Type Of Carbon Source Research Articles

In-situ construction of magnetic raspberry-like ZnO/C supporting different transition metal (Fe, Co, Ni) species with high adsorption-photocatalysis efficiency

Organic pollutants that are difficult to degrade with potential biological toxicity are challenges in the environmental field. Magnetic raspberry microspheres of three transition metal (Fe, Co, Ni) nitrate sources were prepared by simple chemical route using zinc gluconate aqueous solution as precursor, the adsorption-catalytic efficiency of which was studied in detail. The effects of the types of transition metal sources, zinc sources, carbon sources and addition amount on the phase composition, structure and properties were investigated. The specific surface area of the products under the optimal conditions is 531, 687 and 592 m2/g, which are 28, 36 and 31 times higher than that of the products with glucose porous carbon alone. In addition, the products also show excellent photoelectric, paramagnetic properties and stability. Interestingly, the phase compositions are Fe/ZnO/ZnFe2O4, Co/ZnO and ZnO/Ni3ZnC0.7 coated with carbon substrate, quite different when the same amount of Fe, Co and Ni nitrates introduced into hydrothermal system, demonstrating heterojunction/doping, doping and heterojunction effects, respectively. Within 40 min, the microspheres could rapidly remove 65.6 mg/g, 146.1 mg/g and 114.6 mg/g of Rhodamine B, respectively, higher than the adsorption of glucose carbon (18.8 mg/g), of which the adsorption processes were in accordance with Pseudo second kinetics and Langmuir monolayer adsorption. These findings not only provide a strategy for the construction of magnetic raspberry microspheres ZnO/C composites with transition metal nitrate salts, but also contribute to the analysis of adsorption-photocatalysis mechanism, which has practical application in the environmental field.

Effects of adding different carbon sources on the microbial behavior of sulfate-reducing bacteria in sulfate-containing wastewater

Excessive sulfate levels pose a threat to the environment and human health. To address the problem of sulfate pollution and provide a basis for sulfate removal and sulfur recovery, this study searched for organics readily available to sulfate-reducing bacteria (SRB). To investigate the utilization characteristics of different organic matter by SRB, this study investigated microbial sulfate reduction under different carbon sources, including alcohols, small organic acids and sugars, and at different carbon-sulfur (C/S) ratios. Differences in the conversion pathways of different carbon sources were the main factors affecting the sulfate reduction process. Due to the presence of incompletely oxidizing SRB (incomplete oxidizers), the rapid incomplete oxidation of sugars and alcohols that produced acetic acid inhibited the activity of SRB by lowering the solution pH. In contrast, the conversion of small organic acids with stable pH produced more sulfides. Among all the tested carbon sources, faster sulfate reduction was observed using propionate, lactate, ethanol and formate, and the optimal C/S ratio was three times higher than the stoichiometric ratio. The type of carbon source also influenced sulfate reduction by shaping the microbial community. The presence of ethanol and propionate favored the vigorous proliferation of the incomplete oxidizers Desulfomicrobiaceae and Desulfovibrionaceae, while the completely oxidizing SRB Desulfuromonadaceae and Desulfococcaceae dominated formate-containing cultures. Incomplete oxidizers generally grow faster and tend to have higher electron transport system activity but lower carbon source utilization efficiency.

The polyHIS Tract of Yeast AMPK Coordinates Carbon Metabolism with Iron Availability.

Energy status in all eukaryotic cells is sensed by AMP-kinases. We have previously found that the poly-histidine tract at the N-terminus of S. cerevisiae AMPK (Snf1) inhibits its function in the presence of glucose via a pH-regulated mechanism. We show here that in the absence of glucose, the poly-histidine tract has a second function, linking together carbon and iron metabolism. Under conditions of iron deprivation, when different iron-intense cellular systems compete for this scarce resource, Snf1 is inhibited. The inhibition is via an interaction of the poly-histidine tract with the low-iron transcription factor Aft1. Aft1 inhibition of Snf1 occurs in the nucleus at the nuclear membrane, and only inhibits nuclear Snf1, without affecting cytosolic Snf1 activities. Thus, the temporal and spatial regulation of Snf1 activity enables a differential response to iron depending upon the type of carbon source. The linkage of nuclear Snf1 activity to iron sufficiency ensures that sufficient clusters are available to support respiratory enzymatic activity and tests mitochondrial competency prior to activation of nuclear Snf1.

