Comparative Proteome Profiling of Extracellular Vesicles from Three Growth Phases of Haematococcus pluvialis under High Light and Sodium Acetate Stresses.

Extracellular vesicles (EVs) are nano-sized particles involved in intercellular communications that intrinsically possess many attributes as a modern drug delivery platform. Haematococcus pluvialis-derived EVs (HpEVs) can be potentially exploited as a high-value-added bioproduct during astaxanthin production. The encapsulation of HpEV cargo is a crucial key for the determination of their biological functions and therapeutic potentials. However, little is known about the composition of HpEVs, limiting insights into their biological properties and application characteristics. This study examined the protein composition of HpEVs from three growth phases of H. pluvialis grown under high light (350 µmol·m-2·s-1) and sodium acetate (45 mM) stresses. A total of 2038 proteins were identified, the majority of which were associated with biological processes including signal transduction, cell proliferation, cell metabolism, and the cell response to stress. Comparative analysis indicated that H. pluvialis cells sort variant proteins into HpEVs at different physiological states. It was revealed that HpEVs from the early growth stage of H. pluvialis contain more proteins associated with cellular functions involved in primary metabolite, cell division, and cellular energy metabolism, while HpEVs from the late growth stage of H. pluvialis were enriched in proteins involved in cell wall synthesis and secondary metabolism. This is the first study to report and compare the protein composition of HpEVs from different growth stages of H. pluvialis, providing important information on the development and production of functional microalgal-derived EVs.

Roles of nanoparticles in arsenic mobility and microbial community composition in arsenic-enriched soils.

Environmental effects of nano remediation engineering of arsenic (As) pollution need to be considered. In this study, the roles of Fe2O3 and TiO2 nanoparticles (NPs) on the microbial mediated As mobilization from As contaminated soil were investigated. The addition of Fe2O3 and TiO2 NPs restrained As(V) release, and stimulated As(III) release. As(V) concentration decreased by 94% and 93% after Fe2O3 addition, and decreased by 89% and 45% after TiO2 addition compared to the Biotic and Biotic+Acetate (amended with sodium acetate) controls, respectively. The maximum values of As(III) were 20.5 and 27.1 µg/L at 48 d after Fe2O3 and TiO2 NPs addition, respectively, and were higher than that in Biotic+Acetate control (12.9 µg/L). The released As co-precipitated with Fe in soils in the presence of Fe2O3 NPs, but adsorbed on TiO2 NPs in the presence of TiO2 NPs. Moreover, the addition of NPs amended with sodium acetate as the electron donor clearly promoted As(V) reduction induced by microbes. The NPs addition changed the relative abundance of soil bacterial community, while Proteobacteria (42.8%-70.4%), Planctomycetes (2.6%-14.3%), and Firmicutes (3.5%-25.4%) were the dominant microorganisms in soils. Several potential As/Fe reducing bacteria were related to Pseudomonas, Geobacter, Desulfuromonas, and Thiobacillus. The addition of Fe2O3 and TiO2 NPs induced to the decrease of arrA gene. The results indicated that the addition of NPs had a negative impact on soil microbial population in a long term. The findings offer a relatively comprehensive assessment of Fe2O3 and TiO2 NPs effects on As mobilization and soil bacterial communities.

Acetyl-CoA is a key molecule for nephron progenitor cell pool maintenance.

Nephron endowment at birth impacts long-term renal and cardiovascular health, and it is contingent on the nephron progenitor cell (NPC) pool. Glycolysis modulation is essential for determining NPC fate, but the underlying mechanism is unclear. Combining RNA sequencing and quantitative proteomics we identify 267 genes commonly targeted by Wnt activation or glycolysis inhibition in NPCs. Several of the impacted pathways converge at Acetyl-CoA, a co-product of glucose metabolism. Notably, glycolysis inhibition downregulates key genes of the Mevalonate/cholesterol pathway and stimulates NPC differentiation. Sodium acetate supplementation rescues glycolysis inhibition effects and favors NPC maintenance without hindering nephrogenesis. Six2Cre-mediated removal of ATP-citrate lyase (Acly), an enzyme that converts citrate to acetyl-CoA, leads to NPC pool depletion, glomeruli count reduction, and increases Wnt4 expression at birth. Sodium acetate supplementation counters the effects of Acly deletion on cap-mesenchyme. Our findings show a pivotal role of acetyl-CoA metabolism in kidney development and uncover new avenues for manipulating nephrogenesis and preventing adult kidney disease.

