Biochemical profiling, prediction of total lipid content and fatty acid profile in oleaginous yeasts by FTIR spectroscopy

Response mechanism of Saccharomyces cerevisiae under benzoic acid stress in ethanol fermentation

Sugarcane molasses is an ideal economical raw material for ethanol production because of its wide availability, low cost and nutrient content. However, benzoic acid compounds with toxic effects on yeast cells are commonly found in sugarcane molasses. At present, the molecular mechanism of the toxic effects of benzoic acid on Saccharomyces cerevisiae has not been elucidated. Here, the toxic effect of exogenous benzoic acid on S. cerevisiae GJ2008 cells was studied, and the genes differentially expressed in S. cerevisiae GJ2008 after 1.2 g/L benzoic acid stress were identified via Illumina RNA-Seq technology. The results indicated that benzoic acid significantly inhibited yeast cell growth, prolonged their rapid growth period, and ultimately reduced their biomass. During ethanol fermentation using 250 g/L sucrose under 1.2 g/L benzoic acid stress, several adverse effects were observed, such as high residual sugar content, low ethanol concentration and low fermentation efficiency. In addition, the cell morphology was damaged, the cell membrane permeability increased, intracellular nucleic acid and protein leakage increased, and the malondialdehyde content significantly increased. Moreover, the cells protected themselves by significantly increasing the intracellular glycerol content. Fourier transform infrared spectroscopy proved that benzoic acid could reduce the degree of unsaturation and increase cell membrane permeability by changing the yeast cell wall and cell membrane composition, leading to cell damage and even death. Transcriptomic analysis revealed that under benzoic acid stress, the expression of genes associated with sucrose and starch metabolism, thiamine metabolism, the glycolysis pathway, fructose and mannose metabolism, galactose metabolism and ABC transporters was significantly downregulated. The expression of genes related to ribosomes, lipid metabolism, ribosome biosynthesis, nucleic acid metabolism, arginine and proline metabolism, RNA polymerase, metabolism related to cofactor synthesis, and biosynthesis of valine, leucine, and isoleucine was significantly upregulated. These results indicated that benzoic acid inhibited glycolysis and reduced sugar absorption and utilization and ATP energy supply in yeast cells. In response to stress, genes related to the ribosome bioanabolic pathway were upregulated to promote protein synthesis. On the other hand, the expression of ELO1, SUR4, FEN1 and ERG1 was upregulated, which led to extension of long-chain fatty acids and accumulation of ergosterol to maintain cell membrane structure. In conclusion, this paper provides important insights into the mechanism underlying the toxicity of benzoic acid to yeast cells and for realizing high-concentration ethanol production by sugarcane molasses fermentation.

Bioactive compounds from fermented Vernonia amygdalina leaf: Potent antibiotics against multidrug-resistant Escherichia coli and Salmonella typhi

Antibiotic resistance microorganisms (ARMs), particularly gram-negative bacteria, pose a global health threat. The effects of fermentation on phytochemicals are numerous, and exploring this potential is the focus of drug development. The study investigated the role of fermentation in modifying V. amygdalina leaf secondary metabolites as an effective antibiotic against Escherichia. coli, Bacillus subtilis and Salmonella typhi. This work showed that fermentation increased the content of lycopene, flavonoid and carotenoid compounds but decreased chlorophyll, soluble protein and phenol. Pearson's correlation heatmap showed a strong correlation between microbial activities and secondary metabolic changes. The methanolic extract of fermented V. amygdalina leaf pulp (at day 9) showed significant antioxidant and anti-inflammatory activities. The GCMS and FTIR results showed unique compounds and structural modifications at different intervals of the fermentation period. In-vitro and in-silico analyses showed that fermentation did not alter the inhibition rate against B. subtilis; however, E. coli and S. typhi were significantly inhibited by fermented V. amygdalina pulp extracts. In-silico analyses showed that 4,6-Cholestadien-3β-ol- a compound present only on the ninth day of fermentation-was responsible for the inhibition of the gram-negative bacteria via the substitution of multiple non-ionic interactions of some key catalytic site residues with non-ionic types, thereby denying ionisation and salt-bridge properties that porins explore to resist antibiotics; and higher binding affinity to OmpC and OmpF than ampicillin. Therefore, this steroid-derived compound may open a new pipeline for developing ion-independent multi-target antibiotics against broad-spectrum multidrug-resistant gram-positive and gram-negative bacteria in food and pharmaceutical purposes.

Supplementary information

The online version contains supplementary material available at 10.1007/s40203-024-00277-2.

Enhancement of lipid synthesis by the transcription factor Asg1 in Saitozyma podzolica zwy-2-3 under dissolved oxygen stress

Microbial oils have been of considerable interest as food additives and biofuel resources due to high lipid contents, but lipid accumulation of oleaginous microorganisms can be induced by environmental stresses, such as dissolved oxygen (DO), which limit large-scale lipid production. Here, DO stress gave rise to the endogenous nitric oxide (NO) level to mediate S-nitrosylation of SpAsg1, regulating the lipid accumulation in Saitozyma podzolica zwy-2-3. Notably, qRT-PCR, yeast one-hybrid, dual-luciferase reporter assays, and metabolomics analysis exhibited that overexpression of SpAsg1 promoted lipid synthesis by directly regulation of glucose metabolism, enhancing glucose uptake, ATP and NADPH contents under DO stress. Meanwhile, SpAsg1 improved the antioxidant capacity to reduce the intracellular reactive oxygen species (ROS) and NO levels. Overall, we systematically investigated the regulation of SpAsg1 on lipid metabolism of S. podzolica zwy-2-3 under DO stress, which sheds light on further studies for alleviating oxygen limitation of lipid production in microbial industry.

Human anti-apoptotic Bcl-2 and Bcl-xL proteins protect yeast cells from aging induced oxidative stress

Aging is a degenerative, biological, and time-dependent process that affects all organisms. Yeast aging is a physiological phenomenon characterized by the progressive transformation of yeast cells, resulting in modifications to their viability and vitality. Aging in yeast cells is comparable to that in higher organisms in some respects; however, due to their straightforward and well-characterized genetic makeup, these cells present unique advantages when it comes to researching the aging process. Here, we assessed the impact of human anti-apoptotic Bcl-2 and Bcl-xL proteins on aging using a yeast model. The findings clearly showed that these proteins exhibited remarkable anti-aging properties in yeast cells. Our data indicate that the presence of both proteins enhanced the reproductive survival of aging cells, likely by effecting the components functioning as both pro- and anti-oxidants, depending on the stage of yeast cell lifespan. Both proteins partially protected yeast cells from aging-related morphological deformations and cellular damage during the aging period. In particular, Bcl-xL expressing yeast cells reached the maximum activity levels for almost all of the major antioxidant enzymes and the total antioxidant status on the 8th day of lifespan and could provide effective protection at the latest stage of the investigated aging period. The chemometric data analysis of IR spectra confirmed the findings of the morphological and biochemical analyses. In this regard, specifically, understanding the mechanism of action on the cellular redox state of Bcl-xL in yeast may facilitate comprehension of its indirect antioxidant function in higher eukaryotes.

Revisiting the activity of two poly(vinyl chloride)- and polyethylene-degrading enzymes

Biocatalytic degradation of non-hydrolyzable plastics is a rapidly growing field of research, driven by the global accumulation of waste. Enzymes capable of cleaving the carbon-carbon bonds in synthetic polymers are highly sought-after as they may provide tools for environmentally friendly plastic recycling. Despite some reports of oxidative enzymes acting on non-hydrolyzable plastics, including polyethylene or poly(vinyl chloride), the notion that these materials are susceptible to efficient enzymatic degradation remains controversial, partly driven by a general lack of studies independently reproducing previous observations. Here, we attempt to replicate two recent studies reporting that deconstruction of polyethylene and poly(vinyl chloride) can be achieved using an insect hexamerin from Galleria mellonella (so-called "Ceres") or a bacterial catalase-peroxidase from Klebsiella sp., respectively. Reproducing previously described experiments, we do not observe any activity on plastics using multiple reaction conditions and multiple substrate types. Digging deeper into the discrepancies between the previous data and our observations, we show how and why the original experimental results may have been misinterpreted.