Study on Biodegradation Characteristics of Industrial Phenol-Containing Wastewater by Biological Co-Metabolism Technology

Biological co-metabolism is an economical and efficient technique for treating refractory organic matter, and in recent years, it has been widely used in the treatment of chlorophenol-containing wastewater. It has been found that many conditions affect the bio co-metabolism efficiency, such as the carbon source type, carbon source content, microorganism types, and environmental factors. The carbon source concentration experiment showed that when the dosage ratio of sodium acetate to black aniline powder was 1:2, the degradation rate of black aniline powder was 82%, and the removal rate was 92.9%. When tetrachlorophenol increased from 210 mg/L to 2100 mg/L, the tetrachlorophenol was increased in the effluent, and the microorganism's activity was inhibited. Besides, the sedimentation performance of activated sludge was also damaged. The temperature test showed that the removed 4-chlorophenol was as high as 2100 mg/L at 35 °C, and the apparent 4-chlorophenol residue in the effluent could be detected at 20 °C. Therefore, by appropriately controlling the external operating conditions of the reactor, the co-metabolism of refractory organic such as chlorophenols can be achieved.

Coupled mixotrophic denitrification and utilization of refractory organics driven by Mn redox circulation for significantly enhanced nitrogen removal

Coupled mixotrophic denitrification and degradation of organics driven by redox transition of Mn for nitrogen removal has attracted much attention. Herein, this study explored the removal performance and mechanisms for nitrogen and refractory organics from secondary effluent in up-flow MnOx biofilter. Results showed that the removal of organics and nitrate was significantly enhanced by the synergistic process of heterotrophic denitrification and Mn(II)-driven autotrophic denitrification (MnAD), which were originated from the facilitation of Mn circulation. But nitrate removal was closely related to the types of carbon source and Mn(II) concentration. Single small molecular carbon source (glucose) performed better than mixed carbon source (humic acid and glucose) in nitrate removal process (74.8% in stage 1–2 vs. 54.1% in stage 3–5). And raising external Mn(II) concentration increased the contribution of MnAD (60.2% in stage 5 vs. 46.5% in stage 3) to nitrate removal. Furthermore, the relationship between Mn/N transformation and microbial community structure shifts revealed that the redox transition between Mn(II) and Mn(IV) promoted the enrichment of denitrogenation bacteria and functional genes, thus contributing to pollutants removal. Our studies expand the knowledge of MnOx-mediated pollutants removal processes and support the potential application of MnOx for removal of residual refractory organics and nitrogen.

Molecular mechanisms through which different carbon sources affect denitrification by Thauera linaloolentis: Electron generation, transfer, and competition

