Ecosystem service valuation and multi-scenario simulation in the Ebinur Lake Basin using a coupled GMOP-PLUS model.

The Ebinur Lake Basin is an ecologically sensitive area in an arid region. Investigating its land use and land cover (LULC) change and assessing and predicting its ecosystem service value (ESV) are of great importance for the stability of the basin's socioeconomic development and sustainable development of its ecological environment. Based on LULC data from 1990, 2000, 2010, and 2020, we assessed the ESV of the Ebinur Lake Basin and coupled the grey multi-objective optimization model with the patch generation land use simulation model to predict ESV changes in 2035 under four scenarios: business-as-usual (BAU) development, rapid economic development (RED), ecological protection (ELP), and ecological-economic balance (EEB). The results show that from 1990 to 2020, the basin was dominated by grassland (51.23%) and unused land (27.6%), with a continuous decrease in unused land and an increase in cultivated land. In thirty years, the total ESV of the study area increased from 18.62 billion to 67.28 billion yuan, with regulation and support services being the dominant functions. By 2035, cultivated land increased while unused land decreased in all four scenarios compared with that in 2020. The total ESV in 2035 under the BAU, RED, ELP, and EEB scenarios was 68.83 billion, 64.47 billion, 67.99 billion, and 66.79 billion yuan, respectively. In the RED and EEB scenarios, ESV decreased by 2.81 billion and 0.49 billion yuan, respectively. In the BAU scenario, provisioning and regulation services increased by 6.05% and 2.93%, respectively. The ELP scenario, focusing on ecological and environmental protection, saw an increase in ESV for all services. This paper can assist policymakers in optimizing land use allocation and provide scientific support for the formulation of land use strategies and sustainable ecological and environmental development in the inland river basins of arid regions.

Dynamic simulation of landscape ecological security and analysis of coupling coordination degree: A case study of Bole.

The ecological security of oasis cities in arid and semi-arid regions is highly susceptible to changes in regional landscape patterns and the degree of coordination between human activities and the environment. At the same time, the ecological security of urban landscapes also profoundly affects the success of regional economic and environmental coordination and development. This study is based on land use data from 1990, 2000, 2010, and 2020, as well as land use data from the natural development scenario (NLD), economic development scenario (ECD), ecological development scenario (ELD) and ecological-economic development scenario (EED) simulated by the patch-generating land use simulation (PLUS) model in 2030. From the perspective of production-living-ecological land (PLEL), it analyzes the changes in the past and future landscape ecological security and coupling coordination characteristics of Bole. The results show that from 1990 to 2020, Bole was mainly dominated by grassland ecological land (GEL) and other ecological land (OEL), accounting for a total proportion of 69.51%, with a large increase in production and living land area; the average value of landscape ecological risk is decreasing, and the landscape ecological security of Bole is developing towards benignity; the area of highly coupled coordination zone is decreasing continuously, while that of basic coordination zone and moderate coordination zone is increasing continuously. Under the 2030 EED scenario, the overall changes in various types of land use are not significant, and the average value of landscape ecological risk is the smallest, but it is higher than that in 2020 as a whole; under EED scenario, the area of highly coordinated zone and moderate coordinated zone is the largest among four scenarios, and the best coupling coordination level among the four scenarios. Landscape ecological security and its coupling coordination will be affected by land use patterns. Optimizing regional land use patterns is of great significance for improving urban landscape ecological security and sustainable high-quality development.

[Theoretical analysis and practical applications of the catalytic mechanism of flavonoid 6-hydroxylase].

Insufficient catalytic efficiency of flavonoid 6-hydroxylases in the fermentative production of scutellarin leads to the formation of at least about 18% of by-products. Here, the catalytic mechanisms of two flavonoid 6-hydroxylases, CYP82D4 and CYP706X, were investigated by molecular dynamics simulations and quantum chemical calculations. Our results show that CYP82D4 and CYP706X have almost identical energy barriers at the rate-determining step and thus similar reaction rates, while the relatively low substrate binding energy of CYP82D4 may facilitate product release, which is directly responsible for its higher catalytic efficiency. Based on the study of substrate entry and release processes, the catalytic efficiency of the L540A mutation of CYP82D4 increased by 1.37-fold, demonstrating the feasibility of theoretical calculations-guided engineering of flavonoid 6-hydroxylase. Overall, this study reveals the catalytic mechanism of flavonoid 6-hydroxylases, which may facilitate the modification and optimization of flavonoid 6-hydroxylases for efficient fermentative production of scutellarin.