Improvement and enhancement of oligosaccharide production from Lactobacillus acidophilus using statistical experimental designs and its inhibitory effect on colon cancer.

Colorectal cancer (CRC) is the third cause of death by cancers worldwide and is one of the most common cancer types reported in both Egypt and the United States. The use of probiotics as a dietary therapy is increasing either as a prevention or as a treatment for many diseases, particularly, in the case of CRC. The increasing acceptance of lactic acid bacterial (LAB) oligosaccharides as bioactive agents has led to an increase in the demand for the large-scale production of LAB-oligosaccharides using fermentation technology. Therefore, in the current study, we are using the Plackett- Burman design (PBD) approach, where sixteen experimental trials were applied to optimize the production of the target oligosaccharide LA-EPS-20079 from Lactobacillus acidophilus. Glucose, yeast extract and sodium acetate trihydrate were the top three significant variables influencing LA-EPS production. The maximum concentration of LA-EPS-20079 achieved by L. acidophilus was 526.79 µg/ml. Furthermore, Box-Behnken design (BBD) as response surface methodology (RSM) was used to complete the optimization procedure. The optimal levels of the chosen variables which were 30.0 g/l, glucose; 5 g/l, yeast extract and 10.0 g/l sodium acetate trihydrate with the predicted LA-EPS-20079 concentration of 794.82 µg/ml. Model validity reached 99.93% when the results were verified. Both optimized trials showed great cytotoxic effects against colon cancer line (CaCo-2) with inhibition percentages ranging from 64.6 to 81.9%. Moreover, downregulation in the expression level of BCL2 and Survivin genes was found with a fold change of 3.377 and 21.38, respectively. Finally, we concluded that the optimized LA-EPS-20079 has maintained its anticancer effect against the CaCo-2 cell line that was previously reported by our research group.

Mixotrophic Cultivation of a Native Cyanobacterium, Pseudanabaena mucicola GO0704, to Produce Phycobiliprotein and Biodiesel.

Global warming has accelerated in recent decades due to the continuous consumption of petroleum-based fuels. Cyanobacteria-derived biofuels are a promising carbon-neutral alternative to fossil fuels that may help achieve a cleaner environment. Here, we propose an effective strategy based on the large-scale cultivation of a newly isolated cyanobacterial strain to produce phycobiliprotein and biodiesel, thus demonstrating the potential commercial applicability of the isolated microalgal strain. A native cyanobacterium was isolated from Goryeong, Korea, and identified as Pseudanabaena mucicola GO0704 through 16s RNA analysis. The potential exploitation of P. mucicola GO0704 was explored by analyzing several parameters for mixotrophic culture, and optimal growth was achieved through the addition of sodium acetate (1 g/l) to the BG-11 medium. Next, the cultures were scaled up to a stirred-tank bioreactor in mixotrophic conditions to maximize the productivity of biomass and metabolites. The biomass, phycobiliprotein, and fatty acids concentrations in sodium acetate-treated cells were enhanced, and the highest biodiesel productivity (8.1 mg/l/d) was achieved at 96 h. Finally, the properties of the fuel derived from P. mucicola GO0704 were estimated with converted biodiesels according to the composition of fatty acids. Most of the characteristics of the final product, except for the cloud point, were compliant with international biodiesel standards [ASTM 6761 (US) and EN 14214 (Europe)].

Antioxidant Activity and Kinetic Characterization of Chlorella vulgaris Growth under Flask-Level Photoheterotrophic Growth Conditions.