The evaluation of Starmerella magnoliae X3 as a biodiesel feedstock based on triacylglycerol (TAG) production, lipid productivity, and fatty acid profile under nitrogen limitation and acidic pH conditions

The effects of four initial culture pH values (3, 4, 5, and 6) and nitrogen limitation on growth, TAG accumulation, lipid production, fatty acid profile, and estimated biodiesel quality of Starmerella magnoliae X3 were investigated. TAG and lipid levels were measured by Nile Red fluorescence and sulfo-phospho-vanilin (SPV) techniques, respectively. The results showed that a combination of nitrogen limitation and acidic pH significantly (p < 0.05) increased TAG accumulation, total lipid contents, and lipid productivity in Starmerella magnoliae X3 compared to the control group. Under nitrogen limitation, the highest TAG accumulation was achieved at initial pHs of 3 and 5 after 72 h of cultivation, and the highest lipid productivity (0.306 g L-1 d-1) was observed after 48 h at pH 3; the major fatty acids at the four pH values were oleic acid (63.6%-64%), palmitoleic acid (11.3%-12.5%), stearic acid (9.7%-11.4%), and palmitic acid (9.4%-10%). In addition, both stresses were associated with lower iodine value and higher cetane number of the biodiesel compared to the control. These findings suggest that cultivation in a low-nitrogen medium at an initial pH of 3 or 5 holds promise in increasing TAG production in Starmerella magnoliae X3.

Bioenergy feedstock production in Chlamydomonas reinhardtii (microalgae) cultivated under mixotrophic growth with cellulose hydrolysate from agricultural waste

In the present study, cellulose purified from finger millet agricultural waste is subjected to enzymatic hydrolysis, and the hydrolysate (predominantly glucose) is used as a carbon source supplement in the media for the mixotrophic growth of Chlamydomonas reinhardtii. Interestingly, a switch between excess starch production and excess lipid (triacylglycerols, TAG) production occurs by a small change in hydrolysate concentration in the media. Starch production increased 4.5-fold with respect to the photoautotrophic control, with a glucose concentration of 3 mg/mL in the media after hydrolysate addition. This culture had TAG production enhancement by 1.5-fold. However, mixotrophic cultivation with 4 mg/mL glucose concentration in the media with hydrolysate addition resulted in TAG productivity enhancement by 4.2-fold compared to control and starch amount increase of 1.3-fold. The organic carbon source (glucose) and the inorganic carbon source (citrate ions) in the hydrolysate together played a role in this delicate switching between starch and lipid pathways. Proteins, starch, and TAG molecules are analyzed in the microalgal cells grown under different conditions with FTIR spectroscopy, a rapid, high-throughput method of biomolecular estimation. High-resolution single-cell AFM studies of the cell wall structure reveal enhanced corrugations in surface morphology during mixotrophic growth with cellulose hydrolysate, illustrating an adaptive mechanism with improved mechanical stress management. Lipid droplet morphology at the single-cell level points to two distinct mechanisms of lipid accumulation: one in which the lipids are segregated as droplets, and the other in which lipid molecules are uniformly dispersed in the cytosol as unresolved, ultra-small droplets. The present study therefore analyzes both the bulk and the single-cell level changes when cellulose hydrolysate is used as a carbon source for Chlamydomonas reinhardtii mixotrophic cultivation, which serves a four-fold purpose: value from waste, fixation of atmospheric CO2, production of lipids for biodiesel, and starch for bioethanol.

Global biochemical profiling of fast-growing Antarctic bacteria isolated from meltwater ponds by high-throughput FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy is a biophysical technique used for non-destructive biochemical profiling of biological samples. It can provide comprehensive information about the total cellular biochemical profile of microbial cells. In this study, FTIR spectroscopy was used to perform biochemical characterization of twenty-nine bacterial strains isolated from the Antarctic meltwater ponds. The bacteria were grown on two forms of brain heart infusion (BHI) medium: agar at six different temperatures (4, 10, 18, 25, 30, and 37°C) and on broth at 18°C. Multivariate data analysis approaches such as principal component analysis (PCA) and correlation analysis were used to study the difference in biochemical profiles induced by the cultivation conditions. The observed results indicated a strong correlation between FTIR spectra and the phylogenetic relationships among the studied bacteria. The most accurate taxonomy-aligned clustering was achieved with bacteria cultivated on agar. Cultivation on two forms of BHI medium provided biochemically different bacterial biomass. The impact of temperature on the total cellular biochemical profile of the studied bacteria was species-specific, however, similarly for all bacteria, lipid spectral region was the least affected while polysaccharide region was the most affected by different temperatures. The biggest temperature-triggered changes of the cell chemistry were detected for bacteria with a wide temperature tolerance such Pseudomonas lundensis strains and Acinetobacter lwoffii BIM B-1558.

Highly Stable Self-Cleaning Paints Based on Waste-Valorized PNC-Doped TiO2 Nanoparticles

Adding photocatalytically active TiO2 nanoparticles (NPs) to polymeric paints is a feasible route toward self-cleaning coatings. While paint modification by TiO2-NPs may improve photoactivity, it may also cause polymer degradation and release of toxic volatile organic compounds. To counterbalance adverse effects, a synthesis method for nonmetal (P, N, and C)-doped TiO2-NPs is introduced, based purely on waste valorization. PNC-doped TiO2-NP characterization by vibrational and photoelectron spectroscopy, electron microscopy, diffraction, and thermal analysis suggests that TiO2-NPs were modified with phosphate (P=O), imine species (R=N-R), and carbon, which also hindered the anatase/rutile phase transformation, even upon 700 °C calcination. When added to water-based paints, PNC-doped TiO2-NPs achieved 96% removal of surface-adsorbed pollutants under natural sunlight or UV, paralleled by stability of the paint formulation, as confirmed by micro-Fourier transform infrared (FTIR) surface analysis. The origin of the photoinduced self-cleaning properties was rationalized by three-dimensional (3D) and synchronous photoluminescence spectroscopy, indicating that the dopants led to 7.3 times stronger inhibition of photoinduced e-/h+ recombination when compared to a benchmark P25 photocatalyst.

Fed-batch fermentation of Mucor circinelloides reveals significant improvement in biomass and lipid accumulation through performance evaluation, chemical analysis, and expression profiling

This study aimed to improve the lipid and biomass yields of Mucor circinelloides WJ11 by implementing four different fed-batch fermentation strategies, varied in time and glucose concentration (S1-S4). The S1 fermentation strategy yielded the highest biomass, lipid, and fatty acid content (22 ± 0.7 g/L, 53 ± 1.2 %, and 28 ± 1.6 %) after 120 and 144 h, respectively. The γ-linolenic acid titer of 0.75 ± 0.0 g/L was greatest in S3 after 48 h. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to analyze the transcription of key genes involved in lipid accumulation. The glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and ATP-citrate lyase genes showed increased expression levels. Fourier-transform infrared (FTIR) spectroscopy was used to analyze the biochemical profile during fermentation strategies. Optimal abiotic factors for production efficiency included pH 6.5, 25-26 °C, 15 % (v/v) inoculum, 500 rpm, 20 %-30 % dissolved oxygen, and 120 h fermentation. Glucose co-feeding offers valuable insights to develop effective fermentation strategies for lipid production.

Explorative characterization and taxonomy-aligned comparison of alterations in lipids and other biomolecules in Antarctic bacteria grown at different temperatures

Temperature significantly impacts bacterial physiology, metabolism and cell chemistry. In this study, we analysed lipids and the total cellular biochemical profile of 74 fast-growing Antarctic bacteria grown at different temperatures. Fatty acid diversity and temperature-induced alterations aligned with bacterial classification-Gram-groups, phylum, genus and species. Total lipid content, varied from 4% to 19% of cell dry weight, was genus- and species-specific. Most bacteria increased lipid content at lower temperatures. The effect of temperature on the profile was complex and more species-specific, while some common for all bacteria responses were recorded. Gram-negative bacteria adjusted unsaturation and acyl chain length. Gram-positive bacteria adjusted methyl branching (anteiso-/iso-), chain length and unsaturation. Fourier transform infrared spectroscopy analysis revealed Gram-, genus- and species-specific changes in the total cellular biochemical profile triggered by temperature fluctuations. The most significant temperature-related alterations detected on all taxonomy levels were recorded for mixed region 1500-900 cm-1 , specifically the band at 1083 cm-1 related to phosphodiester groups mainly from phospholipids (for Gram-negative bacteria) and teichoic/lipoteichoic acids (for Gram-positive bacteria). Some changes in protein region were detected for a few genera, while the lipid region remained relatively stable despite the temperature fluctuations.

Are all yeast biosurfactants really capable of lowering surface tension below 30 mN/m ?