Antifungal Activity of Cadinane-Type Sesquiterpenes from Eupatorium adenophorum against Wood-Decaying Fungi.

The present study aimed to evaluate the antifungal activities of Eupatorium adenophorum against four strains of wood-decaying fungi, including Inonotus hispida, Inonotus obliquus, and Inonotus cuticularis. Bioguided isolation of the methanol extract of E. adenophorum by silica gel column chromatography and high-performance liquid chromatography afforded six cadinane-type sesquiterpenes. Their structures were identified by nuclear magnetic resonance and MS analyses. According to the antifungal results, the inhibition rate of the compound was between 59.85 % and 77.98 % at a concentration of 200 µg/mL. The EC50 values ranged from 74.5 to 187.4 µg/mL.

iTRAQ-Based Quantitative Proteomic Analysis of Arthrobacter simplex in Response to Cortisone Acetate and Its Mutants with Improved Δ1-Dehydrogenation Efficiency.

Arthrobacter simplex is extensively used for cortisone acetate (CA) biotransformation in industry, but the Δ1-dehydrogenation molecular fundamental remains unclear. Herein, the comparative proteome revealed several proteins with the potential role in this reaction, which were mainly involved in lipid or amino acid transport and metabolism, energy production and conversion, steroid degradation, and transporter. The influences of six proteins were further confirmed, where pps, MceGA, yrbE4AA, yrbE4BA, and hyp2 showed positive impacts, while hyp1 exhibited a negative effect. Additionally, KsdD5 behaved as the best catalytic enzyme. By the combined manipulation in multiple genes under the control of a stronger promoter, an optimal strain with better catalytic enzyme activity, substrate transportation, and cell stress tolerance was created. After biotechnology optimization, the production peak and productivity were, respectively, boosted by 4.1- and 4.0-fold relative to the initial level. Our work broadens the understanding of the Δ1-dehydrogenation mechanism, also providing effective strategies for excellent steroid-transforming strains.

Proteomic Profiling and Stress Response in Pediococcus acidilactici under Acetic Acid.

Lactic acid bacteria are indispensable functional microorganisms for cereal vinegar brewing, but cell activities are inhibited by the dominant acetic acid stress. Herein, an acetic-acid-tolerant strain isolated previously was identified as Pediococcus acidilactici, which also exhibited good resistance to other stresses during vinegar brewing. Proteomics analysis evidenced that differentially expressed proteins involved in the glycolysis and gluconeogenesis pathway, pyruvate metabolism, and sugar phosphotransferase system were all downregulated. Meanwhile, saturation of fatty acids and antioxidant enzymes was strengthened. The effects of several proteins on the resistance of P. acidilactici and Lactobacillus lactis relied on the types of strain and stress. AccA and AcpP participating in fatty acid metabolism and biosynthesis and Mnc related to stress response were found to protect cells by modifying fatty acid compositions and reinforcing the antioxidant defense system. Our works deepen the mechanisms of P. acidilactici under acetic acid and offer targets for engineering cell tolerance.

Quantifying impacts of climate dynamics and land-use changes on water yield service in the agro-pastoral ecotone of northern China.