C. vulgaris is a unicellular microalgae, whose growth depends on the conditions in which it is found, synthesizing primary and secondary metabolites in different proportions. Therefore, we analyzed and established conditions in which it was possible to increase the yields of metabolites obtained at the flask level, which could then be scaled to the photobioreactor level. As a methodology, a screening design was applied, which evaluated three factors: type of substrate (sodium acetate or glycerol); substrate concentration; and exposure-time to red light (photoperiod: 16:8 and 8:16 light/darkness). The response variables were: cell division; biomass; substrate consumption; and antioxidant activity in intracellular metabolites (ABTS•+ and DPPH•). As a result, the sodium acetate condition of 0.001 g/L, in a photoperiod of 16 h of light, presented a doubling time (Td = 4.84 h) and a higher rate of division (σ = 0.20 h-1), having a final biomass concentration of 2.075 g/L. In addition, a higher concentration of metabolites with antioxidant activity was found in the sodium acetate (0.629 Trolox equivalents mg/L ABTS•+ and 0.630 Trolox equivalents mg/L DPPH•). For the glycerol, after the same photoperiod (16 h of light and 8 h of darkness), the doubling time (Td) was 4.63 h, with a maximum division rate of σ = 0.18 h-1 and with a biomass concentration at the end of the kinetics of 1.4 g/L. Sodium acetate under long photoperiods, therefore, is ideal for the growth of C. vulgaris, which can then be scaled to the photobioreactor level.

Diversity-triggered bottom-up trophic interactions impair key soil functions under lindane pollution stress.

A growing amount of evidence suggests that microbial diversity loss may have negative effects on soil ecosystem function. However, less attention has been paid to the determinants of the relationship between community diversity and soil functioning under pollution stress. Here we manipulated microbial diversity to observe how biotic and abiotic factors influenced soil multi-functions (e.g. lindane degradation, soil respiration and nutrient cycling). Results showed that protist community was more sensitive to dilution, pollution stress, and sodium acetate addition than bacterial and fungal community. Acetate addition accelerated the lindane removal. Any declines in microbial diversity reduced the specialized soil processes (NO3-N production, and N2O flux), but increased soil respiration rate. Dilution led to a significant increase in consumers-bacterial and fungi-bacterial interaction as evidenced by co-occurrence network, which possibly played roles in maintaining microbiome stability and resilience. Interestingly, pollution stress and resource availability weaken the relationship between microbial diversity and soil functions through the bottom-up trophic interaction and environmental preference of soil microbiome. Overall, this work provides experimental evidence that loss in microbial diversity, accompanied with changes in trophic interactions mediated biotic and abiotic factors, could have important consequences for specialized soil functioning in farmland ecosystems.

Production of caproic acid by Rummeliibacillus suwonensis 3B-1 isolated from the pit mud of strong-flavor baijiu.

Caproic acid is the precursor of ethyl caproate, the main representative flavor substance of strong-flavor baijiu (SFB). Caproic acid-producing bacteria are considered to be the most important type of acid-producing microorganisms in the pit mud of the SFB ecosystem. In this study, the Rummeliibacillus suwonensis 3B-1 with a high yield of caproic acid (4.064 g/L) was screened from SFB pit mud. The genome of the R. suwonensis 3B-1 was sequenced, the total size was found to be 4117,671 bp and a calculated GC content of 35.86%. The caproic acid biosynthesis pathway was identified and analyzed, and it showed that 3B-1 could not only use ethanol, but it could also use glucose and other carbon sources as substrates to produce caproic acid. According to the genome analysis and with an optimized medium, the optimal conditions for caproic acid production were yeast powder at 3 g/L, sodium acetate at 15 g/L, and 1% biotin at 8 mL/100 mL. The yield of caproic acid reached 4.627 g/L, an increase of 13.9%, which was higher than that of general caproic acid bacteria. This is the first report of the synthesis of caproic acid by R. suwonensis. This strain could be used to produce caproic acid, an artificial pit mud preparation, and/or an enhanced inoculum in the production of SFB.

Mechanisms of Sodium-Acetate-Induced DHA Accumulation in a DHA-Producing Microalga, Crypthecodinium sp. SUN.