The study discusses pitfalls in attempts to determine reliable surface tension values for the culture media and their extracts for two biosurfactant-producing yeast strains: Rhodotorula graminis and Rhodotorula babjevae. The values obtained from an Axisymmetric Drop Shape Analysis (ADSA) tensiometer showed systematically more and more shallow dynamic surface tension decays, suggesting a deterioration of their surface activity. The rate of this apparent surface activity loss was shown to depend on the sample history, with slower changes observed in vigorously shaken samples. On the other hand, the force-based Wilhelmy plate method provided apparently stable surface tension values of the order of 30 mN/m, in accordance with numerous previous literature reports on similar yeast biosurfactants. Both observations can be justified by the presence of an oil emulsified by biosurfactants produced by the yeast. We show that the odd (apparent) surface tension results are in fact the measurement artifacts resulting from slow demulsification and subsequent oil-spreading assisted by the yeast biosurfactants. The apparent surface tension reduction is thus indeed caused by the presence of biosurfactants, but its value does not represent their real adsorption in a thermodynamic sense. Consequently, the often reported in the literature very low surface tension values for the yeast culture media, of the order of 30 ± 5 mN/m, should be treated with caution, especially if the emulsion stabilized with the biosurfactant had not been fully destabilized prior to the measurement.

A Sphingolipidomic Profiling Approach for Comparing X-ray-Exposed and Unexposed HepG2 Cells

An analytical method based on tandem mass spectrometry-shotgun is presently proposed to obtain sphingolipidomic profiles useful for the characterization of lipid extract from X-ray-exposed and unexposed hepatocellular carcinoma cells (HepG2). To obtain a targeted lipidic profile from a specific biological system, the best extraction method must be identified before instrumental analysis. Accordingly, four different classic lipid extraction protocols were compared in terms of efficiency, specificity, and reproducibility. The performance of each procedure was evaluated using the Fourier-transform infrared spectroscopic technique; subsequently, the quality of extracts was estimated using electrospray ionization tandem mass spectrometry. The selected procedure based on chloroform/methanol/water was successfully used in mass spectrometry-based shotgun sphingolipidomics, allowing for evaluation of the response of cells to X-ray irradiation, the most common anticancer therapy. Using a relative quantitative approach, the changes in the sphingolipid profiles of irradiated cell extracts were demonstrated, confirming that lipidomic technologies are also useful tools for studying the key sphingolipid role in regulating cancer growth during radiotherapy.

Oleaginous yeasts for biochemicals, biofuels and food from lignocellulose-hydrolysate and crude glycerol

Microbial lipids produced from lignocellulose and crude glycerol (CG) can serve as sustainable alternatives to vegetable oils, whose production is, in many cases, accompanied by monocultures, land use changes or rain forest clearings. Our projects aim to understand the physiology of microbial lipid production by oleaginous yeasts, optimise the production and establish novel applications of microbial lipid compounds. We have established methods for fermentation and intracellular lipid quantification. Following the kinetics of lipid accumulation in different strains, we found high variability in lipid formation even between very closely related oleaginous yeast strains on both, wheat straw hydrolysate and CG. For example, on complete wheat straw hydrolysate, we saw that one Rhodotorula glutinis strain, when starting assimilating D-xylosealso assimilated the accumulated lipids, while a Rhodotorula babjevae strain could accumulate lipids on D-xylose. Two strains (Rhodotorula toruloides CBS 14 and R. glutinis CBS 3044) were found to be the best out of 27 tested to accumulate lipids on CG. Interestingly, the presence of hemicellulose hydrolysate stimulated glycerol assimilation in both strains. Apart from microbial oil, R. toruloides also produces carotenoids. The first attempts of extraction using the classical acetone-based method showed that β-carotene is the major carotenoid. However, there are indications that there are also substantial amounts of torulene and torularhodin, which have a very high potential as antioxidants.

Source separation of human excreta: Effect on resource recovery via pyrolysis

More people globally are now using on-site sanitation technologies than sewered connections. The management of faecal sludge generated by on-site facilities is still challenging and requires an understanding of all sanitation service chain components and their interactions; from source conditions to treatment and resource recovery. This study aimed to improve the current lack of knowledge regarding these interactions, by establishing a quantifiable relationship between human excreta source separation and resource recovery via pyrolysis. The effects of source separation of faeces and urine on biochar quality were investigated for different pyrolysis temperatures (450 °C, 550 °C, 650 °C) and this information was used to assess energy and nutrient recovery. Results quantify the benefits of urine diversion for nitrogen recovery (70% of total N losses during thermal treatment avoided) and show an increase in the liming potential of the produced faecal-based biochars. The quality of produced solid fuels is also improved when source-separated faeces (SSF) are used as a feedstock for pyrolysis, including a 50% increase in char calorific value. On the other hand, biochars from mixed urine and faeces (MUF) are more rich in phosphorus and potassium, and surface morphology investigation indicates higher porosity compared to SSF biochars. The high salinity of MUF biochars should be considered before agricultural applications. For both biochar types (SSF, MUF), the presence of phosphate compounds of high fertiliser value was confirmed by X-ray diffraction analysis, and temperatures around 500 °C are recommended to optimise nutrient and carbon behaviour when pyrolysing human excreta. These findings can be used for the design of circular faecal sludge management systems, linking resource recovery objectives to source conditions, and vice-versa. Ultimately, achieving consistent resource recovery from human excreta can act as an incentive for universal access to safe and sustainable sanitation.

A Comparative Study of the Synthesis and Characterization of Biogenic Selenium Nanoparticles by Two Contrasting Endophytic Selenobacteria

The present study examined the biosynthesis and characterization of selenium nanoparticles (SeNPs) using two contrasting endophytic selenobacteria, one Gram-positive (Bacillus sp. E5 identified as Bacillus paranthracis) and one Gram-negative (Enterobacter sp. EC5.2 identified as Enterobacter ludwigi), for further use as biofortifying agents and/or for other biotechnological purposes. We demonstrated that, upon regulating culture conditions and selenite exposure time, both strains were suitable "cell factories" for producing SeNPs (B-SeNPs from B. paranthracis and E-SeNPs from E. ludwigii) with different properties. Briefly, dynamic light scattering (DLS), transmission electron microscopy (TEM), and atomic force microscopy (AFM) studies revealed that intracellular E-SeNPs (56.23 ± 4.85 nm) were smaller in diameter than B-SeNPs (83.44 ± 2.90 nm) and that both formulations were located in the surrounding medium or bound to the cell wall. AFM images indicated the absence of relevant variations in bacterial volume and shape and revealed the existence of layers of peptidoglycan surrounding the bacterial cell wall under the conditions of biosynthesis, particularly in the case of B. paranthracis. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) showed that SeNPs were surrounded by the proteins, lipids, and polysaccharides of bacterial cells and that the numbers of the functional groups present in B-SeNPs were higher than in E-SeNPs. Thus, considering that these findings support the suitability of these two endophytic stains as potential biocatalysts to produce high-quality Se-based nanoparticles, our future efforts must be focused on the evaluation of their bioactivity, as well as on the determination of how the different features of each SeNP modulate their biological action and their stability.

A biochemical, theoretical and immunohistochemical study comparing the therapeutic efficacy of curcumin and taurine on T-2 toxin induced hepatotoxicity in rats

Introduction: Foodborne trichothecene T-2 Toxin, is a highly toxic metabolite produced by Fusarium species contaminating animal and human food, causing multiple organ failure and health hazards. T-2 toxins induce hepatotoxicity via oxidative stress causing hepatocytes cytotoxicity and genotoxicity. In this study, curcumin and taurine were investigated and compared as antioxidants against T-2-provoked hepatotoxicity. Methods: Wistar rats were administrated T-2 toxin sublethal oral dose (0.1 mg/kg) for 2 months, followed by curcumin (80 mg/kg) and taurine (50 mg/kg) for 3 weeks. Biochemical assessment of liver enzymes, lipid profiles, thiobarbituric acid reactive substances (TBARs), AFU, TNF-α, total glutathione, molecular docking, histological and immunohistochemical markers for anti-transforming growth factor-β1 (TGFβ1), double-strand DNA damage (H2AX), regeneration (KI67) and apoptosis (Active caspase3) were done. Results and Discussion: Compared to T-2 toxin, curcumin and taurine treatment significantly ameliorated hepatoxicity as; hemoglobin, hematocrit and glutathione, hepatic glycogen, and KI-67 immune-reactive hepatocytes were significantly increased. Although, liver enzymes, inflammation, fibrosis, TGFβ1 immunoexpressing and H2AX and active caspase 3 positive hepatocytes were significantly decreased. Noteworthy, curcumin's therapeutic effect was superior to taurine by histomorphometry parameters. Furthermore, molecular docking of the structural influence of curcumin and taurine on the DNA sequence showed curcumin's higher binding affinity than taurine. Conclusion: Both curcumin and taurine ameliorated T-2 induced hepatotoxicity as strong antioxidative agents with more effectiveness for curcumin.