Large-scale revegetation practices have lasted approximately two decades in the agro-pastoral ecotone of northern China (AENC), and their impacts on hydrological and ecological effects remain poorly understood. Previous studies largely focused on assessing water yield service (WYs) based on several fixed time points, whereas time series information-continuous WYs dynamics were more reliable and valuable in decision-making about water sustainability goals. This study analyzed the interannual WYs trend and relative roles of its drivers in the last 20 years based on a newly proposed approach, and revealed the past, present and future impacts of revegetation on WYs. The final results indicated that the annual WYs averaged approximately 97 mm and exhibited an increasing trend of 1.96 mm year-1 (p = 0.086) during 2000-2019, in which climate and land-use changes were responsible for 88% and 12% of WYs variations, respectively. From 2000 to 2019, WYs was pronouncedly 1.47 mm year-1 (p = 0.119) lower in the afforestation area than in the nonafforestation area, but the precipitation in the two regions had a statistically insignificant difference (p = 0.97). Future revegetation scenarios showed great potential for the shrinkage of WYs provision, even approaching a maximum of 50 mm at a local scale. Even so, the afforestation-induced reductions in blue water and benefits in green water both should receive equal attention. Specifically, any attempts to assess WYs or other climate-driven ecosystem services using discontinuous years as the study period must be taken with extreme caution.

Genomewide Transcriptome Responses of Arthrobacter simplex to Cortisone Acetate and its Mutants with Enhanced Δ1-Dehydrogenation Efficiency.

Due to its superior Δ1-dehydrogenation ability, Arthrobacter simplex has been widely used for the biotransformation of cortisone acetate (CA) into prednisone acetate (PA) in the steroid industry. However, its molecular fundamentals are still unclear. Herein, the genome organization, gene regulation, and previously unreported genes involved in Δ1-dehydrogenation are revealed through genome and transcriptome analysis. A comparative study of transcriptomes of an industrial strain induced by CA or at different biotransformation periods was performed. By overexpression, the roles of six genes in CA conversion were confirmed, among which sufC and hsaA behaved better by reinforcing catalytic enzyme activity and substrate transmembrane transport. Additionally, GroEL endowed cells with the strongest stress tolerance by alleviating oxidative damage and enhancing energy levels. Finally, an optimal strain was created by coexpressing three genes, achieving 46.8 and 70.6% increase in PA amount and productivity compared to the initial values, respectively. Our study expanded the understanding of the Δ1-dehydrogenation mechanism and offered an effective approach for excellent steroid-transforming strains.

Efficient One-Step Biocatalytic Multienzyme Cascade Strategy for Direct Conversion of Phytosterol to C-17-Hydroxylated Steroids.

Steroidal 17-carbonyl reduction is crucial to the production of natural bioactive steroid medicines, and boldenone (BD) is one of the important C-17-hydroxylated steroids. Although efforts have been made to produce BD through biotransformation, the challenges of the complex transformation process, high substrate costs, and low catalytic efficiencies have yet to be mastered. Phytosterol (PS) is the most widely accepted substrate for the production of steroid medicines due to its similar foundational structure and ubiquitous sources. 17ß-Hydroxysteroid dehydrogenase (17ßHSD) and its native electron donor play significant roles in the 17ß-carbonyl reduction reaction of steroids. In this study, we bridged 17ßHSD with a cofactor regeneration strategy in Mycobacterium neoaurum to establish a one-step biocatalytic carbonyl reduction strategy for the efficient biosynthesis of BD from PS for the first time. After investigating different intracellular electron transfer strategies, we rationally designed the engineered strain with the coexpression of 17ßhsd and the glucose-6-phosphate dehydrogenase (G6PDH) gene in M. neoaurum. With the establishment of an intracellular cofactor regeneration strategy, the ratio of [NADPH]/[NADP+] was maintained at a relatively high level, the yield of BD increased from 17% (in MNR M3M-ayr1S.c) to 78% (in MNR M3M-ayr1&g6p with glucose supplementation), and the productivity was increased by 6.5-fold. Furthermore, under optimal glucose supplementation conditions, the yield of BD reached 82%, which is the highest yield reported for transformation from PS in one step. This study demonstrated an excellent strategy for the production of many other valuable carbonyl reduction steroidal products from natural inexpensive raw materials. IMPORTANCE Steroid C-17-carbonyl reduction is one of the important transformations for the production of valuable steroidal medicines or intermediates for the further synthesis of steroidal medicines, but it remains a challenge through either chemical or biological synthesis. Phytosterol can be obtained from low-cost residues of waste natural materials, and it is preferred as the economical and applicable substrate for steroid medicine production by Mycobacterium. This study explored a green and efficient one-step biocatalytic carbonyl reduction strategy for the direct conversion of phytosterol to C-17-hydroxylated steroids by bridging 17ß-hydroxysteroid dehydrogenase with a cofactor regeneration strategy in Mycobacterium neoaurum. This work has practical value for the production of many valuable hydroxylated steroids from natural inexpensive raw materials.