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid (PUFA) that is critical for the intelligence and visual development of infants. Crypthecodinium is the first microalga approved by the Food and Drug Administration for DHA production, but its relatively high intracellular starch content restricts fatty acid accumulation. In this study, different carbon sources, including glucose (G), sodium acetate (S) and mixed carbon (M), were used to investigate the regulatory mechanisms of intracellular organic carbon distribution in Crypthecodinium sp. SUN. Results show that glucose favored cell growth and starch accumulation. Sodium acetate limited glucose utilization and starch accumulation but caused a significant increase in total fatty acid (TFA) accumulation and the DHA percentage. Thus, the DHA content in the S group was highest among three groups and reached a maximum (10.65% of DW) at 96 h that was 2.92-fold and 2.24-fold of that in the G and M groups, respectively. Comparative transcriptome analysis showed that rather than the expression of key genes in fatty acids biosynthesis, increased intracellular acetyl-CoA content appeared to be the key regulatory factor for TFA accumulation. Additionally, metabolome analysis showed that the accumulated DHA-rich metabolites of lipid biosynthesis might be the reason for the higher TFA content and DHA percentage of the S group. The present study provides valuable insights to guide further research in DHA production.

[Succession and PICRUSt2-based Predicted Functional Analysis of Microbial Communities During the Sludge Bulking Occurrence and Restoration in One-stage Combined Partial Nitritation and ANAMMOX Process].

This study was based on the pilot one-stage combined partial nitritation and ANAMMOX process (CPNA), using data mining and analysis of 16S rRNA high-throughput sequencing data of activated sludge in the process of sludge bulking and recovery, combined with PISCRUSt2. The function prediction analysis aimed to reveal the microbial community changes and the characteristics of nitrogen metabolism and carbon metabolism at different stages of sludge bulking and recovery of the one-stage CPNA process. The results of the study showed that the microbial α-diversity in the sludge bulking and recovery process first increased and then declined. The relative abundance of Nitrosomonas, Candidatus_Brocadia, and Thaurea decreased in the sludge-bulking stage from 12.36%, 11.86%, and 0.272% to 5.97%, 8.30%, and 0.061%, whereas the relative abundance of Candidatus Kuenenia remained stable. The relative abundance of Levilinea, Longilinea, and Turicibacter increased from 0.031%, 0.018%, and 0.009% to 0.055%, 0.025%, and 0.033%. The PICRUSt2 function prediction analysis results showed that there were a total of 47 functional enzyme genes involved in nitrogen metabolism, of which nitrification, denitrification, dissimilative nitrate reduction (DNRA), assimilation nitrate reduction (ANRA), and nitrogen fixation were relatively abundant. The degrees of each had changed. During the sludge-bulking stage, the relative abundance of the ammonia monooxygenase gene (pmoABC-amoABC) and the hydroxylamine dehydrogenase gene hao decreased, whereas the relative abundance of the nitrate-reducing gene increased at the initial stage and then showed a downward trend. Carbon metabolism analysis showed that sodium acetate had a promoting effect on the heterotrophic growth of the CPNA process, but the energy metabolism and glucose production of sodium acetate were not active.

Enhanced sulfonamides removal via microalgae-bacteria consortium via co-substrate supplementation.

Both co-cultivation and co-substrate addition strategies have exhibited massive potential in microalgae-based antibiotic bioremediation. In this study, glucose and sodium acetate were employed as co-substrate in the cultivation of microalgae-bacteria consortium for enhanced sulfadiazine (SDZ) and sulfamethoxazole (SMX) removal. Glucose demonstrated a two-fold increase in biomass production with a maximum specific growth rate of 0.63 ± 0.01 d-1 compared with sodium acetate. The supplementation of co-substrate enhanced the degradation of SDZ significantly up to 703 ± 18% for sodium acetate and 290 ± 22% for glucose, but had almost no effect on SMX. The activities of antioxidant enzymes, including peroxidase, superoxide dismutase and catalase decreased with co-substrate supplementation. Chlorophyll a was associated with protection against sulfonamides and chlorophyll b might contribute to SDZ degradation. The addition of co-substrates influenced bacterial community structure greatly. Glucose enhanced the relative abundance of Proteobacteria, while sodium acetate improved the relative abundance of Bacteroidetes significantly.

Genome-Based Taxonomy of Brevundimonas with Reporting Brevundimonas huaxiensis sp. nov.

