 complex formation and its role in the phosphatase cascade that regulates the function of Pah1 phosphatidate phosphatase.

Flow analysis of abrasive micro-blasting with glycerol and acrylamideas carrier medium using computational fluid dynamics

Continuous growth is observed in the fieldofNon-Traditional machining where the machiningof newly developing materials is the need of the current segment. Nowadays Abrasive Fluid Jet Machining has used to machine a wide range of elastic and plastic materials including aerospace, automobile, ordinance and combat as well as day to day lifeapplications which require high strength to weight ratios. In Abrasive fluid jet machining, the abrasives are mixed with a liquid to form a slurry. The cutting performance is degraded by the rapid wear of the nozzle by the flow of the Abrasive Fluid mixture through the nozzles that lead to the divergence of the Abrasive Fluid Jet. The Angle of impingement affects the machining responses such that total cutting time has its influence. The Wear characteristics of the Nozzle Material are critical for such machining. The Nozzle inlet pressure of the abrasive fluid jet has a magnanimous effect on the erosion characteristics inside the nozzle. An analysis was carried out with constant Nozzle Taper angle and with Glycerol & Acrylamide solution as a carrier medium. The aim of this work is to analyze the effect of inlet operating pressure on wall shear and exit kinetic energy with respect to glycerol and Acrylamide solution. The two-phase flow analysis was carried by using a computational fluid dynamics tool CFX. The availability of optimized process parameters of abrasive fluid jet machining is limited to water practically. The other Carrier Medium for Abrasive Fluid Jet Machining can be explored widely. In this case, computational fluid dynamics analysis might provide better results than the real-time experimental work.

Optimization of trace elements in purified glycerol for microbial lipid and citric acid production by Yarrowia lipolytica SKY7

Purified glycerol obtained after acid treatment of crude glycerol solution was used as the carbon source for lipid and citric acid production using Y. lipolytica SKY7. Although purified glycerol was high in phosphorus, it was important to investigate the impact of fortification of trace elements in the medium on cell growth, lipid and citric acid (CA) production. When all the trace elements (including phosphates and sulfates) required for growth and lipid production were added to the purified glycerol medium, high biomass (51.67 g/L) and lipid concentration (19.47 g/L) were observed at 96 h of fed-batch fermentation with low CA concentration of 5.42 g/L. The purified glycerol medium without additional trace elements gave low biomass (27.67 g/L), lipid concentration (9.35 g/L) at 80 h of fed-batch fermentation, but gave high CA concentration (24.51 g/L). When purified glycerol was provided with only sulfates or all elements except KH2PO4, low biomass (32.59 g/L and 38.52 g/L) and citric acid concentration (1 g/L and 2.42 g/L) were obtained at 96 h.

Measuring of translational and rotational local temperatures of a single gold nanocrescent in glycerol

The gold nanocrescent (NC) particles possess a strong plasmon resonance which gives them a strong scattering cross section. They can thus be easily tracked using dark-field microscopy. In this study, we improved the optical configuration setup of dark-field video microscope to simultaneously measure the translational and rotational local temperatures within a glycerol medium. The translational and rotational local temperatures have been measured on the same single gold nanocrescent particle when it was excited by green and red laser. The rotational local temperature was measured by the technique of rotational scattering correlation spectroscopy (RSCS) and the translational local temperature was measured by tracking a single nanoparticle technique through the determination of translational diffusion coefficient under Brownian motion. The result showed that the translational local temperature was significant lower than the rotational local temperature for the same single gold nanocrescent. Remarkablely, we can affirm that the heterogeneity of the optical environment leads to the difference between these two temperatures. The obtained results have a great potential to probe the local nanorheology of a material.