Improving Biotransformation Efficiency of Arthrobacter simplex by Enhancement of Cell Stress Tolerance and Enzyme Activity.

Arthrobacter simplex exhibits excellent Δ1-dehydrogenation ability, but the acquisition of the desirable strain is limited due to lacking of comprehensive genetic manipulation. Herein, a promoter collection for fine-tuning gene expression was achieved. Next, the expression level was enhanced and directed evolution of the global transcriptional factor (IrrE) was applied to enhance cell viability in systems containing more substrate and ethanol, thus contributing to higher production. IrrE promotes a stronger antioxidant defense system, more energy generation, and changed signal transduction. Using a stronger promoter, the enzyme activities were boosted but their positive effects on biotransformation performance were inferior to cell stress tolerance when exposed to challenging systems. Finally, an optimal strain was created by collectively reinforcing cell stress tolerance and catalytic enzyme activity, achieving a yield 261.8% higher relative to the initial situation. Our study provided effective methods for steroid-transforming strains with high efficiency.

Identification, Biological Characteristics, and Active Site Residues of 3-Ketosteroid Δ1-Dehydrogenase Homologues from Arthrobacter simplex.

3-Ketosteroid Δ1-dehydrogenase (KsdD) is the key enzyme responsible for Δ1-dehydrogenation, which is one of the most valuable reactions for steroid catabolism. Arthrobacter simplex has been widely used in the industry due to its superior bioconversion efficiency, but KsdD information is not yet fully clear. Here, five KsdD homologues were identified in A. simplex CGMCC 14539. Bioinformatic analysis indicated their distinct properties and structures. Each KsdD was functionally confirmed by transcriptional response, overexpression, and heterologous expression. The substantial difference in substrate profiles might be related to the enzyme loop structure. Two promising enzymes (KsdD3 and KsdD5) were purified and characterized, exhibiting strong organic solvent tolerance and clear preference for 4-ene-3-oxosteroids. KsdD5 seemed to be more versatile due to good activity on substrates with or without a substituent at C11 and high optimal temperature and also possessed unique residues. It is the first time that KsdDs have been comprehensively disclosed in the A. simplex industrial strain.

GC × GC-MS analysis and hypolipidemic effects of polyphenol extracts from Shanxi-aged vinegar in rats under a high fat diet.

Oxidative stress, inflammation and gut microbiota disorders can be induced by long-term high-fat diets (HFD). In order to confirm that polyphenols can improve these symptoms, polyphenols from Shanxi-aged vinegar (SAVEP) were extracted, and the components were detected by Comprehensive two-dimensional gas chromatography mass spectrometry (GC × GC-MS). 41 polyphenols include 18 phenolic acids and 17 polyphenols, which have not been reported. The mechanism of SAVEP on oxidative stress and inflammatory stress induced by HFD in rats and its regulating effect on intestinal flora disorder were studied. The results showed that SAVEP could significantly improve the lipid, inflammatory stress and oxidative stress related indicators compared with the Model group ("Model" refers to the group that successfully constructed a hyperlipidemia model by feeding HFD without any drugs or SAVEP in subsequent experiments.). In addition, SAVEP decreased the Firmicutes/Bacteroidetes ratio compared with the Model group, and elevated the relative abundance of beneficial bacteria. Conclusively, SAVEP can alleviate the oxidative stress and inflammatory stress caused by HFD, improving intestinal microbial disorders. The Spearman's correlation analysis revealed that Desulfovibrio, Lactobacillus and Akkermansia were correlated negatively with all of the inflammatory indicators, whereas Ruminococcus was the opposite. These results suggest that SAVEP may be a novel strategy against oxidative stress and inflammation, restoring the normal microbial community ecology of the gut and the treatment of metabolic syndromes.