Brevundimonas is a genus of Gram-negative bacteria widely distributed in nature and is also an opportunistic pathogen causing health care-associated infections. Brevundimonas strain 090558T was recovered from a blood culture of a cancer patient and was subjected to genome sequencing and analysis. The average nucleotide identity and in silico DNA-DNA hybridization values between 090558T and type strains of Brevundimonas species were 78.76% to 93.94% and 19.8% to 53.9%, respectively, below the cutoff to define bacterial species. Detailed phenotypic tests were performed, suggesting that 090558T can be differentiated from other Brevundimonas species by its ability to assimilate sodium acetate but not to utilize glucose, trypsin, or ß-glucosidase. Strain 090558T (GDMCC 1.1871T or KCTC 82165T) therefore represents a novel Brevundimonas species, for which the name Brevundimonas huaxiensis sp. nov. is proposed. All Brevundimonas genomes available in GenBank (accessed on 25 January 2021) were retrieved, discarding those labeled "excluded from RefSeq" by GenBank, and included 82 genomes for precise species curation. In addition to the 21 Brevundimonas species with genomes of type strains available, we identified 29 Brevundimonas taxa that either belong to the 12 Brevundimonas species without available genomes of type strains or represent novel species. We found that more than half (57.3%) of the 82 Brevundimonas genomes need to be corrected for species assignation, including species mislabeling of a type strain. Our analysis highlights the complexity of Brevundimonas taxonomy. We also found that only some Brevundimonas species are associated with human infections, and more studies are warranted to understand their pathogenicity and epidemiology. IMPORTANCEBrevundimonas is a genus of the family Caulobacteraceae and comprises 33 species. Brevundimonas can cause various infections but remains poorly studied. In this study, we reported a novel Brevundimonas species, Brevundimonas huaxiensis, based on genome and phenotype studies of strain 090558T recovered from human blood. We then examined the species assignations of all Brevundimonas genomes (n = 82) in GenBank and found that in addition to the known Brevundimonas species with genome sequences of type strains available, there are 29 Brevundimonas taxa based on genome analysis, which need to be further studied using phenotype-based methods to establish their species status. Our study significantly updates the taxonomy of Brevundimonas and enhances our understanding of this genus of clinical relevance. The findings also encourage future studies on the characterization of novel Brevundimonas species.

High-throughput transcriptome sequencing and comparative analysis of Escherichia coli and Schizosaccharomyces pombe in respiratory and fermentative growth.

In spite of increased complexity in eukaryotes compared to prokaryotes, several basic metabolic and regulatory processes are conserved. Here we explored analogies in the eubacteria Escherichia coli and the unicellular fission yeast Schizosaccharomyces pombe transcriptomes under two carbon sources: 2% glucose; or a mix of 2% glycerol and 0.2% sodium acetate using the same growth media and growth phase. Overall, twelve RNA-seq libraries were constructed. A total of 593 and 860 genes were detected as differentially expressed for E. coli and S. pombe, respectively, with a log2 of the Fold Change ≥ 1 and False Discovery Rate ≤ 0.05. In aerobic glycolysis, most of the expressed genes were associated with cell proliferation in both organisms, including amino acid metabolism and glycolysis. In contrast in glycerol/acetate condition, genes related to flagellar assembly and membrane proteins were differentially expressed such as the general transcription factors fliA, flhD, flhC, and flagellum assembly genes were detected in E. coli, whereas in S. pombe genes for hexose transporters, integral membrane proteins, galactose metabolism, and ncRNAs related to cellular stress were overexpressed. In general, our study shows that a conserved "foraging behavior" response is observed in these eukaryotic and eubacterial organisms in gluconeogenic carbon sources.

The response surface optimization of exopolysaccharide produced by Weissella confusa XG-3 and its rheological property.

The response surface methodology (RSM) was used to optimize the exopolysaccharide (EPS) production by a lactic acid bacteria (LAB) Weissella confusa XG-3. Two-level factorial design screened three significantly influencing factors sucrose, initial pH and sodium acetate. Central composite design (CCD) predicted under the condition of sucrose 80.1 g L-1, initial pH 5.8 and sodium acetate 3.7 g L-1, the maximal EPS yield obtained a 2.9-fold increase, reaching 97.5 ± 1.1 g L-1. This maximal value was far exceeding EPS production by other W. confusa species strains reported so far. The results suggested that W. confusa XG-3 had a potential for large-scale EPS production. The rheological properties of XG-3 EPS was further investigated. It was a typical non-Newtonian fluid, exhibiting pseudo-plastic behavior. The EPS concentration and temperature exerted positive and negative impact on apparent viscosity, respectively. The XG-3 EPS maintained relatively higher viscosity at moderate pH (6-8). The intrinsic viscosity [η] was 409.7 (25 °C) and 201.7 (35 °C), which was relevant to temperature but irrelevant to EPS concentration. This EPS efficiently coagulated sucrose-supplemented milk in a concentration-dependent manner. These results indicated that XG-3 EPS had an applicable potential in food processing fields especially dairy products.