Characterizing the molecular mechanism through which different carbon sources affect the denitrification process would provide a basis for the proper selection of carbon sources, thus avoiding excessive carbon source dosing and secondary pollution while also improving denitrification efficiency. Here, we selected Thauera linaloolentis as a model organism of denitrification, whose genomic information was elucidated by draft genome sequencing and KEGG annotations, to investigate the growth kinetics, denitrification performances and characteristics of metabolic pathways under diverse carbon source conditions. We reconstructed a metabolic network of Thauera linaloolentis based on genomic analysis to help develop a systematic method of researching electron pathways. Our findings indicated that carbon sources with simple metabolic pathways (e.g., ethanol and sodium acetate) promoted the reproduction of Thauera linaloolentis, and its maximum growth density reached OD600 = 0.36 and maximum specific growth rate reached 0.145 h−1. These carbon sources also accelerated the denitrification process without the accumulation of intermediates. Nitrate could be reduced completely under any carbon source condition; but in the “glucose group”, the maximum accumulation of nitrite was 117.00 mg/L (1.51 times more than that in the “ethanol group”, which was 77.41 mg/L), the maximum accumulation of nitric oxide was 363.02 μg/L (7.35 times more than that in the “ethanol group”, which was 49.40 μg/L), and the maximum accumulation of nitrous oxide was 22.58 mg/L (26.56 times more than that in the “ethanol group”, which was 0.85 mg/L). Molecular biological analyses demonstrated that diverse types of carbon sources directly induced different carbon metabolic activities, resulting in variations in electron generation efficiency. Furthermore, the activities of the electron transport system were positively correlated with different carbon metabolic activities. Finally, these differences were reflected in the phenomenon of electronic competition between denitrifying reductases. Thus we concluded that this was the main molecular mechanism through which the carbon source type affected the denitrification process. In brief, carbon sources with simple metabolic pathways induced higher efficiency of electron generation, transfer, and competition, which promoted rapid proliferation and complete denitrification; otherwise Thauera linaloolentis would grow slowly and intermediate products would accumulate seriously. Our study established a method to evaluate and optimize carbon source utilization efficiency based on confirmed molecular mechanisms.

Single Strain-Triggered Biogeochemical Cycle of Arsenic.

The microbial metabolism of arsenic plays a prominent role in governing the biogeochemical cycle of arsenic. Although diverse microbes are known to be involved in the redox transformation of inorganic arsenic, the underlying mechanisms about the arsenic redox cycle mediated by a single microbial strain remain unclear yet. Herein, we discover that Shewanella putrefaciens CN32, a well-known arsenate-respiring and dissimilatory metal-reducing bacterium, could mediate the reversible arsenic redox transformation under aerobic conditions. Genetic analysis shows that S. putrefaciens CN32 contains both ars and arr operon but lacks an As(III) oxidase encoding gene. Arsenic(V) reduction tests demonstrate that the ars operon is advantageous but not essential for As(V) respiration in S. putrefaciens CN32. The Arr complex encoded by the arr operon not only plays a crucial role in arsenate respiration under anaerobic conditions but also participates in the sequential process of As(V) reduction and As(III) oxidation under aerobic conditions. The Arr enzyme also contributes to the microbial As(III) resistance. The expression and catalysis directionality of Arr in S. putrefaciens CN32 are regulated by the carbon source types. Our results highlight the complexity of arsenic redox biotransformation in environments and provide new insights into the important contribution of Arr to the As biogeochemical cycle in nature.

Production of gamma-aminobutyric acid (GABA) by Bacillus subtilis BBEL02 fermentation using nitrogen-rich industrial wastes as crude feedstocks

Industrial-scale fermentation of γ-aminobutyric acid (GABA) is often limited by high cost of the starting raw materials. Increasing commercial applications of GABA in various industries have urged the research on finding the alternative substrates for the GABA production. The effects of concentration of different types of carbon and nitrogen sources; concentration of monosodium glutamate (MSG) in the defined medium for GABA production using the newly isolated Bacillus subtilis BBEL02 were studied. The feasibility of corn steep liquor (CSL) and soybean hydrolysate (SBH) as the replacement of nitrogen sources in the fermentation media for GABA production was also investigated. Highest GABA content (10.9 gL−1) and productivity (3.7 gL−1d−1) were achieved with defined medium containing 1 % (w/v) glucose, 2 % (v/v) SBH and 5 % (w/v) MSG. Dissolved oxygen (DO) of 80 % in 2-L fermenter presented the highest productivity (4.2 gL−1d−1) and GABA concentration (12.5 gL−1), however DO of 50 % was preferred because of the lower rotation speed to prevent cells deterioration.