Determination of active sites on the synthesis of novel Lewis acidic deep eutectic solvent catalysts and kinetic studies in microalgal biodiesel production

Experimental and theoretical considerations for kinetic modeling of the transesterification reaction of microalgae lipids into biodiesel were investigated using Lewis acid deep eutectic solvents (DESs) as a catalyst. The acid sites involved in the reaction were characterized using acetonitrile as a probe to understand the mechanism. DES ChCl-SnCl2 (choline chloride-tin ii chloride) showed higher catalytic activity in transesterification due to its higher acidity compared to DES ChCl-ZnCl2 (choline chloride-zinc chloride). This was illustrated by geometric optimization of the DES structures through density functional theory (DFT) which showed that the metal centers furthest from the choline moiety are the most acidic and the bond lengths of Sn-Cl were between 2.56 and 2.77 Å, and were greater than the Zn-Cl bond lengths from 2.30 to 2.48 Å, making the ChCl-SnCl2 DES more acidic and more suitable for the biodiesel production. The fatty acid methyl ester (FAME) conversion from microalgae lipid was 36.75 mg g-1 under ideal conditions (6 molar ratio methanol-lipid with 8 vol% DES dosage in methanol at 140 °C for 420 min). The activation energy is found to be 36.3 kJ mol-1 based on the pseudo-first-order reaction, in addition, the DES catalyst (ChCl-SnCl2) drove the reaction chemically and did not show mass transfer limitation. Information from this study can help to advance the development of an efficient and environmentally friendly industrial biodiesel production technology.

Multiscale spectroscopic analysis of lipids in dimorphic and oleaginous Mucor circinelloides accommodate sustainable targeted lipid production

BACKGROUND

Oleaginous fungi have versatile metabolism and able to transform a wide range of substrates into lipids, accounting up to 20-70% of their total cell mass. Therefore, oleaginous fungi are considered as an alternative source of lipids. Oleaginous fungi can accumulate mainly acyl glycerides and free fatty acids which are localized in lipid droplets. Some of the oleaginous fungi possessing promising lipid productivity are dimorphic and can exhibit three cell forms, flat hyphae, swollen hyphae and yeast-like cells. To develop sustainable targeted fungal lipid production, deep understanding of lipogenesis and lipid droplet chemistry in these cell forms is needed at multiscale level. In this study, we explored the potential of infrared spectroscopy techniques for examining lipid droplet formation and accumulation in different cell forms of the dimorphic and oleaginous fungus Mucor circinelloides.

RESULTS

Both transmission- and reflectance-based spectroscopy techniques are shown to be well suited for studying bulk fungal biomass. Exploring single cells with infrared microspectroscopy reveals differences in chemical profiles and, consequently, lipogenesis process, for different cell forms. Yeast-like cells of M. circinelloides exhibited the highest absorbance intensities for lipid-associated peaks in comparison to hyphae-like cell forms. Lipid-to-protein ratio, which is commonly used in IR spectroscopy to estimate lipid yield was the lowest in flat hyphae. Swollen hyphae are mainly composed of lipids and characterized by more uniform distribution of lipid-to-protein concentration. Yeast-like cells seem to be comprised mostly of lipids having the largest lipid-to-protein ratio among all studied cell forms. With infrared nanospectroscopy, variations in the ratios between lipid fractions triglycerides and free fatty acids and clear evidence of heterogeneity within and between lipid droplets are illustrated for the first time.

CONCLUSIONS

Vibrational spectroscopy techniques can provide comprehensive information on lipogenesis in dimorphic and oleaginous fungi at the levels of the bulk of cells, single cells and single lipid droplets. Unicellular spectra showed that various cell forms of M. circinelloides differs in the total lipid content and profile of the accumulated lipids, where yeast-like cells are the fatty ones and, therefore, could be considered as preferable cell form for producing lipid-rich biomass. Spectra of single lipid droplets showed an indication of possible droplet-to-droplet and within-droplet heterogeneity.

Exploring the identification of multiple bacteria on stainless steel using multi-scale spectral imaging from microscopic to macroscopic

This work investigates non-contact reflectance spectral imaging techniques, i.e. microscopic Fourier transform infrared (FTIR) imaging, macroscopic visible-near infrared (VNIR), and shortwave infrared (SWIR) spectral imaging, for the identification of bacteria on stainless steel. Spectral images of two Gram-positive (GP) bacteria (Bacillus subtilis (BS) and Lactobacillus plantarum (LP)), and three Gram-negative (GN) bacteria (Escherichia coli (EC), Cronobacter sakazakii (CS), and Pseudomonas fluorescens (PF)), were collected from dried suspensions of bacterial cells dropped onto stainless steel surfaces. Through the use of multiple independent biological replicates for model validation and testing, FTIR reflectance spectral imaging was found to provide excellent GP/GN classification accuracy (> 96%), while the fused VNIR-SWIR data yielded classification accuracy exceeding 80% when applied to the independent test sets. However, classification within gram type was far less reliable, with lower accuracies for classification within the GP (< 75%) and GN (≤ 51%) species when calibration models were applied to the independent test sets, underlining the importance of independent model validation when dealing with samples of high biological variability.

Bifunctional Co3O4/ZSM-5 Mesoporous Catalysts for Biodiesel Production via Esterification of Unsaturated Omega-9 Oleic Acid

In the present work, two sets of the Co/ZSM-5 mesoporous catalysts with different acidity and Co loadings varying from 1 to 5 and 10 wt% were prepared using mesoporous ZSM-5-A (Si/Al = 50) and ZSM-5-B (Si/Al = 150) as support. X-ray diffraction (XRD) analysis showed that the Co3O4 phase was formed in the surface of catalysts and the reducibility of Co3O4 nanoparticles on the ZSM-5-B was greater in comparison with that on the ZSM-5-A solid. In situ FTIR of pyridine adsorption characterization confirmed that all of the Co/ZSM-5 catalysts contained both Lewis (L) and Brønsted (B) acid sites, with a relatively balanced B/L ratio ranging from 0.61 to 1.94. Therefore, the Si/Al molar ratio in ZSM-5 affected both the surface acidity and the cobalt oxide reducibility. In the esterification of unsaturated omega-9 oleic acid with methanol, under the optimal reaction conditions (temperature 160 °C, catalyst concentration 2 g/L, methanol/oleic acid molar ratio 30, and reaction time 180 min), the biodiesel selectivity reached 95.1% over the most active 10 wt% Co/ZSM-5-B catalyst. The higher esterification activity of the Co/ZSM-5-B catalysts can be correlated with the greater amount of B and L acid sites, the balanced B/L ratio, and the higher reducibility of Co3O4 nanoparticles. The oleic acid esterification reaction followed the bifunctional mechanism of combining metal function (dispersed Co3O4 with a greater reducibility) with the acidity function (both B and L acid sites with a relative balanced B/L ratio) on the catalysts, which may help in providing a deep understanding of the esterification pathways and benefiting the design of novel bifunctional catalysts for biofuel production.

Sustainable Production of Biodiesel Using UV Mutagenesis as a Strategy to Enhance the Lipid Productivity in R. mucilaginosa

The future of petroleum-based fuel is biodiesel. Biodiesel is an eco-friendly fuel that can be used in any diesel engine without any alterations. Researchers have focused on biodiesel that can be produced from microbial lipids extracted from high lipid-yielding microbes. In this study, microbial cultures were screened for high lipid-yielding capabilities and mutated using UV radiation at three different time intervals of 30, 75, and 90 min. The Nile red fluorescence method was used to analyze high lipid-yielding microbes. An outstanding increase in biomass and lipid productivity was noted when the microbes were exposed to UV for 30 min. For example, an M30-8 UV-mutated strain produced a lipid yield of 68.5%. The lipids produced from the wild and mutated strains were analyzed using GCMS and FTIR spectrophotometric analysis. Then, the lipids extracted from both wild VS3 and UV-mutated M30-8 strains were transesterified using a base catalyst and the produced biodiesel was analyzed using ASTM standards. The aim and objective of the research was to mutate high lipid-yielding microbes by using UV radiation and produce biodiesel from the lipids extracted from both wild and UV-mutated strains.