Global regulator engineering enhances bioelectricity generation in Pseudomonas aeruginosa-inoculated MFCs.

The electricigens with high-electroactivity is essential for resolving the low electricity power output (EPT) of microbial fuel cells (MFCs). However, the manipulation by single functional genes shows limitation because electroactivity is a complex phenotype controlled by multiple genes. Herein, global regulator engineering (GRE) was developed to optimize the electroactivity of an isolated strain (Pseudomonas aeruginosa P3-A-11) using an exogenous global regulator IrrE (ionizing radiation resistance E linkage group) as an object. The GRE was implemented through in vitro random mutagenesis by error-prone PCR and in vivo high-through screening comprised of cultures color assay, PYO measurement and MFCs operation. Four mutants with higher electroactivity were obtained, among which, the mutant 11/M2-59 not only displayed the maximal power density, but also exhibited stronger salt tolerance, consequently showing good performance of MFCs in the presence of salt. Apart from the reduced internal resistance, the increase in phenazines amounts primarily contributed to EPT improvement, which was realized by enhancing the core biosynthesis pathway and affecting other pathways (such as central metabolism pathway, quorum sensing system, regulatory network). Notably, IrrE exerted its positive effect on electroactivity even without native regulators (such as PmpR and RpoS). In addition, the significant fluctuations in expression levels of stress-responsive genes mediated by GRE were closely associated with the enhanced salt tolerance. This work demonstrated that GRE was an effective approach for simultaneously optimizing multiple phenotypes (such as electroactivity and stress tolerance), and thus would provide more opportunities to create high-efficiency electricigens and further promoted the practical application of MFCs.

Efficient repeated batch production of androstenedione using untreated cane molasses by Mycobacterium neoaurum driven by ATP futile cycle.

The biotransformation of phytosterol to androstenedione (AD) by mycobacteria is a unique process accompanied by energy-producing. However, high intracellular ATP content can severely inhibit the efficient production of AD. In this study, a novel citrate-based ATP futile cycle (AFC) and pyruvate-based AFC were constructed for the first time. Application of AFCs reduced intracellular ATP and propionyl-CoA levels and increased NAD+/NADH ratios and cell viability. The forced consumption of ATP promotes the transcription of critical genes in propionyl-CoA metabolism. The synergistic effect of enhanced propionyl-CoA metabolism and AFC increased AD conversion yield from 60.6% to 97.3%. The AD productivity was further improved by repeated batch fermentation using untreated cane molasses. The maximum productivity was 181% higher than that of the original strain. Therefore, the strategy of combining AFC and repeated batch fermentation is a valuable tool for the efficient and low-cost production of AD and other steroidal pharmaceutical precursors.

Improving phytosterol biotransformation at low nitrogen levels by enhancing the methylcitrate cycle with transcriptional regulators PrpR and GlnR of Mycobacterium neoaurum.