Thauera sp. Sel9, a new bacterial strain for polyhydroxyalkanoates production from volatile fatty acids

Thauera is one of the main genera involved in polyhydroxyalkanoate (PHA) production in microbial mixed cultures (MMCs) from volatile fatty acids (VFAs). However, no Thauera strains involved in PHA accumulation have been obtained in pure culture so far. This study is the first report of the isolation and characterization of a Thauera sp. strain, namely Sel9, obtained from a sequencing batch reactor (S-SBR) set up for the selection of PHA storing biomass. The 16S rRNA gene evidenced a high sequence similarity with T. butanivorans species. Genome sequencing identified all genes involved in PHA synthesis, regulation and degradation. The strain Sel9 was able to grow with an optimum of chemical oxygen demand-to-nitrogen (COD:N) ratio ranging from 4.7 to 18.9. Acetate, propionate, butyrate and valerate were used as sole carbon and energy sources: a lag phase of 72 h was observed in presence of propionate. Final production of PHAs, achieved with a COD:N ratio of 75.5, was 60.12 ± 2.60 %, 49.31 ± 0.7 %, 37.31 ± 0.43 % and 18.06 ± 3.81 % (w/w) by using butyrate, acetate, valerate and propionate as substrates, respectively. Also, the 3-hydroxybutyrate/3-hydroxyvalerate ratio reflected the type of carbon sources used: 12.30 ± 0.82 for butyrate, 3.56 ± 0.02 for acetate, 0.93 ± 0.03 for valerate and 0.76 ± 0.02 for propionate. The results allow a better elucidation of the role of Thauera in MMCs and strongly suggest a possible exploitation of Thauera sp. Sel9 for a cost-effective and environmentally friendly synthesis of PHAs using VFAs as substrate.

Enhanced production of amyrin in Yarrowia lipolytica using a combinatorial protein and metabolic engineering approach

BackgroundAmyrin is an important triterpenoid and precursor to a wide range of cosmetic, pharmaceutical and nutraceutical products. In this study, we metabolically engineered the oleaginous yeast, Yarrowia lipolytica to produce α- and β-amyrin on simple sugar and waste cooking oil.ResultsWe first validated the in vivo enzymatic activity of a multi-functional amyrin synthase (CrMAS) from Catharanthus roseus, by expressing its codon-optimized gene in Y. lipolytica and assayed for amyrins. To increase yield, prevailing genes in the mevalonate pathway, namely HMG1, ERG20, ERG9 and ERG1, were overexpressed singly and in combination to direct flux towards amyrin biosynthesis. By means of a semi-rational protein engineering approach, we augmented the catalytic activity of CrMAS and attained ~ 10-folds higher production level on glucose. When applied together, protein engineering with enhanced precursor supplies resulted in more than 20-folds increase in total amyrins. We also investigated the effects of different fermentation conditions in flask cultures, including temperature, volumetric oxygen mass transfer coefficient and carbon source types. The optimized fermentation condition attained titers of at least 100 mg/L α-amyrin and 20 mg/L β-amyrin.ConclusionsThe design workflow demonstrated herein is simple and remarkably effective in amplifying triterpenoid biosynthesis in the yeast Y. lipolytica.

Relationship of phosphorus removal, extracellular polymeric substances characteristics, and microbial community diversity in an aerobic moving bed biofilm reactor: Effect of carbon sources

The aerobic moving bed biofilm reactor (AMBBR) was established to explore the effect of carbon source types (sodium acetate, sodium propionate and starch) on phosphorus removal, extracellular polymeric substances (EPS) composition, variation of Polyhydroxyalkanoate (PHA) and glycogen, and microbial community structure. The results showed that carbon source of sodium propionate improved the pollutant removal efficiency in the AMBBR system. The removal efficiency of COD, NH4+-N, total phosphorus (TP) and PO43- reached to 91.72 ± 2.85 %, 86.76 ± 2.02 %, 72.14 ± 1.70 % and 71.66 ± 2.60 % respectively. Sodium propionate tends to favor the stability and growth of the carrier attached biofilm. TP concentration of the tightly bound EPS (TB-EPS) showed a significant positive correlation (R = 0.929 **, p = 0.01) with TB-EPS protein (PN) concentration in the carrier attached biofilm. Under sodium propionate condition, PHA and Glycogen accumulating concentration as well as the phosphorus accumulating and release amount exhibited the highest during one cycle of the AMBBR. Sodium propionate improved the growth of nitrite oxidizing bacteria (NOB), denitrifying bacteria (DNB), phosphorus accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs). However, Pseudpmonas as a well-known denitrifying phosphorus accumulating bacteria (DNPAOs) was greatly increased under sodium acetate condition. Principal component analysis (PCA) results revealed that the abundance of Candidatus_Accumulibacter (PAOs) and Dechloromonas (DNPAOs) were strongly correlated with TB-EPS PN concentration. These results indicated that suitable carbon source type could enhance phosphorus removal by improving the growth of EPS and metabolism of microbial community.