Identification, Quantification and Kinetic Study of Carotenoids and Lipids in Rhodotorula toruloides CBS 14 Cultivated on Wheat Straw Hydrolysate

Production of carotenoids and lipids by Rhodotorula toruloides CBS 14 cultivated on wheat straw hydrolysate was investigated. An ultra-high-performance liquid chromatography (UHPLC) method for carotenoid quantification was developed and validated. Saponification effects on individual carotenoid quantification were identified, and lipid and carotenoid kinetics during cultivation were determined. The carotenoids β-carotene, γ-carotene, torularhodin, and torulene were identified; β-carotene was the major carotenoid, reaching a maximum of 1.48 mg/100 g dry weight. Recoveries of the carotenoids were between 66 and 76%, except torulene and torularhodin, which had lower recoveries due to saponification effects. Total carotenoid content in saponified and unsaponified yeast extract, respectively, determined by UHPLC or photometer, respectively, was 1.99 mg/100 g and 4.02 mg β-EQ/100 g dry weight. Growth kinetics showed a positive correlation between carotenoid content and lipid accumulation. β-carotene was the major carotenoid at all time points. At the end of the cultivation, triacylglycerols (TAGs) were the major lipid class, with 58.1 ± 3.32% of total lipids. There was also a high proportion of free fatty acids, reaching from 20.5 to 41.8% of total lipids. Oleic acid (C18:1) was the major fatty acid. The lipid yield at the end of the cultivation was 0.13 g/g of sugar consumed.

Temperature- and Nutrients-Induced Phenotypic Changes of Antarctic Green Snow Bacteria Probed by High-Throughput FTIR Spectroscopy

Simple Summary

Green snow microorganisms play an important role in biogeochemical cycle and carbon sink processes and they can be a source of biotechnologically interesting cell factories. A wide temperature tolerance is a unique property of bacteria isolated from cold environments, which has received great attention in the last years. The present paper examines the growth and chemical profile flexibility for green snow bacteria exposed to different temperature and nutrient fluctuations. By applying high-throughput chemical phenotyping with FTIR spectroscopy we discovered chemical changes possessed by green snow bacteria when grown at high/low temperature and rich/minimal media.

Abstract

Temperature fluctuations and nutrient composition are the main parameters influencing green snow microbiome. In this study we investigated the influence of temperature and nutrient conditions on the growth and cellular chemical profile of bacteria isolated from green snow. Chemical profiling of the green snow bacteria was done by high-throughput FTIR spectroscopy combined with multivariate data analysis. We showed that temperature and nutrients fluctuations strongly affect growth ability and chemical profile of the green snow bacteria. The size of colonies for green snow bacteria grown at higher (25 °C) and lower (4 °C and 10 °C) than optimal temperature (18 °C) was smaller. All isolates grew on rich medium, and only 19 isolates were able to grow on synthetic minimal media. Lipid and mixed spectral regions showed to be phylogeny related. FTIR fingerprinting indicates that lipids are often affected by the temperature fluctuations. Growth on different media resulted in the change of the whole chemical profile, where lipids showed to be more affected than proteins and polysaccharides. Correlation analysis showed that nutrient composition is clearly strongly influencing chemical changes in the cells, followed by temperature.

Simultaneous Raman and Infrared Spectroscopy of Stable Isotope Labelled Escherichia coli

We report the use of a novel technology based on optical photothermal infrared (O-PTIR) spectroscopy for obtaining simultaneous infrared and Raman spectra from the same location of the sample allowing us to study bacterial metabolism by monitoring the incorporation of 13C- and 15N-labeled compounds. Infrared data obtained from bulk populations and single cells via O-PTIR spectroscopy were compared to conventional Fourier transform infrared (FTIR) spectroscopy in order to evaluate the reproducibility of the results achieved by all three approaches. Raman spectra acquired were concomitant with infrared data from bulk populations as well as infrared spectra collected from single cells, and were subjected to principal component analysis in order to evaluate any specific separation resulting from the isotopic incorporation. Similar clustering patterns were observed in infrared data acquired from single cells via O-PTIR spectroscopy as well as from bulk populations via FTIR and O-PTIR spectroscopies, indicating full incorporation of heavy isotopes by the bacteria. Satisfactory discrimination between unlabeled (viz. 12C14N), 13C14N- and 13C15N-labeled bacteria was also obtained using Raman spectra from bulk populations. In this report, we also discuss the limitations of O-PTIR technology to acquire Raman data from single bacterial cells (with typical dimensions of 1 × 2 µm) as well as spectral artifacts induced by thermal damage when analyzing very small amounts of biomass (a bacterium tipically weighs ~ 1 pg).

Attenuated Total Reflection (ATR) Micro-Fourier Transform Infrared (Micro-FT-IR) Spectroscopy to Enhance Repeatability and Reproducibility of Spectra Derived from Single Specimen Organic-Walled Dinoflagellate Cysts

The chemical composition of recent and fossil organic-walled dinoflagellate cyst walls and its diversity is poorly understood and analyses on single microscopic specimens are rare. A series of infrared spectroscopic experiments resulted in the proposition of a standardized attenuated total reflection micro-Fourier transform infrared-based method that allows the collection of robust data sets consisting of spectra from individual dinocysts. These data sets are largely devoid of nonchemical artifacts inherent to other infrared spectrochemical methods, which have typically been used to study similar specimens in the past. The influence of sample preparation, specimen morphology and size and spectral data processing steps is also assessed within this methodological framework. As a result, several guidelines are proposed which facilitate the collection and qualitative interpretation of highly reproducible and repeatable spectrochemical data. These, in turn, pave the way for a systematic exploration of dinocyst chemistry and its assessment as a chemotaxonomical tool or proxy.

Transcriptomic analysis of formic acid stress response in Saccharomyces cerevisiae

Formic acid is a representative small molecule acid in lignocellulosic hydrolysate that can inhibit the growth of Saccharomyces cerevisiae cells during alcohol fermentation. However, the mechanism of formic acid cytotoxicity remains largely unknown. In this study, RNA-Seq technology was used to study the response of S. cerevisiae to formic acid stress at the transcriptional level. Scanning electron microscopy and Fourier transform infrared spectroscopy were conducted to observe the surface morphology of yeast cells. A total of 1504 genes were identified as being differentially expressed, with 797 upregulated and 707 downregulated genes. Transcriptomic analysis showed that most genes related to glycolysis, glycogen synthesis, protein degradation, the cell cycle, the MAPK signaling pathway, and redox regulation were significantly induced under formic acid stress and were involved in protein translation and synthesis amino acid synthesis genes were significantly suppressed. Formic acid stress can induce oxidative stress, inhibit protein biosynthesis, cause cells to undergo autophagy, and activate the intracellular metabolic pathways of energy production. The increase of glycogen and the decrease of energy consumption metabolism may be important in the adaptation of S. cerevisiae to formic acid. In addition, formic acid can also induce sexual reproduction and spore formation. This study through transcriptome analysis has preliminarily reveal the molecular response mechanism of S. cerevisiae to formic acid stress and has provided a basis for further research on methods used to improve the tolerance to cell inhibitors in lignocellulose hydrolysate.

Starch Rich Chlorella vulgaris: High-Throughput Screening and Up-Scale for Tailored Biomass Production

The use of microalgal starch has been studied in biorefinery frameworks to produce bioethanol or bioplastics, however, these products are currently not economically viable. Using starch-rich biomass as an ingredient in food applications is a novel way to create more value while expanding the product portfolio of the microalgal industry. Optimization of starch production in the food-approved species Chlorella vulgaris was the main objective of this study. High-throughput screening of biomass composition in response to multiple stressors was performed with FTIR spectroscopy. Nitrogen starvation was identified as an important factor for starch accumulation. Moreover, further studies were performed to assess the role of light distribution, investigating the role of photon supply rates in flat panel photobioreactors. Starch-rich biomass with up to 30% starch was achieved in cultures with low inoculation density (0.1 g L−1) and high irradiation (1800 µmol m−2 s−1). A final large-scale experiment was performed in 25 L tubular reactors, achieving a maximum of 44% starch in the biomass after 12 h in nitrogen starved conditions.