Microbial degradation of two highly persistent fluorinated fungicides - epoxiconazole and fludioxonil.

Biodegradation of two highly persistent fluorinated fungicides, epoxiconazole (EPO) and fludioxonil (FLU), by microbial consortia enriched from estuarine sediment and agricultural soil is reported. After an enrichment period of 6 months, four microbial consortia were able to completely remove and defluorinate the fungicides in co-metabolic conditions. Defluorination was biologically mediated and results suggest it is not a primary catabolic step, as fungicide removal was always faster than its defluorination. Three of the four enriched consortia had similar biodegradation performances in the absence of a co-substrate. Biodegradation kinetics revealed that microbial degradation followed a first-order kinetics, with cultures being capable of biodegrading concentrations up to 10 mg L-1 of EPO or FLU, in a maximum of 21 days. Estimated half-life values for these compounds were significantly lower than those reported in literature, highlighting the unique metabolic performance of the obtained consortia. Analysis of their microbial composition revealed that they integrate several bacterial species belonging to the Proteobacteria phylum, with the most common genera being Pseudomonas, Ochrobactrum and Comamonas. This is the first study providing clear evidence on the biodegradation of EPO and FLU, opening doors for the design of bioremediation technologies for the recovery of ecosystems polluted with such recalcitrant compounds.

Mixture design as a potential tool in modeling the effect of light wavelength on Dunaliella salina cultivation: an alternative solution to increase microalgae lipid productivity for biodiesel production.

For a feasible microalgae biodiesel, increasing lipid productivity is a key parameter. An important cultivation parameter is light wavelength (λ). It can affect microalgal growth, lipid yield, and fatty acid composition. In the current study, the mixture design was used as an alternative to model the influence of the λ on the Dunaliella salina lipid productivity. The illumination was considered to be the mixture of different λ (the light colors blue, red, and green). All experiments were performed with and without sodium acetate (4 g/L), as carbon source, allowing the identification of the impact of the cultivation regimen (autotrophic or mixotrophic). Without sodium acetate, the highest lipid productivity was obtained using blue and red light. The use of mixotrophic cultivations significantly enhanced the results. The optimum obtained result was mixotrophic cultivation under 65% blue and 35% green light, resulting in biomass productivity of 105.06 mgL-1day-1, a lipid productivity of 53.47 mgL-1day-1, and lipid content of 50.89%. The main fatty acids of the oil obtained in this cultivation were oleic acid (36.52%) and palmitic acid (18.31%).

Artificial color light sources and precursor feeding enhance plumbagin production of the carnivorous plants Drosera burmannii and Drosera indica.

Plumbagin is the main pharmacologically active compound of carnivorous plants in the genera Drosera. It possesses various pharmacological activities, including anticancer and antimalarial activities, and is used in traditional medicine. In this study, we reported a sustainable production system of plumbagin by adding sodium acetate and L-alanine as precursors to in vitro cultures of Drosera burmannii Vahl and Drosera indica L. In addition, plumbagin production was reported in the cultures subjected to different color LED lights. The highest plumbagin level (aerial part 14.625 ±â€¯1.007 mg·g-1 DW and root part 1.806 ±â€¯0.258 mg·g-1 DW) was observed in D. indica cultured under blue LED light for 14 days, and further culturing did not increase plumbagin production. In addition, plumbagin enhancement by precursor feeding (9.850 ±â€¯0.250 mg·g-1 DW, 1.2-fold) was observed in the aerial part of D. indica treated with 50 mg·L-1 sodium acetate for 3 days. Comparing both plants, up to 700-fold higher plumbagin was observed in D. indica than in D. burmannii. Moreover, in both plants, the aerial part accumulated higher plumbagin (up to 10-fold) than the roots. This is the first report on the effect of artificial LED lights on the plumbagin level of Dorsera plants. The culturing of D. indica under blue LED light showed enhanced plumbagin levels and suggests a fast and simple system for the in vitro production of plumbagin.