Effects of External Carbon Sources on Ultimate Nitrogen Removal Performance and Microbial Community in Secondary Effluent Treating Process

Adding external carbon sources is an important method for advanced nitrogen removal of secondary effluent in wastewater treatment plants (WWTPs). In order to compare the denitrification performance and economy of different carbon sources sufficiently, as well as the effect of long-term addition of carbon sources on the microbial population structure, four single carbon sources (methanol, ethanol, glucose, and sodium acetate) and four types of composite carbon sources were prepared by mixing sodium acetate and ethanol with a higher reaction rate and cheap glucose. The results showed that the effluent ρ(NOx--N) concentration of all systems was less than 1.0 mg·L-1 during the experiment. For single-carbon source systems, ethanol had the fastest denitrification rate, followed by sodium acetate and methanol; that of the glucose was the slowest. In the composite carbon source systems, the sodium acetate/glucose (1:1) with COD/ρ(N) was 6, which was equivalent to the results of sodium acetate/glucose (1:3), ethanol/glucose(1:1), and ethanol/glucose (1:3) with COD/ρ(N) of 9, 10, and 10, respectively. The sodium acetate/glucose (1:1) system had the fastest reaction rate and the best economy. High-throughput sequencing results showed that after more than 70 days of operation, the structure of the microbial community had changed completely. In the glucose-related system, the abundance of Candidatus Saccharibacteria, which is not popular in typical nitrogen removal systems, increased from 1.16% of seed sludge to 47.37%, and Saccharibacteria_genera_incertae_sedis correspondingly became the dominant community. This study not only provides a more comprehensive comparison for the selection of carbon sources in WWTPs with ultimate nitrogen removal but also provides basic data for the role of carbon sources in the domestication of microbial communities.

Enhancement of nutrients removal and biomass accumulation of algal-bacterial symbiosis system by optimizing the concentration and type of carbon source in the treatment of swine digestion effluent

The algae-bacteria symbiosis system (ABS) is used to effectively solve the problems of low carbon/nitrogen (C/N) ratio, low biodegradability and high ammonia toxicity in swine digestion effluent. This study examined the effects of the concentration and type of carbon source on ABS in the pollutants removal especially ammonia. When C/N ratio was 30:1 and carbon source was sodium acetate, the ABS was most conducive to the removal of nitrogen, phosphorus and COD, and to the accumulation of biomass and lipids. To make the wastewater discharge meet the relevant standard, the ABS + mono-cultivation of algae reprocessing system (MAS), was applied to actual swine digestion effluent. Through adjusting the C/N ratio in ABS to 30:1, the biomass concentration was 2.06 times higher than that of raw wastewater, and the removal efficiencies of NH4+-N, TN, TP and COD increased by 1.43, 1.46, 1.95 and 1.28 times, respectively. The final concentrations of NH4+-N, TN, TP and COD after the treatment of ABS (C/N ratio of 30:1) + MAS, were 16.98 ± 1.07 mg L−1, 18.72 ± 1.81 mg L−1, 0.48 ± 0.01 mg L−1 and 263.49 ± 11.89 mg L−1, respectively, reached the Chinese discharge standards for livestock and poultry wastewater. Bacterial community analysis showed that the dominant species of the ABS (C/N ratio of 30:1) was Corynebacterium (genus level). This study revealed that adjusting the concentration and type of carbon source was helpful to the nutrient cycling and resource utilization of ABS, indicating a feasible technique for treating high ammonia nitrogen digestate.