Aspergillus caespitosus ASEF14, an oleaginous fungus as a potential candidate for biodiesel production using sago processing wastewater (SWW)

Background

Oleaginous microorganisms are sustainable alternatives for the production of biodiesel. Among them, oleaginous fungi are known for their rapid growth, short life cycles, no light requirement, easy scalability, and the ability to grow in cheap organic resources. Among all the sources used for biodiesel production, industrial wastewater streams have been least explored. We used oleaginous fungi to decontaminate sago processing wastewater and produce biodiesel.

Results

Among the 15 isolates screened for lipid production and starch utilization using the Nile red staining assay and amylase plate screening, three isolates accumulated > 20% (w/w) of their dry cell mass as lipids. The isolate ASEF14 exhibited the highest lipid accumulation (> 40%) and was identified as Aspergillus caespitosus based on the 28S rRNA gene sequencing. The maximum lipid content of 54.4% in synthetic medium (SM) and 37.2% in sago processing wastewater (SWW) was produced by the strain. The Fourier-transform infrared (FTIR) spectroscopy of the fungal oil revealed the presence of functional peaks corresponding to major lipids. Principal component analysis (PCA) of the FTIR data revealed major changes in the fatty acid composition during the transition from the growth phase (Days 1–3) to the lipid accumulation phase (Days 4–7). The fatty acid methyl esters (FAME) analysis of fungal oil from SWW contained 43.82% and 9.62% of saturated and monounsaturated fatty acids, respectively. The composition and percentage of individual FAME derived from SWW were different from SM, indicating the effect of nutrient and fermentation time. The fuel attributes of the SM- and SWW-grown fungal biodiesel (kinematic viscosity, iodine value, cetane number, cloud and pour point, linolenic acid content, FA > 4 double bonds) met international (ASTM D6751, EN 14214) and national (IS 15607) biodiesel standards. In addition to biodiesel production, the strain removed various contaminants such as total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), dissolved oxygen (DO), chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), and cyanide up to 58.6%, 53.0%, 35.2%, 94.5%, 89.3%, 91.3%, 74.0%, 47.0%, and 53.84%, respectively, from SWW.

Conclusion

These findings suggested that A. caespitosus ASEF14 is a potential candidate with high lipid accumulating ability (37.27%), capable of using SWW as the primary growth medium. The medium and incubation time alter the FAME profile of this fungus. The physical properties of fungal oil were in accordance with the biodiesel standards. Moreover, it decontaminated SWW by reducing several polluting nutrients and toxicants. The fungal biodiesel produced by this cost-effective method could serve as an alternate path to meet global energy demand.

Yeasts of the Blastobotrys genus are promising platform for lipid-based fuels and oleochemicals production

Strains of the yeast genus Blastobotrys (subphylum Saccharomycotina) represent a valuable biotechnological resource for basic biochemistry research, single-cell protein, and heterologous protein production processes. Species of this genus are dimorphic, non-pathogenic, thermotolerant, and can assimilate a variety of hydrophilic and hydrophobic substrates. These can constitute a single-cell oil platform in an emerging bio-based economy as oleaginous traits have been discovered recently. However, the regulatory network of lipogenesis in these yeasts is poorly understood. To keep pace with the growing market demands for lipid-derived products, it is critical to understand the lipid biosynthesis in these unconventional yeasts to pinpoint what governs the preferential channelling of carbon flux into lipids instead of the competing pathways. This review summarizes information relevant to the regulation of lipid metabolic pathways and prospects of metabolic engineering in Blastobotrys yeasts for their application in food, feed, and beyond, particularly for fatty acid-based fuels and oleochemicals. KEY POINTS: • The production of biolipids by heterotrophic yeasts is reviewed. • Summary of information concerning lipid metabolism regulation is highlighted. • Special focus on the importance of diacylglycerol acyltransferases encoding genes in improving lipid production is made.

Rapid classification of chromoblastomycosis agents genera by infrared spectroscopy and chemometrics supervised by sequencing of rDNA regions

Chromoblastomycosis (CBM) is a skin and subcutaneous infection caused by species of seven fungal genera. Identification of CBM species is performed by DNA sequencing of one or more genes, which becomes a time-consuming work. Fourier Transform Infrared Spectroscopy (FTIR) has been used for the identification of other microorganisms, however, only one CBM genus was evaluated by FTIR analysis to date. Therefore, the study is aimed to differentiate the CBM agents for identification at genera level using FTIR supervised by Internal Transcribed Spacer (ITS) rDNA region. Seventy-seven isolates of the main five CBM genera were prepared for Attenuated Total Reflection FTIR (ATR-FTIR) with a new methodology using slices of dry fungus in glass fixing-modeling proposed in this study. The algorithm Hierarchical Cluster Analysis (HCA) was used to analyze the differences and similarities between species through the spectra. Orthogonal Partial Least Square Discriminant Analysis (OPLS-DA) allowed to correctly classify all samples of five CBM genera. The ATR-FTIR/OPLS-DA models highlighted important contributions of regions attributed to NH and OH stretching, amide I of proteins, polysaccharides bands and fingerprint region for the complete differentiation of the genera investigated. Thus, FTIR can be a fast and inexpensive alternative for identification of CBM agents.

Oleaginous yeasts respond differently to carbon sources present in lignocellulose hydrolysate

BACKGROUND

Microbial oils, generated from lignocellulosic material, have great potential as renewable and sustainable alternatives to fossil-based fuels and chemicals. By unravelling the diversity of lipid accumulation physiology in different oleaginous yeasts grown on the various carbon sources present in lignocellulose hydrolysate (LH), new targets for optimisation of lipid accumulation can be identified. Monitoring lipid formation over time is essential for understanding lipid accumulation physiology. This study investigated lipid accumulation in a variety of oleaginous ascomycetous and basidiomycetous strains grown in glucose and xylose and followed lipid formation kinetics of selected strains in wheat straw hydrolysate (WSH).

RESULTS

Twenty-nine oleaginous yeast strains were tested for their ability to utilise glucose and xylose, the main sugars present in WSH. Evaluation of sugar consumption and lipid accumulation revealed marked differences in xylose utilisation capacity between the yeast strains, even between those belonging to the same species. Five different promising strains, belonging to the species Lipomyces starkeyi, Rhodotorula glutinis, Rhodotorula babjevae and Rhodotorula toruloides, were grown on undiluted wheat straw hydrolysate and lipid accumulation was followed over time, using Fourier transform-infrared (FTIR) spectroscopy. All five strains were able to grow on undiluted WSH and to accumulate lipids, but to different extents and with different productivities. R. babjevae DVBPG 8058 was the best-performing strain, accumulating 64.8% of cell dry weight (CDW) as lipids. It reached a culture density of 28 g/L CDW in batch cultivation, resulting in a lipid content of 18.1 g/L and yield of 0.24 g lipids per g carbon source. This strain formed lipids from the major carbon sources in hydrolysate, glucose, acetate and xylose. R. glutinis CBS 2367 also consumed these carbon sources, but when assimilating xylose it consumed intracellular lipids simultaneously. Rhodotorula strains contained a higher proportion of polyunsaturated fatty acids than the two tested Lipomyces starkeyi strains.

CONCLUSIONS

There is considerable metabolic diversity among oleaginous yeasts, even between closely related species and strains, especially when converting xylose to biomass and lipids. Monitoring the kinetics of lipid accumulation and identifying the molecular basis of this diversity are keys to selecting suitable strains for high lipid production from lignocellulose.

Sequencing batch airlift reactors (SBAR): a suitable technology for treatment and valorization of mineral oil wastewaters towards lipids production

Produced water (PW) and spent oil-based wastewaters are some of the largest mineral oil wastewaters produced. Due to the high toxicity of hydrocarbons, several countries set stringent discharge limits and its treatment is compulsory before discharge. In this work, biological treatment of mineral oil wastewaters coupled with the production of bacterial lipids is demonstrated in sequential batch airlift reactors (SBAR). Two SBAR (2 L working volume) were used for treatment of PW and lubricant-based wastewater (LW), inoculated with Alcanivorax borkumensis SK2 (SBAR_Ab+PW) and Rhodococcus opacus B4 (SBAR_R.o+LW), respectively. A total petroleum hydrocarbon removal (TPH) efficiency up to 96% and 80% were achieved for SBAR_Ab+PW and SBAR_R.o+LW, respectively. Intracellular lipids production in SBAR_Ab+PW increased when lower TPH/N ratios and higher feast stage duration were applied (up to 0.74 g g^-1 cell dry weight (CDW)), whereas in SBAR_R.o+LW higher lipids production was observed for higher TPH/N ratios (0.94 g g^-1 in CDW). Triacylglycerols (TAG) were the main intracellular lipid accumulated in both SBAR_Ab+PW and SBAR_R.o+LW operations, while wax ester (WE) production was only observed extracellularly in the SBAR_Ab+PW.