Effect of carbon source on lipid accumulation and biodiesel production of Yarrowia lipolytica.

Yarrowia lipolytica (Y. lipolytica) is an oleaginous yeast that can utilize hydrophobic substrates as carbon source to produce single-cell lipids for biodiesel production. This study attempts to increase the lipid accumulation ability of Y. lipolytica by first gradually elevating pure oil substrate concentration during the cultivation and then adding short-chain carbon compounds, such as glucose and sodium acetate, to a culture substance according to the optimal oil concentration. Results showed that Y. lipolytica cultured under 40.0 g L-1 oil concentration showed higher lipids (2.97 g L-1) and lipid content (37.35%, DW) compared with that cultured under 20.0 g L-1, where the corresponding values were 1.91 g L-1 and 24.46%. By contrast, the lipid content of Y. lipolytica increased from 37.35 to 41.50% when the substrate was changed from 40.0 g L-1 pure oil to 5% sodium acetate combined with 95% oil under the same total carbon concentration. However, lipid accumulation did not increase even though 15% sodium acetate or 5% glucose, or 15% glucose was added to the combined substrate. Moreover, the lipid biomodification of Y. lipolytica was evident when it was cultured under the oil concentration of 20.0 g L-1. Therefore, the lipid accumulation of Y. lipolytica can be elevated through the gradient increase of oil concentration and by adding a suitable amount of easily degradable carbon source. Furthermore, the lipid biomodification of Y. lipolytica improves biodiesel quality.

The potential growth and lipid accumulation in Coccomyxa subellipsoidea triggered by glucose combining with sodium acetate.

Carbon sources whether types or magnitudes were fateful in terms of stimulating growth and lipids accumulation in microalgae applied for biodiesel production. The set scenario of this work was to investigate the feasibilities of glucose (G) combining with sodium acetate (SA) carbon sources in enhancing biomass and lipid accumulation in Coccomyxa subellipsoidea. The results demonstrated that C. subellipsoidea subjected to the combination feeding of G (20 g/L) and SA (12 g/L) achieved the favorable biomass (5.22 g/L) and lipid content (52.16%). The resulting lipid productivity (388.96 mg/L/day) was 1.33- to 7.60-fold more than those of sole G or SA as well as other combinations of G and SA. Even though the total fatty acids of C. subellipsoidea cells treated with the optimal combination of G and SA showed no noticeable increment in comparison with sole G or SA, the proportion of monounsaturated C18:1 (over 48.69%) and the content of C18:3 (< 12%) were commendable in high-quality algal biodiesel production. Further, such fascinating lipid accumulation in C. subellipsoidea cells treated with G combining with SA might be attributed to that G promoted glycolysis as well as SA activated glyoxylate shunt and TCA cycle to synergistically provide sufficient acetyl-CoA precursors for lipid accumulation. These findings hinted the potential of the combination of carbon sources in enhancing the overall lipid productivity to offset alga-based biodiesel production cost and would guide other alga strains cultivation.

A pilot-scale deep bed denitrification filter for secondary effluent treatment using sodium acetate as external carbon.

A pilot-scale quartz sand deep bed denitrification filter (DBDF) using sodium acetate as the additional carbon source was implemented to treat secondary effluent, with a high nitrate nitrogen (NO3 -N) concentration and low C/N ratio, from an urban municipal water resource recovery facility. By the 18th day, results showed that the removal efficiency of NO3 -N and the chemical oxygen demand (COD) were stable at above 85% and 70%, respectively. When the filter layer depth was set to 1,600 mm and the concentration of additional sodium acetate was maintained at 51 mg/L, the total nitrogen and COD concentrations of the DBDF effluent were stabilized below 5 and 30 mg/L, respectively. The quartz sand DBDF had a good effect on the removal of dissolved organic matter, especially for aromatic protein-like and tryptophan protein-like substances. Bacteria with denitrification function, such as Cloacibacterium and Zoogloea, became increasingly dominant with increasing filling layer depth. PRACTITIONER POINTS: The denitrification filter had a good effect on the removal of aromatic protein-like and tryptophan protein-like substances. Cloacibacterium and Zoogloea became increasingly dominant with increasing filling layer depth.