Lysine acetylation decreases enzyme activity and protein level of Escherichia coli lactate dehydrogenase

Lactate is an important bulk chemical with widespread applications and a major byproduct of other chemicals bioprocess in microbial fermentation. Lactate dehydrogenase A (LdhA) catalyzes the synthesis of lactate from pyruvate. Lysine acetylation is an evolutionarily conserved post-translational modification; however, the mechanisms underlying the regulation of LdhA function by lysine acetylation in Escherichia coli remain poorly understood. Herein, we demonstrate acetylation of E. coli LdhA occurs via enzymatic and non-enzymatic mechanisms. Further, we show carbon source type and concentration affect the lysine acetylation status of LdhA via a non-enzymatic mechanism. Lysine acetylation significantly inhibits the enzymatic activity and protein level of LdhA. The results of the present study demonstrate lysine acetylation of E. coli LdhA is irreversible. Understanding of the effects of lysine acetylation on LdhA function may provide a new perspective for regulating lactate production in microbial synthesis.

Abiotic Hydrocarbons Generation Simulated by Fischer‐Tropsch Synthesis under Hydrothermal Conditions in Ultra‐deep Basins

AbstractFTT experiments with water as a hydrogen source and three types of possible carbon sources in the subsurface (diiron nonacarbonyl, siderite and formic acid, representing CO, CO2 and a simple organic acid, respectively) were carried out in this study. Our experimental results showed that n‐alkanes with the highest carbon number of C33 were produced when CO was used as a carbon source (series A); a variety of polycyclic aromatic hydrocarbons (PAHs) were detected in series B with CO2 as a carbon source; gaseous hydrocarbons were also detected with formic acid added (series C). The different products in the three series showed that there were different hydrocarbon generation mechanisms and reaction processes with different carbon sources. The generation of long‐chain n‐alkanes in series A provided experimental support for the formation of abiogenic petroleum underground, which was of significance to early membranes on the Earth. PAHs in series B provide experimental support for the possibility of an abiotic source of reduced carbon on other planets. The carbon isotopes of gaseous hydrocarbons produced by CO exhibited a partial reversed order (δ13C1 < δ13C2 > δ13C3 > δ13C4 > δ13C5), while the gaseous hydrocarbons produced by CO2 and HCOOH showed a positive order (δ13C1 < δ13C2 < δ13C3 < δ13C4 < δ13C5). Based on these, the alkylene mechanism and the carbonyl insertion mechanism were used to reasonably explain these characteristics.

VARIASI SUMBER KARBON TERHADAP PRODUKSI BIOSURFAKTAN OLEH BAKTERI HALOFILIK ISOLAT TAMBAK GARAM KAJHU ACEH BESAR

This research has isolated one type of halophilic bacterial strain from the salt pond of Kajhu Village with the code KJ-AB2. This bacterium grew optimally at 10% (w/v) NaCl so it was classified as moderate halophilic bacteria. Several types of halophilic bacteria are known to produce biosurfactants. Biosurfactants are surface active agents that are widely used in several pharmaceutical, food dan petroleum industries. The production of biosurfactants is strongly influenced by the type of carbon source used for bacterial growth. Olive oil, palm oil, sunflower oil, glucose dan glycerol are types of carbon sources used to see their effect in producing biosurfactants. This isolate growed well on the five carbon sources with an average OD600 2.001±0.293 at 72 hours of fermentation. Biosurfactant production was measured by oil spreading test (OST) every 24 hours until 120 hours of fermentation. The highest OST value was obtained when KJ-AB2 isolate was grown on biosurfactant production media using olive oil, sunflower oil dan palm oil with an average OST value of 5.6±0.6 cm, 4.7±0.6 cm, dan 4.6±0.7 cm, respectively.

The importance of understanding the regulation of bacterial metabolism.

The importance of understanding the regulation of bacterial metabolism.

Microplastics a Novel Substratum for Polyhydroxyalkanoate (PHA)-Producing Bacteria in Aquatic Environments.