Assessing encapsulation of curcumin in cocoliposome: In vitro study

Curcumin has been known and used in the medical and industrial world. One way to improve its stability, bioavailability and its medical applications is using encapsulation method. In this research, we studied cocoliposome (coconut liposome) as the encapsulation material. The encapsulation efficiency (EE), loading capacity (LC), release rate (RR), as well as the free radical scavenging activity, measured by inhibition ratio (IR), of curcumin in encapsulation product were studied on varying cholesterol compositions and in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.4) conditions. We found that curcumin encapsulation in cocoliposome (CCL) formulation was influenced by cholesterol composition and pH conditions. The EE, LC and free radical scavenging activity diminished under both the SIF and SGF conditions when the cholesterol concentration enhanced. However, the RR increased as the cholesterol intensified. The condition to acquire the most favorable encapsulation parameter values was at 10% cholesterol composition. Furthermore, the IR results at 10% cholesterol concentration of CCL was 67.70 and 82.13% in SGF and SIF milieu, respectively. The CCL formulation thrived better under SIF conditions for free radical scavenging activities.

Recent advances in lipid metabolic engineering of oleaginous yeasts

With the increasing demand to develop a renewable and sustainable biolipid feedstock, several species of non-conventional oleaginous yeasts are being explored. Apart from the platform oleaginous yeast Yarrowia lipolytica, the understanding of metabolic pathway and, therefore, exploiting the engineering prospects of most of the oleaginous species are still in infancy. However, in the past few years, enormous efforts have been invested in Rhodotorula, Rhodosporidium, Lipomyces, Trichosporon, and Candida genera of yeasts among others, with the rapid advancement of engineering strategies, significant improvement in genetic tools and techniques, generation of extensive bioinformatics and omics data. In this review, we have collated these recent progresses to make a detailed and insightful summary of the major developments in metabolic engineering of the prominent oleaginous yeast species. Such a comprehensive overview would be a useful resource for future strain improvement and metabolic engineering studies for enhanced production of lipid and lipid-derived chemicals in oleaginous yeasts.

Isolation and characterization of fast-growing green snow bacteria from coastal East Antarctica

Snow microorganisms play a significant role in climate change and affecting the snow melting rate in the Arctic and Antarctic regions. While research on algae inhabiting green and red snow has been performed extensively, bacteria dwelling in this biotope have been studied to a much lesser extent. In this study, we performed 16S rRNA gene amplicon sequencing of two green snow samples collected from the coastal area of the eastern part of Antarctica and conducted genotypic and phenotypic profiling of 45 fast-growing bacteria isolated from these samples. 16S rRNA gene amplicon sequencing of two green snow samples showed that bacteria inhabiting these samples are mostly represented by families Burkholderiaceae (46.31%), Flavobacteriaceae (22.98%), and Pseudomonadaceae (17.66%). Identification of 45 fast-growing bacteria isolated from green snow was performed using 16S rRNA gene sequencing. We demonstrated that they belong to the phyla Actinobacteria and Proteobacteria, and are represented by the genera Arthrobacter, Cryobacterium, Leifsonia, Salinibacterium, Paeniglutamicibacter, Rhodococcus, Polaromonas, Pseudomonas, and Psychrobacter. Nearly all bacterial isolates exhibited various growth temperatures from 4°C to 25°C, and some isolates were characterized by a high level of enzymatic activity. Phenotyping using Fourier transform infrared (FTIR) spectroscopy revealed a possible accumulation of intracellular polymer polyhydroxyalkanoates (PHA) or lipids in some isolates. The bacteria showed different lipids/PHA and protein profiles. It was shown that lipid/PHA and protein spectral regions are the most discriminative for differentiating the isolates.

Conversion of sugar beet residues into lipids by Lipomyces starkeyi for biodiesel production

BACKGROUND

Lipids from oleaginous yeasts emerged as a sustainable alternative to vegetable oils and animal fat to produce biodiesel, the biodegradable and environmentally friendly counterpart of petro-diesel fuel. To develop economically viable microbial processes, the use of residual feedstocks as growth and production substrates is required.

RESULTS

In this work we investigated sugar beet pulp (SBP) and molasses, the main residues of sugar beet processing, as sustainable substrates for the growth and lipid accumulation by the oleaginous yeast Lipomyces starkeyi. We observed that in hydrolysed SBP the yeast cultures reached a limited biomass, cellular lipid content, lipid production and yield (2.5 g/L, 19.2%, 0.5 g/L and 0.08 g/g, respectively). To increase the initial sugar availability, cells were grown in SBP blended with molasses. Under batch cultivation, the cellular lipid content was more than doubled (47.2%) in the presence of 6% molasses. Under pulsed-feeding cultivation, final biomass, cellular lipid content, lipid production and lipid yield were further improved, reaching respectively 20.5 g/L, 49.2%, 9.7 g/L and 0.178 g/g. Finally, we observed that SBP can be used instead of ammonium sulphate to fulfil yeasts nitrogen requirement in molasses-based media for microbial oil production.

CONCLUSIONS

This study demonstrates for the first time that SBP and molasses can be blended to create a feedstock for the sustainable production of lipids by L. starkeyi. The data obtained pave the way to further improve lipid production by designing a fed-batch process in bioreactor.

Metal and Phosphate Ions Show Remarkable Influence on the Biomass Production and Lipid Accumulation in Oleaginous Mucor circinelloides

The biomass of Mucor circinelloides, a dimorphic oleaginous filamentous fungus, has a significant nutritional value and can be used for single cell oil production. Metal ions are micronutrients supporting fungal growth and metabolic activity of cellular processes. We investigated the effect of 140 different substrates, with varying amounts of metal and phosphate ions concentration, on the growth, cell chemistry, lipid accumulation, and lipid profile of M. circinelloides. A high-throughput set-up consisting of a Duetz microcultivation system coupled to Fourier transform infrared spectroscopy was utilized. Lipids were extracted by a modified Lewis method and analyzed using gas chromatography. It was observed that Mg and Zn ions were essential for the growth and metabolic activity of M. circinelloides. An increase in Fe ion concentration inhibited fungal growth, while higher concentrations of Cu, Co, and Zn ions enhanced the growth and lipid accumulation. Lack of Ca and Cu ions, as well as higher amounts of Zn and Mn ions, enhanced lipid accumulation in M. circinelloides. Generally, the fatty acid profile of M. circinelloides lipids was quite consistent, irrespective of media composition. Increasing the amount of Ca ions enhanced polyphosphates accumulation, while lack of it showed fall in polyphosphate.

Biotransformation of Animal Fat-By Products into ARA-Enriched Fermented Bioproducts by Solid-State Fermentation of Mortierella alpina

Solid-state fermentation (SSF) is a powerful fermentation technology for valorizing rest materials and by-products of different origin. Oleaginous Zygomycetes fungi are often used in SSF as an effective cell factory able to valorize a wide range of hydrophilic and hydrophobic substrates and produce lipid-enriched bioproducts. In this study, for the first time, the strain Mortierella alpina was used in SSF for the bioconversion of animal fat by-products into high value fermented bioproducts enriched with arachidonic acid (ARA). Two cereals-based matrixes mixed with four different concentrations of animal fat by-product were evaluated for finding optimal conditions of a fat-based SSF. All obtained fermented bioproducts were found to be enriched with ARA. The highest substrate utilization (25.8%) was reached for cornmeal and it was almost double than for the respective wheat bran samples. Similarly, total fatty acid content in a fermented bioproduct prepared on cornmeal is almost four times higher in contrast to wheat bran-based bioproduct. Although in general the addition of an animal fat by-product caused a gradual cessation of ARA yield in the obtained fermented bioproduct, the content of ARA in fungal biomass was higher. Thus, M. alpina CCF2861 effectively transformed exogenous fatty acids from animal fat substrate to ARA. Maximum yield of 32.1 mg of ARA/g of bioproduct was reached when using cornmeal mixed with 5% (w/w) of an animal fat by-product as substrate. Furthermore, implementation of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy in characterization of obtained SSF bioproducts was successfully tested as an alternative tool for complex analysis, compared to traditional time-consuming methods.