BACKGROUND: Androstenedione (AD) is an important steroid medicine intermediate that is obtained via the degradation of phytosterols by mycobacteria. The production process of AD is mainly the degradation of the phytosterol aliphatic side chain, which is accompanied by the production of propionyl CoA. Excessive accumulation of intracellular propionyl-CoA produces a toxic effect in mycobacteria, which restricts the improvement of production efficiency. The 2-methylcitrate cycle pathway (MCC) plays a significant role in the detoxification of propionyl-CoA in bacterial. The effect of the MCC on phytosterol biotransformation in mycobacteria has not been elucidated in detail. Meanwhile, reducing fermentation cost has always been an important issue to be solved in the optimizing of the bioprocess. RESULTS: There is a complete MCC in Mycobacterium neoaurum (MNR), prpC, prpD and prpB in the prp operon encode methylcitrate synthase, methylcitrate dehydratase and methylisocitrate lyase involved in MCC, and PrpR is a specific transcriptional activator of prp operon. After the overexpression of prpDCB and prpR in MNR, the significantly improved transcription levels of prpC, prpD and prpB were observed. The highest conversion ratios of AD obtained by MNR-prpDBC and MNR-prpR increased from 72.3 ± 2.5% to 82.2 ± 2.2% and 90.6 ± 2.6%, respectively. Through enhanced the PrpR of MNR, the in intracellular propionyl-CoA levels decreased by 43 ± 3%, and the cell viability improved by 22 ± 1% compared to MNR at 96 h. The nitrogen transcription regulator GlnR repressed prp operon transcription in a nitrogen-limited medium. The glnR deletion enhanced the transcription level of prpDBC and the biotransformation ability of MNR. MNR-prpR/ΔglnR was constructed by the overexpression of prpR in the glnR-deleted strain showed adaptability to low nitrogen. The highest AD conversion ratio by MNR-prpR/ΔglnR was 92.8 ± 2.7% at low nitrogen level, which was 1.4 times higher than that of MNR. CONCLUSION: Improvement in phytosterol biotransformation after the enhancement of propionyl-CoA metabolism through the combined modifications of the prp operon and glnR of mycobacteria was investigated for the first time. The overexpress of prpR in MNR can increase the transcription of essential genes (prpC, prpD and prpB) of MCC, reduce the intracellular propionyl-CoA level and improve bacterial viability. The knockout of glnR can enhance the adaptability of MNR to the nitrogen source. In the MNRΔglnR strain, overexpress of prpR can achieve efficient production of AD at low nitrogen levels, thus reducing the production cost. This strategy provides a reference for the economic and effective production of other valuable steroid metabolites from phytosterol in the pharmaceutical industry.

Compatible solutes adaptive alterations in Arthrobacter simplex during exposure to ethanol, and the effect of trehalose on the stress resistance and biotransformation performance.

Ethanol-tolerant Arthrobacter simplex is desirable since ethanol facilitates hydrophobic substrates dissolution on an industrial scale. Herein, alterations in compatible solutes were investigated under ethanol stress. The results showed that the amount of trehalose and glycerol increased while that of glutamate and proline decreased. The trehalose protectant role was verified and its concentration was positively related to the degree of cell tolerance. otsA, otsB and treS, three trehalose biosynthesis genes in A. simplex, also enhanced Escherichia coli stress tolerance, but the increased tolerance was dependent on the type and level of the stress. A. simplex strains accumulating trehalose showed a higher productivity in systems containing more ethanol and substrate because of better viability. The underlying mechanisms of trehalose were involved in better cell integrity, higher membrane stability, stronger reactive oxygen species scavenging capacity and higher energy level. Therefore, trehalose was a general protectant and the upregulation of its biosynthesis by genetic modification enhanced cell stress tolerance, consequently promoted productivity.

Economical production of androstenedione and 9α-hydroxyandrostenedione using untreated cane molasses by recombinant mycobacteria.

Production of androstenedione (AD) and 9α-hydroxyandrostenedione (9α-OH-AD) by recombinant mycobacteria using untreated cane molasses and hydrolysate of mycobacterial cells (HMC) was investigated for the first time. B-vitamins feeding experiment and reverse transcription-PCR analysis showed that propionyl-CoA carboxylase (PCC) plays an important role in the phytosterol biotransformation of mycobacteria. The respective AD and 9α-OH-AD conversion ratios were increased by 2.91 and 1.48 times through coexpression of PCC and NADH dehydrogenase. The highest conversion ratios of AD and 9α-OH-AD obtained by using a co-feeding strategy of cane molasses and HMC reached 96.38% and 95.04%, respectively, and the total costs of carbon and nitrogen sources for the culture medium were reduced by 29.89% and 49.49%, respectively. Taking the results together, untreated cane molasses and HMC can be used for the economical production of steroidal pharmaceutical precursors by mycobacteria. This study offers an economical and green strategy for steroidal pharmaceutical precursor production.

A highly efficient step-wise biotransformation strategy for direct conversion of phytosterol to boldenone.