Polyhydroxyalkanoates (PHA) being biological polymers have attracted great attention. PHA have similar properties to that of synthetic plastic and are biodegradable. To discourage plastic pollution in the environment alternative solutions to the plastic pollution has to be readily available. High cost in production of PHA limits the production of these polymers at industrial scale. Bacteria are screened for PHA from diverse niches to meet the current requirements of cheap PHA production at industrial level. The microbial biofilm formed on the surface of microplastic could be a potential source in providing bacteria of economic importance. This paper is an attempt to search microplastic niche for potential PHA producers. PHA production variation was observed with different parameters such as type of carbon source, nitrogen source concentration and also time of incubation. Bacillus sp. CM27 showed maximum PHA yield up to 32.1% among other isolates at 48 h with 2% glucose as carbon source. Optimization of media leads to increase in PHA yield (37.69%) of CDW in Bacillus sp. CM27. Amino acid sequence of Bacillus sp.CM27 showed the presence of PhaC box with sequence, G-Y-C-M-G-G having cysteine in the middle of the box. The extracted polymer was confirmed by FTIR spectroscopy.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00284-022-02929-y.

Bacterial Resuscitation from Starvation-Induced Dormancy Results in Phenotypic Diversity Coupled with Translational Activity Depending on Carbon Substrate Availability.

Dormancy is a survival strategy of stressed bacteria inhabiting a various environment. Frequent dormant-active transitions owing to environmental changes play an important role in functional redundancy. However, a proper understanding of the phenotypic changes in bacteria during these transitions remains to be clarified. In this study, orthogonal approaches, such as electron microscopy, flow cytometry, and Raman spectroscopy, which can evaluate phenotypic heterogeneity at the single-cell level, were used to observe morphological and molecular phenotypic changes in resuscitated cells, and RNA sequencing (RNASeq) was used to determine the genetic characteristics associated with phenotypes. Within 12h of the resuscitation process, morphological (cell size and shape) and physiological (growth and viability) characteristics as well as molecular phenotypes (cellular components) were found to be recovered to the extent that they were similar to those in active cells. The recovery rate and detailed phenotypic properties of the resuscitated cells differed significantly depending on the type or concentration of carbon sources. RNASeq analysis revealed that genes related to translation were significantly upregulated under all resuscitation conditions. The simpler the carbon source (e.g., glucose), the higher the expression of genes involved in cellular repair, and the more complex the carbon source (e.g., beef extract), the higher the expression of genes associated with increased energy production associated with cellular aerobic respiration. This study of phenotypic plasticity of resuscitated cells provides fundamental insight into understanding the adaptive fine-tuning of the microbiome in response to environmental changes and the functional redundancy resulting from phenotype heterogeneity.

Production and Characterization of Rhamnolipids Produced by Pseudomonas aeruginosa DBM 3774: Response Surface Methodology Approach.

Rhamnolipids are extensively studied biosurfactants due to their potential in many industrial applications, eco-friendly production and properties. However, their availability for broader application is severely limited by their production costs, therefore the optimization of efficacy of their cultivation gains significance as well as the information regarding the physio-chemical properties of rhamnolipids resulting from various cultivation strategies. In this work, the bioprocess design focused on optimization of the rhamnolipid yield of Pseudomonas aeruginosa DBM 3774 utilizing the response surface methodology (RSM). Six carbon sources were investigated for their effect on the rhamnolipid production. The RSM prediction improved the total rhamnolipid yield from 2.2 to 13.5 g/L and the rhamnolipid productivity from 11.6 to 45.3 mg/L/h. A significant effect of the carbon source type, concentration and the C/N ratio on the composition of the rhamnolipid congeners has been demonstrated for cultivation of P. aeruginosa DBM 3774 in batch cultivation. Especially, changes in presence of saturated fatty acid in the rhamnolipid congeners, ranging from 18.8% of unsaturated fatty acids (carbon source glycerol; 40 g/L) to 0% (sodium citrate 20 g/L) were observed. This demonstrates possibilities of model based systems as basis in cultivation of industrially important compounds like biosurfactants rhamnolipids and the importance of detailed study of interconnection between cultivation conditions and rhamnolipid mixture composition and properties.