Revealing the Potential of Lipid and β-Glucans Coproduction in Basidiomycetes Yeast

Beta (β)-glucans are polysaccharides composed of D-glucose monomers. Nowadays, β-glucans are gaining attention due to their attractive immunomodulatory biological activities, which can be utilized in pharmaceutical or food supplementation industries. Some carotenogenic Basidiomycetes yeasts, previously explored for lipid and carotenoid coproduction, could potentially coproduce a significant amount of β-glucans. In the present study, we screened eleven Basidiomycetes for the coproduction of lipids and β-glucans. We examined the effect of four different C/N ratios and eight different osmolarity conditions on the coproduction of lipids and β-glucans. A high-throughput screening approach employing microcultivation in microtiter plates, Fourier Transform Infrared (FTIR) spectroscopy and reference analysis was utilized in the study. Yeast strains C. infirmominiatum CCY 17-18-4 and R. kratochvilovae CCY 20-2-26 were identified as the best coproducers of lipids and β-glucans. In addition, C. infirmominiatum CCY 17-18-4, R. kratochvilovae CCY 20-2-26 and P. rhodozyma CCY 77-1-1 were identified as the best alternative producers of β-glucans. Increased C/N ratio led to increased biomass, lipid and β-glucans production for several yeast strains. Increased osmolarity had a negative effect on biomass and lipid production while the β-glucan production was positively affected.

Microcultivation and FTIR spectroscopy-based screening revealed a nutrient-induced co-production of high-value metabolites in oleaginous Mucoromycota fungi

Mucoromycota fungi possess a versatile metabolism and can utilize various substrates for production of industrially important products, such as lipids, chitin/chitosan, polyphosphates, pigments, alcohols and organic acids. However, as far as commercialisation is concerned, establishing industrial biotechnological processes based on Mucoromycota fungi is still challenging due to the high production costs compared to the final product value. Therefore, the development of co-production concept is highly desired since more than one valuable product could be produced at the time and the process has a potentially higher viability. To develop such biotechnological strategy, we applied a high throughput approach consisting of micro-titre cultivation and FTIR spectroscopy. This approach allows single-step biochemical fingerprinting of either fungal biomass or growth media without tedious extraction of metabolites. The influence of two types of nitrogen sources and different levels of inorganic phosphorus on the co-production of lipids, chitin/chitosan and polyphosphates for nine different oleaginous Mucoromycota fungi was evaluated. FTIR analysis of biochemical composition of Mucoromycota fungi and biomass yield showed that variation in inorganic phosphorus had higher effect when inorganic nitrogen source-ammonium sulphate-was used. It was observed that: (1) Umbelopsis vinacea reached almost double biomass yield compared to other strains when yeast extract was used as nitrogen source while phosphorus limitation had little effect on the biomass yield; (2) Mucor circinelloides, Rhizopus stolonifer, Amylomyces rouxii, Absidia glauca and Lichtheimia corymbifera overproduced chitin/chitosan under the low pH caused by the limitation of inorganic phosphorus; (3) Mucor circinelloides, Amylomyces rouxii, Rhizopus stolonifer and Absidia glauca were able to store polyphosphates in addition to lipids when high concentration of inorganic phosphorus was used; (4) the biomass and lipid yield of high-value lipid producers Mortierella alpina and Mortierella hyalina were significantly increased when high concentrations of inorganic phosphorus were combined with ammonium sulphate, while the same amount of inorganic phosphorus combined with yeast extract showed negative impact on the growth and lipid accumulation. FTIR spectroscopy revealed the co-production potential of several oleaginous Mucoromycota fungi forming lipids, chitin/chitosan and polyphosphates in a single cultivation process.

The FT-IR and Raman Spectroscopies as Tools for Biofilm Characterization Created by Cariogenic Streptococci

Fourier transform infrared (FT-IR) and Raman spectroscopy and mapping were applied to the analysis of biofilms produced by bacteria of the genus Streptococcus. Bacterial biofilm, also called dental plaque, is the main cause of periodontal disease and tooth decay. It consists of a complex microbial community embedded in an extracellular matrix composed of highly hydrated extracellular polymeric substances and is a combination of salivary and bacterial proteins, lipids, polysaccharides, nucleic acids, and inorganic ions. This study confirms the value of Raman and FT-IR spectroscopies in biology, medicine, and pharmacy as effective tools for bacterial product characterization.

Pleurotus Mushrooms Content in Glucans and Ergosterol Assessed by ATR-FTIR Spectroscopy and Multivariate Analysis

Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy was used to monitor the infrared absorption spectra of 79 mushroom samples from 29 Pleurotus ostreatus, P. eryngii and P. nebrodensis strains cultivated on wheat straw, grape marc and/or by-products of the olive industry. The spectroscopic analysis provided a chemical insight into the mushrooms examined, while qualitative and quantitative differences in regions related to proteins, phenolic compounds and polysaccharides were revealed among the species and substrates studied. Moreover, by using advanced chemometrics, correlations of the recorded mushrooms’ spectra versus their content in glucans and ergosterol, commonly determined through traditional analytical techniques, allowed the development of models predicting such contents with a good predictive power (R²: 0.80–0.84) and accuracy (low root mean square error, low relative error and representative to the predicted compounds spectral regions used for the calibrations). Findings indicate that FTIR spectroscopy could be exploited as a potential process analytical technology tool in the mushroom industry to characterize mushrooms and to assess their content in bioactive compounds.

Growing a circular economy with fungal biotechnology: a white paper

Fungi have the ability to transform organic materials into a rich and diverse set of useful products and provide distinct opportunities for tackling the urgent challenges before all humans. Fungal biotechnology can advance the transition from our petroleum-based economy into a bio-based circular economy and has the ability to sustainably produce resilient sources of food, feed, chemicals, fuels, textiles, and materials for construction, automotive and transportation industries, for furniture and beyond. Fungal biotechnology offers solutions for securing, stabilizing and enhancing the food supply for a growing human population, while simultaneously lowering greenhouse gas emissions. Fungal biotechnology has, thus, the potential to make a significant contribution to climate change mitigation and meeting the United Nation’s sustainable development goals through the rational improvement of new and established fungal cell factories. The White Paper presented here is the result of the 2nd Think Tank meeting held by the EUROFUNG consortium in Berlin in October 2019. This paper highlights discussions on current opportunities and research challenges in fungal biotechnology and aims to inform scientists, educators, the general public, industrial stakeholders and policymakers about the current fungal biotech revolution.

Simultaneous lipid production for biodiesel feedstock and decontamination of sago processing wastewater using Candida tropicalis ASY2

BACKGROUND

Without sufficient alternatives to crude oil, as demand continues to rise, the global economy will undergo a drastic decline as oil prices explode. Dependence on crude oil and growing environmental impairment must eventually be overcome by creating a sustainable and profitable alternative based on renewable and accessible feedstock. One of the promising solutions for the current and near-future is the substitution of fossil fuels with sustainable liquid feedstock for biofuel production. Among the different renewable liquid feedstock's studied, wastewater is the least explored one for biodiesel production. Sago wastewater is the byproduct of the cassava processing industry and has starch content ranging from 4 to 7%. The present investigation was aimed to produce microbial lipids from oleaginous yeast, Candida tropicalis ASY2 for use as biodiesel feedstock and simultaneously decontaminate the sago processing wastewater for reuse. Initial screening of oleaginous yeast to find an efficient amylolytic with maximum lipid productivity resulted in a potent oleaginous yeast strain, C. tropicalis ASY2, that utilizes SWW as a substrate. Shake flask experiments are conducted over a fermentation time of 240 h to determine a suitable fatty acid composition using GC-FID for biodiesel production with simultaneous removal of SWW pollutants using ASY2.

RESULTS

The maximum biomass of 0.021 g L^-1 h^-1 and lipid productivity of 0.010 g L^-1 h^-1 was recorded in SWW with lipid content of 49%. The yeast strain degraded cyanide in SWW (79%) and also removed chemical oxygen demand (COD), biological oxygen demand (BOD), nitrate (NO₃), ammoniacal (NH₄), and phosphate (PO₄) ions (84%, 92%, 100%, 98%, and 85%, respectively). GC-FID analysis of fatty acid methyl esters (FAME) revealed high oleic acid content (41.33%), which is one of the primary fatty acids for biodiesel production.

CONCLUSIONS

It is evident that the present study provides an innovative and ecologically sustainable technology that generates valuable fuel, biodiesel using SWW as a substrate and decontaminates for reuse.