Collaborative microbial communities are ubiquitous in nature and exhibit appealing functions for enhanced production of natural products, which provides new possibility for biotechnology development. In this study, we bridged Mycobacterium neoaurum with Pichia pastoris to establish a step-wise biotransformation strategy for efficient biosynthesis of boldenone (BD) from phytosterol (PS). Firstly, the producing strains were rationally designed with overexpression of 3-ketosteroid-Δ1-dehydrogenase (KsdD) and 17ß-hydroxysteroid dehydrogenase (17ßHSD) in M. neoaurum and P. pastoris, respectively. Then, to shorten the total biotransformation process and provide reducing power, semi-batch fermentation strategy and glucose supplementation strategy were introduced at side-chain degradation stage and carbonyl reduction stage, respectively. Under the optimal transformation conditions, the productivity of BD was increased from 10% to 76% and the total biotransformation process was shortened by 41.7%, which is the shortest among the ever reported. Our results demonstrated an excellent biological strategy for production of many other valuable microbial products from bioresources.

Carbon dioxide sequestration accompanied by bioenergy generation using a bubbling-type photosynthetic algae microbial fuel cell.

This study developed a bubbling-type photosynthetic algae microbial fuel cell (B-PAMFC) to treat synthetic wastewater and capture CO2 using Chlorella vulgaris with simultaneous power production. The performance of B-PAMFC in CO2 fixation and bioenergy production was compared with the photosynthetic algae microbial fuel cell (PAMFC) and bubbling photobioreactor. Different nitrogen sources for C. vulgaris growth, namely sodium nitrate, urea, ammonium acetate and acetamide were studied. The maximum CO2 fixation rate in B-PAMFC with 2.8 g L-1 urea reached 605.3 mg L-1 d-1, 3.86-fold higher than that in PAMFC. Urea also enhanced the solution absorption of CO2. Furthermore, the B-PAMFC reached a high lipid productivity of 105.9 mg L-1 d-1. An energy balance analysis indicated that B-PAMFC had a maximum net energy of 1.824 kWh m-3, making it a lab-scale energy-positive system. The B-PAMFC with urea as nitrogen source would provide an attractive strategy for simultaneous CO2 sequestration and bioenergy production.

The ethanol-induced global alteration in Arthrobacter simplex and its mutants with enhanced ethanol tolerance.

Arthrobacter simplex has received considerable interests due to its superior Δ1-dehydrogenation ability. Ethanol used as co-solvent is a stress commonly encountered during biotransformation. Therefore, studies of ethanol tolerance of A. simplex are of great importance to improve the biotransformation efficiency. In this paper, the combined analysis of physiological properties, cell compositions, stress-responsive metabolites, and proteome profiles was carried out to achieve a global view of ethanol tolerance of A. simplex. Under sublethal conditions, cell permeability and membrane fluidity exhibited concentration-dependent increase by affecting the contents or compositions of cell peptidoglycan, lipids, phospholipids, and fatty acids. Among them, cis-trans isomerization of unsaturated fatty acids was a short-term and reversible process, while the changes in phospholipid headgroups and increase in saturation degree of fatty acids were long-term and irreversible processes, which collectively counteracted the elevated membrane fluidity caused by ethanol and maintained the membrane stability. The decreased intracellular ATP content was observed at high ethanol concentration since proton motive force responsible for driving ATP synthesis was dissipated. The involvement of trehalose and glycerol, oxidative response, and DNA damage were implicated due to their changes in positive proportion to ethanol concentration. Proteomic data supported that ethanol invoked a global alteration, among which, the change patterns of proteins participated in the biosynthesis of cell wall and membrane, energy metabolism, compatible solute metabolism, and general stress response were consistent with observations from cell compositions and stress-responsive metabolites. The protective role of proteins participated in DNA repair and antioxidant system under ethanol stress was validated by overexpression of the related genes. This is the first demonstration on ethanol tolerance mechanism of A. simplex, and the current studies also provide targets to engineer ethanol tolerance of A. simplex.